[REL] v1.3.1

# v1.3.1

Fixes

- components: fix issue with t-call in nested t-slot (parent component was incorrect)

.github/workflows/deploy.yml

@@ -0,0 +1,27 @@
+# This workflow will do a clean install of node dependencies, build the source code and run tests across different versions of node
+# For more information see: https://help.github.com/actions/language-and-framework-guides/using-nodejs-with-github-actions
+
+name: Node.js CI
+
+on:
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        node-version: [10.x, 12.x, 14.x]
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Use Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v1
+      with:
+        node-version: ${{ matrix.node-version }}
+    - run: npm install
+    - run: npm run test
+    - run: npm run prettier

.gitignore

@@ -15,6 +15,7 @@ yarn-debug.log*
 yarn-error.log*
 
 package-lock.json
+yarn.lock
 
 #ide's
 .vscode
@@ -23,4 +24,8 @@ package-lock.json
 node_modules
 
 # Extras temp file
-/tools/owl.js
+/tools/owl.js
+
+release-notes.md
+
+.rpt2_cache

README.md

@@ -1,47 +1,56 @@
-<h1 align="center">🦉 <a href="https://odoo.github.io/owl/">Odoo Web Library</a> 🦉</h1>
+<h1 align="center">🦉 <a href="https://odoo.github.io/owl/">OWL Framework</a> 🦉</h1>
 
-_A no nonsense web framework for structured, dynamic and maintainable applications_
+_Class based components with hooks, reactive state and concurrent mode_
 
 ## Project Overview
 
-The Odoo Web Library (OWL) is a smallish (~18kb gzipped) UI framework intended to
+The Odoo Web Library (OWL) is a smallish (~<20kb gzipped) UI framework intended to
 be the basis for the [Odoo](https://www.odoo.com/) Web Client. Owl is a modern
 framework, written in Typescript, taking the best ideas from React and Vue in a
 simple and consistent way. Owl's main features are:
 
 - a declarative component system,
 - a reactivity system based on hooks,
-- a store implementation (for state management),
-- a small frontend router
+- concurrent mode by default,
+- a store and a frontend router
 
-Owl components are defined with ES6 classes, they use QWeb templates, an underlying
-virtual dom, integrates beautifully with hooks, and the rendering is asynchronous.
+Owl components are defined with ES6 classes, they use QWeb templates, an
+underlying virtual DOM, integrates beautifully with hooks, and the rendering is
+asynchronous.
 
-**Try it online!** An online playground is available at [https://odoo.github.io/owl/playground](https://odoo.github.io/owl/playground) to let you experiment with the Owl framework. There
-are some code examples to showcase some interesting features.
+**Try it online!** An online playground is available at
+[https://odoo.github.io/owl/playground](https://odoo.github.io/owl/playground)
+to let you experiment with the Owl framework. There are some code examples to
+showcase some interesting features.
 
-Owl is currently mostly stable.  Possible future changes are explained in the
+Owl is currently stable.  Possible future changes are explained in the
 [roadmap](roadmap.md).
 
+## Why Owl?
+
+Why did Odoo decide to make Yet Another Framework?  This is really a question
+that deserves [a long answer](doc/miscellaneous/why_owl.md). But in short, we believe that
+while the current state of the art frameworks are excellent, they are not
+optimized for our use case, and there is still room for something else.
+
+If you are interested in a comparison with React or Vue, you will
+find some more additional information [here](doc/miscellaneous/comparison.md).
+
 ## Example
 
 Here is a short example to illustrate interactive components:
 
 ```javascript
-import { Component, QWeb, useState } from "owl";
-import { xml } from "owl/tags";
+const { Component, useState, mount } = owl;
+const { xml } = owl.tags;
 
 class Counter extends Component {
   static template = xml`
-    <button t-on-click="increment">
+    <button t-on-click="state.value++">
       Click Me! [<t t-esc="state.value"/>]
     </button>`;
 
   state = useState({ value: 0 });
-
-  increment() {
-    this.state.value++;
-  }
 }
 
 class App extends Component {
@@ -54,12 +63,11 @@ class App extends Component {
   static components = { Counter };
 }
 
-const app = new App({ qweb: new QWeb() });
-app.mount(document.body);
+mount(App, { target: document.body });
 ```
 
-Note that the counter component is made reactive with the [`useState`](doc/hooks.md#usestate)
-hook. Also, all examples here uses the `xml` helper to define inline templates.
+Note that the counter component is made reactive with the [`useState` hook](doc/reference/hooks.md#usestate).
+Also, all examples here uses the [`xml` helper](doc/reference/tags.md#xml-tag) to define inline templates.
 But this is not mandatory, many applications will load templates separately.
 
 More interesting examples can be found on the
@@ -83,10 +91,9 @@ requirements are common and code needs to be maintained by large teams.
 
 Owl is not designed to be fast nor small (even though it is quite good on those
 two topics). It is a no nonsense framework to build applications. There is only
-one way to define components (with classes).
+one way to define components (with classes). There is no black magic. It just
+works.
 
-If you are interested in a comparison with React or Vue, you will
-find some more information [here](doc/comparison.md).
 
 ## Documentation
 
@@ -94,178 +101,26 @@ A complete documentation for Owl can be found here:
 
 - [Main documentation page](doc/readme.md).
 
-The most important sections are:
+Some of the most important pages are:
 
-- [Quick Start](doc/quick_start.md)
-- [Component](doc/component.md)
-- [Hooks](doc/hooks.md)
+- [Tutorial: TodoList application](doc/learning/tutorial_todoapp.md)
+- [How to start an Owl project](doc/learning/quick_start.md)
+- [QWeb templating language](doc/reference/qweb_templating_language.md)
+- [Component](doc/reference/component.md)
+- [Hooks](doc/reference/hooks.md)
 
-Found an issue in the documentation? A broken link? Some outdated information?
-Submit a PR!
 
-## Installing/Building
+## Installing Owl
+
+Owl is available on `npm` and can be installed with the following command:
+
+```
+npm install @odoo/owl
+```
 
 If you want to use a simple `<script>` tag, the last release can be downloaded here:
 
-- [owl-0.24.0.js](https://github.com/odoo/owl/releases/download/v0.24.0/owl.js)
-- [owl-0.24.0.min.js](https://github.com/odoo/owl/releases/download/v0.24.0/owl.min.js)
-
-Some npm scripts are available:
-
-| Command          | Description                                        |
-| ---------------- | -------------------------------------------------- |
-| `npm install`    | install every dependency required for this project |
-| `npm run build`  | build a bundle of _owl_ in the _/dist/_ folder     |
-| `npm run minify` | minify the prebuilt owl.js file                    |
-| `npm run test`   | run all (owl) tests                                |
-
-## Quick Overview
-
-Owl components in an application are used to define a (dynamic) tree of components.
-
-```
-        Root
-        /   \
-       A     B
-      / \
-     C   D
-```
-
-**Environment:** the root component is special: it is created with an environment,
-which should contain a `QWeb` instance. The environment is then automatically
-propagated to each sub components (and accessible in the `this.env` property).
-
-```js
-const env = { qweb: new QWeb() };
-const app = new App(env);
-app.mount(document.body);
-```
-
-The environment is mostly static. Each application is free to add anything to
-the environment, which is very useful, since this can be accessed by each sub
-component. Some good use case for that is some configuration keys, session
-information or generic services (such as doing rpcs, or accessing local storage).
-Doing it this way means that components are easily testable: we can simply
-create a test environment with mock services.
-
-**State:** each component can manage its own local state. It is a simple ES6
-class, there are no special rules:
-
-```js
-class Counter extends Component {
-  static template = xml`
-    <button t-on-click="increment">
-      Click Me! [<t t-esc="state.value"/>]
-    </button>`;
-
-  state = { value: 0 };
-
-  increment() {
-    this.state.value++;
-    this.render();
-  }
-}
-```
-
-The example above shows a component with a local state. Note that since there
-is nothing magical to the `state` object, we need to manually call the `render`
-function whenever we update it. This can quickly become annoying (and not
-efficient if we do it too much). There is a better way: using the `useState`
-hook, which transforms an object into a reactive version of itself:
-
-```js
-const { useState } = owl.hooks;
-
-class Counter extends Component {
-  static template = xml`
-    <button t-on-click="increment">
-      Click Me! [<t t-esc="state.value"/>]
-    </button>`;
-
-  state = useState({ value: 0 });
-
-  increment() {
-    this.state.value++;
-  }
-}
-```
-
-Note that the `t-on-click` handler can even be replaced by an inline statement:
-
-```xml
-    <button t-on-click="state.value++">
-```
-
-**Props:** sub components often needs some information from their parents. This
-is done by adding the required information to the template. This will then be
-accessible by the sub component in the `props` object. Note that there is an
-important rule here: the information contained in the `props` object is not
-owned by the sub component, and should never be modified.
-
-```js
-class Child extends Component {
-  static template = xml`<div>Hello <t t-esc="props.name"/></div>`;
-}
-
-class Parent extends Component {
-  static template = xml`
-    <div>
-        <Child name="'Owl'" />
-        <Child name="'Framework'" />
-    </div>`;
-  static components = { Child };
-}
-```
-
-**Communication:** there are multiple ways to communicate information between
-components. However, the two most important ways are the following:
-
-- from parent to children: by using `props`,
-- from a children to one of its parent: by triggering events.
-
-The following example illustrate both mechanisms:
-
-```js
-class OrderLine extends Component {
-  static template = xml`
-    <div t-on-click="add">
-        <div><t t-esc="props.line.name"/></div>
-        <div>Quantity: <t t-esc="props.line.quantity"/></div>
-    </div>`;
-
-  add() {
-    this.trigger("add-to-order", { line: props.line });
-  }
-}
-
-class Parent extends Component {
-  static template = xml`
-    <div t-on-add-to-order="addToOrder">
-        <OrderLine
-            t-foreach="orders"
-            t-as="line"
-            line="line" />
-    </div>`;
-  static components = { OrderLine };
-  orders = useState([{ id: 1, name: "Coffee", quantity: 0 }, { id: 2, name: "Tea", quantity: 0 }]);
-
-  addToOrder(event) {
-    const line = event.detail.line;
-    line.quantity++;
-  }
-}
-```
-
-In this example, the `OrderLine` component trigger a `add-to-order` event. This
-will generate a DOM event which will bubble along the DOM tree. It will then be
-intercepted by the parent component, which will then get the line (from the
-`detail` key) and then increment its quantity. See the section on [event handling](doc/component.md#event-handling)
-for more details on how events work.
-
-Note that this example would have also worked if the `OrderLine` component
-directly modifies the `line` object. However, this is not a good practice: this
-only works because the `props` object received by the child component is reactive,
-so the child component is then coupled to the parents implementation.
+- [owl-1.3.1](https://github.com/odoo/owl/releases/tag/v1.3.1)
 
 ## License
 

doc/learning/how_to_debug.md

@@ -0,0 +1,43 @@
+# 🦉 How to debug Owl applications 🦉
+
+Non trivial applications become quickly more difficult to understand. It is then
+useful to have a solid understanding of what is going on. To help with that,
+logging useful information is extremely valuable. There is a [javascript file](../../tools/debug.js) which can be evaluated in an application.
+
+Once it is executed, it will log a lot of information on each component main hooks. The following code is a minified version to make it easier to copy/paste:
+
+```
+function debugOwl(t,e){let n,o="[OWL_DEBUG]";function r(t){let e;try{e=JSON.stringify(t||{})}catch(t){e="<JSON error>"}return e.length>200&&(e=e.slice(0,200)+"..."),e}if(Object.defineProperty(t.Component,"current",{get:()=>n,set(s){n=s;const i=s.constructor.name;if(e.componentBlackList&&e.componentBlackList.test(i))return;if(e.componentWhiteList&&!e.componentWhiteList.test(i))return;let l;Object.defineProperty(n,"__owl__",{get:()=>l,set(n){!function(n,s,i){let l=`${s}<id=${i}>`,c=t=>console.log(`${o} ${l} ${t}`),u=t=>(!e.methodBlackList||!e.methodBlackList.includes(t))&&!(e.methodWhiteList&&!e.methodWhiteList.includes(t));u("constructor")&&c(`constructor, props=${r(n.props)}`);u("willStart")&&t.hooks.onWillStart(()=>{c("willStart")});u("mounted")&&t.hooks.onMounted(()=>{c("mounted")});u("willUpdateProps")&&t.hooks.onWillUpdateProps(t=>{c(`willUpdateProps, nextprops=${r(t)}`)});u("willPatch")&&t.hooks.onWillPatch(()=>{c("willPatch")});u("patched")&&t.hooks.onPatched(()=>{c("patched")});u("willUnmount")&&t.hooks.onWillUnmount(()=>{c("willUnmount")});const d=n.__render.bind(n);n.__render=function(...t){c("rendering template"),d(...t)};const h=n.render.bind(n);n.render=function(...t){const e=n.__owl__;let o="render";return e.isMounted||e.currentFiber||(o+=" (warning: component is not mounted, this render has no effect)"),c(o),h(...t)};const p=n.mount.bind(n);n.mount=function(...t){return c("mount"),p(...t)}}(s,i,(l=n).id)}})}}),e.logScheduler){let e=t.Component.scheduler.start,n=t.Component.scheduler.stop;t.Component.scheduler.start=function(){this.isRunning||console.log(`${o} scheduler: start running tasks queue`),e.call(this)},t.Component.scheduler.stop=function(){this.isRunning&&console.log(`${o} scheduler: stop running tasks queue`),n.call(this)}}if(e.logStore){let e=t.Store.prototype.dispatch;t.Store.prototype.dispatch=function(t,...n){return console.log(`${o} store: action '${t}' dispatched. Payload: '${r(n)}'`),e.call(this,t,...n)}}}
+debugOwl(owl, {
+  // componentBlackList: /App/,  // regexp
+  // componentWhiteList: /SomeComponent/, // regexp
+  // methodBlackList: ["mounted"], // list of method names
+  // methodWhiteList: ["willStart"], // list of method names
+  logScheduler: false,  // display/mute scheduler logs
+  logStore: true,     // display/mute store logs
+});
+```
+
+The above code, once pasted somewhere in the main javascript file of an owl
+application, will log information looking like this:
+
+```
+[OWL_DEBUG] TodoApp<id=1> constructor, props={}
+[OWL_DEBUG] TodoApp<id=1> mount
+[OWL_DEBUG] TodoApp<id=1> willStart
+[OWL_DEBUG] TodoApp<id=1> rendering template
+[OWL_DEBUG] TodoItem<id=2> constructor, props={"id":2,"completed":false,"title":"hey"}
+[OWL_DEBUG] TodoItem<id=2> willStart
+[OWL_DEBUG] TodoItem<id=3> constructor, props={"id":4,"completed":false,"title":"aaa"}
+[OWL_DEBUG] TodoItem<id=3> willStart
+[OWL_DEBUG] TodoItem<id=2> rendering template
+[OWL_DEBUG] TodoItem<id=3> rendering template
+[OWL_DEBUG] TodoItem<id=3> mounted
+[OWL_DEBUG] TodoItem<id=2> mounted
+[OWL_DEBUG] TodoApp<id=1> mounted
+```
+
+Each component has an internal `id`, which is very useful when debugging.
+
+Note that it is certainly useful to run this code at some point in an application,
+just to get a feel of what each user action implies, for the framework.

doc/learning/how_to_test.md

@@ -0,0 +1,130 @@
+# 🦉 How to test Components 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Unit Tests](#unit-tests)
+
+## Overview
+
+It is a good practice to test applications and components to ensure that they
+behave as expected. There are many ways to test a user interface: manual
+testing, integration testing, unit testing, ...
+
+In this section, we will discuss how to write unit tests for components.
+
+## Unit Tests
+
+Writing unit tests for Owl components really depends on the testing framework
+used in a project. But usually, it involves the following steps:
+
+- create a test file: for example `SomeComponent.test.js`,
+- in that file, import the code for `SomeComponent`,
+- add a test case:
+  - create a real DOM element to use as test fixture,
+  - create a test environment
+  - create an instance of `SomeComponent`, mount it to the fixture
+  - interact with the component and assert some properties.
+
+To help with this, it is useful to have a `helper.js` file that contains some
+common utility functions:
+
+```js
+export function makeTestFixture() {
+  let fixture = document.createElement("div");
+  document.body.appendChild(fixture);
+  return fixture;
+}
+
+export function nextTick() {
+  let requestAnimationFrame = owl.Component.scheduler.requestAnimationFrame;
+  return new Promise(function(resolve) {
+    setTimeout(() => requestAnimationFrame(() => resolve()));
+  });
+}
+
+export function makeTestEnv() {
+    // application specific. It needs a way to load actual templates
+    const templates = ...;
+
+    return {
+        qweb: new QWeb(templates),
+        ..., // each service can be mocked here
+    };
+}
+```
+
+With such a file, a typical test suite for Jest will look like this:
+
+```js
+// in SomeComponent.test.js
+import { SomeComponent } from "../../src/ui/SomeComponent";
+import { nextTick, makeTestFixture, makeTestEnv} from '../helpers';
+
+
+//------------------------------------------------------------------------------
+// Setup
+//------------------------------------------------------------------------------
+let fixture: HTMLElement;
+let env: Env;
+
+beforeEach(() => {
+  fixture = makeTestFixture();
+  env = makeTestEnv();
+  // we set here the default environment for each component created in the test
+  Component.env = env;
+});
+
+afterEach(() => {
+  fixture.remove();
+});
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+describe("SomeComponent", () => {
+  test("component behaves as expected", async () => {
+    const props = {...}; // depends on the component
+    const comp = await mount(SomeComponent, { target: fixture, props });
+
+    // do some assertions
+    expect(...).toBe(...);
+
+    fixture.querySelector('button').click();
+    await nextTick();
+
+    // some other assertions
+    expect(...).toBe(...);
+  });
+});
+```
+
+Note that Owl does wait for the next animation frame to actually update the DOM.
+This is why it is necessary to wait with the `nextTick` (or other methods) to
+make sure that the DOM is up-to-date.
+
+It is sometimes useful to wait until Owl is completely done updating components
+(in particular, if we have a highly concurrent user interface). This next
+helper simply polls every 20ms the internal Owl task queue and returns a promise
+which resolves when it is empty:
+
+```js
+function afterUpdates() {
+  return new Promise((resolve, reject) => {
+    let timer = setTimeout(poll, 20);
+    let counter = 0;
+    function poll() {
+      counter++;
+      if (owl.Component.scheduler.tasks.length) {
+        if (counter > 10) {
+          reject(new Error("timeout"));
+        } else {
+          timer = setTimeout(poll);
+        }
+      } else {
+        resolve();
+      }
+    }
+  });
+}
+```

doc/learning/how_to_write_sfc.md

@@ -0,0 +1,52 @@
+# 🦉 How to write Single File Components 🦉
+
+It is very useful to group code by feature instead of by type of file. It makes
+it easier to scale application to larger size.
+
+To do so, Owl has two small helpers that make it easy to define a
+template or a stylesheet inside a javascript (or typescript) file: the
+[`xml`](../reference/tags.md#xml-tag) and [`css`](../reference/tags.md#css-tag)
+helper.
+
+This means that the template, the style and the javascript code can be defined in
+the same file. For example:
+
+```js
+const { Component } = owl;
+const { xml, css } = owl.tags;
+
+// -----------------------------------------------------------------------------
+// TEMPLATE
+// -----------------------------------------------------------------------------
+const TEMPLATE = xml/* xml */ `
+	<div class="main">
+		<Sidebar/>
+		<Content />
+	</div>`;
+
+// -----------------------------------------------------------------------------
+// STYLE
+// -----------------------------------------------------------------------------
+const STYLE = css/* css */ `
+  .main {
+    display: grid;
+    grid-template-columns: 200px auto;
+  }
+`;
+
+// -----------------------------------------------------------------------------
+// CODE
+// -----------------------------------------------------------------------------
+class Main extends Component {
+  static template = TEMPLATE;
+  static style = STYLE;
+  static components = { Sidebar, Content };
+
+  // rest of component...
+}
+```
+
+Note that the above example has an inline xml comment, just after the `xml` call.
+This is useful for some editor plugins, such as the VS Code addon
+`Comment tagged template`, which, if installed, add syntax highlighting to the
+content of the template string.

doc/learning/overview.md

@@ -0,0 +1,133 @@
+# 🦉 Quick Overview 🦉
+
+Owl components in an application are used to define a (dynamic) tree of components.
+
+```
+        Root
+        /   \
+       A     B
+      / \
+     C   D
+```
+
+**State:** each component can manage its own local state. It is a simple ES6
+class, there are no special rules:
+
+```js
+class Counter extends Component {
+  static template = xml`
+    <button t-on-click="increment">
+      Click Me! [<t t-esc="state.value"/>]
+    </button>`;
+
+  state = { value: 0 };
+
+  increment() {
+    this.state.value++;
+    this.render();
+  }
+}
+```
+
+The example above shows a component with a local state. Note that since there
+is nothing magical to the `state` object, we need to manually call the `render`
+function whenever we update it. This can quickly become annoying (and not
+efficient if we do it too much). There is a better way: using the `useState`
+hook, which transforms an object into a reactive version of itself:
+
+```js
+const { useState } = owl.hooks;
+
+class Counter extends Component {
+  static template = xml`
+    <button t-on-click="increment">
+      Click Me! [<t t-esc="state.value"/>]
+    </button>`;
+
+  state = useState({ value: 0 });
+
+  increment() {
+    this.state.value++;
+  }
+}
+```
+
+Note that the `t-on-click` handler can even be replaced by an inline statement:
+
+```xml
+    <button t-on-click="state.value++">
+```
+
+**Props:** sub components often needs some information from their parents. This
+is done by adding the required information to the template. This will then be
+accessible by the sub component in the `props` object. Note that there is an
+important rule here: the information contained in the `props` object is not
+owned by the sub component, and should never be modified.
+
+```js
+class Child extends Component {
+  static template = xml`<div>Hello <t t-esc="props.name"/></div>`;
+}
+
+class Parent extends Component {
+  static template = xml`
+    <div>
+        <Child name="'Owl'" />
+        <Child name="'Framework'" />
+    </div>`;
+  static components = { Child };
+}
+```
+
+**Communication:** there are multiple ways to communicate information between
+components. However, the two most important ways are the following:
+
+- from parent to children: by using `props`,
+- from a children to one of its parent: by triggering events.
+
+The following example illustrate both mechanisms:
+
+```js
+class OrderLine extends Component {
+  static template = xml`
+    <div t-on-click="add">
+        <div><t t-esc="props.line.name"/></div>
+        <div>Quantity: <t t-esc="props.line.quantity"/></div>
+    </div>`;
+
+  add() {
+    this.trigger("add-to-order", { line: this.props.line });
+  }
+}
+
+class Parent extends Component {
+  static template = xml`
+    <div t-on-add-to-order="addToOrder">
+        <OrderLine
+            t-foreach="orders"
+            t-as="line"
+            line="line" />
+    </div>`;
+  static components = { OrderLine };
+  orders = useState([
+    { id: 1, name: "Coffee", quantity: 0 },
+    { id: 2, name: "Tea", quantity: 0 },
+  ]);
+
+  addToOrder(event) {
+    const line = event.detail.line;
+    line.quantity++;
+  }
+}
+```
+
+In this example, the `OrderLine` component trigger a `add-to-order` event. This
+will generate a DOM event which will bubble along the DOM tree. It will then be
+intercepted by the parent component, which will then get the line (from the
+`detail` key) and then increment its quantity. See the page on [event handling](../reference/event_handling.md)
+for more details on how events work.
+
+Note that this example would have also worked if the `OrderLine` component
+directly modifies the `line` object. However, this is not a good practice: this
+only works because the `props` object received by the child component is reactive,
+so the child component is then coupled to the parents implementation.

doc/learning/quick_start.md

@@ -0,0 +1,408 @@
+# 🦉 How to start an Owl project 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Simple html file](#simple-html-file)
+- [With a static server](#with-a-static-server)
+- [Standard Javascript project](#standard-javascript-project)
+
+## Overview
+
+Each software project has its specific needs. Many of these needs can be solved
+with some tooling: `webpack`, `gulp`, css preprocessor, bundlers, transpilers, ...
+
+Because of that, it is usually not simple to just start a project. Some
+frameworks provide their own tooling to help with that. But then, you have to
+integrate and learn how these applications work.
+
+Owl is designed to be used with no tooling at all. Because of that, Owl can
+"easily" be integrated in a modern build toolchain. In this section, we will
+discuss a few different setups to start a project. Each of these setups has
+advantages and disadvantages in different situations.
+
+## Simple html file
+
+The simplest possible setup is the following: a simple javascript file with your
+code. To do that, let us create the following file structure:
+
+```
+hello_owl/
+  index.html
+  owl.js
+  app.js
+```
+
+The file `owl.js` can be downloaded from the last release published at
+[https://github.com/odoo/owl/releases](https://github.com/odoo/owl/releases). It
+is a single javascript file which export all Owl into the global `owl` object.
+
+Now, `index.html` should contain the following:
+
+```html
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <title>Hello Owl</title>
+    <script src="owl.js"></script>
+    <script src="app.js"></script>
+  </head>
+  <body></body>
+</html>
+```
+
+And `app.js` should look like this:
+
+```js
+const { Component, mount } = owl;
+const { xml } = owl.tags;
+const { whenReady } = owl.utils;
+
+// Owl Components
+class App extends Component {
+  static template = xml`<div>Hello Owl</div>`;
+}
+
+// Setup code
+function setup() {
+  mount(App, target: { document.body })
+}
+
+whenReady(setup);
+```
+
+Now, simply loading this html file in a browser should display a welcome message.
+This setup is not fancy, but it is extremely simple. There are no tooling at
+all required. It can be slightly optimized by using the minified build of Owl.
+
+## With a static server
+
+The previous setup has a big disadvantage: the application code is located in a
+single file. Obviously, we could split it in several files and add multiple
+`<script>` tags in the html page, but then we need to make sure the script are
+inserted in the proper order, we need to export each file content in global
+variables and we lose autocompletion across files.
+
+There is a low tech solution to this issue: using native javascript modules.
+This however has a requirement: for security reasons, browsers will not accept
+modules on content served through the `file` protocol. This means that we need
+to use a static server.
+
+Let us start a new project with the following file structure:
+
+```
+hello_owl/
+  src/
+    app.js
+    index.html
+    main.js
+    owl.js
+```
+
+As previously, the file `owl.js` can be downloaded from the last release published at
+[https://github.com/odoo/owl/releases](https://github.com/odoo/owl/releases).
+
+Now, `index.html` should contain the following:
+
+```html
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <title>Hello Owl</title>
+    <script src="owl.js"></script>
+    <script src="main.js" type="module"></script>
+  </head>
+  <body></body>
+</html>
+```
+
+Not that the `main.js` script tag has the `type="module"` attribute. This means
+that the browser will parse the script as a module, and load all its dependencies.
+
+Here is the content of `app.js` and `main.js`:
+
+```js
+// app.js ----------------------------------------------------------------------
+const { Component, mount } = owl;
+const { xml } = owl.tags;
+
+export class App extends Component {
+  static template = xml`<div>Hello Owl</div>`;
+}
+
+// main.js ---------------------------------------------------------------------
+import { App } from "./app.js";
+
+function setup() {
+  mount(App, { target: document.body });
+}
+
+owl.utils.whenReady(setup);
+```
+
+The `main.js` file import the `app.js` file. Note that the import statement has
+a `.js` suffix, which is important. Most text editor can understand this syntax
+and will provide autocompletion.
+
+Now, to execute this code, we need to serve the `src` folder statically. A low
+tech way to do that is to use for example the python `SimpleHTTPServer` feature:
+
+```
+$ cd src
+$ python -m SimpleHTTPServer 8022    # now content is available at localhost:8022
+```
+
+Another more "javascripty" way to do it is to create a `npm` application. To do
+that, we can add the following `package.json` file at the root of the project:
+
+```json
+{
+  "name": "hello_owl",
+  "version": "0.1.0",
+  "description": "Starting Owl app",
+  "main": "src/index.html",
+  "scripts": {
+    "serve": "serve src"
+  },
+  "author": "John",
+  "license": "ISC",
+  "devDependencies": {
+    "serve": "^11.3.0"
+  }
+}
+```
+
+We can now install the `serve` tool with the command `npm install`, and then,
+start a static server with the simple `npm run serve` command.
+
+## Standard Javascript project
+
+The previous setup works, and is certainly good for some usecases, including
+quick prototyping. However, it lacks some useful features, such as livereload,
+a test suite, or bundling the code in a single file.
+
+Each of these features, and many others, can be done in many different ways.
+Since it is really not trivial to configure such a project, we provide here an
+example that can be used as a starting point.
+
+Our standard Owl project has the following file structure:
+
+```
+hello_owl/
+  public/
+    index.html
+  src/
+    components/
+      App.js
+    main.js
+  tests/
+    components/
+      App.test.js
+    helpers.js
+  .gitignore
+  package.json
+  webpack.config.js
+```
+
+This project as a `public` folder, meant to contain all static assets, such as
+images and styles. The `src` folder has the javascript source code, and finally,
+`tests` contains the test suite.
+
+Here is the content of `index.html`:
+
+```html
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <title>Hello Owl</title>
+  </head>
+  <body></body>
+</html>
+```
+
+Note that there are no `<script>` tag here. They will be injected by webpack.
+Now, let's have a look at the javascript files:
+
+```js
+// src/components/App.js -------------------------------------------------------
+import { Component, tags, useState } from "@odoo/owl";
+
+const { xml } = tags;
+
+export class App extends Component {
+  static template = xml`<div t-on-click="update">Hello <t t-esc="state.text"/></div>`;
+  state = useState({ text: "Owl" });
+  update() {
+    this.state.text = this.state.text === "Owl" ? "World" : "Owl";
+  }
+}
+
+// src/main.js -----------------------------------------------------------------
+import { utils, mount } from "@odoo/owl";
+import { App } from "./components/App";
+
+function setup() {
+  mount(App, { target: document.body });
+}
+
+utils.whenReady(setup);
+
+// tests/components/App.test.js ------------------------------------------------
+import { App } from "../../src/components/App";
+import { makeTestFixture, nextTick, click } from "../helpers";
+import { mount } from "@odoo/owl";
+
+let fixture;
+
+beforeEach(() => {
+  fixture = makeTestFixture();
+});
+
+afterEach(() => {
+  fixture.remove();
+});
+
+describe("App", () => {
+  test("Works as expected...", async () => {
+    await mount(App, { target: fixture });
+    expect(fixture.innerHTML).toBe("<div>Hello Owl</div>");
+
+    click(fixture, "div");
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div>Hello World</div>");
+  });
+});
+
+// tests/helpers.js ------------------------------------------------------------
+import { Component } from "@odoo/owl";
+import "regenerator-runtime/runtime";
+
+export async function nextTick() {
+  return new Promise(function (resolve) {
+    setTimeout(() => Component.scheduler.requestAnimationFrame(() => resolve()));
+  });
+}
+
+export function makeTestFixture() {
+  let fixture = document.createElement("div");
+  document.body.appendChild(fixture);
+  return fixture;
+}
+
+export function click(elem, selector) {
+  elem.querySelector(selector).dispatchEvent(new Event("click"));
+}
+```
+
+Finally, here is the configuration files `.gitignore`, `package.json` and
+`webpack.config.js`:
+
+```
+node_modules/
+package-lock.json
+dist/
+```
+
+```json
+{
+  "name": "hello_owl",
+  "version": "0.1.0",
+  "description": "Demo app",
+  "main": "src/index.html",
+  "scripts": {
+    "test": "jest",
+    "build": "webpack --mode production",
+    "dev": "webpack-dev-server --mode development"
+  },
+  "author": "Someone",
+  "license": "ISC",
+  "devDependencies": {
+    "@babel/core": "^7.8.4",
+    "@babel/plugin-proposal-class-properties": "^7.8.3",
+    "babel-jest": "^25.1.0",
+    "babel-loader": "^8.0.6",
+    "babel-plugin-transform-es2015-modules-commonjs": "^6.26.2",
+    "html-webpack-plugin": "^3.2.0",
+    "jest": "^25.1.0",
+    "regenerator-runtime": "^0.13.3",
+    "serve": "^11.3.0",
+    "webpack": "^4.41.5",
+    "webpack-cli": "^3.3.10",
+    "webpack-dev-server": "^3.10.2"
+  },
+  "dependencies": {
+    "@odoo/owl": "^1.0.4"
+  },
+  "babel": {
+    "plugins": ["@babel/plugin-proposal-class-properties"],
+    "env": {
+      "test": {
+        "plugins": ["transform-es2015-modules-commonjs"]
+      }
+    }
+  },
+  "jest": {
+    "verbose": false,
+    "testRegex": "(/tests/.*(test|spec))\\.js?$",
+    "moduleFileExtensions": ["js"],
+    "transform": {
+      "^.+\\.[t|j]sx?$": "babel-jest"
+    }
+  }
+}
+```
+
+```js
+const path = require("path");
+const HtmlWebpackPlugin = require("html-webpack-plugin");
+
+const host = process.env.HOST || "localhost";
+
+module.exports = function (env, argv) {
+  const mode = argv.mode || "development";
+  return {
+    mode: mode,
+    entry: "./src/main.js",
+    output: {
+      filename: "main.js",
+      path: path.resolve(__dirname, "dist"),
+    },
+    module: {
+      rules: [
+        {
+          test: /\.jsx?$/,
+          loader: "babel-loader",
+          exclude: /node_modules/,
+        },
+      ],
+    },
+    resolve: {
+      extensions: [".js", ".jsx"],
+    },
+    devServer: {
+      contentBase: path.resolve(__dirname, "public/index.html"),
+      compress: true,
+      hot: true,
+      host,
+      port: 3000,
+      publicPath: "/",
+    },
+    plugins: [
+      new HtmlWebpackPlugin({
+        inject: true,
+        template: path.resolve(__dirname, "public/index.html"),
+      }),
+    ],
+  };
+};
+```
+
+With this setup, we can now use the following script commands:
+
+```
+npm run build # build the full application in prod mode in dist/
+
+npm run dev # start a dev server with livereload
+
+npm run test # run the jest test suite
+```

doc/misc.md

@@ -1,23 +0,0 @@
-# 🦉 Miscellaneous 🦉
-
-## `AsyncRoot`
-
-When this component is used, a new rendering sub tree is created, such that the
-rendering of that component (and its children) is not tied to the rendering of
-the rest of the interface. It can be used on an asynchronous component, to
-prevent it from delaying the rendering of the whole interface, or on a
-synchronous one, such that its rendering isn't delayed by other (asynchronous)
-components. Note that this directive has no effect on the first rendering, but
-only on subsequent ones (triggered by state or props changes).
-
-```xml
-<div t-name="ParentComponent">
-  <SyncChild />
-  <AsyncRoot>
-     <AsyncChild/>
-  </AsyncRoot>
-</div>
-```
-
-The `AsyncRoot` assumes that there is exactly one root node inside it. It can
-be a dom node or a component.

doc/miscellaneous/comparison.md

@@ -79,7 +79,7 @@ additional tools, we made a lot of effort to make the most of the web platform.
 
 For example, Owl uses the standard `xml` parser that comes with every browser.
 Because of that, Owl did not have to write its own template parser. Another
-example is the [`xml`](tags.md#xml-tag) tag helper function, which makes use of
+example is the [`xml`](../reference/tags.md#xml-tag) tag helper function, which makes use of
 native template literals to allow in a natural way to write `xml` templates
 directly in the javascript code. This can be easily integrated with editor
 plugins to have autocompletion inside the template.
@@ -127,7 +127,7 @@ structured than a template language. Note that the tooling is quite impressive:
 there is a syntax highlighter for jsx here on github!
 
 By comparison, here is the equivalent Owl component, written with the
-[`xml`](tags.md#xml-tag) tag helper:
+[`xml`](../reference/tags.md#xml-tag) tag helper:
 
 ```js
 class Clock extends Component {
@@ -251,17 +251,17 @@ keeps track of who get data, and retrigger a render when it was changed.
 Owl store is a little bit like a mix of redux and vuex: it has actions (but not
 mutations), and like VueX, it keeps track of the state changes. However, it does
 not notify a component when the state changes. Instead, components need to connect
-to the store like in redux, with the `useStore` hook (see the [store documentation](store.md#connecting-a-component)).
+to the store like in redux, with the `useStore` hook (see the [store documentation](../reference/store.md#connecting-a-component)).
 
 ```javascript
 const actions = {
   increment({ state }, val) {
     state.counter.value += val;
-  }
+  },
 };
 
 const state = {
-  counter: { value: 0 }
+  counter: { value: 0 },
 };
 const store = new owl.Store({ state, actions });
 
@@ -270,11 +270,12 @@ class Counter extends Component {
       <button t-name="Counter" t-on-click="dispatch('increment')">
         Click Me! [<t t-esc="counter.value"/>]
       </button>`;
-  counter = useStore(state => state.counter);
+  counter = useStore((state) => state.counter);
   dispatch = useDispatch();
 }
 
-const counter = new Counter({ store, qweb });
+Counter.env.store = store;
+const counter = new Counter();
 ```
 
 ## Hooks
@@ -314,7 +315,7 @@ This work is based on the new ideas introduced by React hooks.
 
 From the way React and Vue introduce their hooks, it may look like hooks are not
 compatible with class components. However, this is not the case, as shown by
-Owl [hooks](hooks.md). They are inspired by both React and Vue. For example,
+Owl [hooks](../reference/hooks.md). They are inspired by both React and Vue. For example,
 the `useState` hook is named after React, but its API is closer to the `reactive`
 Vue hook.
 

doc/miscellaneous/rendering.md

@@ -0,0 +1,32 @@
+# 🦉 Rendering Pipeline 🦉
+
+We explain here how Owl is designed, from the perspective of its rendering
+pipeline.
+
+Warning: these notes are technical by nature, and intended for people working
+on Owl (or interested in understanding its design).
+
+## Overview
+
+A rendering occurs in two phases:
+
+- virtual rendering: this generates the virtual dom in memory, asynchronously
+- patch: applies a virtual tree to the screen (synchronously)
+
+There are several classes involved in a rendering:
+
+- components
+- a scheduler
+- fibers: small objects containing some metadata, associated with a rendering of
+  a specific component
+
+Components are organized in a dynamic component tree, visible in the user
+interface. Whenever a rendering is initiated in a component `C`:
+
+- a fiber is created on `C` with the rendering props information
+- the virtual rendering phase starts on C (will asynchronously render all the
+  child components)
+- the fiber is added to the scheduler, which will poll continuously, every
+  animation frame, if the fiber is done
+- once it is done, the scheduler will call the task callback, which will apply
+  the patch (if it was not cancelled in the meantime).

doc/miscellaneous/why_owl.md

@@ -0,0 +1,180 @@
+# 🦉 Why Owl ? 🦉
+
+The common wisdom is that one should not reinvent the wheel, because that would
+waste effort and resources. It is certainly true in many cases. A javascript
+framework is a considerable investment, so it is quite logical to ask the question:
+why did Odoo decide to make OWL instead of using a standard/well known framework,
+such as React or Vue?
+
+As you might expect, the answer to that question is not simple. But most of the
+reasons discussed in this page are a consequence from a single fact: Odoo is
+extremely modular.
+
+This means, for example, that the core parts of Odoo are not aware, before runtime,
+of what files will be loaded/executed, or what will be the state of the UI. Because
+of that, Odoo cannot rely on a standard build toolchain. Also, this implies that
+the core parts of Odoo need to be extremely generic. In other words, Odoo is not
+really an application with a user interface. It is an application which generates
+a dynamic user interface. And most frameworks are not up to the task.
+
+Betting on Owl was not an easy choice to make, because there certainly are a lot
+of conflicting needs that we want to carefully balance. Choosing anything other
+than a well known framework is bound to be controversial. This page will explain
+some of the reason why we still believe that building Owl is a worthwile
+endeavour.
+
+## Strategy
+
+It is true that we want to keep control of our technology, in the sense that we
+do not want to depend on Facebook or Google, or any other large (or small)
+company. If they decide to change their license, or to go in a direction that
+will not work for us, this may be a problem. This is even more true because
+Odoo is not a conventional javascript application, and our needs are probably
+quite different as most other applications.
+
+## Class components
+
+It is clear that the biggest frameworks are moving away from class components.
+There is an implicit assumption that class components are terrible, and that
+functional programming is the way to go. React even goes as far as to say that
+classes are confusing for developers.
+
+While there is some truth to that, and to the fact that composition is certainly
+a good mechanism for code reuse, we believe that classes and inheritance are
+important tools.
+
+Sharing code between generic components with inheritance is the way Odoo built
+its web client. And it is clear that inheritance is not the root of all evils.
+It is often a perfectly simple and appropriate solution. What matter most is
+the architectural decisions.
+
+Also, Odoo has another specific use out of class components: each method of a
+class provides an extension point for addons. This may not be a clean architecture
+pattern, but it is a pragmatic decision that served Odoo well: classes are
+sometimes monkey-patched to add behaviour from the outside. A little bit like
+mixins, but from the outside.
+
+Using React or Vue would make it significantly harder to monkey patch components,
+because a lot of the state is hidden in their internals.
+
+## Tooling
+
+React or Vue have a huge community, and a lot of effort have been made into their
+tooling. This is wonderful, but at the same time, a pretty big issue for Odoo:
+since the assets are totally dynamic (and could change whenever the user installs
+or removes an addon), we need to have all that kind of tooling on the production
+servers. This is certainly not ideal.
+
+Also, this makes it very complicated to setup Vue or React tools: Odoo code is
+not a simple file that import other files. It changes all the time, assets
+are bundled differently in different contexts. This is the reason why Odoo has
+its own module system, which are resolved at runtime, by the browser. The
+dynamic nature of Odoo means that we often need to delay work as late as possible
+(in other word, we want a JIT user interface!)
+
+Our ideal framework has minimal (mandatory) tooling, which makes it easier to
+deploy. Using React without JSX, or Vue without vue file is not very appealing.
+
+At the same time, Owl is designed to solve this issue: it compiles templates
+by the browser, it doesn't need much code for that, since we use the XML parser
+built into each browser. Owl works with or without any additional tooling. It
+can use template strings to write single file components, and is easy to integrate
+in any html page, with a simple `<script>` tag.
+
+## Template based
+
+Odoo stores templates as XML documents in a database. This is very powerful, since
+this allow the use of xpaths to customize other templates. This is a very
+important feature of odoo, and one of the key to Odoo modularity.
+
+Because of that, we still expect to write our templates in an XML document.
+Weirdly enough, no major framework uses XML to store templates, even though it
+is extremely convenient.
+
+So, using React or Vue means that we need to make a template compiler. For React,
+that would be a compiler that would take a QWeb template, and convert it to a
+React render function. For Vue, it would convert it to a Vue template. Then
+we need to bundle the vue template compiler as well.
+
+Not only this would be complex (compiling a templating language into another is
+not an easy task), but it would negatively impact the developer experience as
+well. Writing Vue or React components in a QWeb template would certainly be
+awkward, and very confusing.
+
+## Developer Experience
+
+This brings us to the following point: developer experience. We see this choice
+as an investment for the future, and we want to make onboarding developers as
+easy as possible.
+
+While many javascript professionals clearly think that react/vue is not difficult
+(which is true to some extent), it is alsy true that many non js specialists are
+overwhelmed with the frontend world: functional components, hooks, and many other
+fancy words. Also, what is available in the compilation context may be difficult,
+there is a lot of black magic going on in pretty much every framework. Vue
+somehow join various namespaces into one, under the hood, and add various internal
+keys. Svelte transform the code. React require that state transformations are
+deep, and not shallow.
+
+Owl is trying very hard to have a simple and familiar API. It uses classes. Its
+reactivity system is explicit, not implicit. The scoping rules are obvious. In
+case of doubt, we err on the side of not implementing a feature.
+
+It is certainly different from React or Vue, but at the same time, kind of
+familiar for experienced developers.
+
+## JIT compilation
+
+There is also a clear trend in the frontend world to compile code
+as much as possible ahead of time. Most frameworks will compile templates ahead
+of time. And now Svelte is trying to compile the JS code away, so it can remove
+itself from the bundle.
+
+This is certainly reasonable for many usecases. However, this is not what Odoo
+needs: Odoo will fetch templates from the database and need to compile them only
+at the last possible moment, so we can apply all necessary xpaths.
+
+Even more: Odoo needs to be able to generate (and compile) templates at runtime.
+Currently, Odoo form views interpret an xml description. But the form view code
+then needs to do a lot of complicated operations. With Owl, we will be able to
+transform a view description into a QWeb template, then compile that and use it
+immediately.
+
+## Reactivity
+
+There are other design choices that we feel are not optimal in other frameworks.
+For example, the reactivity system. We like the way Vue did it, but it has a
+flaw: it is not really optional. There is actually a way to opt out of the reactivity
+system by freezing the state, but then, it is freezed.
+
+And there certainly are situations where we need a state, which is not read-only,
+and not observed. For example, imagine a spreadsheet component. It may have a
+very large internal state, and it knows exactly when it needs to be rendered
+(basically, whenever the user performs some action). Then, observing its state
+is a net performance loss, both for the CPU and the memory.
+
+## Concurrency
+
+Many applications are happy to simply display a spinner whenever a new asynchronous
+action is performed, but Odoo wants a different user experience: most asynchronous
+state changes are not displayed until ready. This is sometimes called a concurrent
+mode: the UI is rendered in memory, and displayed only when it is ready (and
+only if it has not been cancelled by subsequent user actions).
+
+React has now an experimental concurrent mode, but it was not ready when Owl
+started. Vue has not really an equivalent API (suspense is not what we need).
+
+Also, React concurrent mode is complex to use. Concurrency was one of the rare
+strong point of the former Odoo js framework (widgets), and we feel that Owl has
+now a very strong concurrent mode, which is simple and powerful at the same time.
+
+## Conclusion
+
+This lengthy discussion showed that there are many small and not so small reasons
+that current standard frameworks are not tailored to our needs. It is perfectly
+fine, because they each chose a different set of tradeoffs.
+
+However, we feel that there is still room in the framework world for something
+that is different. For a framework that makes choices compatible with Odoo.
+
+And that is why we built Owl 🦉.

doc/quick_start.md

@@ -1,100 +0,0 @@
-# 🦉 Quick Start 🦉
-
-## Static Server
-
-Let us assume that we have a static server running somewhere. We could then
-simply add an html page with a few extra files.
-
-### HTML and CSS
-
-In a file `index.html`:
-
-```html
-<!DOCTYPE html>
-<html lang="en">
-  <head>
-    <meta charset="UTF-8" />
-    <title>My OWL App</title>
-    <link href="app.css" rel="stylesheet" />
-    <script src="owl-X.Y.Z.js"></script>
-  </head>
-  <body>
-    <div id="main"></div>
-    <script src="app.js" type="module"></script>
-  </body>
-</html>
-```
-
-In `app.css`:
-
-```css
-button {
-  color: darkred;
-  font-size: 30px;
-  width: 220px;
-}
-```
-
-Also, let's not forget to add a release of OWL (`owl-X.Y.Z.js`)
-
-### XML
-
-In `templates.xml`:
-
-```xml
-<templates>
-   <button t-name="clickcounter" t-on-click="increment">
-      Click Me! [<t t-esc="state.value"/>]
-    </button>
-</templates>
-```
-
-### JS
-
-To build an application (or a sub-part of an application), we need two things:
-
-- an environment: it is the global context in which we are working. It needs to
-  contain a QWeb instance (preloaded with templates), and anything else that we
-  need. In practice, it could be used to contain some user session information, some
-  configuration keys (for example, isMobile = true/false if we are in mobile mode).
-
-- a description of the user interface: there should be a root component, which can
-  have sub components
-
-Here are a few steps that we may take to get started:
-
-- get the templates
-- create a qweb engine, with the templates
-- create an environment
-- create an instance of the root component
-- mount the root component to a DOM element
-
-Let us now add the javascript to make it work, in `app.js`:
-
-```javascript
-const useState = owl.hooks.useState;
-
-class ClickCounter extends owl.Component {
-  static template = "clickcounter";
-  state = useState({ value: 0 });
-
-  increment() {
-    this.state.value++;
-  }
-}
-
-//------------------------------------------------------------------------------
-// Application initialization
-//------------------------------------------------------------------------------
-async function start() {
-  const templates = await owl.utils.loadFile("templates.xml");
-  const env = {
-    qweb: new owl.QWeb(templates)
-  };
-  const counter = new ClickCounter(env);
-  const target = document.getElementById("main");
-  await counter.mount(target);
-}
-
-start();
-```

doc/readme.md

@@ -1,75 +1,57 @@
 # 🦉 OWL Documentation 🦉
 
-## Owl Content
+## Learning Owl
 
-Owl is a javascript library that contains some core classes and function to help
-build applications. Here is a complete representation of its content:
+Are you new to Owl? This is the place to start!
 
-```
-owl
-    Component
-    Context
-    QWeb
-    Store
-    useState
-    core
-        EventBus
-        Observer
-    hooks
-        onWillStart
-        onMounted
-        onWillUpdateProps
-        onWillPatch
-        onPatched
-        onWillUnmount
-        useContext
-        useState
-        useRef
-        useSubEnv
-        useStore
-        useDispatch
-        useGetters
-    misc
-        AsyncRoot
-    router
-        Link
-        RouteComponent
-        Router
-    tags
-        xml
-    utils
-        debounce
-        escape
-        loadJS
-        loadFile
-        shallowEqual
-        whenReady
-```
-
-Note that for convenience, the `useState` hook is also exported at the root of the `owl` object.
+- [Tutorial: create a TodoList application](learning/tutorial_todoapp.md)
+- [Quick Overview](learning/overview.md)
+- [How to start an Owl project](learning/quick_start.md)
+- [How to test Components](learning/how_to_test.md)
+- [How to write Single File Components](learning/how_to_write_sfc.md)
+- [How to write debug Owl applications](learning/how_to_debug.md)
 
 ## Reference
 
-- [Animations](animations.md)
-- [Component](component.md)
-- [Context](context.md)
-- [Event Bus](event_bus.md)
-- [Hooks](hooks.md)
-- [Misc](misc.md)
-- [Observer](observer.md)
-- [QWeb](qweb.md)
-- [Router](router.md)
-- [Store](store.md)
-- [Tags](tags.md)
-- [Utils](utils.md)
-- [Virtual DOM](vdom.md)
+You will find here a complete reference of every feature, class or object
+provided by Owl.
 
-## Learning Resources
+- [Animations](reference/animations.md)
+- [Browser](reference/browser.md)
+- [Component](reference/component.md)
+- [Content](reference/content.md)
+- [Concurrency Model](reference/concurrency_model.md)
+- [Configuration](reference/config.md)
+- [Context](reference/context.md)
+- [Environment](reference/environment.md)
+- [Event Bus](reference/event_bus.md)
+- [Event Handling](reference/event_handling.md)
+- [Error Handling](reference/error_handling.md)
+- [Hooks](reference/hooks.md)
+- [Mounting a component](reference/mounting.md)
+- [Miscellaneous Components](reference/misc.md)
+- [Observer](reference/observer.md)
+- [Props](reference/props.md)
+- [Props Validation](reference/props_validation.md)
+- [QWeb Templating Language](reference/qweb_templating_language.md)
+- [QWeb Engine](reference/qweb_engine.md)
+- [Router](reference/router.md)
+- [Store](reference/store.md)
+- [Slots](reference/slots.md)
+- [Tags](reference/tags.md)
+- [Utils](reference/utils.md)
 
-- [Quick Start](quick_start.md)
+## Other Topics
 
-## Miscellaneous
+This section provides miscellaneous document that explains some topics
+which cannot be considered either a tutorial, or reference documentation.
 
-- [Comparison with React/Vue](comparison.md)
-- [Tooling](tooling.md)
-- [Templates to start Owl applications (external link)](https://github.com/ged-odoo/owl-templates)
+- [Owl architecture: the Virtual DOM](miscellaneous/vdom.md)
+- [Owl architecture: the rendering pipeline](miscellaneous/rendering.md)
+- [Comparison with React/Vue](miscellaneous/comparison.md)
+- [Why did Odoo built Owl?](miscellaneous/why_owl.md)
+
+---
+
+Found an issue in the documentation? A broken link? Some outdated information?
+Please open an issue or submit a PR!

doc/reference/animations.md

@@ -52,21 +52,20 @@ sequence of events will happen:
 At node insertion:
 
 - the css classes `name-enter` and `name-enter-active` will be added directly
-  when the node is inserted into the DOM,
+  when the node is inserted into the DOM.
 - on the next animation frame: the css class `name-enter` will be removed and the
   class `name-enter-to` will be added (so they can be used to trigger css
-  transition effects),
-- the css class `name-enter-active` will be removed whenever a css transition
-  ends.
+  transition effects).
+- at the end of the transition, `name-enter-to` and `name-enter-active` will be removed.
 
 At node destruction:
 
 - the css classes `name-leave` and `name-leave-active` will be added before the
-  node is removed to the DOM,
-- the css class `name-leave` will be removed on the next animation frame (so it
-  can be used to trigger css transition effects),
-- the css class `name-leave-active` will be removed whenever a css transition
-  ends. Only then will the element be removed from the DOM.
+  node is removed to the DOM.
+- on the next animation frame: the css class `name-leave` will be removed and the
+  class `name-leave-to` will be added (so they can be used to trigger css
+  transition effects).
+- at the end of the transition, `name-leave-to` and `name-leave-active` will be removed.
 
 For example, a simple fade in/out effect can be done with this:
 
@@ -93,3 +92,36 @@ Notes:
 
 Owl does not support more than one transition on a single node, so the
 `t-transition` expression must be a single value (i.e. no space allowed).
+
+## SCSS Mixins
+
+If you use SCSS, you can use mixins to make generic animations. Here is an exemple with a fade in / fade out animation:
+
+```scss
+@mixin animation-fade($time, $name) {
+  .#{$name}_fade-enter-active,
+  .#{$name}_fade-active {
+    transition: all $time;
+  }
+
+  .#{$name}_fade-enter {
+    opacity: 0;
+  }
+
+  .#{$name}_fade-leave-to {
+    opacity: 0;
+  }
+}
+```
+
+Usage:
+
+```scss
+@include animation-fade(0.5s, "o_notification");
+```
+
+You can now have in your template:
+
+```xml
+<SomeTag  t-transition="o_notification_fade"/>
+```

doc/reference/browser.md

@@ -0,0 +1,33 @@
+# 🦉 Browser 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Browser Content](#browser-content)
+
+## Overview
+
+The browser object contains some browser native APIs, such as `setTimeout`, that
+are used by Owl and its utility functions. They are exposed with the intent of
+making them mockable if necessary.
+
+```js
+owl.browser.setTimeout === window.setTimeout; // return true
+```
+
+For now, this object contains some functions that are not used by Owl. They
+will eventually be removed in Owl 2.0.
+
+## Browser Content
+
+More specifically, the `browser` object contains the following methods and objects:
+
+- `setTimeout`
+- `clearTimeout`
+- `setInterval`
+- `clearInterval`
+- `requestAnimationFrame`
+- `random`
+- `Date`
+- `fetch`
+- `localStorage`

doc/reference/component.md

@@ -10,20 +10,22 @@
   - [Static Properties](#static-properties)
   - [Methods](#methods)
   - [Lifecycle](#lifecycle)
+    - [`constructor(parent, props)`](#constructorparent-props)
+    - [`setup()`](#setup)
+    - [`willStart()`](#willstart)
+    - [`mounted()`](#mounted)
+    - [`willUpdateProps(nextProps)`](#willupdatepropsnextprops)
+    - [`willPatch()`](#willpatch)
+    - [`patched(snapshot)`](#patchedsnapshot)
+    - [`willUnmount()`](#willunmount)
+    - [`catchError(error)`](#catcherrorerror)
   - [Root Component](#root-component)
-  - [Environment](#environment)
   - [Composition](#composition)
-  - [Event Handling](#event-handling)
   - [Form Input Bindings](#form-input-bindings)
-  - [`t-key` Directive](#t-key-directive)
-  - [Semantics](#semantics)
-  - [Props Validation](#props-validation)
   - [References](#references)
-  - [Slots](#slots)
-  - [Asynchronous Rendering](#asynchronous-rendering)
-  - [Error Handling](#error-handling)
+  - [Dynamic sub components](#dynamic-sub-components)
   - [Functional Components](#functional-components)
-  - [SVG components](#svg-components)
+  - [SVG Components](#svg-components)
 
 ## Overview
 
@@ -43,7 +45,7 @@ OWL components are the building blocks for user interface. They are designed to
    and follow the QWeb specification. This is a requirement for Odoo.
 
 OWL components are defined as a subclass of Component. The rendering is
-exclusively done by a [QWeb](qweb.md) template (which needs to be preloaded in QWeb).
+exclusively done by a [QWeb](qweb_templating_language.md) template (which needs to be preloaded in QWeb).
 Rendering a component generates a virtual dom representation
 of the component, which is then patched to the DOM, in order to apply the changes in an efficient way.
 
@@ -81,8 +83,8 @@ a state object is defined, by using the `useState` hook. It is not mandatory to
 ## Reference
 
 An Owl component is a small class which represents a component or some UI element.
-It exists in the context of an environment (`env`), which is propagated from a
-parent to its children. The environment needs to have a QWeb instance, which
+It exists in the context of an [environment](environment.md) (`env`), which is propagated from a
+parent to its children. The environment needs to have a [QWeb](qweb_templating_language.md) instance, which
 will be used to render the component template.
 
 Be aware that the name of the component may be significant: if a component does
@@ -167,7 +169,7 @@ to be called in the constructor.
 - **`el`** (HTMLElement | null): reference to the DOM root node of the element. It is `null` when the
   component is not mounted.
 
-- **`env`** (Object): the component environment, which contains a QWeb instance.
+- **`env`** (Object): the component [environment](environment.md), which contains a QWeb instance.
 
 - **`props`** (Object): this is an object containing all the properties given by
   the parent to a child component. For example, in the following situation,
@@ -205,13 +207,13 @@ to be called in the constructor.
 * **`props`** (Object, optional): if given, this is an object that describes the
   type and shape of the (actual) props given to the component. If Owl mode is
   `dev`, this will be used to validate the props each time the component is
-  created/updated. See [Props Validation](#props-validation) for more information.
+  created/updated. See [Props Validation](props_validation.md) for more information.
 
   ```js
   class Counter extends owl.Component {
     static props = {
       initialValue: Number,
-      optional: true
+      optional: true,
     };
   }
   ```
@@ -224,11 +226,15 @@ to be called in the constructor.
   ```js
   class Counter extends owl.Component {
     static defaultProps = {
-      initialValue: 0
+      initialValue: 0,
     };
   }
   ```
 
+- **`style`** (string, optional): it should be the return value of the [`css` tag](tags.md#css-tag),
+  which is used to inject stylesheet whenever the component is visible on the
+  screen.
+
 There is another static property defined on the `Component` class: `current`.
 This property is set to the currently being defined component (in the constructor).
 This is the way [hooks](hooks.md) are able to get a reference to the target
@@ -238,36 +244,69 @@ component.
 
 We explain here all the public methods of the `Component` class.
 
-- **`mount(target, renderBeforeRemount=false)`** (async): this is the main way a
+- **`mount(target, options)`** (async): this is the main way a
   component is added to the DOM: the root component is mounted to a target
-  HTMLElement. Obviously, this is asynchronous, since each children need to be
+  HTMLElement (or document fragment). Obviously, this is asynchronous, since each children need to be
   created as well. Most applications will need to call `mount` exactly once, on
   the root component.
 
-  The `renderBeforeRemount` argument is useful when a component is unmounted and remounted.
-  In that case, we may want to rerender the component _before_ it is remounted, if
-  we know that its state (or something in the environment, or ...) has changed.
-  In that case, it should simply set to `true`.
+  The `options` argument is an optional object with a `position` key. The
+  `position` key can have three possible values: `first-child`, `last-child`, `self`.
 
-- **`unmount()`**: in case a component needs to be detached/removed from the DOM, this
+  - `first-child`: with this option, the component will be prepended inside the target,
+  - `last-child` (default value): with this option, the component will be
+    appended in the target element,
+  - `self`: the target will be used as the root element for the component. This
+    means that the target has to be an HTMLElement (and not a document fragment).
+    In this situation, it is possible that the component cannot be unmounted. For
+    example, if its target is `document.body`.
+
+  Note that if a component is mounted, unmounted and remounted, it will be
+  automatically re-rendered to ensure that changes in its state (or something
+  in the environment, or in the store, or ...) will be taken into account.
+
+  If a component is mounted inside an element or a fragment which is not in the
+  DOM, then it will be rendered fully, but not active: the `mounted` hooks will
+  not be called. This is sometimes useful if we want to load an application in
+  memory. In that case, we need to mount the root component again in an element
+  which is in the DOM:
+
+  ```js
+  const app = new App();
+  await app.mount(document.createDocumentFragment());
+  // app is rendered in memory, but not active
+  await app.mount(document.body);
+  // app is now visible
+  ```
+
+  Note that the normal way of mounting an application is by using the `mount`
+  method on a component class, not by creating the instance by hand. See the
+  documentation on [mounting applications](mounting.md).
+
+* **`unmount()`**: in case a component needs to be detached/removed from the DOM, this
   method can be used. Most applications should not call `unmount`, this is more
   useful to the underlying component system.
 
-- **`render()`** (async): calling this method directly will cause a rerender. Note
+* **`render()`** (async): calling this method directly will cause a rerender. Note
   that this should be very rare to have to do it manually, the Owl framework is
   most of the time responsible for doing that at an appropriate moment.
 
   Note that the render method is asynchronous, so one cannot observe the updated
   DOM in the same stack frame.
 
-- **`shouldUpdate(nextProps)`**: this method is called each time a component's props
+* **`shouldUpdate(nextProps)`**: this method is called each time a component's props
   are updated. It returns a boolean, which indicates if the component should
   ignore a props update. If it returns false, then `willUpdateProps` will not
   be called, and no rendering will occur. Its default implementation is to
-  always return true. This is an optimization, similar to React's `shouldComponentUpdate`. Most of the time, this should not be used, but it
-  can be useful if we are handling large number of components.
+  always return true. Note that this is an optimization, similar to React's `shouldComponentUpdate`. Most of the time, this should not be used, but it
+  can be useful if we are handling large number of components. Since this is an
+  optimization, Owl has the freedom to ignore the result of `shouldUpdate` in
+  some cases (for example, if a component is remounted, or if we want to force
+  a full rerender of the UI). However, if `shouldUpdate` returns true, then Owl
+  provides the guarantee that the component will be rendered at some point in
+  the future (except if the component is destroyed or if some part of the UI crashes).
 
-- **`destroy()`**. As its name suggests, this method will remove the component,
+* **`destroy()`**. As its name suggests, this method will remove the component,
   and perform all necessary cleanup, such as unmounting the component, its children,
   removing the parent/children relationship. This method should almost never be
   called directly (except maybe on the root component), but should be done by the
@@ -284,16 +323,16 @@ A solid and robust component system needs useful hooks/methods to help
 developers write components. Here is a complete description of the lifecycle of
 a owl component:
 
-| Method                                           | Description                                                  |
-| ------------------------------------------------ | ------------------------------------------------------------ |
-| **[constructor](#constructorparent-props)**      | constructor                                                  |
-| **[willStart](#willstart)**                      | async, before first rendering                                |
-| **[mounted](#mounted)**                          | just after component is rendered and added to the DOM        |
-| **[willUpdateProps](#willupdatepropsnextprops)** | async, before props update                                   |
-| **[willPatch](#willpatch)**                      | just before the DOM is patched                               |
-| **[patched](#patchedsnapshot)**                  | just after the DOM is patched                                |
-| **[willUnmount](#willunmount)**                  | just before removing component from DOM                      |
-| **[catchError](#catcherrorerror)**               | catch errors (see [error handling section](#error-handling)) |
+| Method                                           | Description                                                 |
+| ------------------------------------------------ | ----------------------------------------------------------- |
+| **[setup](#setup)**                              | setup                                                       |
+| **[willStart](#willstart)**                      | async, before first rendering                               |
+| **[mounted](#mounted)**                          | just after component is rendered and added to the DOM       |
+| **[willUpdateProps](#willupdatepropsnextprops)** | async, before props update                                  |
+| **[willPatch](#willpatch)**                      | just before the DOM is patched                              |
+| **[patched](#patchedsnapshot)**                  | just after the DOM is patched                               |
+| **[willUnmount](#willunmount)**                  | just before removing component from DOM                     |
+| **[catchError](#catcherrorerror)**               | catch errors (see [error handling page](error_handling.md)) |
 
 Notes:
 
@@ -331,6 +370,23 @@ class ClickCounter extends owl.Component {
 }
 ```
 
+Hook functions can be called in the constructor.
+
+#### `setup()`
+
+_setup_ is run just after the component is constructed. It is a lifecycle method,
+very similar to the _constructor_, except that it does not receive any argument.
+
+It is a valid method to call hook functions. Note that one of the main reason to
+have the `setup` hook in the component lifecycle is to make it possible to
+monkey patch it. It is a common need in the Odoo ecosystem.
+
+```javascript
+setup() {
+  useSetupAutofocus();
+}
+```
+
 #### `willStart()`
 
 willStart is an asynchronous hook that can be implemented to
@@ -370,8 +426,8 @@ will slightly slow down the component.
 #### `willUpdateProps(nextProps)`
 
 The willUpdateProps is an asynchronous hook, called just before new props
-are set. This is useful if the component needs some asynchronous task
-performed, depending on the props (for example, assuming that the props are
+are set. This is useful if the component needs to perform an asynchronous task,
+depending on the props (for example, assuming that the props are
 some record Id, fetching the record data).
 
 ```javascript
@@ -386,14 +442,13 @@ and performs a similar job).
 #### `willPatch()`
 
 The willPatch hook is called just before the DOM patching process starts.
-It is not called on the initial render. This is useful to read some
+It is not called on the initial render. This is useful to read
 information from the DOM. For example, the current position of the
 scrollbar.
 
 Note that modifying the state is not allowed here. This method is called just
 before an actual DOM patch, and is only intended to be used to save some local
-DOM state. Also, it will not be called if the component is not in the DOM (this can
-happen with components with `t-keepalive`).
+DOM state. Also, it will not be called if the component is not in the DOM.
 
 #### `patched(snapshot)`
 
@@ -402,8 +457,8 @@ likely via a change in its state/props or environment).
 
 This method is not called on the initial render. It is useful to interact
 with the DOM (for example, through an external library) whenever the
-component was patched. Note that this hook will not be called if the compoent is
-not in the DOM (this can happen with components with `t-keepalive`).
+component was patched. Note that this hook will not be called if the component is
+not in the DOM.
 
 Updating the component state in this hook is possible, but not encouraged.
 One needs to be careful, because updates here will create an additional rendering, which in
@@ -413,7 +468,7 @@ careful at avoiding endless cycles.
 #### `willUnmount()`
 
 willUnmount is a hook that is called each time just before a component is unmounted from
-the DOM. This is a good place to remove some listeners, for example.
+the DOM. This is a good place to remove listeners, for example.
 
 ```javascript
   mounted() {
@@ -429,8 +484,8 @@ This is the opposite method of `mounted`.
 #### `catchError(error)`
 
 The `catchError` method is useful when we need to intercept and properly react
-to (rendering) errors that occur in some sub components. See the section on
-[error handling](#error-handling).
+to (rendering) errors that occur in some sub components. See the page on
+[error handling](error_handling.md).
 
 ### Root Component
 
@@ -441,49 +496,17 @@ of an Owl application has to be created manually:
 ```js
 class App extends owl.Component { ... }
 
-const qweb = new owl.QWeb(TEMPLATES);
-const env = { qweb: qweb };
-const app = new App(env);
+const app = new App();
 app.mount(document.body);
 ```
 
-The root component needs an environment.
+The root component does not have a parent nor `props` (see note below). It will be setup with an
+[environment](environment.md) (either the `env` defined on its class, or a
+default empty environment).
 
-### Environment
-
-In Owl, an environment is an object with a `qweb` key, which has to be a
-[QWeb](qweb.md) instance. This qweb instance will be used to render everything.
-
-The environment is meant to contain (mostly) static global information and
-methods for the whole application. For example, settings keys (`mode` to determine
-if we are in desktop or mobile mode, or `theme`: dark or light), `rpc` methods,
-session information, ...
-
-The environment will be given to each child, unchanged, in the `env` property.
-This can be very useful to share common information/methods. For example, all
-rpcs can be made through a `rpc` method in the environment. This makes it very
-easy to test a component.
-
-Updating the environment is not as simple as changing a component's state: its
-content is not observed, so updates will not be reflected immediately in the
-user interface. There is however a mechanism to force root widgets to rerender
-themselves whenever the environment is modified: one only needs to call the
-`forceUpdate` method on the QWeb instance. For example, a responsive environment
-could be done like this:
-
-```js
-function setupResponsivePlugin(env) {
-  const isMobile = () => window.innerWidth <= 768;
-  env.isMobile = isMobile();
-  const updateEnv = owl.utils.debounce(() => {
-    if (env.isMobile !== isMobile()) {
-      env.isMobile = !env.isMobile;
-      env.qweb.forceUpdate();
-    }
-  }, 15);
-  window.addEventListener("resize", updateEnv);
-}
-```
+Note: a root component can however be given a `props` object in its constructor,
+like this: `new App(null, {some: 'object'});`. It will not be a true `props`
+object, managed by Owl (so, for example, it will never be updated).
 
 ### Composition
 
@@ -537,68 +560,10 @@ the static `components` key, then fallbacks on the global registry.
 _Props_: In this example, the child component will receive the object `{count: 4}` in its
 constructor. This will be assigned to the `props` variable, which can be accessed
 on the component (and also, in the template). Whenever the state is updated, then
-the sub component will also be updated automatically.
+the sub component will also be updated automatically. See the [props section](props.md)
+for more information.
 
-Note that there are some restrictions on prop names: `class`, `style` and any
-string which starts with `t-` are not allowed.
-
-It is not common, but sometimes we need a dynamic component name and/or dynamic props. In this case,
-the `t-component` directive can also be used to accept dynamic values with string interpolation (like the [`t-attf-`](qweb.md#dynamic-attributes) directive):
-
-```xml
-<div t-name="ParentComponent">
-    <t t-component="ChildComponent{{id}}" />
-</div>
-```
-
-```js
-class ParentComponent {
-  static components = { ChildComponent1, ChildComponent2 };
-  state = { id: 1 };
-}
-```
-
-And the `t-props` directive can be used to specify totally dynamic props:
-
-```xml
-<div t-name="ParentComponent">
-    <Child t-props="some.obj"/>
-</div>
-```
-
-```js
-class ParentComponent {
-  static components = { Child };
-  some = { obj: { a: 1, b: 2 } };
-}
-```
-
-There is an even more dynamic way to use `t-component`: its value can be an
-expression evaluating to an actual component class. In that case, this is the
-class that will be used to create the component:
-
-```js
-class A extends Component<any, any, any> {
-  static template = xml`<span>child a</span>`;
-}
-class B extends Component<any, any, any> {
-  static template = xml`<span>child b</span>`;
-}
-class App extends Component<any, any, any> {
-  static template = xml`<t t-component="myComponent" t-key="state.child"/>`;
-
-  state = { child: "a" };
-
-  get myComponent() {
-    return this.state.child === "a" ? A : B;
-  }
-}
-```
-
-In this example, the component `App` selects dynamically the concrete sub
-component class.
-
-**CSS and style:** there is some specific support to allow the parent to declare
+**CSS and style:** Owl allows the parent to declare
 additional css classes or style for the sub component: css declared in `class`, `style`, `t-att-class` or `t-att-style` will be added to the
 root component element.
 
@@ -611,7 +576,7 @@ root component element.
 Warning: there is a small caveat with dynamic class attributes: since Owl needs
 to be able to add/remove proper classes whenever necessary, it needs to be aware
 of the possible classes. Otherwise, it will not be able to make the difference
-between a valid css class added by the component, or some custom code, and a
+between a valid css class added by the component, or other custom code, and a
 class that need to be removed. This is why we only support the explicit syntax
 with a class object:
 
@@ -619,115 +584,6 @@ with a class object:
 <MyComponent t-att-class="{a: state.flagA, b: state.flagB}" />
 ```
 
-### Event Handling
-
-In a component's template, it is useful to be able to register handlers on some
-elements to some specific events. This is what makes a template _alive_. There
-are four different use cases.
-
-1. Register an event handler on a DOM node (_pure_ DOM event)
-2. Register an event handler on a component (_pure_ DOM event)
-3. Register an event handler on a DOM node (_business_ DOM event)
-4. Register an event handler on a component (_business_ DOM event)
-
-A _pure_ DOM event is directly triggered by a user interaction (e.g. a `click`).
-
-```xml
-<button t-on-click="someMethod">Do something</button>
-```
-
-This will be roughly translated in javascript like this:
-
-```js
-button.addEventListener("click", component.someMethod.bind(component));
-```
-
-The suffix (`click` in this example) is simply the name of the actual DOM
-event.
-
-A _business_ DOM event is triggered by a call to `trigger` on a component.
-
-```xml
-<MyComponent t-on-menu-loaded="someMethod" />
-```
-
-```js
- class MyComponent {
-     someWhere() {
-         const payload = ...;
-         this.trigger('menu-loaded', payload);
-     }
- }
-```
-
-The call to `trigger` generates a [_CustomEvent_](https://developer.mozilla.org/docs/Web/Guide/Events/Creating_and_triggering_events)
-of type `menu-loaded` and dispatches it on the component's DOM element
-(`this.el`). The event bubbles and is cancelable. The parent component listening
-to event `menu-loaded` will receive the payload in its `someMethod` handler
-(in the `detail` property of the event), whenever the event is triggered.
-
-```js
- class ParentComponent {
-     someMethod(ev) {
-         const payload = ev.detail;
-         ...
-     }
- }
-```
-
-By convention, we use KebabCase for the name of _business_ events.
-
-
-The `t-on` directive allows to prebind some arguments. For example,
-
-```xml
-<button t-on-click="someMethod(expr)">Do something</button>
-```
-
-Here, `expr` is a valid Owl expression, so it could be `true` or some variable
-from the rendering context.
-
-One can also directly specify inline statements. For example,
-
-```xml
-<button t-on-click="state.counter++">Increment counter</button>
-```
-
-Here, `state` must be defined in the rendering context (typically the component)
-as it will be translated to:
-```js
-button.addEventListener("click", () => { component.state.counter++; });
-```
-
-
-In order to remove the DOM event details from the event handlers (like calls to
-`event.preventDefault`) and let them focus on data logic, _modifiers_ can be
-specified as additional suffixes of the `t-on` directive.
-
-| Modifier   | Description                                                       |
-| ---------- | ----------------------------------------------------------------- |
-| `.stop`    | calls `event.stopPropagation()` before calling the method         |
-| `.prevent` | calls `event.preventDefault()` before calling the method          |
-| `.self`    | calls the method only if the `event.target` is the element itself |
-
-```xml
-<button t-on-click.stop="someMethod">Do something</button>
-```
-
-Note that modifiers can be combined (ex: `t-on-click.stop.prevent`), and that
-the order may matter. For instance `t-on-click.prevent.self` will prevent all
-clicks while `t-on-click.self.prevent` will only prevent clicks on the element
-itself.
-
-Finally, empty handlers are tolerated as they could be defined only to apply
-modifiers. For example,
-
-```xml
-<button t-on-click.stop="">Do something</button>
-```
-
-This will simply stop the propagation of the event.
-
 ### Form Input Bindings
 
 It is very common to need to be able to read the value out of an html `input` (or
@@ -802,7 +658,7 @@ The `t-model` directive works with `<input>`, `<input type="checkbox">`,
 </div>
 ```
 
-Like event handling, the `t-model` directive accepts some modifiers:
+Like event handling, the `t-model` directive accepts the following modifiers:
 
 | Modifier  | Description                                                          |
 | --------- | -------------------------------------------------------------------- |
@@ -821,213 +677,6 @@ update a number whenever the change is done.
 
 Note: the online playground has an example to show how it works.
 
-### `t-key` Directive
-
-Even though Owl tries to be as declarative as possible, the DOM does not fully
-expose its state declaratively in the DOM tree. For example, the scrolling state,
-the current user selection, the focused element or the state of an input are not
-set as attribute in the DOM tree. This is why we use a virtual dom
-algorithm to keep the actual DOM node as much as possible. However, this is
-sometimes not enough, and we need to help Owl decide if an element is actually
-the same, or is different. The `t-key` directive is used to give an identity to an element.
-
-There are three main use cases:
-
-- _elements in a list_:
-
-  ```xml
-    <span t-foreach="todos" t-as="todo" t-key="todo.id">
-        <t t-esc="todo.text" />
-    </span>
-  ```
-
-- _`t-if`/`t-else`_
-
-- _animations_: give a different identity to a component. Ex: thread id with
-  animations on add/remove message.
-
-### Semantics
-
-We give here an informal description of the way components are created/updated
-in an application. Here, ordered lists describe actions that are executed
-sequentially, bullet lists describe actions that are executed in parallel.
-
-**Scenario 1: initial rendering** Imagine we want to render the following component tree:
-
-```
-        A
-       / \
-      B   C
-         / \
-        D   E
-```
-
-Here is what happen whenever we mount the root
-component (with some code like `app.mount(document.body)`).
-
-1. `willStart` is called on `A`
-
-2. when it is done, template `A` is rendered.
-
-   - component `B` is created
-     1. `willStart` is called on `B`
-     2. template `B` is rendered
-   - component `C` is created
-     1. `willStart` is called on `C`
-     2. template `C` is rendered
-        - component `D` is created
-          1. `willStart` is called on `D`
-          2. template `D` is rendered
-        - component `E` is created
-          1. `willStart` is called on `E`
-          2. template `E` is rendered
-
-3. component `A` is patched into a detached DOM element. This will create the actual
-   component `A` DOM structure. The patching process will cause recursively the
-   patching of the `B`, `C`, `D` and `E` DOM trees. (so the actual full DOM tree is created
-   in one pass)
-
-4. the component `A` root element is actually appended to `document.body`
-
-5. The method `mounted` is called recursively on all components in the following
-   order: `B`, `D`, `E`, `C`, `A`.
-
-**Scenario 2: rerendering a component**. Now, let's assume that the user clicked on some
-button in `C`, and this results in a state update, which is supposed to:
-
-- update `D`,
-- remove `E`,
-- add new component `F`.
-
-So, the component tree should look like this:
-
-```
-        A
-       / \
-      B   C
-         / \
-        D   F
-```
-
-Here is what Owl will do:
-
-1. because of a state change, the method `render` is called on `C`
-2. template `C` is rendered again
-
-   - component `D` is updated:
-     1. hook `willUpdateProps` is called on `D` (async)
-     2. template `D` is rerendered
-   - component `F` is created:
-     1. hook `willStart` is called on `E` (async)
-     2. template `F` is rendered
-
-3. `willPatch` hooks are called recursively on components `C`, `D` (not on `F`,
-   because it is not mounted yet)
-
-4. component `C` is patched, which will cause recursively:
-
-   2. `willUnmount` hook on `E`, then destruction of `E`,
-   3. (initial) patching of `F`, then hook `mounted` is called on `F`
-
-5. patching of `D`
-
-6. `patched` hooks are called on `D`, `C`
-
-### Props Validation
-
-As an application becomes complex, it may be quite unsafe to define props in an informal way. This leads to two issues:
-
-- hard to tell how a component should be used, by looking at its code.
-- unsafe, it is easy to send wrong props into a component, either by refactoring a component, or one of its parents.
-
-A props type system would solve both issues, by describing the types and shapes
-of the props. Here is how it works in Owl:
-
-- `props` key is a static key (so, different from `this.props` in a component instance)
-- it is optional: it is ok for a component to not define a `props` key.
-- props are validated whenever a component is created/updated
-- props are only validated in `dev` mode (see [tooling page](tooling.md#development-mode))
-- if a key does not match the description, an error is thrown
-- it validates keys defined in (static) `props`. Additional keys given by the
-  parent will cause an error.
-
-For example:
-
-```js
-class ComponentA extends owl.Component {
-    static props = ['id', 'url'];
-
-    ...
-}
-
-class ComponentB extends owl.Component {
-  static props = {
-    count: {type: Number},
-    messages: {
-      type: Array,
-      element: {type: Object, shape: {id: Boolean, text: 'string' }
-    },
-   date: Date,
-   combinedVal: [Number, Boolean]
-  };
-
-  ...
-}
-```
-
-- it is an object or a list of strings
-- a list of strings is a simplified props definition, which only lists the name
-  of the props. Also, if the name ends with `?`, it is considered optional.
-- all props are by default required, unless they are defined with `optional: true`
-  (in that case, validation is only done if there is a value)
-- valid types are: `Number, String, Boolean, Object, Array, Date, Function`, and all
-  constructor functions (so, if you have a `Person` class, it can be used as a type)
-- arrays are homogeneous (all elements have the same type/shape)
-
-For each key, a `prop` definition is either a boolean, a constructor, a list of constructors, or an object:
-
-- a boolean: indicate that the props exists, and is mandatory.
-- a constructor: this should describe the type, for example: `id: Number` describe
-  the props `id` as a number
-- a list of constructors. In that case, this means that we allow more than one
-  type. For example, `id: [Number, String]` means that `id` can be either a string
-  or a number.
-- an object. This makes it possible to have more expressive definition. The following sub keys are then allowed:
-  - `type`: the main type of the prop being validated
-  - `element`: if the type was `Array`, then the `element` key describes the type of each element in the array. It is optional (not set means that we only validate the array, not its elements),
-  - `shape`: if the type was `Object`, then the `shape` key describes the interface of the object. It is optional (not set means that we only validate the object, not its elements)
-
-Examples:
-
-```js
-  // only the existence of those 3 keys is documented
-  static props = ['message', 'id', 'date'];
-```
-
-```js
-  // size is optional
-  static props = ['message', 'size?'];
-```
-
-```js
-  static props = {
-    messageIds: {type: Array, element: Number},  // list of number
-    otherArr: {type: Array},   // just array. no validation is made on sub elements
-    otherArr2: Array,   // same as otherArr
-    someObj: {type: Object},  // just an object, no internal validation
-    someObj2: {
-      type: Object,
-      shape: {
-        id: Number,
-        name: {type: String, optional: true},
-        url: String
-      ]},    // object, with keys id (number), name (string, optional) and url (string)
-    someFlag: Boolean,     // a boolean, mandatory (even if `false`)
-    someVal: [Boolean, Date],   // either a boolean or a date
-    otherValue: true,     // indicates that it is a prop
-  };
-```
-
 ### References
 
 The `useRef` hook is useful when we need a way to interact with some inside part
@@ -1084,163 +733,50 @@ Note that these two examples uses the suffix `ref` to name the reference. This
 is not mandatory, but it is a useful convention, so we do not forget to access
 it with the `el` or `comp` suffix.
 
-### Slots
+### Dynamic sub components
 
-To make generic components, it is useful to be able for a parent component to _inject_
-some sub template, but still be the owner. For example, a generic dialog component
-will need to render some content, some footer, but with the parent as the
-rendering context.
-
-This is what _slots_ are for.
+It is not common, but sometimes we need a dynamic component name. In this case,
+the `t-component` directive can also be used to accept dynamic values with string interpolation (like the [`t-attf-`](qweb_templating_language.md#dynamic-attributes) directive):
 
 ```xml
-<div t-name="Dialog" class="modal">
-  <div class="modal-title"><t t-esc="props.title"/></div>
-  <div class="modal-content">
-    <t t-slot="content"/>
-  </div>
-  <div class="modal-footer">
-    <t t-slot="footer"/>
-  </div>
-</div>
-```
-
-Slots are defined by the caller, with the `t-set` directive:
-
-```xml
-<div t-name="SomeComponent">
-  <div>some component</div>
-  <Dialog title="Some Dialog">
-    <t t-set="content">
-      <div>hey</div>
-    </t>
-    <t t-set="footer">
-      <button t-on-click="doSomething">ok</button>
-    </t>
-  </Dialog>
-</div>
-```
-
-In this example, the component `Dialog` will render the slots `content` and `footer`
-with its parent as rendering context. This means that clicking on the button
-will execute the `doSomething` method on the parent, not on the dialog.
-
-Default slot: the first element inside the component which is not a named slot will
-be considered the `default` slot. For example:
-
-```xml
-<div t-name="Parent">
-  <Child>
-    <span>some content</span>
-  </Child>
-</div>
-
-<div t-name="Child">
-  <t t-slot="default"/>
-</div>
-```
-
-### Asynchronous Rendering
-
-Working with asynchronous code always adds a lot of complexity to a system. Whenever
-different parts of a system are active at the same time, one needs to think
-carefully about all possible interactions. Clearly, this is also true for Owl
-components.
-
-There are two different common problems with Owl asynchronous rendering model:
-
-- any component can delay the rendering (initial and subsequent) of the whole
-  application
-- for a given component, there are two independant situations that will trigger an
-  asynchronous rerendering: a change in the state, or a change in the props.
-  These changes may be done at different times, and Owl has no way of knowing
-  how to reconcile the resulting renderings.
-
-Here are a few tips on how to work with asynchronous components:
-
-1. Minimize the use of asynchronous components!
-2. Maybe move the asynchronous logic in a store, which then triggers (mostly)
-   synchronous renderings
-3. Lazy loading external libraries is a good use case for async rendering. This
-   is mostly fine, because we can assume that it will only takes a fraction of a
-   second, and only once (see [`owl.utils.loadJS`](utils.md#loadjs))
-4. For all the other cases, the [`AsyncRoot`](misc.md#asyncroot) component is there to help you. When
-   this component is met, a new rendering
-   sub tree is created, such that the rendering of that component (and its
-   children) is not tied to the rendering of the rest of the interface. It can
-   be used on an asynchronous component, to prevent it from delaying the
-   rendering of the whole interface, or on a synchronous one, such that its
-   rendering isn't delayed by other (asynchronous) components. Note that this
-   directive has no effect on the first rendering, but only on subsequent ones
-   (triggered by state or props changes).
-
-   ```xml
-   <div t-name="ParentComponent">
-     <SyncChild />
-     <AsyncRoot>
-        <AsyncChild/>
-     </AsyncRoot>
-   </div>
-   ```
-
-### Error Handling
-
-By default, whenever an error occurs in the rendering of an Owl application, we
-destroy the whole application. Otherwise, we cannot offer any guarantee on the
-state of the resulting component tree. It might be hopelessly corrupted, but
-without any user-visible state.
-
-Clearly, it sometimes is a little bit extreme to destroy the application. This
-is why we have a builtin mechanism to handle rendering errors (and errors coming
-from lifecycle hooks): the `catchError` hook.
-
-Whenever the `catchError` lifecycle hook is implemented, all errors coming from
-sub components rendering and/or lifecycle method calls will be caught and given
-to the `catchError` method. This allows us to properly handle the error, and to
-not break the application.
-
-For example, here is how we could implement an `ErrorBoundary` component:
-
-```xml
-<div t-name="ErrorBoundary">
-    <t t-if="state.error">
-        Error handled
-    </t>
-    <t t-else="1">
-        <t t-slot="default" />
-    </t>
+<div t-name="ParentComponent">
+    <t t-component="ChildComponent{{id}}" />
 </div>
 ```
 
 ```js
-class ErrorBoundary extends Component {
-  state = useState({ error: false });
+class ParentComponent {
+  static components = { ChildComponent1, ChildComponent2 };
+  state = { id: 1 };
+}
+```
 
-  catchError() {
-    this.state.error = true;
+There is an even more dynamic way to use `t-component`: its value can be an
+expression evaluating to an actual component class. In that case, this is the
+class that will be used to create the component:
+
+```js
+class A extends Component<any, any, any> {
+  static template = xml`<span>child a</span>`;
+}
+class B extends Component<any, any, any> {
+  static template = xml`<span>child b</span>`;
+}
+class App extends Component<any, any, any> {
+  static template = xml`<t t-component="myComponent" t-key="state.child"/>`;
+
+  state = { child: "a" };
+
+  get myComponent() {
+    return this.state.child === "a" ? A : B;
   }
 }
 ```
 
-Using the `ErrorBoundary` is then extremely simple:
+In this example, the component `App` selects dynamically the concrete sub
+component class.
 
-```xml
-<ErrorBoundary><SomeOtherComponent/></ErrorBoundary>
-```
-
-Note that we need to be careful here: the fallback UI should not throw any
-error, otherwise we risk going into an infinite loop.
-
-Also, it may be useful to know that whenever an error is caught, it is then
-broadcasted to the application by an event on the `qweb` instance. It may be
-useful, for example, to log the error somewhere.
-
-```js
-env.qweb.on("error", null, function(error) {
-  // do something
-  // react to the error
-});
-```
+Note that the `t-component` directive can only be used on `<t>` nodes.
 
 ### Functional Components
 
@@ -1253,7 +789,7 @@ template rendered with `props`. In Owl, this can be done by
 simply defining a template, that will access the `props` object:
 
 ```js
-const Welcome = xml`<h1>Hello, {props.name}</h1>`;
+const Welcome = xml`<h1>Hello, <t t-esc="props.name"/></h1>`;
 
 class MyComponent extends Component {
   static template = xml`
@@ -1303,8 +839,8 @@ class RootNode extends Component {
     children: [
       { label: "b" },
       { label: "c", children: [{ label: "d" }, { label: "e" }] },
-      { label: "f", children: [{ label: "g" }] }
-    ]
+      { label: "f", children: [{ label: "g" }] },
+    ],
   };
 }
 ```

doc/reference/concurrency_model.md

@@ -0,0 +1,183 @@
+# 🦉 Concurrency Model 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Rendering Components](#rendering-components)
+- [Semantics](#semantics)
+- [Asynchronous Rendering](#asynchronous-rendering)
+
+## Overview
+
+Owl was designed from the very beginning with asynchronous components. This comes
+from the `willStart` and the `willUpdateProps` lifecycle hooks. With these
+methods, it is possible to build complex highly concurrent applications.
+
+Owl concurrent mode has several benefits: it makes it possible to delay the
+rendering until some asynchronous operation is complete, it makes it possible
+to lazy load libraries, while keeping the previous screen completely functional.
+It is also good for performance reasons: Owl uses it to only apply the result of
+many different renderings only once in an animation frame. Owl can cancel
+a rendering that is no longer relevant, restart it, reuse it in some cases.
+
+But even though using concurrency is quite simple (and is the default behaviour),
+asynchrony is difficult, because it introduces an additional dimension that
+vastly increase the complexity of an application. This section will explain
+how Owl manages this complexity, how concurrent rendering works in a general way.
+
+## Rendering Components
+
+The word _rendering_ is a little vague, so, let us explain more precisely the
+process by which Owl components are displayed on a screen.
+
+When a component is mounted or updated, a new rendering is started. It has
+two phases: _virtual rendering_ and _patching_.
+
+### Virtual rendering
+
+This phase represent the process of rendering a template, in memory, which create a virtual representation of the desired component html). The output of this phase is a
+virtual DOM.
+
+It is asynchronous: each subcomponents needs to either be created (so, `willStart`
+will need to be called), or updated (which is done with the `willUpdateProps`
+method). This is completely a recursive process: a component is the root of a
+component tree, and each sub component needs to be (virtually) rendered.
+
+### Patching
+
+Once a rendering is complete, it will be applied on the next animation frame.
+This is done synchronously: the whole component tree is patched to the real
+DOM.
+
+## Semantics
+
+We give here an informal description of the way components are created/updated
+in an application. Here, ordered lists describe actions that are executed
+sequentially, bullet lists describe actions that are executed in parallel.
+
+**Scenario 1: initial rendering** Imagine we want to render the following component tree:
+
+```
+        A
+       / \
+      B   C
+         / \
+        D   E
+```
+
+Here is what happen whenever we mount the root
+component (with some code like `app.mount(document.body)`).
+
+1. `willStart` is called on `A`
+
+2. when it is done, template `A` is rendered.
+
+   - component `B` is created
+     1. `willStart` is called on `B`
+     2. template `B` is rendered
+   - component `C` is created
+     1. `willStart` is called on `C`
+     2. template `C` is rendered
+        - component `D` is created
+          1. `willStart` is called on `D`
+          2. template `D` is rendered
+        - component `E` is created
+          1. `willStart` is called on `E`
+          2. template `E` is rendered
+
+3. each components are patched into a detached DOM element, in the following order:
+   `E`, `D`, `C`, `B`, `A`. (so the actual full DOM tree is created
+   in one pass)
+
+4. the component `A` root element is actually appended to `document.body`
+
+5. The method `mounted` is called recursively on all components in the following
+   order: `E`, `D`, `C`, `B`, `A`.
+
+**Scenario 2: rerendering a component**. Now, let's assume that the user clicked on some
+button in `C`, and this results in a state update, which is supposed to:
+
+- update `D`,
+- remove `E`,
+- add new component `F`.
+
+So, the component tree should look like this:
+
+```
+        A
+       / \
+      B   C
+         / \
+        D   F
+```
+
+Here is what Owl will do:
+
+1. because of a state change, the method `render` is called on `C`
+2. template `C` is rendered again
+
+   - component `D` is updated:
+     1. hook `willUpdateProps` is called on `D` (async)
+     2. template `D` is rerendered
+   - component `F` is created:
+     1. hook `willStart` is called on `F` (async)
+     2. template `F` is rendered
+
+3. `willPatch` hooks are called recursively on components `C`, `D` (not on `F`,
+   because it is not mounted yet)
+
+4. components `F`, `D` are patched in that order
+
+5. component `C` is patched, which will cause recursively:
+
+   1. `willUnmount` hook on `E`
+   2. destruction of `E`,
+
+6. `mounted` hook is called on `F`, `patched` hooks are called on `D`, `C`
+
+Tags are very small helpers to make it easy to write inline templates. There is
+only one currently available tag: `xml`, but we plan to add other tags later,
+such as a `css` tag, which will be used to write [single file components](../learning/how_to_write_sfc.md).
+
+### Asynchronous Rendering
+
+Working with asynchronous code always adds a lot of complexity to a system. Whenever
+different parts of a system are active at the same time, one needs to think
+carefully about all possible interactions. Clearly, this is also true for Owl
+components.
+
+There are two different common problems with Owl asynchronous rendering model:
+
+- any component can delay the rendering (initial and subsequent) of the whole
+  application
+- for a given component, there are two independant situations that will trigger an
+  asynchronous rerendering: a change in the state, or a change in the props.
+  These changes may be done at different times, and Owl has no way of knowing
+  how to reconcile the resulting renderings.
+
+Here are a few tips on how to work with asynchronous components:
+
+1. Minimize the use of asynchronous components!
+2. Maybe move the asynchronous logic in a store, which then triggers (mostly)
+   synchronous renderings
+3. Lazy loading external libraries is a good use case for async rendering. This
+   is mostly fine, because we can assume that it will only takes a fraction of a
+   second, and only once (see [`owl.utils.loadJS`](utils.md#loadjs))
+4. For all the other cases, the [`AsyncRoot`](misc.md#asyncroot) component is there to help you. When
+   this component is met, a new rendering
+   sub tree is created, such that the rendering of that component (and its
+   children) is not tied to the rendering of the rest of the interface. It can
+   be used on an asynchronous component, to prevent it from delaying the
+   rendering of the whole interface, or on a synchronous one, such that its
+   rendering isn't delayed by other (asynchronous) components. Note that this
+   directive has no effect on the first rendering, but only on subsequent ones
+   (triggered by state or props changes).
+
+   ```xml
+   <div t-name="ParentComponent">
+     <SyncChild />
+     <AsyncRoot>
+        <AsyncChild/>
+     </AsyncRoot>
+   </div>
+   ```

doc/reference/config.md

@@ -0,0 +1,44 @@
+# 🦉 Config 🦉
+
+The Owl framework is designed to work in many situations. However, it is
+sometimes necessary to customize some behaviour. This is done by using the
+global `config` object. It provides two settings:
+
+- [`mode`](#mode) (default value: `prod`),
+- [`enableTransitions`](#enabletransitions) (default value: `true`).
+
+## Mode
+
+By default, Owl is in _production_ mode, this means that it will try to do its
+job fast, and skip some expensive operations. However, it is sometimes necessary
+to have better information on what is going on, this is the purpose
+of the `dev` mode.
+
+Owl has a mode flag, in `owl.config.mode`. Its default value is `prod`, but
+it can be set to `dev`:
+
+```js
+owl.config.mode = "dev";
+```
+
+Note that templates compiled with the `prod` settings will not be recompiled.
+So, changing this setting is best done at startup.
+
+An important job done by the `dev` mode is to validate props for each component
+creation and update. Also, extra props will cause an error.
+
+## `enableTransitions`
+
+Transitions are usually nice, but they can cause issues in some specific cases,
+such as automated tests. It is uncomfortable having to wait for a transition
+to end before moving to the next step.
+
+To solve this issue, Owl can be configured to ignore the `t-transition` directive.
+To do that, one only needs to set the `enableTransitions` flag to false:
+
+```js
+owl.config.enableTransitions = false;
+```
+
+Note that it suffers from the same drawback as the "dev" mode: all compiled
+templates, if any, will keep their current behaviours.

doc/reference/content.md

@@ -0,0 +1,40 @@
+# 🦉 Owl Content 🦉
+
+Here is a complete visual representation of everything exported by the `owl`
+global object.
+
+For example, `Component` is available at `owl.Component` and `EventBus` is
+exported as `owl.core.EventBus`.
+
+```
+browser
+Component                               misc
+Context                                     AsyncRoot
+QWeb                                        Portal
+mount                                   router
+Store                                       Link
+useState                                    RouteComponent
+config                                      Router
+    mode
+core                                    tags
+    EventBus                                css
+    Observer                                xml
+hooks                                   utils
+    onWillStart                             debounce
+    onMounted                               escape
+    onWillUpdateProps                       loadJS
+    onWillPatch                             loadFile
+    onPatched                               shallowEqual
+    onWillUnmount                           whenReady
+    useContext
+    useState
+    useRef
+    useComponent
+    useEnv
+    useSubEnv
+    useStore
+    useDispatch
+    useGetters
+```
+
+Note that for convenience, the `useState` hook is also exported at the root of the `owl` object.

doc/reference/context.md

@@ -28,10 +28,7 @@ context, and add it to the environment:
 
 ```js
 const deviceContext = new Context({ isMobile: true });
-const env = {
-  qweb: new QWeb(TEMPLATES),
-  deviceContext
-};
+App.env.deviceContext = deviceContext;
 ```
 
 If we want to make it completely responsive, we need to update its value whenever
@@ -56,14 +53,14 @@ fact that we are in a mobile or desktop mode.
 ```js
 class SomeComponent extends Component {
   static template = xml`
-        <div>
-          <t t-if=device.isMobile>
-             some simplified user interface
-          </t>
-          <t t-else="1">
-             some more sopthisticated user interface
-          </t>
-    `;
+    <div>
+      <t t-if=device.isMobile>
+          some simplified user interface
+      </t>
+      <t t-else="">
+          a more advanced user interface
+      </t>
+    </div>`;
   device = useContext(this.env.deviceContext);
 }
 ```

doc/reference/environment.md

@@ -0,0 +1,136 @@
+# 🦉 Environment 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Setting an Environment](#setting-an-environment)
+- [Using a sub environment](#using-a-sub-environment)
+- [Content of an Environment](#content-of-an-environment)
+- [Special keys](#special-keys)
+
+## Overview
+
+An environment is an object which contains a [`QWeb` instance](qweb_engine.md). Whenever
+a root component is created, it is assigned an environment (see
+[below](#setting-an-environment) for more info on this). This environment is
+then automatically given to each sub component (and accessible in the `this.env`
+property).
+
+```
+    Root
+    /  \
+   A    B
+```
+
+This way, all components share the same `QWeb` instance. Owl internally requires
+that the environment has a `qweb` key which maps to a
+[`QWeb`](qweb_engine.md) instance. This is the QWeb instance that will be used to
+render each templates in this specific component tree. Note that if no `QWeb`
+instance is provided, Owl will simply generate it on the fly.
+
+The environment is mostly static. Each application is free to add anything to
+the environment, which is very useful, since this can be accessed by each sub
+component.
+
+## Setting an environment
+
+An Owl application needs an [environment](environment.md) to be executed. The
+environment has an important key: the [QWeb](qweb_engine.md) instance, which will render
+all templates.
+
+Whenever a root component `App` is mounted, Owl will setup a valid environment by
+following the next steps:
+
+- take the `env` object defined on `App.env` (if no `env` was explicitly setup,
+  this will return the empty `env` object defined on `Component`)
+- if `env.qweb` is not set, then Owl will create a `QWeb` instance.
+
+The correct way to customize an environment is to simply set it up on the root
+component class, before the first component is created:
+
+```js
+const env = {
+    _t: myTranslateFunction,
+    user: {...},
+    services: {
+        ...
+    },
+};
+mount(App, { target: document.body, env });
+```
+
+It is also possible to simply share an environment between all root components,
+by simply doing this:
+
+```js
+Component.env = myEnv; // will be the default env for all components
+```
+
+Note that this environment is the global owl environment for an application. The
+next section explains how to extend an environment for a specific sub component
+and its children.
+
+## Using a sub environment
+
+It is sometimes useful to add one (or more) specific keys to the environment,
+from the perspective of a specific component and its children. In that case, the
+solution presented above will not work, since it sets the global environment.
+
+There is a hook for this situation: [`useSubEnv`](hooks.md#usesubenv).
+
+```js
+class FormComponent extends Component {
+  constructor(parent, props) {
+    super(parent, props);
+    useSubEnv({ myKey: someValue });
+  }
+}
+```
+
+## Content of an Environment
+
+Some good use cases for additional keys in the environment are:
+
+- some configuration keys,
+- session information,
+- generic services (such as doing rpcs).
+
+Doing it this way means that components are easily testable: we can simply
+create a test environment with mock services.
+
+For example:
+
+```js
+async function myEnv() {
+  const templates = await loadTemplates();
+  const qweb = new QWeb({ templates });
+  const session = getSession();
+
+  return {
+    _t: myTranslateFunction,
+    session: session,
+    qweb: qweb,
+    services: {
+      localStorage: localStorage,
+      rpc: rpc,
+    },
+    debug: false,
+    inMobileMode: true,
+  };
+}
+
+async function start() {
+  const env = await myEnv();
+  mount(App, { target: document.body, env });
+}
+```
+
+## Special Keys
+
+There are two special key/value added by Owl if not provided in the environment:
+the `QWeb` instance and a `browser` object:
+
+- `qweb` will be set to an empty `QWeb` instance. This is absolutely necessary
+  for Owl to be able to render anything
+- `browser`: this is an object that contains some common access points to the
+  browser methods with a side effect. See [browser](browser.md) for more information. Note that the browser object will be removed from the environment in Owl 2.0.

doc/reference/error_handling.md

@@ -0,0 +1,81 @@
+# 🦉 Error Handling 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Example](#example)
+- [Reference](#reference)
+
+## Overview
+
+By default, whenever an error occurs in the rendering of an Owl application, we
+destroy the whole application. Otherwise, we cannot offer any guarantee on the
+state of the resulting component tree. It might be hopelessly corrupted, but
+without any user-visible state.
+
+Clearly, it sometimes is a little bit extreme to destroy the application. This
+is why we have a builtin mechanism to handle rendering errors (and errors coming
+from lifecycle hooks): the `catchError` hook.
+
+## Example
+
+For example, here is how we could implement an `ErrorBoundary` component:
+
+```xml
+<div t-name="ErrorBoundary">
+    <t t-if="state.error">
+        Error handled
+    </t>
+    <t t-else="">
+        <t t-slot="default" />
+    </t>
+</div>
+```
+
+```js
+class ErrorBoundary extends Component {
+  state = useState({ error: false });
+
+  catchError() {
+    this.state.error = true;
+  }
+}
+```
+
+Using the `ErrorBoundary` is then extremely simple:
+
+```xml
+<ErrorBoundary><SomeOtherComponent/></ErrorBoundary>
+```
+
+Note that we need to be careful here: the fallback UI should not throw any
+error, otherwise we risk going into an infinite loop (also, see the page on
+[slots](slots.md) for more information on the `t-slot` directive).
+
+## Reference
+
+Whenever the `catchError` lifecycle hook is implemented, all errors coming from
+sub components rendering and/or lifecycle method calls will be caught and given
+to the `catchError` method. This allows us to properly handle the error, and to
+not break the application.
+
+There are important things to know:
+
+- If an error that occured in the internal rendering cycle is not caught, then
+  Owl will destroy the full application. This is done on purpose, because Owl
+  cannot guarantee that the state is not corrupted from this point on.
+
+- errors coming from event handlers are NOT managed by `catchError` or any other
+  owl mechanism. This is up to the application developer to properly recover
+  from an error
+
+Also, it may be useful to know that whenever an error is caught, it is then
+broadcasted to the application by an event on the `qweb` instance. It may be
+useful, for example, to log the error somewhere.
+
+```js
+env.qweb.on("error", null, function (error) {
+  // do something
+  // react to the error
+});
+```

doc/reference/event_bus.md

@@ -7,7 +7,7 @@ triggering events, and callbacks.
 ```js
 const bus = new owl.core.EventBus();
 
-bus.on("some-event", null, function(...args) {
+bus.on("some-event", null, function (...args) {
   console.log(...args);
 });
 

doc/reference/event_handling.md

@@ -0,0 +1,151 @@
+# 🦉 Event Handling 🦉
+
+## Content
+
+- [Event Handling](#event-handling)
+- [Business DOM Events](#business-dom-events)
+- [Inline Event Handlers](#inline-event-handlers)
+- [Modifiers](#modifiers)
+
+## Event Handling
+
+In a component's template, it is useful to be able to register handlers on DOM
+elements to some specific events. This is what makes a template _alive_. There
+are four different use cases.
+
+1. Register an event handler on a DOM node (_pure_ DOM event)
+2. Register an event handler on a component (_pure_ DOM event)
+3. Register an event handler on a DOM node (_business_ DOM event)
+4. Register an event handler on a component (_business_ DOM event)
+
+A _pure_ DOM event is directly triggered by a user interaction (e.g. a `click`).
+
+```xml
+<button t-on-click="someMethod">Do something</button>
+```
+
+This will be roughly translated in javascript like this:
+
+```js
+button.addEventListener("click", component.someMethod.bind(component));
+```
+
+The suffix (`click` in this example) is simply the name of the actual DOM
+event.
+
+## Business DOM Events
+
+A _business_ DOM event is triggered by a call to `trigger` on a component.
+
+```xml
+<MyComponent t-on-menu-loaded="someMethod" />
+```
+
+```js
+ class MyComponent {
+     someWhere() {
+         const payload = ...;
+         this.trigger('menu-loaded', payload);
+     }
+ }
+```
+
+The call to `trigger` generates an `OwlEvent`, a subclass of [_CustomEvent_](https://developer.mozilla.org/docs/Web/Guide/Events/Creating_and_triggering_events)
+with an additional attribute `originalComponent` (the component that triggered
+the event). The generated event is of type `menu-loaded` and dispatches it on
+the component's DOM element (`this.el`). The event bubbles and is cancelable.
+The parent component listening to event `menu-loaded` will receive the payload
+in its `someMethod` handler (in the `detail` property of the event), whenever
+the event is triggered.
+
+```js
+ class ParentComponent {
+     someMethod(ev) {
+         const payload = ev.detail;
+         ...
+     }
+ }
+```
+
+By convention, we use KebabCase for the name of _business_ events.
+
+The `t-on` directive allows to prebind its arguments. For example,
+
+```xml
+<button t-on-click="someMethod(expr)">Do something</button>
+```
+
+Here, `expr` is a valid Owl expression, so it could be `true` or some variable
+from the rendering context.
+
+### Type Hinting
+
+Note that if you work with Typescript, the `trigger` method is generic on the type of the payload.
+
+You can then describe the type of the event, so you will see typing errors...
+
+```typescript
+this.trigger<MyCustomPayload>("my-custom-event", payload);
+```
+
+```typescript
+myCustomEventHandler(ev: OwlEvent<MyCustomPayload>) { ... }
+```
+
+## Inline Event Handlers
+
+One can also directly specify inline statements. For example,
+
+```xml
+<button t-on-click="state.counter++">Increment counter</button>
+```
+
+Here, `state` must be defined in the rendering context (typically the component)
+as it will be translated to:
+
+```js
+button.addEventListener("click", () => {
+  context.state.counter++;
+});
+```
+
+Warning: inline expressions are evaluated in the context of the template. This
+means that they can access the component methods and properties. But if they set
+a key, the inline statement will actually not modify the component, but a key in
+a sub scope.
+
+```xml
+<button t-on-click="value = 1">Set value to 1 (does not work!!!)</button>
+<button t-on-click="state.value = 1">Set state.value to 1 (work as expected)</button>
+```
+
+## Modifiers
+
+In order to remove the DOM event details from the event handlers (like calls to
+`event.preventDefault`) and let them focus on data logic, _modifiers_ can be
+specified as additional suffixes of the `t-on` directive.
+
+| Modifier   | Description                                                                                                              |
+| ---------- | ------------------------------------------------------------------------------------------------------------------------ |
+| `.stop`    | calls `event.stopPropagation()` before calling the method                                                                |
+| `.prevent` | calls `event.preventDefault()` before calling the method                                                                 |
+| `.self`    | calls the method only if the `event.target` is the element itself                                                        |
+| `.capture` | bind the event handler in [capture](https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener) mode. |
+
+```xml
+<button t-on-click.stop="someMethod">Do something</button>
+```
+
+Note that modifiers can be combined (ex: `t-on-click.stop.prevent`), and that
+the order may matter. For instance `t-on-click.prevent.self` will prevent all
+clicks while `t-on-click.self.prevent` will only prevent clicks on the element
+itself.
+
+Finally, empty handlers are tolerated as they could be defined only to apply
+modifiers. For example,
+
+```xml
+<button t-on-click.stop="">Do something</button>
+```
+
+This will simply stop the propagation of the event.

doc/reference/hooks.md

@@ -17,9 +17,12 @@
   - [`useContext`](#usecontext)
   - [`useRef`](#useref)
   - [`useSubEnv`](#usesubenv)
+  - [`useExternalListener`](#useexternallistener)
   - [`useStore`](#usestore)
   - [`useDispatch`](#usedispatch)
   - [`useGetters`](#usegetters)
+  - [`useComponent`](#usecomponent)
+  - [`useEnv`](#useenv)
   - [Making customized hooks](#making-customized-hooks)
 
 ## Overview
@@ -128,7 +131,7 @@ class SomeComponent extends Component {
 ### One rule
 
 There is only one rule: every hook for a component has to be called in the
-constructor (or in class fields):
+constructor, in the _setup_ method, or in class fields:
 
 ```js
 // ok
@@ -144,6 +147,13 @@ class SomeComponent extends Component {
   }
 }
 
+// also ok
+class SomeComponent extends Component {
+  setup() {
+    this.state = useState({ value: 0 });
+  }
+}
+
 // not ok: this is executed after the constructor is called
 class SomeComponent extends Component {
   async willStart() {
@@ -152,9 +162,15 @@ class SomeComponent extends Component {
 }
 ```
 
-In a hook, the `Component.current` static property is the reference to the
-component instance that is currently being created. Hooks need to be called in
-the constructor to ensure that this reference is properly set.
+As you can see, the `useState` hook does not need to be given a reference to
+the component. This is possible because there is a way to get a reference to the
+current component: the `Component.current` static property is the reference to the
+component instance that is currently being created.
+
+Hooks need to be called in the constructor to ensure that this reference is
+properly set. This is also a good thing for performance reasons (Owl can use
+this to optimize its implementation), and for a clean architecture (this makes
+it easier for developers to understand what is really happening in a component).
 
 ### `useState`
 
@@ -181,6 +197,9 @@ class Counter extends owl.Component {
 }
 ```
 
+It is important to remember that `useState` only works with objects or arrays. It
+is necessary, since Owl needs to react to a change in state.
+
 ### `onMounted`
 
 `onMounted` is not a user hook, but is a building block designed to help make useful
@@ -249,7 +268,7 @@ function useLoader() {
   }
 
   onWillStart(() => updateRecord(component.props.id));
-  onWillUpdateProps(nextProps => updateRecord(nextProps.id));
+  onWillUpdateProps((nextProps) => updateRecord(nextProps.id));
 
   return record;
 }
@@ -287,6 +306,7 @@ class Parent extends Component {
     // here, if component is mounted, refs are active:
     // - this.divRef.el is the div HTMLElement
     // - this.subRef.comp is the instance of the sub component
+    // - this.subRef.el is the root HTML node of the sub component (i.e. this.subRef.comp.el)
   }
 }
 ```
@@ -294,11 +314,14 @@ class Parent extends Component {
 As shown by the example above, html elements are accessed by using the `el`
 key, and components references are accessed with `comp`.
 
-Note: if used on a component, the reference will be set in the `refs`
-variable between `willPatch` and `patched`.
+Notes:
+
+- if used on a component, the reference will be set in the `refs`
+  variable between `willPatch` and `patched`,
+- on a component, accessing `ref.el` will get the root node of the component.
 
 The `t-ref` directive also accepts dynamic values with string interpolation
-(like the [`t-attf-`](qweb.md#dynamic-attributes) and
+(like the [`t-attf-`](qweb_templating_language.md#dynamic-attributes) and
 `t-component` directives). For example,
 
 ```xml
@@ -341,6 +364,17 @@ will be added to the parent environment. Note that it will extend, not replace
 the parent environment. And of course, the parent environment will not be
 affected.
 
+### `useExternalListener`
+
+The `useExternalListener` hook helps solve a very common problem: adding and removing
+a listener on some target whenever a component is mounted/unmounted. For example,
+a dropdown menu (or its parent) may need to listen to a `click` event on `window`
+to be closed:
+
+```js
+useExternalListener(window, "click", this.closeMenu);
+```
+
 ### `useStore`
 
 The `useStore` hook is the entry point for a component to connect to the store.
@@ -356,6 +390,16 @@ The `useDispatch` hook is the way for components to get a reference to the store
 The `useGetters` hook is the way for components to get a reference to the store
 getters. See the [store documentation](store.md) for more information.
 
+### `useComponent`
+
+The `useComponent` hook is useful as a building block for some customized hooks,
+that may need a reference to the component calling them.
+
+### `useEnv`
+
+The `useEnv` hook is useful as a building block for some customized hooks,
+that may need a reference to the env of the component calling them.
+
 ### Making customized hooks
 
 Hooks are a wonderful way to organize the code of a complex component by feature
@@ -410,13 +454,11 @@ not the solution to every problem.
 
   ```js
   function useRouter() {
-    return Component.current.env.router;
+    const env = useEnv();
+    return env.router;
   }
   ```
 
   This means that we give control to the application developer to create the
   router, which is good, so they can set it up, subclass it, ... And then, to
   test our components, we can just add a mock router in the environment.
-
-Note: the code above makes use of the `Component.current` property. This is the
-way hooks are able to get a reference to the component currently being created.

doc/reference/misc.md

@@ -0,0 +1,133 @@
+# 🦉 Miscellaneous 🦉
+
+## Content
+
+- [Portal](#portal)
+- [AsyncRoot](#asyncroot)
+
+## `Portal`
+
+### Overview
+
+The component `Portal` is meant to be used as a transparent way to 'teleport' a piece
+of DOM to the node represented by its sole `target` props.
+
+This component aims at helping the implementation of the needed infrastructure
+for modals (as in `bootstrap-modal`).
+
+### Usage
+
+The content it will teleport is defined within the `<Portal>` node and
+internally uses the `default` [Slot](slots.md).
+
+This slot must contain only **one** node, which in turn can have as many children as necessary.
+
+The element under which the content will be teleported is represented as a selector
+by the `target` props which only accepts a string as value.
+
+The `target` props only supports static selector, and is not meant to be passed to `Portal`
+as a variable. Namely, `<Portal target="'body'" />` is the intended use.
+By contrast, `<Portal target="state.target" />` is not supported.
+
+The component `Portal` has no particular state, rather it is meant to be a slave to its parent,
+and ultimately just a way for the parent to teleport a piece of its own DOM elsewhere.
+
+The `Portal`'s root node is always `<portal/>` and is placed where the teleported content
+_would have_ been. It is this element that the [teleported events](#expected-behaviors) are re-directed on.
+
+### Example
+
+The canonic use-case is to implement a Dialog, where a Component may choose to break the natural
+workflow to help the user put in some data, which it could use later on.
+
+JavaScript:
+
+```js
+const { Component, mount } = owl;
+const { Portal } = owl.misc;
+
+class TeleportedComponent extends Component {}
+class App extends Component {
+  static components = { Portal, TeleportedComponent };
+}
+
+mount(App, { target: document.body });
+```
+
+XML:
+
+```xml
+<templates>
+    <div t-name="TeleportedComponent">
+        <span>I will move soon enough</span>
+    </div>
+
+    <div t-name="App">
+        <span>I am like the rest of us</span>
+        <Portal target="'body'">
+            <TeleportedComponent />
+        </Portal>
+    </div>
+</templates>
+```
+
+In this example, the `Portal` component will teleport the `TeleportedComponent`'s `div` as a child of the `body`.
+`TeleportedComponent` is acting as a Dialog here.
+
+The resulting DOM will look like:
+
+```xml
+<body>
+    <div>
+        <span>I am like the rest of us</span>
+        <portal></portal>
+    </div>
+    <div>
+        <span>I will move soon enough</span>
+    </div>
+</body>
+```
+
+### Expected Behaviors
+
+The teleported piece is updated as any other `Component`'s DOM and in the same sequence.
+Namely the teleported piece will be updated in function of its parents components, and patched as
+a normal child.
+
+The [_business_ events](event_handling.md#business-dom-events) triggered by a child component will be stopped
+to not bubble outside of the `target`. They will, on the other hand, be re-directed onto the
+`Portal`'s root node and bubble up the DOM as if it were triggered by a regular child component.
+
+Beware that those re-directed events are copies of the original event.
+They have:
+
+- The same payload.
+- The same `originalComponent` than their original counterpart,
+  that is the actual Component that triggered it.
+- A **different** `target` property than their original counterpart.
+  The `target` of a re-directed event is necessarily the `Portal`'s root node.
+
+Pure DOM events do not follow this pattern and are free to bubble their natural, unaltered way
+up to the `body`.
+
+## `AsyncRoot`
+
+When this component is used, a new rendering sub tree is created, such that the
+rendering of that component (and its children) is not tied to the rendering of
+the rest of the interface. It can be used on an asynchronous component, to
+prevent it from delaying the rendering of the whole interface, or on a
+synchronous one, such that its rendering isn't delayed by other (asynchronous)
+components. Note that this directive has no effect on the first rendering, but
+only on subsequent ones (triggered by state or props changes).
+
+```xml
+<div t-name="ParentComponent">
+  <SyncChild />
+  <AsyncRoot>
+     <AsyncChild/>
+  </AsyncRoot>
+</div>
+```
+
+The `AsyncRoot` assumes that there is exactly one root node inside it. It can
+be a dom node or a component.

doc/reference/mounting.md

@@ -0,0 +1,60 @@
+# 🦉 Mounting an application 🦉
+
+## Content
+
+- [Overview](#overview)
+- [API](#api)
+
+## Overview
+
+Mounting an Owl application is done by using the `mount` method (available in
+`owl.mount` if you are using the iife build, or it can be directly imported
+from `owl` if you are using a module system):
+
+```js
+const mount = { owl }; // if owl is available as an object
+
+const env = { ... };
+const app = await mount(MyComponent, { target: document.body, env });
+```
+
+Another example:
+
+```js
+const config = {
+  env: ...,
+  props: ...,
+  target: document.body,
+  position: "self",
+};
+const app = await mount(App, config);
+```
+
+A common way to initialize an application is to first setup an environment,
+then to call the `mount` method.
+
+## API
+
+Mount takes two parameters:
+
+- `C`, which should be a component class (NOT instance),
+- `params`, which is an object with the following keys:
+  - `target (HTMLElement | DocumentFragment)`: the target of the mount operation
+  - `env (optional, Env)` an environment
+  - `position (optional, "first-child" | "last-child" | "self")` the position
+    where it should be mounted (see below for more informations)
+  - `props (optional, any)`: some initial values that are given as props. Useful
+    when the root component is configurable, or when testing sub components
+
+Here are the various positions supported by Owl:
+
+- `first-child`: with this option, the component will be prepended inside the target,
+- `last-child` (default value): with this option, the component will be
+  appended in the target element,
+- `self`: the target will be used as the root element for the component. This
+  means that the target has to be an HTMLElement (and not a document fragment).
+  In this situation, it is possible that the component cannot be unmounted. For
+  example, if its target is `document.body`.
+
+The `mount` method returns a promise that resolves to the instance of the created
+component.

doc/reference/observer.md

@@ -15,7 +15,7 @@ use cases, there is no need to directly instantiate an observer.
 For example, this code will display `update` in the console:
 
 ```javascript
-const observer = new owl.Observer();
+const observer = new owl.core.Observer();
 observer.notifyCB = () => console.log("update");
 const obj = observer.observe({ a: { b: 1 } });
 
@@ -39,14 +39,14 @@ is incremented every time the value is observed. Sometimes, it can be useful
 to obtain that number:
 
 ```js
-const observer = new owl.Observer();
+const observer = new owl.core.Observer();
 const obj = observer.observe({ a: { b: 1 } });
 
-observer.deepRevNumber(obj.a); // 1
+observer.revNumber(obj.a); // 1
 obj.a.b = 2;
 
-observer.deepRevNumber(obj.a); // 2
+observer.revNumber(obj.a); // 2
 ```
 
-The `deepRevNumber` can also return 0, which indicates that the value is not
+The `revNumber` can also return 0, which indicates that the value is not
 observed.

doc/reference/props.md

@@ -0,0 +1,97 @@
+# 🦉 Props 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Definition](#definition)
+- [Good Practices](#good-practices)
+- [Dynamic Props](#dynamic-props)
+
+## Overview
+
+In Owl, `props` (short for _properties_) is an object which contains every piece
+of data given to a component by its parent.
+
+```js
+class Child extends Component {
+  static template = xml`<div><t t-esc="props.a"/><t t-esc="props.b"/></div>`;
+}
+
+class Parent extends Component {
+  static template = xml`<div><Child a="state.a" b="'string'"/></div>`;
+  static components = { Child };
+  state = useState({ a: "fromparent" });
+}
+```
+
+In this example, the `Child` component receives two props from its parent: `a`
+and `b`. They are collected into a `props` object by Owl, with each value being
+evaluated in the context of the parent. So, `props.a` is equal to `'fromparent'` and
+`props.b` is equal to `'string'`.
+
+Note that `props` is an object that only makes sense from the perspective of the
+child component.
+
+## Definition
+
+The `props` object is made of every attributes defined on the template, with the
+following exceptions:
+
+- every attribute starting with `t-` are not props (they are QWeb directives),
+- `style` and `class` attributes are excluded as well (they are applied by Owl on
+  the root element of the component).
+
+In the following example:
+
+```xml
+<div>
+    <ComponentA a="state.a" b="'string'"/>
+    <ComponentB t-if="state.flag" model="model"/>
+    <ComponentC style="color:red;" class="left-pane" />
+</div>
+```
+
+the `props` object contains the following keys:
+
+- for `ComponentA`: `a` and `b`,
+- for `ComponentB`: `model`,
+- for `ComponentC`: empty object
+
+## Good Practices
+
+A `props` object is a collection of values that come from the parent. As such,
+they are owned by the parent, and should never be modified by the child:
+
+```js
+class MyComponent extends Component {
+  constructor(parent, props) {
+    super(parent, props);
+    props.a.b = 43; // Never do that!!!
+  }
+}
+```
+
+Props should be considered readonly, from the perspective of the child component.
+If there is a need to modify them, then the request to update them should be
+sent to the parent (for example, with an event).
+
+Any value can go in a props. Strings, objects, classes, or even callbacks could
+be given to a child component (but then, in the case of callbacks, communicating
+with events seems more appropriate).
+
+## Dynamic Props
+
+The `t-props` directive can be used to specify totally dynamic props:
+
+```xml
+<div t-name="ParentComponent">
+    <Child t-props="some.obj"/>
+</div>
+```
+
+```js
+class ParentComponent {
+  static components = { Child };
+  some = { obj: { a: 1, b: 2 } };
+}
+```

doc/reference/props_validation.md

@@ -0,0 +1,103 @@
+# 🦉 Props Validation 🦉
+
+As an application becomes complex, it may be quite unsafe to define props in an informal way. This leads to two issues:
+
+- hard to tell how a component should be used, by looking at its code.
+- unsafe, it is easy to send wrong props into a component, either by refactoring a component, or one of its parents.
+
+A props type system solves both issues, by describing the types and shapes
+of the props. Here is how it works in Owl:
+
+- `props` key is a static key (so, different from `this.props` in a component instance)
+- it is optional: it is ok for a component to not define a `props` key.
+- props are validated whenever a component is created/updated
+- props are only validated in `dev` mode (see [config page](config.md#mode))
+- if a key does not match the description, an error is thrown
+- it validates keys defined in (static) `props`. Additional keys given by the
+  parent will cause an error.
+
+For example:
+
+```js
+class ComponentA extends owl.Component {
+    static props = ['id', 'url'];
+
+    ...
+}
+
+class ComponentB extends owl.Component {
+  static props = {
+    count: {type: Number},
+    messages: {
+      type: Array,
+      element: {type: Object, shape: {id: Boolean, text: String }
+    },
+   date: Date,
+   combinedVal: [Number, Boolean]
+  };
+
+  ...
+}
+```
+
+- it is an object or a list of strings
+- a list of strings is a simplified props definition, which only lists the name
+  of the props. Also, if the name ends with `?`, it is considered optional.
+- all props are by default required, unless they are defined with `optional: true`
+  (in that case, validation is only done if there is a value)
+- valid types are: `Number, String, Boolean, Object, Array, Date, Function`, and all
+  constructor functions (so, if you have a `Person` class, it can be used as a type)
+- arrays are homogeneous (all elements have the same type/shape)
+
+For each key, a `prop` definition is either a boolean, a constructor, a list of constructors, or an object:
+
+- a boolean: indicate that the props exists, and is mandatory.
+- a constructor: this should describe the type, for example: `id: Number` describe
+  the props `id` as a number
+- a list of constructors. In that case, this means that we allow more than one
+  type. For example, `id: [Number, String]` means that `id` can be either a string
+  or a number.
+- an object. This makes it possible to have more expressive definition. The following sub keys are then allowed (but not mandatory):
+  - `type`: the main type of the prop being validated
+  - `element`: if the type was `Array`, then the `element` key describes the type of each element in the array. If it is not set, then we only validate the array, not its elements,
+  - `shape`: if the type was `Object`, then the `shape` key describes the interface of the object. If it is not set, then we only validate the object, not its elements,
+  - `validate`: this is a function which should return a boolean to determine if
+    the value is valid or not. Useful for custom validation logic.
+
+Examples:
+
+```js
+  // only the existence of those 3 keys is documented
+  static props = ['message', 'id', 'date'];
+```
+
+```js
+  // size is optional
+  static props = ['message', 'size?'];
+```
+
+```js
+  static props = {
+    messageIds: {type: Array, element: Number},  // list of number
+    otherArr: {type: Array},   // just array. no validation is made on sub elements
+    otherArr2: Array,   // same as otherArr
+    someObj: {type: Object},  // just an object, no internal validation
+    someObj2: {
+      type: Object,
+      shape: {
+        id: Number,
+        name: {type: String, optional: true},
+        url: String
+      ]},    // object, with keys id (number), name (string, optional) and url (string)
+    someFlag: Boolean,     // a boolean, mandatory (even if `false`)
+    someVal: [Boolean, Date],   // either a boolean or a date
+    otherValue: true,     // indicates that it is a prop
+    kindofsmallnumber: {
+      type: Number,
+      validate: n => (0 <= n && n <= 10)
+    },
+    size: {
+      validate:  e => ["small", "medium", "large"].includes(e)
+    },
+  };
+```

doc/reference/qweb_engine.md

@@ -0,0 +1,151 @@
+# 🦉 QWeb Engine 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Reference](#reference)
+
+## Overview
+
+[QWeb](https://www.odoo.com/documentation/13.0/reference/qweb.html) is the primary
+templating engine used by Odoo. The QWeb class in the OWL project is an
+implementation of that specification with a few interesting points:
+
+- it compiles templates into functions that output a virtual DOM instead of a
+  string. This is necessary for the component system.
+- it has a few extra directives: `t-component`, `t-on`, ...
+
+We present in this section the engine, not the templating language.
+
+## Reference
+
+This section is about the javascript code that implements the `QWeb` specification.
+Owl exports a `QWeb` class in `owl.QWeb`. To use it, it just needs to be
+instantiated:
+
+```js
+const qweb = new owl.QWeb();
+```
+
+Its API is quite simple:
+
+- **`constructor(config)`**: constructor. Takes an optional configuration object
+  with an optional `templates` string to add initial
+  templates (see `addTemplates` for more information on format of the string)
+  and an optional `translateFn` translate function (see the section on
+  [translations](#translations)).
+
+  ```js
+  const qweb = new owl.QWeb({ templates: TEMPLATES, translateFn: _t });
+  ```
+
+- **`addTemplate(name, xmlStr, allowDuplicate)`**: add a specific template.
+
+  ```js
+  qweb.addTemplate("mytemplate", "<div>hello</div>");
+  ```
+
+  If the optional `allowDuplicate` is set to `true`, then `QWeb` will simply
+  ignore templates added for a second time. Otherwise, `QWeb` will crash.
+
+- **`addTemplates(xmlStr)`**: add a list of templates (identified by `t-name`
+  attribute).
+
+  ```js
+  const TEMPLATES = `
+    <templates>
+      <div t-name="App" class="main">main</div>
+      <div t-name="OtherComponent">other component</div>
+    </templates>`;
+  qweb.addTemplates(TEMPLATES);
+  ```
+
+- **`render(name, context, extra)`**: renders a template. This returns a `vnode`,
+  which is a virtual representation of the DOM (see [vdom doc](../miscellaneous/vdom.md)).
+
+  ```js
+  const vnode = qweb.render("App", component);
+  ```
+
+- **`renderToString(name, context)`**: renders a template, but returns an html
+  string.
+
+  ```js
+  const str = qweb.renderToString("someTemplate", somecontext);
+  ```
+
+- **`registerTemplate(name, template)`**: static function to register a global
+  QWeb template. This is useful for commonly used components accross the
+  application, and for making a template available to an application without
+  having a reference to the actual QWeb instance.
+
+  ```js
+  QWeb.registerTemplate("mytemplate", `<div>some template</div>`);
+  ```
+
+- **`registerComponent(name, Component)`**: static function to register an OWL Component
+  to QWeb's global registry. Globally registered Components can be used in
+  templates (see the `t-component` directive). This is useful for commonly used
+  components accross the application.
+
+  ```js
+  class Dialog extends owl.Component { ... }
+  QWeb.registerComponent("Dialog", Dialog);
+
+  ...
+
+  class ParentComponent extends owl.Component { ... }
+  qweb.addTemplate("ParentComponent", "<div><Dialog/></div>");
+  ```
+
+In some way, a `QWeb` instance is the core of an Owl application. It is the only
+mandatory element of an [environment](environment.md). As such, it
+has an extra responsibility: it can act as an event bus for internal communication
+between Owl classes. This is the reason why `QWeb` actually extends [EventBus](event_bus.md).
+
+### Translations
+
+If properly setup, Owl QWeb engine can translate all rendered templates. To do
+so, it needs a translate function, which takes a string and returns a string.
+
+For example:
+
+```js
+const translations = {
+  hello: "bonjour",
+  yes: "oui",
+  no: "non",
+};
+const translateFn = (str) => translations[str] || str;
+
+const qweb = new QWeb({ translateFn });
+```
+
+Once setup, all rendered templates will be translated using `translateFn`:
+
+- each text node will be replaced with its translation,
+- each of the following attribute values will be translated as well: `title`,
+  `placeholder`, `label` and `alt`,
+- translating text nodes can be disabled with the special attribute `t-translation`,
+  if its value is `off`.
+
+So, with the above `translateFn`, the following templates:
+
+```xml
+<div>hello</div>
+<div t-translation="off">hello</div>
+<div>Are you sure?</div>
+<input placeholder="hello" other="yes"/>
+```
+
+will be rendered as:
+
+```xml
+<div>bonjour</div>
+<div>hello</div>
+<div>Are you sure?</div>
+<input placeholder="bonjour" other="yes"/>
+```
+
+Note that the translation is done during the compilation of the template, not
+when it is rendered.

doc/reference/qweb_templating_language.md

@@ -1,10 +1,9 @@
-# 🦉 QWeb 🦉
+# 🦉 QWeb Templating Language🦉
 
 ## Content
 
 - [Overview](#overview)
 - [Directives](#directives)
-- [QWeb Engine](#qweb-engine)
 - [Reference](#reference)
   - [White Spaces](#white-spaces)
   - [Root Nodes](#root-nodes)
@@ -14,24 +13,24 @@
   - [Setting Variables](#setting-variables)
   - [Conditionals](#conditionals)
   - [Dynamic Attributes](#dynamic-attributes)
+  - [Dynamic Tag Names](#dynamic-tag-names)
   - [Loops](#loops)
   - [Rendering Sub Templates](#rendering-sub-templates)
+  - [Dynamic Sub Templates](#dynamic-sub-templates)
+  - [Translations](#translations)
   - [Debugging](#debugging)
 
 ## Overview
 
-[QWeb](https://www.odoo.com/documentation/13.0/reference/qweb.html) is the primary templating engine used by Odoo. It is based on the XML format, and used
+[QWeb](https://www.odoo.com/documentation/13.0/reference/qweb.html) is the primary
+templating engine used by Odoo. It is based on the XML format, and used
 mostly to generate HTML. In OWL, QWeb templates are compiled into functions that
 generate a virtual dom representation of the HTML.
 
-Template directives are specified as XML attributes prefixed with `t-`, for instance `t-if` for conditionals, with elements and other attributes being rendered directly.
-
-To avoid element rendering, a placeholder element `<t>` is also available, which executes its directive but doesn’t generate any output in and of itself.
-
 ```xml
 <div>
     <span t-if="somecondition">Some string</span>
-    <ul t-else="1">
+    <ul t-else="">
         <li t-foreach="messages" t-as="message">
             <t t-esc="message"/>
         </li>
@@ -39,131 +38,49 @@ To avoid element rendering, a placeholder element `<t>` is also available, which
 </div>
 ```
 
-The QWeb class in the OWL project is an implementation of that specification
-with a few interesting points:
+Template directives are specified as XML attributes prefixed with `t-`, for
+instance `t-if` for conditionals, with elements and other attributes being
+rendered directly.
 
-- it compiles templates into functions that output a virtual DOM instead of a
-  string. This is necessary for the component system.
-- it has a few extra directives: `t-component`, `t-on`, ...
+To avoid element rendering, a placeholder element `<t>` is also available, which
+executes its directive but doesn’t generate any output in and of itself.
+
+We present in this section the templating language, including its Owl specific
+extensions.
 
 ## Directives
 
-We present here a list of all standard QWeb directives:
+For reference, here is a list of all standard QWeb directives:
 
-| Name                           | Description                                                  |
-| ------------------------------ | ------------------------------------------------------------ |
-| `t-esc`                        | [Outputting safely a value](#outputting-data)                |
-| `t-raw`                        | [Outputting value, without escaping](#outputting-data)       |
-| `t-set`, `t-value`             | [Setting variables](#setting-variables)                      |
-| `t-if`, `t-elif`, `t-else`,    | [conditionally rendering](#conditionals)                     |
-| `t-foreach`, `t-as`            | [Loops](#loops)                                              |
-| `t-att`, `t-attf-*`, `t-att-*` | [Dynamic attributes](#dynamic-attributes)                    |
-| `t-call`                       | [Rendering sub templates](#rendering-sub-templates)          |
-| `t-debug`, `t-log`             | [Debugging](#debugging)                                      |
-| `t-name`                       | [Defining a template (not really a directive)](#qweb-engine) |
+| Name                           | Description                                                    |
+| ------------------------------ | -------------------------------------------------------------- |
+| `t-esc`                        | [Outputting safely a value](#outputting-data)                  |
+| `t-raw`                        | [Outputting value, without escaping](#outputting-data)         |
+| `t-set`, `t-value`             | [Setting variables](#setting-variables)                        |
+| `t-if`, `t-elif`, `t-else`,    | [conditionally rendering](#conditionals)                       |
+| `t-foreach`, `t-as`            | [Loops](#loops)                                                |
+| `t-att`, `t-attf-*`, `t-att-*` | [Dynamic attributes](#dynamic-attributes)                      |
+| `t-call`                       | [Rendering sub templates](#rendering-sub-templates)            |
+| `t-debug`, `t-log`             | [Debugging](#debugging)                                        |
+| `t-translation`                | [Disabling the translation of a node](#translations)           |
+| `t-name`                       | [Defining a template (not really a directive)](qweb_engine.md) |
 
 The component system in Owl requires additional directives, to express various
 needs. Here is a list of all Owl specific directives:
 
-| Name                                                   | Description                                                                         |
-| ------------------------------------------------------ | ----------------------------------------------------------------------------------- |
-| `t-component`, `t-props`, `t-keepalive`, `t-asyncroot` | [Defining a sub component](component.md#composition)                                |
-| `t-ref`                                                | [Setting a reference to a dom node or a sub component](component.md#references)     |
-| `t-key`                                                | [Defining a key (to help virtual dom reconciliation)](component.md#t-key-directive) |
-| `t-on-*`                                               | [Event handling](component.md#event-handling)                                       |
-| `t-transition`                                         | [Defining an animation](animations.md#css-transitions)                              |
-| `t-slot`                                               | [Rendering a slot](component.md#slots)                                              |
-| `t-model`                                              | [Form input bindings](component.md#form-input-bindings)                             |
-
-## QWeb Engine
-
-This section is about the javascript code that implements the `QWeb` specification.
-Owl exports a `QWeb` class in `owl.QWeb`. To use it, it just needs to be
-instantiated:
-
-```js
-const qweb = new owl.QWeb();
-```
-
-Its API is quite simple:
-
-- **`constructor(data)`**: constructor. Takes an optional string to add initial
-  templates (see `addTemplates` for more information on format of the string).
-
-  ```js
-  const qweb = new owl.QWeb(TEMPLATES);
-  ```
-
-- **`addTemplate(name, xmlStr, allowDuplicate)`**: add a specific template.
-
-  ```js
-  qweb.addTemplate("mytemplate", "<div>hello</div>");
-  ```
-
-  If the optional `allowDuplicate` is set to `true`, then `QWeb` will simply
-  ignore templates added for a second time. Otherwise, `QWeb` will crash.
-
-- **`addTemplates(xmlStr)`**: add a list of templates (identified by `t-name`
-  attribute).
-
-  ```js
-  const TEMPLATES = `
-    <templates>
-      <div t-name="App" class="main">main</div>
-      <div t-name="OtherComponent">other component</div>
-    </templates>`;
-  qweb.addTemplates(TEMPLATES);
-  ```
-
-- **`render(name, context, extra)`**: renders a template. This returns a `vnode`,
-  which is a virtual representation of the DOM (see [vdom doc](vdom.md)).
-
-  ```js
-  const vnode = qweb.render("App", component);
-  ```
-
-- **`renderToString(name, context)`**: renders a template, but returns an html
-  string.
-
-  ```js
-  const str = qweb.renderToString("someTemplate", somecontext);
-  ```
-
-- **`registerTemplate(name, template)`**: static function to register a global
-  QWeb template. This is useful for commonly used components accross the
-  application, and for making a template available to an application without
-  having a reference to the actual QWeb instance.
-
-  ```js
-  QWeb.registerTemplate("mytemplate", `<div>some template</div>`);
-  ```
-
-- **`registerComponent(name, Component)`**: static function to register an OWL Component
-  to QWeb's global registry. Globally registered Components can be used in
-  templates (see the `t-component` directive). This is useful for commonly used
-  components accross the application.
-
-  ```js
-  class Dialog extends owl.Component { ... }
-  QWeb.registerComponent("Dialog", Dialog);
-
-  ...
-
-  class ParentComponent extends owl.Component { ... }
-  qweb.addTemplate("ParentComponent", "<div><Dialog/></div>");
-  ```
-
-In some way, a `QWeb` instance is the core of an Owl application. It is the only
-mandatory element of an [environment](component.md#environment). As such, it
-has an extra responsibility: it can act as an event bus for internal communication
-between Owl classes. This is the reason why `QWeb` actually extends [EventBus](event_bus.md).
+| Name                     | Description                                                                     |
+| ------------------------ | ------------------------------------------------------------------------------- |
+| `t-component`, `t-props` | [Defining a sub component](component.md#composition)                            |
+| `t-ref`                  | [Setting a reference to a dom node or a sub component](component.md#references) |
+| `t-key`                  | [Defining a key (to help virtual dom reconciliation)](#loops)                   |
+| `t-on-*`                 | [Event handling](event_handling.md)                                             |
+| `t-transition`           | [Defining an animation](animations.md#css-transitions)                          |
+| `t-slot`                 | [Rendering a slot](slots.md)                                                    |
+| `t-model`                | [Form input bindings](component.md#form-input-bindings)                         |
+| `t-tag`                  | [Rendering nodes with dynamic tag name](#dynamic-tag-names)                     |
 
 ## Reference
 
-We define in this section the specification of how `QWeb` templates should be
-rendered. Note that we only document here the standard QWeb specification. Owl
-specific extensions are documented in various other parts of the documentation.
-
 ### White Spaces
 
 White spaces in a template are handled in a special way:
@@ -187,7 +104,7 @@ precisely, the result of a template rendering should have a single root node:
 <!–– ok: result has one single root node ––>
 <t>
     <div t-if="someCondition">foo</div>
-    <span t-else="1">bar</span>
+    <span t-else="">bar</span>
 </t>
 ```
 
@@ -201,7 +118,7 @@ root nodes.
 ### Expression Evaluation
 
 QWeb expressions are strings that will be processed at compile time. Each variable in
-the javascript expression will be replaced by a lookup in the context (so, the
+the javascript expression will be replaced with a lookup in the context (so, the
 component). For example, `a + b.c(d)` will be converted into:
 
 ```js
@@ -234,14 +151,14 @@ It is useful to explain the various rules that apply on these expressions:
 3. it can use a few special operators to avoid using symbols such as `<`, `>`,
    `&` or `|`. This is useful to make sure that we still write valid XML.
 
-   | Word  | will be replaced by |
-   | ----- | ------------------- |
-   | `and` | `&&`                |
-   | `or`  | `\|\|`              |
-   | `gt`  | `>`                 |
-   | `gte` | `>=`                |
-   | `lt`  | `<`                 |
-   | `lte` | `<=`                |
+   | Word  | replaced with |
+   | ----- | ------------- |
+   | `and` | `&&`          |
+   | `or`  | `\|\|`        |
+   | `gt`  | `>`           |
+   | `gte` | `>=`          |
+   | `lt`  | `<`           |
+   | `lte` | `<=`          |
 
    So, one can write this:
 
@@ -409,6 +326,22 @@ values) or a pair `[key, value]`. For example:
 <div t-att="['a', 'b']"/> <!-- <div a="b"></div> -->
 ```
 
+### Dynamic tag names
+
+When writing generic components or templates, the specific concrete tag for an
+HTML element is not known yet. In those situations, the `t-tag` directive is
+useful. It simply evaluates dynamically an expression to use as a tag name. The
+template:
+
+```xml
+<t t-tag="tag">
+    <span>content</span>
+</t>
+```
+
+will be rendered as `<div><span>content</span></div>` if the `tag` context key
+is set to `div`.
+
 ### Loops
 
 QWeb has an iteration directive `t-foreach` which take an expression returning the
@@ -443,7 +376,7 @@ is equivalent to the previous example.
 or an object (the current item will be the current key).
 
 In addition to the name passed via t-as, `t-foreach` provides a few other
-variables for various data points (note: `$as` will be replaced by the name
+variables for various data points (note: `$as` will be replaced with the name
 passed to `t-as`):
 
 - `$as_value`: the current iteration value, identical to `$as` for lists and
@@ -474,6 +407,81 @@ into the global context.
 <!-- new_variable undefined -->
 ```
 
+Even though Owl tries to be as declarative as possible, the DOM does not fully
+expose its state declaratively in the DOM tree. For example, the scrolling state,
+the current user selection, the focused element or the state of an input are not
+set as attribute in the DOM tree. This is why we use a virtual dom
+algorithm to keep the actual DOM node as much as possible.
+
+However, in some situations, this is not enough, and we need to help Owl decide
+if an element is actually the same, or is a different element with the same
+properties.
+
+Consider the following situation: we have a list of two items `[{text: "a"}, {text: "b"}]`
+and we render them in this template:
+
+```xml
+<p t-foreach="items" t-as="item"><t t-esc="item.text"/></p>
+```
+
+The result will be two `<p>` tags with text `a` and `b`. Now, if we swap them,
+and rerender the template, Owl needs to know what the intent is:
+
+- should Owl actually swap the DOM nodes,
+- or should it keep the DOM nodes, but with an updated text content?
+
+This might look trivial, but it actually matters. These two possibilities lead
+to different results in some cases. For example, if the user selected the text
+of the first `p`, swapping them will keep the selection while updating the
+text content will not.
+
+There are many other cases where this is important: `input` tags with their
+value, css classes and animations, scroll position...
+
+So, the `t-key` directive is used to give an identity to an element. It allows
+Owl to understand if different elements of a list are actually different or not.
+
+The above example could be modified by adding an ID: `[{id: 1, text: "a"}, {id: 2, text: "b"}]`.
+Then, the template could look like this:
+
+```xml
+<p t-foreach="items" t-as="item" t-key="item.id"><t t-esc="item.text"/></p>
+```
+
+The `t-key` directive is useful for lists (`t-foreach`). A key should be
+a unique number or string (objects will not work: they will be cast to the
+`"[object Object]"` string, which is obviously not unique).
+
+Also, the key can be set on a `t` tag or on its children. The following variations
+are all equivalent:
+
+```xml
+<p t-foreach="items" t-as="item" t-key="item.id">
+  <t t-esc="item.text"/>
+</p>
+
+<t t-foreach="items" t-as="item" t-key="item.id">
+  <p t-esc="item.text"/>
+</t>
+
+<t t-foreach="items" t-as="item">
+  <p t-key="item.id" t-esc="item.text"/>
+</t>
+```
+
+If there is no `t-key` directive, Owl will use the index as a default key.
+
+Note: the `t-foreach` directive only accepts arrays (lists) or objects. It does
+not work with other iterables, such as `Set`. However, it is only a matter of
+using the `...` javascript operator. For example:
+
+```xml
+<t t-foreach="...items" t-as="item">...</t>
+```
+
+The `...` operator will convert the `Set` (or any other iterables) into a list,
+which will work with Owl QWeb.
+
 ### Rendering Sub Templates
 
 QWeb templates can be used for top level rendering, but they can also be used
@@ -522,6 +530,46 @@ will result in :
 </div>
 ```
 
+This can be used to define variables scoped to a sub template:
+
+```xml
+<t t-call="other-template">
+    <t t-set="var" t-value="1"/>
+</t>
+<!-- "var" does not exist here -->
+```
+
+### Dynamic sub templates
+
+The `t-call` directive can also be used to dynamically call a sub template,
+using string interpolation. For example:
+
+```xml
+<div t-name="main-template">
+    <t t-call="{{template}}">
+        <em>content</em>
+    </t>
+</div>
+```
+
+Here, the name of the template is obtained from the `template` value in the
+template rendering context.
+
+### Translations
+
+By default, QWeb specify that templates should be translated. If this behaviour
+is not wanted, there is a `t-translation` directive which can turn off
+translations (if it is set to the `off` value), with the following rules:
+
+- each text node will be replaced with its translation,
+- each of the following attribute values will be translated as well: `title`,
+  `placeholder`, `label` and `alt`,
+- translating text nodes can be disabled with the special attribute `t-translation`,
+  if its value is `off`.
+
+See [here](qweb_engine.md#translations) for more information on how to setup a
+translate function in Owl QWeb.
+
 ### Debugging
 
 The javascript QWeb implementation provides two useful debugging directives:
@@ -530,7 +578,7 @@ The javascript QWeb implementation provides two useful debugging directives:
 
 ```xml
 <t t-if="a_test">
-    <t t-debug="">
+    <t t-debug=""/>
 </t>
 ```
 

doc/reference/router.md

@@ -67,6 +67,9 @@ function makeEnvironment() {
     await env.router.start();
     return env;
 }
+
+App.env = makeEnvironment();
+// create root component here
 ```
 
 Notice that the router needs to be started. This is an asynchronous operation

doc/reference/slots.md

@@ -0,0 +1,111 @@
+# 🦉 Slots 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Example](#example)
+- [Reference](#reference)
+
+## Overview
+
+Owl is a template based component system. There is therefore a need to be able
+to make generic components. For example, imagine a generic `Dialog`
+component, which is able to display some arbitrary content.
+
+Obviously, we want to use this component everywhere in our application, to
+display various different content. The `Dialog` component is technically the
+owner of its content, but is only a container. The user of the `Dialog` is
+the component that want to _inject_ something inside the `Dialog`. This is
+exactly what slots are for.
+
+## Example
+
+To make generic components, it is useful to be able for a parent component to _inject_
+some sub template, but still be the owner. For example, a generic dialog component
+will need to render some content, some footer, but with the parent as the
+rendering context.
+
+Slots are inserted with the `t-slot` directive:
+
+```xml
+<div t-name="Dialog" class="modal">
+  <div class="modal-title"><t t-esc="props.title"/></div>
+  <div class="modal-content">
+    <t t-slot="content"/>
+  </div>
+  <div class="modal-footer">
+    <t t-slot="footer"/>
+  </div>
+</div>
+```
+
+Slots are defined by the caller, with the `t-set-slot` directive:
+
+```xml
+<div t-name="SomeComponent">
+  <div>some component</div>
+  <Dialog title="'Some Dialog'">
+    <t t-set-slot="content">
+      <div>hey</div>
+    </t>
+    <t t-set-slot="footer">
+      <button t-on-click="doSomething">ok</button>
+    </t>
+  </Dialog>
+</div>
+```
+
+In this example, the component `Dialog` will render the slots `content` and `footer`
+with its parent as rendering context. This means that clicking on the button
+will execute the `doSomething` method on the parent, not on the dialog.
+
+Note: Owl previously used the `t-set` directive to define the content of a slot.
+This is deprecated and should no longer be used in new code.
+
+## Reference
+
+### Default Slot
+
+The first element inside the component which is not a named slot will
+be considered the `default` slot. For example:
+
+```xml
+<div t-name="Parent">
+  <Child>
+    <span>some content</span>
+  </Child>
+</div>
+
+<div t-name="Child">
+  <t t-slot="default"/>
+</div>
+```
+
+### Default content
+
+Slots can define a default content, in case the parent did not define them:
+
+```xml
+<div t-name="Parent">
+  <Child/>
+</div>
+
+<span t-name="Child">
+  <t t-slot="default">default content</t>
+</span>
+<!-- will be rendered as: <div><span>default content</span></div> -->
+```
+
+Rendering context: the content of the slots is actually rendered with the
+rendering context corresponding to where it was defined, not where it is
+positioned. This allows the user to define event handlers that will be bound
+to the correct component (usually, the grandparent of the slot content).
+
+### Dynamic Slots
+
+The `t-slot` directive is actually able to use any expressions, using string
+interplolation:
+
+```xml
+ <t t-slot="{{current}}" />
+```

doc/reference/store.md

@@ -25,8 +25,8 @@ component should own which part of the state.
 
 Owl's solution to this issue is a centralized store. It is a class that owns
 some (or all) state, and lets the developer update it in a structured way, with
-`actions`. Owl components can then connect to the store, and will be updated if
-necessary.
+`actions`. Owl components can then connect to the store to read their relevant
+state, and they will be rerendered if the state is updated.
 
 Note: Owl store is inspired by React Redux and VueX.
 
@@ -40,14 +40,14 @@ const actions = {
     state.todos.push({
       id: state.nextId++,
       message,
-      isCompleted: false
+      isCompleted: false,
     });
-  }
+  },
 };
 
 const state = {
   todos: [],
-  nextId: 1
+  nextId: 1,
 };
 
 const store = new owl.Store({ state, actions });
@@ -90,7 +90,7 @@ const config = {
   state,
   actions,
   getters,
-  env
+  env,
 };
 const store = new Store(config);
 ```
@@ -110,7 +110,7 @@ const actions = {
     } catch (e) {
       state.loginState = "error";
     }
-  }
+  },
 };
 ```
 
@@ -144,7 +144,7 @@ const actions = {
     state.recordId = recordId;
     const data = await doSomeRPC("/read/", recordId);
     state.recordData = data;
-  }
+  },
 };
 ```
 
@@ -159,7 +159,7 @@ const actions = {
     const data = await doSomeRPC("/read/", recordId);
     state.recordId = recordId;
     state.recordData = data;
-  }
+  },
 };
 ```
 
@@ -187,14 +187,14 @@ transform the data contained in the store.
 ```js
 const getters = {
   getPost({ state }, id) {
-    const post = state.posts.find(p => p.id === id);
-    const author = state.authors.find(a => a.id === post.id);
+    const post = state.posts.find((p) => p.id === id);
+    const author = state.authors.find((a) => a.id === post.id);
     return {
       id,
       author,
-      content: post.content
+      content: post.content,
     };
-  }
+  },
 };
 
 // somewhere else
@@ -208,7 +208,11 @@ Note that getters are not cached.
 ### Connecting a Component
 
 At some point, we need a way to interact with the store from a component. This
-can be done with the help of the three store hooks:
+means that the component needs a reference to the store. By default, it looks
+for it in the `env.store` key. However, this can be configured with the `useStore`
+hook.
+
+Every component-store interactions are done with the help of the three store hooks:
 
 - [`useStore`](#usestore) to subscribe a component to some part of the store state,
 - [`useDispatch`](#usedispatch) to get a reference to a dispatch function,
@@ -220,20 +224,28 @@ Assume we have this store:
 const actions = {
   increment({ state }, val) {
     state.counter.value += val;
-  }
+  },
 };
 
 const state = {
-  counter: { value: 0 }
+  counter: { value: 0 },
 };
 const store = new owl.Store({ state, actions });
 ```
 
+To make it accessible to the complete application, we will put it in the
+environment:
+
+```js
+// in this example, the root component is App
+App.env.store = store;
+```
+
 A counter component can then select this value and dispatch an action like this:
 
 ```js
 class Counter extends Component {
-  counter = useStore(state => state.counter);
+  counter = useStore((state) => state.counter);
   dispatch = useDispatch();
 }
 
@@ -252,15 +264,30 @@ The `useStore` hook is used to select some part of the store state. It accepts
 two arguments:
 
 - a selector function, which takes the store state as first argument (and the
-  component props as second argument) and returns
-  an object or an array (which will be then observed),
-- optionally, an object with a `store` key (if we want to override the default
-  store) and an equality function (if we want to specialize the comparison).
+  component props as second argument) and which must return the part of the
+  store state that will be made available and observed for changes,
+- optionally, an object which can have the following optional keys:
+  - a `store` key containing a store object if we want to use another store than
+    the default store,
+  - an `isEqual` key containing an equality function if we want to specialize
+    the comparison (the function must accept two arguments: the previous result
+    and the new result, and must return whether they are equal),
+  - and an `onUpdate` key containing an update function if we want to execute an
+    arbitrary code every time the selected state changes (the function will
+    receive one argument, the new result, and can execute arbitrary code).
 
-If the `useStore` callback selects a sub part of the store state, the component
+If the `useStore` selector returns a sub part of the store state, the component
 will only be rerendered whenever this part of the state changes. Otherwise, it
-will perform a strict equality check and will update the component every time this
-check fails.
+will perform a strict equality check (unless the `isEqual` option is defined,
+then it will call it) and will update the component every time this check fails.
+
+Note that if the selector function returns a primitive type, the result of
+`useStore` will be immutable and it will not react to changes. In this case, it
+is important to define the `onUpdate` option to properly update the value
+manually when it changes.
+
+Also, the return value from `useStore` is not supposed to be modified. The store
+state should only be updated with actions.
 
 ### `useDispatch`
 

doc/reference/tags.md

@@ -0,0 +1,184 @@
+# 🦉 Tags 🦉
+
+## Content
+
+- [Overview](#overview)
+- [`xml` tag](#xml-tag)
+- [`css` tag](#css-tag)
+
+## Overview
+
+Tags are very small helpers intended to make it easy to write inline templates
+or styles. There are currently two tags: `css` and `xml`. With these functions,
+it is possible to write [single file components](../learning/how_to_write_sfc.md).
+
+## XML tag
+
+The `xml` tag is certainly the most useful tag. It is used to define an inline
+QWeb template for a component. Without tags, creating a standalone component
+would look like this:
+
+```js
+import { Component } from 'owl'
+
+const name = 'some-unique-name';
+const template = `
+    <div>
+        <span t-if="somecondition">text</span>
+        <button t-on-click="someMethod">Click</button>
+    </div>
+`;
+QWeb.registerTemplate(name, template);
+
+class MyComponent extends Component {
+    static template = name;
+
+    ...
+}
+```
+
+With tags, this process is slightly simplified. The name is uniquely generated,
+and the template is automatically registered:
+
+```js
+const { Component } = owl;
+const { xml } = owl.tags;
+
+class MyComponent extends Component {
+    static template = xml`
+        <div>
+            <span t-if="somecondition">text</span>
+            <button t-on-click="someMethod">Click</button>
+        </div>
+    `;
+
+    ...
+}
+```
+
+## CSS tag
+
+The CSS tag is useful to define a css stylesheet in the javascript file:
+
+```js
+class MyComponent extends Component {
+    static template = xml`
+        <div class="my-component">some template</div>
+    `;
+    static css`
+      .my-component {
+          color: red;
+      }
+    `;
+}
+```
+
+The `css` tag registers internally the css information. Then, whenever the first
+instance of the component is created, will add a `<style>` tag to the document
+`<head>`.
+
+Note that to make it more useful, like other css preprocessors, the `css` tag
+accepts a small extension of the css specification: css scopes can be nested,
+and the rules will then be expanded by the `css` helper:
+
+```scss
+.my-component {
+  display: block;
+  .sub-component h {
+    color: red;
+  }
+}
+```
+
+will be formatted as:
+
+```css
+.my-component {
+  display: block;
+}
+.my-component .sub-component h {
+  color: red;
+}
+```
+
+This extension brings another useful feature: the `&` selector which refers to
+the parent selector. For example, we want our component to be red when hovered.
+We would like to write something like:
+
+```scss
+.my-component {
+  display: block;
+  :hover {
+    color: red;
+  }
+}
+```
+
+but it will be formatted as:
+
+```css
+.my-component {
+  display: block;
+}
+.my-component :hover {
+  color: red;
+}
+```
+
+The `&` selector can be used to solve this problem:
+
+```scss
+.my-component {
+  display: block;
+  &:hover {
+    color: red;
+  }
+}
+```
+
+will be formatted as:
+
+```css
+.my-component {
+  display: block;
+}
+.my-component:hover {
+  color: red;
+}
+```
+
+Now, there is no additional processing done by the `css` tag. However, since it
+is done in javascript at runtime, we actually have more power. For example:
+
+1. sharing values between javascript and css:
+
+```js
+import { theme } from "./theme";
+
+class MyComponent extends Component {
+  static template = xml`<div class="my-component">...</div>`;
+  static style = css`
+    .my-component {
+      color: ${theme.MAIN_COLOR};
+      background-color: ${theme.SECONDARY_color};
+    }
+  `;
+}
+```
+
+2. scoping rules to the current component:
+
+```js
+import { generateUUID } from "./utils";
+
+const uuid = generateUUID();
+
+class MyComponent extends Component {
+  static template = xml`<div data-o-${uuid}="">...</div>`;
+  static style = css`
+        [data-o-${uuid}] {
+            color: red;
+        }
+    `;
+}
+```

doc/reference/utils.md

@@ -19,20 +19,20 @@ not ready yet, resolved directly otherwise). If called with a callback as
 argument, it executes it as soon as the DOM ready (or directly).
 
 ```js
-Promise.all([loadFile("templates.xml"), owl.utils.whenReady()]).then(function([templates]) {
-  const qweb = new owl.QWeb(templates);
-  const app = new App({ qweb });
-  app.mount(document.body);
+Promise.all([loadFile("templates.xml"), owl.utils.whenReady()]).then(function ([templates]) {
+  const qweb = new owl.QWeb({ templates });
+  const env = { qweb };
+  await mount(App, { env, target: document.body });
 });
 ```
 
 or alternatively:
 
 ```js
-owl.utils.whenReady(function() {
+owl.utils.whenReady(function () {
   const qweb = new owl.QWeb();
-  const app = new App({ qweb });
-  app.mount(document.body);
+  const env = { qweb };
+  await mount(App, { env, target: document.body });
 });
 ```
 
@@ -62,7 +62,7 @@ initial usecase for this function is to load a template file. For example:
 ```js
 async function makeEnv() {
   const templates = await owl.utils.loadFile("templates.xml");
-  const qweb = new owl.QWeb(templates);
+  const qweb = new owl.QWeb({ templates });
   return { qweb };
 }
 ```

doc/tags.md

@@ -1,47 +0,0 @@
-# 🦉 Tags 🦉
-
-Tags are very small helpers to make it easy to write inline templates. There is
-only one currently available tag: `xml`, but we plan to add other tags later,
-such as a `css` tag, which will be used to write single file components.
-
-## XML tag
-
-Without tags, creating a standalone component would look like this:
-
-```js
-import { Component } from 'owl'
-
-const name = 'some-unique-name';
-const template = `
-    <div>
-        <span t-if="somecondition">text</span>
-        <button t-on-click="someMethod">Click</button>
-    </div>
-`;
-QWeb.registerTemplate(name, template);
-
-class MyComponent extends Component {
-    static template = name;
-
-    ...
-}
-```
-
-With tags, this process is slightly simplified. The name is uniquely generated,
-and the template is automatically registered:
-
-```js
-import { Component } from 'owl'
-import { xml } from 'owl/tags'
-
-class MyComponent extends Component {
-    static template = xml`
-        <div>
-            <span t-if="somecondition">text</span>
-            <button t-on-click="someMethod">Click</button>
-        </div>
-    `;
-
-    ...
-}
-```

doc/tooling.md

@@ -1,87 +0,0 @@
-# 🦉 Tooling 🦉
-
-## Content
-
-- [Overview](#overview)
-- [Development Mode](#development-mode)
-- [Playground](#playground)
-- [Benchmarks](#benchmarks)
-- [Single File Component](#single-file-component)
-
-## Overview
-
-To help work with/improve/learn OWL, there are a few extras tools/settings.
-
-- development mode: enable better error reporting for the developer
-- a playground application: a space to experiment and learn Owl.
-- a benchmarks application: allow comparison with a few common frameworks
-
-The two applications are available in the `tools/` folder, and can be accessed
-by using a static http server. A simple python
-server is available in `server.py`. There is also a npm script to start it:
-`npm run tools` (and its version with a watcher: `npm run tools:watch`).
-
-## Development Mode
-
-By default, Owl is in _production_ mode, this means that it will try to do its
-job fast, and skip some expensive operations. However, in some cases, it is
-convenient to have better information on what is going on, this is the purpose
-of the dev mode.
-
-Owl has a mode flag, in `owl.__info__.mode`. Its default value is `prod`, but
-it can be set to `dev`:
-
-```js
-owl.__info__.mode = "dev";
-```
-
-Note that templates compiled with the `prod` settings will not be recompiled.
-So, changing this setting is best done at startup.
-
-An important job done by the `dev` mode is to validate props for each component
-creation and update. Also, extra props will cause an error.
-
-## Playground
-
-The playground is an important application designed to help learning and
-experimenting with Owl. The last published version of Owl can be tested [online](https://odoo.github.io/owl/playground/).
-
-It is an application similar to `jsFiddle`, but specialized for Owl: there are
-three tabs (`js`, `css` and `xml`), and a simple button `Run` to execute that
-code in an iframe.
-
-## Benchmarks
-
-Note: This is more an internal tool, useful for people working on Owl.
-
-The benchmarks application is a very small application, implemented in different
-frameworks, and in different versions of Owl. This is a simple internal tool,
-useful to compare various performance metrics on some tasks.
-
-## Single File Component
-
-If you want to have `xml` syntax highlighting while using the `xml` helper which
-helps you define inline templates, there is a VS Code addon `Comment tagged template`
-which, if installed, does exactly that. To enable it, you need to add a comment,
-like this:
-
-```js
-// -----------------------------------------------------------------------------
-// TEMPLATE
-// -----------------------------------------------------------------------------
-const TEMPLATE = xml/* xml */ `
-	<div class="main two-columns">
-		<Sidebar/>
-		<Content />
-	</div>`;
-
-// -----------------------------------------------------------------------------
-// CODE
-// -----------------------------------------------------------------------------
-class MyComponent extends Component {
-  static template = TEMPLATE;
-  static components = { Sidebar, Content };
-
-  // rest of component...
-}
-```

package.json

@@ -1,47 +1,61 @@
 {
-  "name": "owl-framework",
-  "version": "0.24.0",
+  "name": "@odoo/owl",
+  "version": "1.3.1",
   "description": "Odoo Web Library (OWL)",
-  "main": "src/index.ts",
+  "main": "dist/owl.cjs.js",
+  "browser": "dist/owl.iife.js",
+  "module": "dist/owl.es.js",
+  "types": "dist/types/index.d.ts",
+  "files": [
+    "dist"
+  ],
+  "engines": {
+    "node": ">=10.15.3"
+  },
   "scripts": {
-    "build:js": "tsc --target esnext --module es6 --outDir dist/owl",
     "build:bundle": "rollup -c",
-    "build": "npm run build:js && npm run build:bundle",
-    "buildcommonjs": "npm run build:js && npm run build:bundle -- -f cjs",
-    "minify": "uglifyjs dist/owl.js -o dist/owl.min.js --compress --mangle",
+    "build": "npm run build:bundle",
     "test": "jest",
     "test:watch": "jest --watch",
     "tools:serve": "python3 tools/server.py || python tools/server.py",
     "tools": "npm run build && npm run tools:serve",
     "pretools:watch": "npm run build",
     "tools:watch": "npm-run-all  --parallel tools:serve \"build:* -- --watch\"",
-    "prettier": "prettier {src/**/*.ts,tests/**/*.ts,doc/**/*.md} --write"
+    "prettier": "prettier {src/*.ts,src/**/*.ts,tests/*.ts,tests/**/*.ts,doc/*.md,doc/**/*.md} --write",
+    "check-formatting": "prettier {src/*.ts,src/**/*.ts,tests/*.ts,tests/**/*.ts,doc/*.md,doc/**/*.md} --check",
+    "publish": "npm run build && npm publish",
+    "release": "node tools/release.js"
   },
   "repository": {
     "type": "git",
     "url": "git+https://github.com/odoo/owl.git"
   },
   "author": "Odoo",
-  "license": "LGPL",
+  "license": "LGPL-3.0-only",
   "bugs": {
     "url": "https://github.com/odoo/owl/issues"
   },
   "homepage": "https://github.com/odoo/owl#readme",
-  "dependencies": {},
   "devDependencies": {
-    "@types/jest": "^23.3.12",
+    "@types/jest": "^23.3.14",
+    "@types/node": "^14.11.8",
+    "chalk": "^3.0.0",
     "cpx": "^1.5.0",
+    "current-git-branch": "^1.1.0",
     "git-rev-sync": "^1.12.0",
+    "github-api": "^3.3.0",
     "jest": "^23.6.0",
     "jest-environment-jsdom": "^24.7.1",
     "live-server": "^1.2.1",
     "npm-run-all": "^4.1.5",
+    "prettier": "^2.0.4",
     "rollup": "^1.6.0",
-    "rollup-plugin-typescript2": "^0.20.1",
+    "rollup-plugin-terser": "^7.0.2",
+    "rollup-plugin-typescript2": "^0.27.3",
     "sass": "^1.16.1",
     "source-map-support": "^0.5.10",
     "ts-jest": "^23.10.5",
-    "typescript": "^3.2.2",
+    "typescript": "^3.7.2",
     "uglify-es": "^3.3.9"
   },
   "jest": {
@@ -64,6 +78,7 @@
     ]
   },
   "prettier": {
-    "printWidth": 100
+    "printWidth": 100,
+    "endOfLine": "auto"
   }
 }

roadmap.md

@@ -1,45 +1,27 @@
 # 🦉 OWL Roadmap 🦉
 
-- Current version: 0.24.0
-- Status: mostly stable
+- Current version: 1.3.1
+- Status: stable
 
 This roadmap is only an attempt at predicting Owl's future.  Everything may
 change!
 
-### October 2019
-
-We plan to complete the following tasks:
-
-- improve API for root widgets (issue #306),
-- replace `t-keepalive`, and maybe `t-transition` by components (issue #295).
-
-### November 2019
-
-Once the previous tasks are done, release version 1.0alpha. This means that the
-API should be stable.  But it could change a little bit if we need it for our
-work on Odoo.
-
-### End of 2019
-
-Release v1.0
-
-- API should be stable,
-- we will use semantic versioning,
-- we will maintain a changelog and an upgrade guide.
 
 ### 1.x
 
 - add chrome and firefox devtools,
-- add support for single file components,
 - fix every bugs,
 - improve documentation,
 - small backward compatible improvements.
 
-### 2.x (2021? 2022?)
+### 2.x (2020? 2021? 2022?)
+
+- stop support for `t-set` directive to define the content of a slot
 
 Maybe:
 
-- reimplement vdom to use *block* system, like Vue 3,
+- reimplement vdom to use *block* system, like Vue 3, which should make Owl
+  much faster
 - refactor `QWeb` to use an intermediate representation (some kind of AST) to
   allow additional optimisations.
 

rollup.config.js

@@ -1,14 +1,70 @@
-import { version } from "./package.json";
+import pkg from "./package.json";
 import git from "git-rev-sync";
+import typescript from 'rollup-plugin-typescript2';
+import { terser } from "rollup-plugin-terser";
+
+const name = "owl";
+const extend = true;
+
+/**
+ * Meta data to be added on the __info__ object.
+ * Used to let external tools know the current owl version.
+ */
+const outro = `
+__info__.version = '${pkg.version}';
+__info__.date = '${new Date().toISOString()}';
+__info__.hash = '${git.short()}';
+__info__.url = 'https://github.com/odoo/owl';
+`;
+
+/**
+ * Generate from a string depicting a path a new path for the minified version.
+ * @param {string} pkgFileName file name
+ */
+function generateMinifiedNameFromPkgName(pkgFileName) {
+  const parts = pkgFileName.split('.');
+  parts.splice(parts.length - 1, 0, "min");
+  return parts.join('.');
+}
+
+/**
+ * Get the rollup config based on the arguments
+ * @param {string} format format of the bundle
+ * @param {string} generatedFileName generated file name
+ * @param {boolean} minified should it be minified
+ */
+function getConfigForFormat(format, generatedFileName, minified = false) {
+  return {
+    file: minified ? generateMinifiedNameFromPkgName(generatedFileName) : generatedFileName,
+    format: format,
+    name: name,
+    extend: extend,
+    outro: outro,
+    plugins: minified ? [terser()] : [],
+    indent: '    ', // indent with 4 spaces
+  };
+}
 
-// rollup.config.js
 export default {
-  input: "dist/owl/index.js",
-  output: {
-    file: "dist/owl.js",
-    format: "iife",
-    name: "owl",
-    extend: true,
-    outro: `exports.__info__.version = '${version}';\nexports.__info__.date = '${new Date().toISOString()}';\nexports.__info__.hash = '${git.short()}';\nexports.__info__.url = 'https://github.com/odoo/owl';`
-  }
+  input: "src/index.ts",
+  output: [
+
+    /**
+     * Read about module formats:
+     *  https://auth0.com/blog/javascript-module-systems-showdown/
+     *  https://medium.com/@kelin2025/so-you-wanna-use-es6-modules-714f48b3a953
+     */
+
+    getConfigForFormat('esm', pkg.module),
+    getConfigForFormat('esm', pkg.module, true),
+    getConfigForFormat('cjs', pkg.main),
+    getConfigForFormat('cjs', pkg.main, true),
+    getConfigForFormat('iife', pkg.browser),
+    getConfigForFormat('iife', pkg.browser, true),
+  ],
+  plugins: [
+    typescript({
+      useTsconfigDeclarationDir: true
+    }),
+  ]
 };

src/browser.ts

@@ -0,0 +1,30 @@
+export interface Browser {
+  setTimeout: Window["setTimeout"];
+  clearTimeout: Window["clearTimeout"];
+  setInterval: Window["setInterval"];
+  clearInterval: Window["clearInterval"];
+  requestAnimationFrame: Window["requestAnimationFrame"];
+  random: Math["random"];
+  Date: typeof Date;
+  fetch: Window["fetch"];
+  localStorage: Window["localStorage"];
+}
+
+let localStorage: Window["localStorage"] | null = null;
+
+export const browser: Browser = {
+  setTimeout: window.setTimeout.bind(window),
+  clearTimeout: window.clearTimeout.bind(window),
+  setInterval: window.setInterval.bind(window),
+  clearInterval: window.clearInterval.bind(window),
+  requestAnimationFrame: window.requestAnimationFrame.bind(window),
+  random: Math.random,
+  Date: window.Date,
+  fetch: (window.fetch || (() => {})).bind(window),
+  get localStorage() {
+    return localStorage || window.localStorage;
+  },
+  set localStorage(newLocalStorage: Window["localStorage"]) {
+    localStorage = newLocalStorage;
+  },
+};

src/component/component.ts

@@ -1,10 +1,13 @@
 import { Observer } from "../core/observer";
+import { OwlEvent } from "../core/owl_event";
 import { CompiledTemplate, QWeb } from "../qweb/index";
-import { h, patch, VNode } from "../vdom/index";
+import { patch, VNode } from "../vdom/index";
 import "./directive";
 import { Fiber } from "./fiber";
 import "./props_validation";
-import { Scheduler } from "./scheduler";
+import { Scheduler, scheduler } from "./scheduler";
+import { activateSheet } from "./styles";
+import { Browser, browser } from "../browser";
 
 /**
  * Owl Component System
@@ -20,8 +23,6 @@ import { Scheduler } from "./scheduler";
 //------------------------------------------------------------------------------
 // Types/helpers
 //------------------------------------------------------------------------------
-const raf = window.requestAnimationFrame.bind(window);
-export const scheduler = new Scheduler(raf);
 
 /**
  * An Env (environment) is an object that will be (mostly) shared between all
@@ -34,7 +35,22 @@ export const scheduler = new Scheduler(raf);
  */
 export interface Env {
   qweb: QWeb;
-  [key: string]: any;
+  browser: Browser;
+}
+
+export type MountPosition = "first-child" | "last-child" | "self";
+
+interface MountOptions {
+  position?: MountPosition;
+}
+
+export const enum STATUS {
+  CREATED,
+  WILLSTARTED, // willstart has been called
+  RENDERED, // first render is completed (so, vnode is now defined)
+  MOUNTED, // is ready, and in DOM. It has a valid el
+  UNMOUNTED, // has a valid el, but is not in DOM
+  DESTROYED,
 }
 
 /**
@@ -42,25 +58,33 @@ export interface Env {
  * useful to typecheck and describe the internal keys used by Owl to manage the
  * component tree.
  */
-interface Internal<T extends Env, Props> {
+interface Internal<T extends Env> {
   // each component has a unique id, useful mostly to handle parent/child
   // relationships
   readonly id: number;
+  depth: number;
   vnode: VNode | null;
   pvnode: VNode | null;
-  isMounted: boolean;
-  isDestroyed: boolean;
+  status: STATUS;
 
   // parent and children keys are obviously useful to setup the parent-children
   // relationship.
-  parent: Component<T, any> | null;
-  children: { [key: number]: Component<T, any> };
+  parent: Component<any, T> | null;
+  children: { [key: number]: Component<any, T> };
   // children mapping: from templateID to componentID. templateID identifies a
   // place in a template. The t-component directive needs it to be able to get
   // the component instance back whenever the template is rerendered.
   cmap: { [key: number]: number };
 
   currentFiber: Fiber | null;
+  // parentLastFiberId is there to help the parent component to detect, among
+  // its children, those that are not used anymore and thus can be destroyed
+  parentLastFiberId: number;
+
+  // when a rendering is initiated by a parent, it may set variables in 'scope'
+  // (typically when the component is rendered in a slot). We need to
+  // store that information in case the component would be re-rendered later on.
+  scope: any;
 
   boundHandlers: { [key: number]: any };
   observer: Observer | null;
@@ -72,22 +96,27 @@ interface Internal<T extends Env, Props> {
   willStartCB: Function | null;
   willUpdatePropsCB: Function | null;
   classObj: { [key: string]: boolean } | null;
-  refs: { [key: string]: Component<T, any> | HTMLElement | undefined } | null;
+  refs: { [key: string]: Component<any, T> | HTMLElement | undefined } | null;
 }
 
+export const portalSymbol = Symbol("portal"); // FIXME
+
 //------------------------------------------------------------------------------
 // Component
 //------------------------------------------------------------------------------
 let nextId = 1;
 
-export class Component<T extends Env, Props extends {}> {
-  readonly __owl__: Internal<Env, Props>;
+export class Component<Props extends {} = any, T extends Env = Env> {
+  readonly __owl__: Internal<T>;
   static template?: string | null = null;
   static _template?: string | null = null;
-  static current: Component<any, any> | null = null;
+  static current: Component | null = null;
   static components = {};
   static props?: any;
   static defaultProps?: any;
+  static env: any = {};
+  // expose scheduler s.t. it can be mocked for testing purposes
+  static scheduler: Scheduler = scheduler;
 
   /**
    * The `el` is the root element of the component.  Note that it could be null:
@@ -107,72 +136,72 @@ export class Component<T extends Env, Props extends {}> {
   /**
    * Creates an instance of Component.
    *
-   * The root component of a component tree needs an environment:
-   *
-   * ```javascript
-   *   const root = new RootComponent(env, props);
-   * ```
-   *
-   * Every other component simply needs a reference to its parent:
-   *
-   * ```javascript
-   *   const child = new SomeComponent(parent, props);
-   * ```
-   *
    * Note that most of the time, only the root component needs to be created by
    * hand.  Other components should be created automatically by the framework (with
    * the t-component directive in a template)
    */
-  constructor(parent: Component<T, any> | T, props?: Props) {
-    const defaultProps = (<any>this.constructor).defaultProps;
+  constructor(parent?: Component<any, T> | null, props?: Props) {
     Component.current = this;
+
+    let constr = this.constructor as any;
+    const defaultProps = constr.defaultProps;
     if (defaultProps) {
-      props = this.__applyDefaultProps(props, defaultProps);
+      props = props || ({} as Props);
+      this.__applyDefaultProps(props, defaultProps);
     }
-    // is this a good idea?
-    //   Pro: if props is empty, we can create easily a component
-    //   Con: this is not really safe
-    //   Pro: but creating component (by a template) is always unsafe anyway
-    this.props = <Props>props || <Props>{};
-    let id: number = nextId++;
-    let p: Component<T, any> | null = null;
-    if (parent instanceof Component) {
-      p = parent;
+    this.props = <Props>props;
+    if (QWeb.dev) {
+      QWeb.utils.validateProps(constr, this.props);
+    }
+
+    const id: number = nextId++;
+    let depth;
+    if (parent) {
       this.env = parent.env;
-      parent.__owl__.children[id] = this;
+      const __powl__ = parent.__owl__;
+      __powl__.children[id] = this;
+      depth = __powl__.depth + 1;
     } else {
-      this.env = parent;
-      if (QWeb.dev) {
-        // we only validate props for root widgets here.  "Regular" widget
-        // props are validated by the t-component directive
-        QWeb.utils.validateProps(this.constructor, this.props);
+      // we are the root component
+      this.env = (this.constructor as any).env;
+      if (!this.env.qweb) {
+        this.env.qweb = new QWeb();
+      }
+      // TODO: remove this in owl 2.0
+      if (!this.env.browser) {
+        this.env.browser = browser;
       }
       this.env.qweb.on("update", this, () => {
-        if (this.__owl__.isMounted) {
-          this.render(true);
-        }
-        if (this.__owl__.isDestroyed) {
-          // this is unlikely to happen, but if a root widget is destroyed,
-          // we want to remove our subscription.  The usual way to do that
-          // would be to perform some check in the destroy method, but since
-          // it is very performance sensitive, and since this is a rare event,
-          // we simply do it lazily
-          this.env.qweb.off("update", this);
+        switch (this.__owl__.status) {
+          case STATUS.MOUNTED:
+            this.render(true);
+            break;
+          case STATUS.DESTROYED:
+            // this is unlikely to happen, but if a root widget is destroyed,
+            // we want to remove our subscription.  The usual way to do that
+            // would be to perform some check in the destroy method, but since
+            // it is very performance sensitive, and since this is a rare event,
+            // we simply do it lazily
+            this.env.qweb.off("update", this);
+            break;
         }
       });
+      depth = 0;
     }
-    const qweb = this.env.qweb;
 
+    const qweb = this.env.qweb;
+    const template = constr.template || this.__getTemplate(qweb);
     this.__owl__ = {
       id: id,
+      depth: depth,
       vnode: null,
       pvnode: null,
-      isMounted: false,
-      isDestroyed: false,
-      parent: p,
+      status: STATUS.CREATED,
+      parent: parent || null,
       children: {},
       cmap: {},
       currentFiber: null,
+      parentLastFiberId: 0,
       boundHandlers: {},
       mountedCB: null,
       willUnmountCB: null,
@@ -181,12 +210,28 @@ export class Component<T extends Env, Props extends {}> {
       willStartCB: null,
       willUpdatePropsCB: null,
       observer: null,
-      renderFn: qweb.render.bind(qweb, this.__getTemplate(qweb)),
+      renderFn: qweb.render.bind(qweb, template),
       classObj: null,
-      refs: null
+      refs: null,
+      scope: null,
     };
+    if (constr.style) {
+      this.__applyStyles(constr);
+    }
+    this.setup();
   }
 
+  /**
+   * setup is run just after the component is constructed. This is the standard
+   * location where the component can setup its hooks. It has some advantages
+   * over the constructor:
+   *  - it can be patched (useful in odoo ecosystem)
+   *  - it does not need to propagate the arguments to the super call
+   *
+   * Note: this method should not be called manually.
+   */
+  setup() {}
+
   /**
    * willStart is an asynchronous hook that can be implemented to perform some
    * action before the initial rendering of a component.
@@ -262,8 +307,11 @@ export class Component<T extends Env, Props extends {}> {
   /**
    * catchError is a method called whenever some error happens in the rendering or
    * lifecycle hooks of a child.
+   *
+   * It needs to be implemented by a component that is designed to handle the
+   * error properly.
    */
-  catchError(error: Error): void {}
+  catchError?(error?: Error): void;
 
   //--------------------------------------------------------------------------
   // Public
@@ -277,36 +325,50 @@ export class Component<T extends Env, Props extends {}> {
    *
    * Note that a component can be mounted an unmounted several times
    */
-  async mount(target: HTMLElement, renderBeforeRemount: boolean = false): Promise<void> {
+  async mount(target: HTMLElement | DocumentFragment, options: MountOptions = {}): Promise<void> {
+    if (!(target instanceof HTMLElement || target instanceof DocumentFragment)) {
+      let message = `Component '${this.constructor.name}' cannot be mounted: the target is not a valid DOM node.`;
+      message += `\nMaybe the DOM is not ready yet? (in that case, you can use owl.utils.whenReady)`;
+      throw new Error(message);
+    }
+    const position = options.position || "last-child";
     const __owl__ = this.__owl__;
-    if (__owl__.isMounted) {
-      return Promise.resolve();
-    }
-    if (__owl__.vnode && !renderBeforeRemount) {
-      target.appendChild(this.el!);
-      if (document.body.contains(target)) {
-        this.__callMounted();
+    const currentFiber = __owl__.currentFiber;
+
+    switch (__owl__.status) {
+      case STATUS.CREATED: {
+        const fiber = new Fiber(null, this, true, target, position);
+        fiber.shouldPatch = false;
+        this.__prepareAndRender(fiber, () => {});
+        return scheduler.addFiber(fiber);
       }
-      return;
-    }
-    const fiber = new Fiber(null, this, this.props, undefined, undefined, false);
-    if (!__owl__.vnode) {
-      this.__prepareAndRender(fiber);
-    } else {
-      this.__render(fiber);
-    }
-    return new Promise(resolve => {
-      scheduler.addFiber(fiber, () => {
-        if (!__owl__.isDestroyed) {
-          this.__patch(fiber.vnode);
-          target.appendChild(this.el!);
-          if (document.body.contains(target)) {
-            this.__callMounted();
-          }
+      case STATUS.WILLSTARTED:
+      case STATUS.RENDERED:
+        currentFiber.target = target;
+        currentFiber.position = position;
+        return scheduler.addFiber(currentFiber);
+
+      case STATUS.UNMOUNTED: {
+        const fiber = new Fiber(null, this, true, target, position);
+        fiber.shouldPatch = false;
+        this.__render(fiber);
+        return scheduler.addFiber(fiber);
+      }
+
+      case STATUS.MOUNTED: {
+        if (position !== "self" && this.el!.parentNode !== target) {
+          const fiber = new Fiber(null, this, true, target, position);
+          fiber.shouldPatch = false;
+          this.__render(fiber);
+          return scheduler.addFiber(fiber);
+        } else {
+          return Promise.resolve();
         }
-        resolve();
-      });
-    });
+      }
+
+      case STATUS.DESTROYED:
+        throw new Error("Cannot mount a destroyed component");
+    }
   }
 
   /**
@@ -314,7 +376,7 @@ export class Component<T extends Env, Props extends {}> {
    * to call willUnmount calls and remove the component from the DOM.
    */
   unmount() {
-    if (this.__owl__.isMounted) {
+    if (this.__owl__.status === STATUS.MOUNTED) {
       this.__callWillUnmount();
       this.el!.remove();
     }
@@ -331,22 +393,33 @@ export class Component<T extends Env, Props extends {}> {
    */
   async render(force: boolean = false): Promise<void> {
     const __owl__ = this.__owl__;
-    if (
-      (!__owl__.isMounted && !__owl__.currentFiber) ||
-      (__owl__.currentFiber && !__owl__.currentFiber.isRendered)
-    ) {
+    const currentFiber = __owl__.currentFiber;
+    if (!__owl__.vnode && !currentFiber) {
       return;
     }
-    const fiber = new Fiber(null, this, this.props, undefined, undefined, force);
-    this.__render(fiber);
-    return new Promise(resolve => {
-      scheduler.addFiber(fiber.root, () => {
-        if (__owl__.isMounted && fiber === fiber.root) {
-          fiber.patchComponents();
+    if (currentFiber && !currentFiber.isRendered && !currentFiber.isCompleted) {
+      return scheduler.addFiber(currentFiber.root);
+    }
+    // if we aren't mounted at this point, it implies that there is a
+    // currentFiber that is already rendered (isRendered is true), so we are
+    // about to be mounted
+    const status = __owl__.status;
+    const fiber = new Fiber(null, this, force, null, null);
+    Promise.resolve().then(() => {
+      if (__owl__.status === STATUS.MOUNTED || status !== STATUS.MOUNTED) {
+        if (fiber.isCompleted || fiber.isRendered) {
+          return;
         }
-        resolve();
-      });
+        this.__render(fiber);
+      } else {
+        // we were mounted when render was called, but we aren't anymore, so we
+        // were actually about to be unmounted ; we can thus forget about this
+        // fiber
+        fiber.isCompleted = true;
+        __owl__.currentFiber = null;
+      }
     });
+    return scheduler.addFiber(fiber);
   }
 
   /**
@@ -360,7 +433,7 @@ export class Component<T extends Env, Props extends {}> {
    */
   destroy() {
     const __owl__ = this.__owl__;
-    if (!__owl__.isDestroyed) {
+    if (__owl__.status !== STATUS.DESTROYED) {
       const el = this.el;
       this.__destroy(__owl__.parent);
       if (el) {
@@ -384,15 +457,8 @@ export class Component<T extends Env, Props extends {}> {
    * up to the parent DOM nodes. Thus, it must be called between mounted() and
    * willUnmount().
    */
-  trigger(eventType: string, payload?: any) {
-    if (this.el) {
-      const ev = new CustomEvent(eventType, {
-        bubbles: true,
-        cancelable: true,
-        detail: payload
-      });
-      this.el.dispatchEvent(ev);
-    }
+  trigger<T = any>(eventType: string, payload?: T) {
+    this.__trigger<T>(this, eventType, payload);
   }
 
   //--------------------------------------------------------------------------
@@ -410,15 +476,14 @@ export class Component<T extends Env, Props extends {}> {
    * Note that it does not call the __callWillUnmount method to avoid visiting
    * all children many times.
    */
-  __destroy(parent: Component<any, any> | null) {
+  __destroy(parent: Component | null) {
     const __owl__ = this.__owl__;
-    const isMounted = __owl__.isMounted;
-    if (isMounted) {
+    if (__owl__.status === STATUS.MOUNTED) {
       if (__owl__.willUnmountCB) {
         __owl__.willUnmountCB();
       }
       this.willUnmount();
-      __owl__.isMounted = false;
+      __owl__.status = STATUS.UNMOUNTED;
     }
     const children = __owl__.children;
     for (let key in children) {
@@ -429,27 +494,21 @@ export class Component<T extends Env, Props extends {}> {
       delete parent.__owl__.children[id];
       __owl__.parent = null;
     }
-    __owl__.isDestroyed = true;
+    __owl__.status = STATUS.DESTROYED;
     delete __owl__.vnode;
+    if (__owl__.currentFiber) {
+      __owl__.currentFiber.isCompleted = true;
+    }
   }
 
   __callMounted() {
     const __owl__ = this.__owl__;
-    const children = __owl__.children;
-    for (let id in children) {
-      const comp = children[id];
-      if (!comp.__owl__.isMounted && this.el!.contains(comp.el)) {
-        comp.__callMounted();
-      }
-    }
-    __owl__.isMounted = true;
-    try {
-      this.mounted();
-      if (__owl__.mountedCB) {
-        __owl__.mountedCB();
-      }
-    } catch (e) {
-      console.error(e); // TODO : add a test
+
+    __owl__.status = STATUS.MOUNTED;
+    __owl__.currentFiber = null;
+    this.mounted();
+    if (__owl__.mountedCB) {
+      __owl__.mountedCB();
     }
   }
 
@@ -459,46 +518,66 @@ export class Component<T extends Env, Props extends {}> {
       __owl__.willUnmountCB();
     }
     this.willUnmount();
-    __owl__.isMounted = false;
+    __owl__.status = STATUS.UNMOUNTED;
+    if (__owl__.currentFiber) {
+      __owl__.currentFiber.isCompleted = true;
+      __owl__.currentFiber.root.counter = 0;
+    }
     const children = __owl__.children;
     for (let id in children) {
       const comp = children[id];
-      if (comp.__owl__.isMounted) {
+      if (comp.__owl__.status === STATUS.MOUNTED) {
         comp.__callWillUnmount();
       }
     }
   }
-
+  /**
+   * Private trigger method, allows to choose the component which triggered
+   * the event in the first place
+   */
+  __trigger<T>(component: Component, eventType: string, payload?: T) {
+    if (this.el) {
+      const ev = new OwlEvent<T>(component, eventType, {
+        bubbles: true,
+        cancelable: true,
+        detail: payload,
+      });
+      const triggerHook = this.env[portalSymbol as any];
+      if (triggerHook) {
+        triggerHook(ev);
+      }
+      this.el.dispatchEvent(ev);
+    }
+  }
   /**
    * The __updateProps method is called by the t-component directive whenever
    * it updates a component (so, when the parent template is rerendered).
    */
-  async __updateProps(
-    nextProps: Props,
-    parentFiber: Fiber,
-    scope: any,
-    vars: any,
-    previousSibling?: Fiber | null
-  ): Promise<void> {
+  async __updateProps(nextProps: Props, parentFiber: Fiber, scope: any): Promise<void> {
+    this.__owl__.scope = scope;
     const shouldUpdate = parentFiber.force || this.shouldUpdate(nextProps);
     if (shouldUpdate) {
       const __owl__ = this.__owl__;
-      const fiber = new Fiber(parentFiber, this, this.props, scope, vars, parentFiber.force);
+      const fiber = new Fiber(parentFiber, this, parentFiber.force, null, null);
       if (!parentFiber.child) {
         parentFiber.child = fiber;
       } else {
-        previousSibling!.sibling = fiber;
+        parentFiber.lastChild!.sibling = fiber;
       }
+      parentFiber.lastChild = fiber;
 
       const defaultProps = (<any>this.constructor).defaultProps;
       if (defaultProps) {
-        nextProps = this.__applyDefaultProps(nextProps, defaultProps);
+        this.__applyDefaultProps(nextProps, defaultProps);
+      }
+      if (QWeb.dev) {
+        QWeb.utils.validateProps(this.constructor, nextProps);
       }
       await Promise.all([
         this.willUpdateProps(nextProps),
-        __owl__.willUpdatePropsCB && __owl__.willUpdatePropsCB(nextProps)
+        __owl__.willUpdatePropsCB && __owl__.willUpdatePropsCB(nextProps),
       ]);
-      if (fiber.isCancelled) {
+      if (fiber.isCompleted) {
         return;
       }
       this.props = nextProps;
@@ -511,65 +590,83 @@ export class Component<T extends Env, Props extends {}> {
    * Main patching method. We call the virtual dom patch method here to convert
    * a virtual dom vnode into some actual dom.
    */
-  __patch(vnode) {
-    const __owl__ = this.__owl__;
-    const target = __owl__.vnode || document.createElement(vnode.sel!);
-    __owl__.vnode = patch(target, vnode);
-    __owl__.currentFiber = null;
+  __patch(target: HTMLElement | VNode | DocumentFragment, vnode: VNode) {
+    this.__owl__.vnode = patch(target as any, vnode);
   }
 
   /**
    * The __prepare method is only called by the t-component directive, when a
-   * subcomponent is created. It gets its scope and vars, if any, from the
+   * subcomponent is created. It gets its scope, if any, from the
    * parent template.
    */
-  __prepare(parentFiber: Fiber, scope: any, vars: any, previousSibling?: Fiber | null) {
-    const fiber = new Fiber(parentFiber, this, this.props, scope, vars, parentFiber.force);
+  __prepare(parentFiber: Fiber, scope: any, cb: CallableFunction): Fiber {
+    this.__owl__.scope = scope;
+    const fiber = new Fiber(parentFiber, this, parentFiber.force, null, null);
     fiber.shouldPatch = false;
     if (!parentFiber.child) {
       parentFiber.child = fiber;
     } else {
-      previousSibling!.sibling = fiber;
+      parentFiber.lastChild!.sibling = fiber;
     }
-    return this.__prepareAndRender(fiber);
+    parentFiber.lastChild = fiber;
+    this.__prepareAndRender(fiber, cb);
+    return fiber;
   }
 
+  /**
+   * Apply the stylesheets defined by the component. Note that we need to make
+   * sure all inherited stylesheets are applied as well.  We then delete the
+   * `style` key from the constructor to make sure we do not apply it again.
+   */
+  private __applyStyles(constr) {
+    while (constr && constr.style) {
+      if (constr.hasOwnProperty("style")) {
+        activateSheet(constr.style, constr.name);
+        delete constr.style;
+      }
+      constr = constr.__proto__;
+    }
+  }
   __getTemplate(qweb: QWeb): string {
     let p = (<any>this).constructor;
     if (!p.hasOwnProperty("_template")) {
-      if (p.template) {
-        p._template = p.template;
-      } else {
-        // here, the component and none of its superclasses defines a static `template`
-        // key. So we fall back on looking for a template matching its name (or
-        // one of its subclass).
+      // here, the component and none of its superclasses defines a static `template`
+      // key. So we fall back on looking for a template matching its name (or
+      // one of its subclass).
 
-        let template: string;
-        while ((template = p.name) && !(template in qweb.templates) && p !== Component) {
-          p = p.__proto__;
-        }
-        if (p === Component) {
-          throw new Error(`Could not find template for component "${this.constructor.name}"`);
-        } else {
-          p._template = template;
-        }
+      let template: string = p.name;
+      while (!(template in qweb.templates) && p !== Component) {
+        p = p.__proto__;
+        template = p.name;
+      }
+      if (p === Component) {
+        throw new Error(`Could not find template for component "${this.constructor.name}"`);
+      } else {
+        p._template = template;
       }
     }
     return p._template;
   }
-  async __prepareAndRender(fiber: Fiber) {
+
+  async __prepareAndRender(fiber: Fiber, cb: CallableFunction) {
     try {
-      await Promise.all([this.willStart(), this.__owl__.willStartCB && this.__owl__.willStartCB()]);
+      const proms = Promise.all([
+        this.willStart(),
+        this.__owl__.willStartCB && this.__owl__.willStartCB(),
+      ]);
+      this.__owl__.status = STATUS.WILLSTARTED;
+      await proms;
+      if (this.__owl__.status === <any>STATUS.DESTROYED) {
+        return Promise.resolve();
+      }
     } catch (e) {
-      errorHandler(e, fiber);
-      fiber.vnode = h("div"); // -> we render this div at the end
+      fiber.handleError(e);
       return Promise.resolve();
     }
-    if (this.__owl__.isDestroyed) {
-      return Promise.resolve();
-    }
-    if (!fiber.isCancelled) {
+    if (!fiber.isCompleted) {
       this.__render(fiber);
+      this.__owl__.status = STATUS.RENDERED;
+      cb();
     }
   }
 
@@ -578,111 +675,107 @@ export class Component<T extends Env, Props extends {}> {
     if (__owl__.observer) {
       __owl__.observer.allowMutations = false;
     }
-    let vnode;
+    let error;
     try {
-      vnode = __owl__.renderFn!(this, {
+      let vnode = __owl__.renderFn!(this, {
         handlers: __owl__.boundHandlers,
-        fiber: fiber
+        fiber: fiber,
       });
+      // we iterate over the children to detect those that no longer belong to the
+      // current rendering: those ones, if not mounted yet, can (and have to) be
+      // destroyed right now, because they are not in the DOM, and thus we won't
+      // be notified later on (when patching), that they are removed from the DOM
+      for (let childKey in __owl__.children) {
+        const child = __owl__.children[childKey];
+        const childOwl = child.__owl__;
+        if (childOwl.status !== STATUS.MOUNTED && childOwl.parentLastFiberId < fiber.id) {
+          // we only do here a "soft" destroy, meaning that we leave the child
+          // dom node alone, without removing it.  Most of the time, it does not
+          // matter, because the child component is already unmounted.  However,
+          // if some of its parent have been unmounted, the child could actually
+          // still be attached to its parent, and this may be important if we
+          // want to remount the parent, because the vdom need to match the
+          // actual DOM
+          child.__destroy(childOwl.parent);
+          if (childOwl.pvnode) {
+            // we remove the key here to make sure that the patching algorithm
+            // is able to make the difference between this pvnode and an eventual
+            // other instance of the same component
+            delete childOwl.pvnode.key;
+            // Since the component has been unmounted, we do not want to actually
+            // call a remove hook.  This is pretty important, since the t-component
+            // directive actually disabled it, so the vdom algorithm will just
+            // not remove the child elm if we don't remove the hook.
+            delete childOwl.pvnode.data!.hook!.remove;
+          }
+        }
+      }
+      if (!vnode) {
+        throw new Error(`Rendering '${this.constructor.name}' did not return anything`);
+      }
+      fiber.vnode = vnode;
+      // we apply here the class information described on the component by the
+      // template (so, something like <MyComponent class="..."/>) to the actual
+      // root vnode
+      if (__owl__.classObj) {
+        const data = vnode.data!;
+        data.class = Object.assign(data.class || {}, __owl__.classObj);
+      }
     } catch (e) {
-      vnode = __owl__.vnode || h("div");
-      errorHandler(e, fiber);
+      error = e;
     }
-    fiber.vnode = vnode;
     if (__owl__.observer) {
       __owl__.observer.allowMutations = true;
     }
 
-    // we apply here the class information described on the component by the
-    // template (so, something like <MyComponent class="..."/>) to the actual
-    // root vnode
-    if (__owl__.classObj) {
-      vnode.data.class = Object.assign(vnode.data.class || {}, __owl__.classObj);
-    }
     fiber.root.counter--;
     fiber.isRendered = true;
-  }
-
-  /**
-   * Only called by qweb t-component directive
-   */
-  __mount(fiber: Fiber, elm: HTMLElement): VNode {
-    if (fiber !== this.__owl__.currentFiber) {
-      fiber = this.__owl__.currentFiber!; // TODO: check if we can remove fiber arg
-    }
-    const vnode = fiber.vnode!;
-    const __owl__ = this.__owl__;
-    if (__owl__.classObj) {
-      (<any>vnode).data.class = Object.assign((<any>vnode).data.class || {}, __owl__.classObj);
-    }
-    __owl__.vnode = patch(elm, vnode);
-    __owl__.currentFiber = null;
-    if (__owl__.parent!.__owl__.isMounted && !__owl__.isMounted) {
-      this.__callMounted();
-    }
-    return __owl__.vnode;
-  }
-
-  /**
-   * Only called by qweb t-component directive (when t-keepalive is set)
-   */
-  __remount() {
-    const __owl__ = this.__owl__;
-    if (!__owl__.isMounted) {
-      __owl__.isMounted = true;
-      this.mounted();
+    if (error) {
+      fiber.handleError(error);
     }
   }
 
   /**
    * Apply default props (only top level).
    *
-   * Note that this method does not modify in place the props, it returns a new
-   * prop object
+   * Note that this method does modify in place the props
    */
-  __applyDefaultProps(props: Object | undefined, defaultProps: Object): Props {
-    props = props ? Object.assign({}, props) : {};
+  __applyDefaultProps(props: Object, defaultProps: Object) {
     for (let propName in defaultProps) {
       if (props![propName] === undefined) {
         props![propName] = defaultProps[propName];
       }
     }
-    return <Props>props;
   }
 }
 
-//------------------------------------------------------------------------------
-// Error handling
-//------------------------------------------------------------------------------
+interface MountParameters {
+  env?: Env;
+  target: HTMLElement | DocumentFragment;
+  props?: any;
+  position?: MountOptions["position"];
+}
 
-Fiber.prototype.handleError = function(error) {
-  errorHandler(error, this);
-};
-/**
- * This is the global error handler for errors occurring in Owl main lifecycle
- * methods.  Caught errors are triggered on the QWeb instance, and are
- * potentially given to some parent component which implements `catchError`.
- *
- * If there are no such component, we destroy everything. This is better than
- * being in a corrupted state.
- */
-function errorHandler(error: Error, fiber: Fiber) {
-  let canCatch = false;
-  let component = fiber.component;
-  let qweb = component.env.qweb;
-  let root = component;
-  while (component && !(canCatch = component.catchError !== Component.prototype.catchError)) {
-    root = component;
-    component = component.__owl__.parent!;
+interface Type<T> extends Function {
+  new (...args: any[]): T;
+}
+
+export async function mount<T extends Type<Component>>(
+  C: T,
+  params: MountParameters
+): Promise<InstanceType<T>> {
+  const { env, props, target } = params;
+  let origEnv = C.hasOwnProperty("env") ? (C as any).env : null;
+  if (env) {
+    ((C as any) as typeof Component).env = env;
   }
-  console.error(error);
-  qweb.trigger("error", error);
-
-  if (canCatch) {
-    setTimeout(() => {
-      component.catchError(error);
-    });
+  const component: Component = new C(null, props);
+  if (origEnv) {
+    (C as any).env = origEnv;
   } else {
-    root.destroy();
+    delete (C as any).env;
   }
+  const position = params.position || "last-child";
+  await component.mount(target, { position });
+  return component as any;
 }

src/component/directive.ts

@@ -1,13 +1,14 @@
 import { QWeb } from "../qweb/index";
 import { INTERP_REGEXP } from "../qweb/compilation_context";
-import { MODS_CODE } from "../qweb/extensions";
+import { makeHandlerCode, MODS_CODE } from "../qweb/extensions";
+import { STATUS } from "./component";
 
 //------------------------------------------------------------------------------
 // t-component
 //------------------------------------------------------------------------------
 
 const T_COMPONENT_MODS_CODE = Object.assign({}, MODS_CODE, {
-  self: "if (e.target !== vn.elm) {return}"
+  self: "if (e.target !== vn.elm) {return}",
 });
 
 QWeb.utils.defineProxy = function defineProxy(target, source) {
@@ -18,11 +19,31 @@ QWeb.utils.defineProxy = function defineProxy(target, source) {
       },
       set(val) {
         source[k] = val;
-      }
+      },
     });
   }
 };
 
+QWeb.utils.assignHooks = function assignHooks(dataObj, hooks) {
+  if ("hook" in dataObj) {
+    const hookObject = dataObj.hook;
+    for (let name in hooks) {
+      const current = hookObject[name];
+      const fn = hooks[name];
+      if (current) {
+        hookObject[name] = (...args) => {
+          current(...args);
+          fn(...args);
+        };
+      } else {
+        hookObject[name] = fn;
+      }
+    }
+  } else {
+    dataObj.hook = hooks;
+  }
+};
+
 /**
  * The t-component directive is certainly a complicated and hard to maintain piece
  * of code.  To help you, fellow developer, if you have to maintain it, I offer
@@ -186,19 +207,18 @@ QWeb.utils.defineProxy = function defineProxy(target, source) {
 
 QWeb.addDirective({
   name: "component",
-  extraNames: ["props", "keepalive"],
+  extraNames: ["props"],
   priority: 100,
   atNodeEncounter({ ctx, value, node, qweb }): boolean {
-    ctx.addLine("//COMPONENT");
-    ctx.rootContext.shouldDefineOwner = true;
+    ctx.addLine(`// Component '${value}'`);
     ctx.rootContext.shouldDefineQWeb = true;
     ctx.rootContext.shouldDefineParent = true;
     ctx.rootContext.shouldDefineUtils = true;
-    let keepAlive = node.getAttribute("t-keepalive") ? true : false;
+    ctx.rootContext.shouldDefineScope = true;
     let hasDynamicProps = node.getAttribute("t-props") ? true : false;
 
     // t-on- events and t-transition
-    const events: [string, string[], string, string][] = [];
+    const events: [string, string][] = [];
     let transition: string = "";
     const attributes = (<Element>node).attributes;
     const props: { [key: string]: string } = {};
@@ -206,54 +226,26 @@ QWeb.addDirective({
       const name = attributes[i].name;
       const value = attributes[i].textContent!;
       if (name.startsWith("t-on-")) {
-        const [eventName, ...mods] = name.slice(5).split(".");
-        let extraArgs;
-        let handlerValue = value.replace(/\(.*\)/, function(args) {
-          extraArgs = args.slice(1, -1);
-          return "";
-        });
-        events.push([eventName, mods, handlerValue, extraArgs]);
+        events.push([name, value]);
       } else if (name === "t-transition") {
-        transition = value;
+        if (QWeb.enableTransitions) {
+          transition = value;
+        }
       } else if (!name.startsWith("t-")) {
         if (name !== "class" && name !== "style") {
           // this is a prop!
-          props[name] = ctx.formatExpression(value);
+          props[name] = ctx.formatExpression(value) || "undefined";
         }
       }
     }
 
-    let key = node.getAttribute("t-key");
-    if (key) {
-      key = ctx.formatExpression(key);
-    }
-
     // computing the props string representing the props object
     let propStr = Object.keys(props)
-      .map(k => k + ":" + props[k])
+      .map((k) => k + ":" + props[k])
       .join(",");
-    let defID = ctx.generateID();
     let componentID = ctx.generateID();
-    let keyID = key && ctx.generateID();
-    if (key) {
-      // we bind a variable to the key (could be a complex expression, so we
-      // want to evaluate it only once)
-      ctx.addLine(`let key${keyID} = 'key' + ${key};`);
-    }
-
-    let locationExpr = `\`__${ctx.generateID()}__`;
-    for (let i = 0; i < ctx.loopNumber - 1; i++) {
-      locationExpr += `\${i${i + 1}}__`;
-    }
-    if (key || ctx.currentKey) {
-      const k = key ? `key${keyID}` : ctx.currentKey;
-      ctx.addLine(`let templateId${componentID} = ${locationExpr}\` + ${k};`);
-    } else {
-      locationExpr += ctx.loopNumber ? `\${i${ctx.loopNumber}}__\`` : "`";
-      ctx.addLine(`let templateId${componentID} = ${locationExpr};`);
-    }
-    const templateId = `templateId${componentID}`;
 
+    const templateKey = ctx.generateTemplateKey();
     let ref = node.getAttribute("t-ref");
     let refExpr = "";
     let refKey: string = "";
@@ -263,18 +255,15 @@ QWeb.addDirective({
       ctx.addLine(`const ${refKey} = ${ctx.interpolate(ref)};`);
       refExpr = `context.__owl__.refs[${refKey}] = w${componentID};`;
     }
-    let transitionsInsertCode = "";
-    if (transition) {
-      transitionsInsertCode = `utils.transitionInsert(vn, '${transition}');`;
-    }
-    let finalizeComponentCode = `w${componentID}.${keepAlive ? "unmount" : "destroy"}();`;
-    if (ref && !keepAlive) {
+    let finalizeComponentCode = `w${componentID}.destroy();`;
+    if (ref) {
       finalizeComponentCode += `delete context.__owl__.refs[${refKey}];`;
     }
     if (transition) {
       finalizeComponentCode = `let finalize = () => {
           ${finalizeComponentCode}
         };
+        delete w${componentID}.__owl__.transitionInserted;
         utils.transitionRemove(vn, '${transition}', finalize);`;
     }
 
@@ -294,7 +283,7 @@ QWeb.addDirective({
         let classDef = classAttr
           .trim()
           .split(/\s+/)
-          .map(a => `'${a}':true`)
+          .map((a) => `'${a}':true`)
           .join(",");
         classObj = `_${ctx.generateID()}`;
         ctx.addLine(`let ${classObj} = {${classDef}};`);
@@ -312,48 +301,31 @@ QWeb.addDirective({
         }
       }
       let eventsCode = events
-        .map(function([eventName, mods, handlerValue, extraArgs]) {
-          let params = "owner";
-          if (extraArgs) {
-            if (ctx.loopNumber) {
-              let argId = ctx.generateID();
-              // we need to evaluate the arguments now, because the handler will
-              // be set asynchronously later when the widget is ready, and the
-              // context might be different.
-              ctx.addLine(`let arg${argId} = ${ctx.formatExpression(extraArgs)};`);
-              params = `owner, arg${argId}`;
-            } else {
-              params = `owner, ${ctx.formatExpression(extraArgs)}`;
-            }
+        .map(function ([name, value]) {
+          const capture = name.match(/\.capture/);
+          name = capture ? name.replace(/\.capture/, "") : name;
+          const { event, handler } = makeHandlerCode(
+            ctx,
+            name,
+            value,
+            false,
+            T_COMPONENT_MODS_CODE
+          );
+          if (capture) {
+            return `vn.elm.addEventListener('${event}', ${handler}, true);`;
           }
-          let handler = `function (e) {`;
-          handler += mods
-            .map(function(mod) {
-              return T_COMPONENT_MODS_CODE[mod];
-            })
-            .join("");
-          if (handlerValue) {
-            handler += `const fn = owner['${handlerValue}'];`;
-            handler += `if (fn) { fn.call(${params}, e); } else { owner.${handlerValue}; }`;
-          }
-          handler += `}`;
-          return `vn.elm.addEventListener('${eventName}', ${handler});`;
+          return `vn.elm.addEventListener('${event}', ${handler});`;
         })
         .join("");
       const styleExpr = tattStyle || (styleAttr ? `'${styleAttr}'` : false);
       const styleCode = styleExpr ? `vn.elm.style = ${styleExpr};` : "";
-      createHook = `vnode.data.hook = {create(_, vn){${styleCode}${eventsCode}}};`;
+      createHook = `utils.assignHooks(vnode.data, {create(_, vn){${styleCode}${eventsCode}}});`;
     }
 
     ctx.addLine(
-      `let w${componentID} = ${templateId} in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap[${templateId}]] : false;`
+      `let w${componentID} = ${templateKey} in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap[${templateKey}]] : false;`
     );
     let shouldProxy = !ctx.parentNode;
-    if (keepAlive) {
-      ctx.addLine(
-        `const fiber${componentID} = Object.assign(Object.create(extra.fiber), {patchQueue: []});`
-      );
-    }
     if (shouldProxy) {
       let id = ctx.generateID();
       ctx.rootContext.rootNode = id;
@@ -381,54 +353,21 @@ QWeb.addDirective({
     }
 
     // SLOTS
-    const varDefs: string[] = [];
     const hasSlots = node.childNodes.length;
-    if (hasSlots) {
-      ctx.rootContext.shouldTrackScope = true;
-      for (let v of Object.values(ctx.variables)) {
-        if (v["id"]) {
-          varDefs.push(v["id"]);
-        }
-      }
-    }
 
-    let scopeVars;
-    if (hasSlots) {
-      let scope = ctx.scopeVars.length ? `Object.assign({}, scope)` : `{}`;
-      let vars = varDefs.length ? `{${varDefs.join(",")}}` : "undefined";
-      scopeVars = `${scope}, ${vars}`;
-    } else {
-      scopeVars = "undefined, undefined";
-    }
+    let scope = hasSlots ? `Object.assign(Object.create(context), scope)` : "undefined";
 
     ctx.addIf(`w${componentID}`);
 
     // need to update component
-    let patchQueueCode = keepAlive ? `fiber${componentID}` : "extra.fiber";
-    if (keepAlive) {
-      // if we have t-keepalive="1", the component could be unmounted, but then
-      // we __updateProps is called.  This is ok, but we do not want to call
-      // the willPatch/patched hooks of the component in this case, so we
-      // disable the patch queue
-      patchQueueCode = `w${componentID}.__owl__.isMounted ? extra.fiber : fiber${componentID}`;
-    }
-    if (QWeb.dev) {
-      ctx.addLine(`utils.validateProps(w${componentID}.constructor, props${componentID})`);
-    }
     let styleCode = "";
     if (tattStyle) {
-      styleCode = `.then(()=>{if (w${componentID}.__owl__.isDestroyed) {return};w${componentID}.el.style=${tattStyle};});`;
+      styleCode = `.then(()=>{if (w${componentID}.__owl__.status === ${STATUS.DESTROYED}) {return};w${componentID}.el.style=${tattStyle};});`;
     }
     ctx.addLine(
-      `w${componentID}.__updateProps(props${componentID}, ${patchQueueCode}${scopeVars &&
-        ", " + scopeVars}, sibling)${styleCode};`
+      `w${componentID}.__updateProps(props${componentID}, extra.fiber, ${scope})${styleCode};`
     );
     ctx.addLine(`let pvnode = w${componentID}.__owl__.pvnode;`);
-    let keepAliveCode = "";
-    if (keepAlive) {
-      keepAliveCode = `pvnode.data.hook.insert = vn => {vn.elm.parentNode.replaceChild(w${componentID}.el,vn.elm);vn.elm=w${componentID}.el;w${componentID}.__remount();};`;
-      ctx.addLine(keepAliveCode);
-    }
     if (registerCode) {
       ctx.addLine(registerCode);
     }
@@ -439,14 +378,11 @@ QWeb.addDirective({
     ctx.addElse();
 
     // new component
-    let dynamicFallback = "";
-    if (!value.match(INTERP_REGEXP)) {
-      dynamicFallback = `|| ${ctx.formatExpression(value)}`;
-    }
+    const contextualValue = value.match(INTERP_REGEXP) ? "false" : ctx.formatExpression(value);
     const interpValue = ctx.interpolate(value);
     ctx.addLine(`let componentKey${componentID} = ${interpValue};`);
     ctx.addLine(
-      `let W${componentID} = context.constructor.components[componentKey${componentID}] || QWeb.components[componentKey${componentID}]${dynamicFallback};`
+      `let W${componentID} = ${contextualValue} || context.constructor.components[componentKey${componentID}] || QWeb.components[componentKey${componentID}];`
     );
 
     // maybe only do this in dev mode...
@@ -454,20 +390,64 @@ QWeb.addDirective({
       `if (!W${componentID}) {throw new Error('Cannot find the definition of component "' + componentKey${componentID} + '"')}`
     );
     ctx.addLine(`w${componentID} = new W${componentID}(parent, props${componentID});`);
-    ctx.addLine(`parent.__owl__.cmap[${templateId}] = w${componentID}.__owl__.id;`);
+    if (transition) {
+      ctx.addLine(`const __patch${componentID} = w${componentID}.__patch;`);
+      ctx.addLine(
+        `w${componentID}.__patch = (t, vn) => {__patch${componentID}.call(w${componentID}, t, vn); if(!w${componentID}.__owl__.transitionInserted){w${componentID}.__owl__.transitionInserted = true;utils.transitionInsert(w${componentID}.__owl__.vnode, '${transition}');}};`
+      );
+    }
+    ctx.addLine(`parent.__owl__.cmap[${templateKey}] = w${componentID}.__owl__.id;`);
 
     if (hasSlots) {
       const clone = <Element>node.cloneNode(true);
-      const slotNodes = clone.querySelectorAll("[t-set]");
+
+      // The next code is a fallback for compatibility reason. It accepts t-set
+      // elements that are direct children with a non empty body as nodes defining
+      // the content of a slot.
+      //
+      // This is wrong, but is necessary to prevent breaking all existing Owl
+      // code using slots. This will be removed in v2.0 someday. Meanwhile,
+      // please use t-set-slot everywhere you need to set the content of a
+      // slot.
+      for (let node of clone.children) {
+        if (node.hasAttribute("t-set") && node.hasChildNodes()) {
+          node.setAttribute("t-set-slot", node.getAttribute("t-set")!);
+          node.removeAttribute("t-set");
+        }
+      }
+      const slotNodes = Array.from(clone.querySelectorAll("[t-set-slot]"));
+      const slotNames = new Set<string>();
       const slotId = QWeb.nextSlotId++;
       ctx.addLine(`w${componentID}.__owl__.slotId = ${slotId};`);
       if (slotNodes.length) {
         for (let i = 0, length = slotNodes.length; i < length; i++) {
           const slotNode = slotNodes[i];
+          // check if this is defined in a sub component (in which case it should
+          // be ignored)
+          let el = slotNode.parentElement;
+          let isInSubComponent = false;
+          while (el !== clone) {
+            if (
+              el!.hasAttribute("t-component") ||
+              el!.tagName[0] === el!.tagName[0].toUpperCase()
+            ) {
+              isInSubComponent = true;
+              break;
+            }
+            el = el.parentElement;
+          }
+          if (isInSubComponent) {
+            continue;
+          }
+          let key = slotNode.getAttribute("t-set-slot")!;
+          if (slotNames.has(key)) {
+            continue;
+          }
+          slotNames.add(key);
+          slotNode.removeAttribute("t-set-slot");
           slotNode.parentElement!.removeChild(slotNode);
-          const key = slotNode.getAttribute("t-set")!;
-          slotNode.removeAttribute("t-set");
-          const slotFn = qweb._compile(`slot_${key}_template`, slotNode, ctx);
+
+          const slotFn = qweb._compile(`slot_${key}_template`, { elem: slotNode, hasParent: true });
           QWeb.slots[`${slotId}_${key}`] = slotFn;
         }
       }
@@ -476,19 +456,18 @@ QWeb.addDirective({
         for (let child of Object.values(clone.childNodes)) {
           t.appendChild(child);
         }
-        const slotFn = qweb._compile(`slot_default_template`, t, ctx);
+        const slotFn = qweb._compile(`slot_default_template`, { elem: t, hasParent: true });
         QWeb.slots[`${slotId}_default`] = slotFn;
       }
     }
 
-    ctx.addLine(`let def${defID} = w${componentID}.__prepare(extra.fiber, ${scopeVars}, sibling);`);
-    // hack: specify empty remove hook to prevent the node from being removed from the DOM
     ctx.addLine(
-      `let pvnode = h('dummy', {key: ${templateId}, hook: {insert(vn) { let nvn=w${componentID}.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;${refExpr}${transitionsInsertCode}},remove() {},destroy(vn) {${finalizeComponentCode}}}});`
+      `let fiber = w${componentID}.__prepare(extra.fiber, ${scope}, () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; ${createHook}});`
     );
-    ctx.addLine(`const fiber = w${componentID}.__owl__.currentFiber;`);
+    // hack: specify empty remove hook to prevent the node from being removed from the DOM
+    const insertHook = refExpr ? `insert(vn) {${refExpr}},` : "";
     ctx.addLine(
-      `def${defID}.then(function () {if (w${componentID}.__owl__.isDestroyed) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; ${createHook}});`
+      `let pvnode = h('dummy', {key: ${templateKey}, hook: {${insertHook}remove() {},destroy(vn) {${finalizeComponentCode}}}});`
     );
     if (registerCode) {
       ctx.addLine(registerCode);
@@ -504,8 +483,8 @@ QWeb.addDirective({
       ctx.addLine(`w${componentID}.__owl__.classObj=${classObj};`);
     }
 
-    ctx.addLine(`sibling = w${componentID}.__owl__.currentFiber || sibling;`);
+    ctx.addLine(`w${componentID}.__owl__.parentLastFiberId = extra.fiber.id;`);
 
     return true;
-  }
+  },
 });

src/component/fiber.ts

@@ -1,5 +1,6 @@
-import { VNode } from "../vdom/index";
-import { Component } from "./component";
+import { h, VNode } from "../vdom/index";
+import { Component, MountPosition, STATUS } from "./component";
+import { scheduler } from "./scheduler";
 
 /**
  * Owl Fiber Class
@@ -15,13 +16,17 @@ import { Component } from "./component";
  */
 
 export class Fiber {
+  static nextId: number = 1;
+  id: number = Fiber.nextId++;
+
   // The force attribute determines if a rendering should bypass the `shouldUpdate`
   // method potentially implemented by a component. It is usually set to false.
   force: boolean;
 
-  // isCancelled means that the rendering corresponding to this fiber and its
-  // children is cancelled. No extra work should be done.
-  isCancelled: boolean = false;
+  // isCompleted means that the rendering corresponding to this fiber's work is
+  // done, either because the component has been mounted or patched, or because
+  // fiber has been cancelled.
+  isCompleted: boolean = false;
 
   // the fibers corresponding to component updates (updateProps) need to call
   // the willPatch and patched hooks from the corresponding component. However,
@@ -41,36 +46,79 @@ export class Fiber {
   // scheduler.
   counter: number = 0;
 
-  scope: any;
-  vars: any;
-  props: any;
+  target: HTMLElement | DocumentFragment | null;
+  position: MountPosition | null;
 
-  component: Component<any, any>;
+  scope: any;
+
+  component: Component;
   vnode: VNode | null = null;
 
   root: Fiber;
   child: Fiber | null = null;
   sibling: Fiber | null = null;
+  lastChild: Fiber | null = null;
   parent: Fiber | null = null;
 
-  constructor(parent: Fiber | null, component: Component<any, any>, props, scope, vars, force) {
-    this.force = force;
-    this.scope = scope;
-    this.vars = vars;
-    this.props = props;
+  error?: Error;
+
+  constructor(
+    parent: Fiber | null,
+    component: Component,
+    force: boolean,
+    target: HTMLElement | DocumentFragment | null,
+    position: MountPosition | null
+  ) {
     this.component = component;
+    this.force = force;
+    this.target = target;
+    this.position = position;
+
+    const __owl__ = component.__owl__;
+    this.scope = __owl__.scope;
 
     this.root = parent ? parent.root : this;
     this.parent = parent;
 
-    let oldFiber = component.__owl__.currentFiber;
-    if (oldFiber && !oldFiber.isCancelled) {
-      this._remapFiber(oldFiber);
+    let oldFiber = __owl__.currentFiber;
+    if (oldFiber && !oldFiber.isCompleted) {
+      this.force = true;
+      if (oldFiber.root === oldFiber && !parent) {
+        // both oldFiber and this fiber are root fibers
+        this._reuseFiber(oldFiber);
+        return oldFiber;
+      } else {
+        this._remapFiber(oldFiber);
+      }
     }
 
     this.root.counter++;
 
-    component.__owl__.currentFiber = this;
+    __owl__.currentFiber = this;
+  }
+
+  /**
+   * When the oldFiber is not completed yet, and both oldFiber and this fiber
+   * are root fibers, we want to reuse the oldFiber instead of creating a new
+   * one. Doing so will guarantee that the initiator(s) of those renderings will
+   * be notified (the promise will resolve) when the last rendering will be done.
+   *
+   * This function thus assumes that oldFiber is a root fiber.
+   */
+  _reuseFiber(oldFiber: Fiber) {
+    oldFiber.cancel(); // cancel children fibers
+    oldFiber.target = this.target || oldFiber.target;
+    oldFiber.position = this.position || oldFiber.position;
+    oldFiber.isCompleted = false; // keep the root fiber alive
+    oldFiber.isRendered = false; // the fiber has to be re-rendered
+    if (oldFiber.child) {
+      // remove relation to children
+      oldFiber.child.parent = null;
+      oldFiber.child = null;
+      oldFiber.lastChild = null;
+    }
+    oldFiber.counter = 1; // re-initialize counter
+    oldFiber.id = Fiber.nextId++;
   }
 
   /**
@@ -81,14 +129,18 @@ export class Fiber {
    */
   _remapFiber(oldFiber: Fiber) {
     oldFiber.cancel();
+    this.shouldPatch = oldFiber.shouldPatch;
     if (oldFiber === oldFiber.root) {
-      oldFiber.root.counter++;
+      oldFiber.counter++;
     }
     if (oldFiber.parent && !this.parent) {
       // re-map links
       this.parent = oldFiber.parent;
       this.root = this.parent.root;
       this.sibling = oldFiber.sibling;
+      if (this.parent.lastChild === oldFiber) {
+        this.parent.lastChild = this;
+      }
       if (this.parent.child === oldFiber) {
         this.parent.child = this;
       } else {
@@ -131,69 +183,165 @@ export class Fiber {
   }
 
   /**
-   * Apply the given patch queue from a fiber.
-   *   1) Call 'willPatch' on the component of each patch
-   *   2) Call '__patch' on the component of each patch
-   *   3) Call 'patched' on the component of each patch, in reverse order
+   * Successfully complete the work of the fiber: call the mount or patch hooks
+   * and patch the DOM. This function is called once the fiber and its children
+   * are ready, and the scheduler decides to process it.
    */
-  patchComponents() {
+  complete() {
+    let component = this.component;
+    this.isCompleted = true;
+    const status = component.__owl__.status;
+    if (status === STATUS.DESTROYED) {
+      return;
+    }
+
+    // build patchQueue
     const patchQueue: Fiber[] = [];
-    const doWork: (Fiber) => Fiber | null = function(f) {
-      if (f.shouldPatch) {
-        patchQueue.push(f);
-      }
+    const doWork: (Fiber) => Fiber | null = function (f) {
+      patchQueue.push(f);
       return f.child;
     };
     this._walk(doWork);
-    let component: Component<any, any> = this.component;
-    this.shouldPatch = false;
     const patchLen = patchQueue.length;
-    try {
-      for (let i = 0; i < patchLen; i++) {
-        component = patchQueue[i].component;
-        if (component.__owl__.willPatchCB) {
-          component.__owl__.willPatchCB();
-        }
-        component.willPatch();
-      }
-    } catch (e) {
-      console.error(e);
-    }
-    try {
+
+    // call willPatch hook on each fiber of patchQueue
+    if (status === STATUS.MOUNTED) {
       for (let i = 0; i < patchLen; i++) {
         const fiber = patchQueue[i];
-        component = fiber.component;
-        component.__patch(fiber.vnode);
-      }
-    } catch (e) {
-      this.handleError(e);
-    }
-    try {
-      for (let i = patchLen - 1; i >= 0; i--) {
-        component = patchQueue[i].component;
-        component.patched();
-        if (component.__owl__.patchedCB) {
-          component.__owl__.patchedCB();
+        if (fiber.shouldPatch) {
+          component = fiber.component;
+          if (component.__owl__.willPatchCB) {
+            component.__owl__.willPatchCB();
+          }
+          component.willPatch();
         }
       }
-    } catch (e) {
-      console.error(e);
     }
-    this.shouldPatch = true;
+
+    // call __patch on each fiber of (reversed) patchQueue
+    for (let i = patchLen - 1; i >= 0; i--) {
+      const fiber = patchQueue[i];
+      component = fiber.component;
+      if (fiber.target && i === 0) {
+        let target;
+        if (fiber.position === "self") {
+          target = fiber.target;
+          if ((target as HTMLElement).tagName.toLowerCase() !== fiber.vnode!.sel) {
+            throw new Error(
+              `Cannot attach '${component.constructor.name}' to target node (not same tag name)`
+            );
+          }
+          // In self mode, we *know* we are to take possession of the target
+          // Hence we manually create the corresponding VNode and copy the "key" in data
+          const selfVnodeData = fiber.vnode!.data ? { key: fiber.vnode!.data.key } : {};
+          const selfVnode = h(fiber.vnode!.sel, selfVnodeData);
+          selfVnode.elm = target;
+          target = selfVnode;
+        } else {
+          target = component.__owl__.vnode || document.createElement(fiber.vnode!.sel!);
+        }
+        component.__patch(target!, fiber.vnode!);
+      } else {
+        if (fiber.shouldPatch) {
+          component.__patch(component.__owl__.vnode!, fiber.vnode!);
+          // When updating a Component's props (in directive),
+          // the component has a pvnode AND should be patched.
+          // However, its pvnode.elm may have changed if it is a High Order Component
+          if (component.__owl__.pvnode) {
+            component.__owl__.pvnode.elm = component.__owl__.vnode!.elm;
+          }
+        } else {
+          component.__patch(document.createElement(fiber.vnode!.sel!), fiber.vnode!);
+          component.__owl__.pvnode!.elm = component.__owl__.vnode!.elm;
+        }
+      }
+      const compOwl = component.__owl__;
+      if (fiber === compOwl.currentFiber) {
+        compOwl.currentFiber = null;
+      }
+    }
+
+    // insert into the DOM (mount case)
+    let inDOM = false;
+    if (this.target) {
+      switch (this.position) {
+        case "first-child":
+          this.target.prepend(this.component.el!);
+          break;
+        case "last-child":
+          this.target.appendChild(this.component.el!);
+          break;
+      }
+      inDOM = document.body.contains(this.component.el);
+      this.component.env.qweb.trigger("dom-appended");
+    }
+
+    // call patched/mounted hook on each fiber of (reversed) patchQueue
+    if (status === STATUS.MOUNTED || inDOM) {
+      for (let i = patchLen - 1; i >= 0; i--) {
+        const fiber = patchQueue[i];
+        component = fiber.component;
+        if (fiber.shouldPatch && !this.target) {
+          component.patched();
+          if (component.__owl__.patchedCB) {
+            component.__owl__.patchedCB();
+          }
+        } else {
+          component.__callMounted();
+        }
+      }
+    } else {
+      for (let i = patchLen - 1; i >= 0; i--) {
+        const fiber = patchQueue[i];
+        component = fiber.component;
+        component.__owl__.status = STATUS.UNMOUNTED;
+      }
+    }
   }
 
   /**
    * Cancel a fiber and all its children.
    */
   cancel() {
-    this._walk(f => {
+    this._walk((f) => {
       if (!f.isRendered) {
         f.root.counter--;
       }
-      f.isCancelled = true;
+      f.isCompleted = true;
       return f.child;
     });
   }
 
-  handleError(e: Error) {}
+  /**
+   * This is the global error handler for errors occurring in Owl main lifecycle
+   * methods.  Caught errors are triggered on the QWeb instance, and are
+   * potentially given to some parent component which implements `catchError`.
+   *
+   * If there are no such component, we destroy everything. This is better than
+   * being in a corrupted state.
+   */
+  handleError(error: Error) {
+    let component = this.component;
+    this.vnode = component.__owl__.vnode || h("div");
+
+    const qweb = component.env.qweb;
+    let root = component;
+    let canCatch = false;
+    while (component && !(canCatch = !!component.catchError)) {
+      root = component;
+      component = component.__owl__.parent!;
+    }
+    qweb.trigger("error", error);
+
+    if (canCatch) {
+      component.catchError!(error);
+    } else {
+      // the 3 next lines aim to mark the root fiber as being in error, and
+      // to force it to end, without waiting for its children
+      this.root.counter = 0;
+      this.root.error = error;
+      scheduler.flush();
+      root.destroy();
+    }
+  }
 }

src/component/props_validation.ts

@@ -11,7 +11,7 @@ import { QWeb } from "../qweb/index";
  * This is why it is only done in 'dev' mode.
  */
 
-QWeb.utils.validateProps = function(Widget, props: Object) {
+QWeb.utils.validateProps = function (Widget, props: Object) {
   const propsDef = (<any>Widget).props;
   if (propsDef instanceof Array) {
     // list of strings (prop names)
@@ -21,7 +21,7 @@ QWeb.utils.validateProps = function(Widget, props: Object) {
         // optional prop
         break;
       }
-      if (!props[propName]) {
+      if (!(propName in props)) {
         throw new Error(`Missing props '${propsDef[i]}' (component '${Widget.name}')`);
       }
     }
@@ -37,12 +37,18 @@ QWeb.utils.validateProps = function(Widget, props: Object) {
         if (propsDef[propName] && !propsDef[propName].optional) {
           throw new Error(`Missing props '${propName}' (component '${Widget.name}')`);
         } else {
-          break;
+          continue;
         }
       }
-      let isValid = isValidProp(props[propName], propsDef[propName]);
+      let isValid;
+      try {
+        isValid = isValidProp(props[propName], propsDef[propName]);
+      } catch (e) {
+        e.message = `Invalid prop '${propName}' in component ${Widget.name} (${e.message})`;
+        throw e;
+      }
       if (!isValid) {
-        throw new Error(`Props '${propName}' of invalid type in component '${Widget.name}'`);
+        throw new Error(`Invalid Prop '${propName}' in component '${Widget.name}'`);
       }
     }
     for (let propName in props) {
@@ -80,17 +86,30 @@ function isValidProp(prop, propDef): boolean {
     return result;
   }
   // propsDef is an object
-  let result = isValidProp(prop, propDef.type);
-  if (propDef.type === Array) {
+  if (propDef.optional && prop === undefined) {
+    return true;
+  }
+  let result = propDef.type ? isValidProp(prop, propDef.type) : true;
+  if (propDef.validate) {
+    result = result && propDef.validate(prop);
+  }
+  if (propDef.type === Array && propDef.element) {
     for (let i = 0, iLen = prop.length; i < iLen; i++) {
       result = result && isValidProp(prop[i], propDef.element);
     }
   }
-  if (propDef.type === Object) {
+  if (propDef.type === Object && propDef.shape) {
     const shape = propDef.shape;
     for (let key in shape) {
       result = result && isValidProp(prop[key], shape[key]);
     }
+    if (result) {
+      for (let propName in prop) {
+        if (!(propName in shape)) {
+          throw new Error(`unknown prop '${propName}'`);
+        }
+      }
+    }
   }
   return result;
 }

src/component/scheduler.ts

@@ -1,4 +1,5 @@
 import { Fiber } from "./fiber";
+import { browser } from "../browser";
 
 /**
  * Owl Scheduler Class
@@ -13,26 +14,61 @@ import { Fiber } from "./fiber";
 
 interface Task {
   fiber: Fiber;
-  callback: () => void;
+  callback: (err?: Error) => void;
 }
 
 export class Scheduler {
   tasks: Task[] = [];
   isRunning: boolean = false;
-  requestAnimationFrame: typeof window.requestAnimationFrame;
+  requestAnimationFrame: Window["requestAnimationFrame"];
 
-  constructor(requestAnimationFrame) {
+  constructor(requestAnimationFrame: Window["requestAnimationFrame"]) {
     this.requestAnimationFrame = requestAnimationFrame;
   }
 
-  addFiber(fiber, callback) {
-    this.tasks.push({ fiber, callback });
-    if (this.isRunning) {
-      return;
-    }
+  start() {
+    this.isRunning = true;
     this.scheduleTasks();
   }
 
+  stop() {
+    this.isRunning = false;
+  }
+
+  addFiber(fiber: Fiber): Promise<void> {
+    // if the fiber was remapped into a larger rendering fiber, it may not be a
+    // root fiber.  But we only want to register root fibers
+    fiber = fiber.root;
+    return new Promise((resolve, reject) => {
+      if (fiber.error) {
+        return reject(fiber.error);
+      }
+      this.tasks.push({
+        fiber,
+        callback: () => {
+          if (fiber.error) {
+            return reject(fiber.error);
+          }
+          resolve();
+        },
+      });
+      if (!this.isRunning) {
+        this.start();
+      }
+    });
+  }
+
+  rejectFiber(fiber: Fiber, reason: string) {
+    fiber = fiber.root;
+    const index = this.tasks.findIndex((t) => t.fiber === fiber);
+    if (index >= 0) {
+      const [task] = this.tasks.splice(index, 1);
+      fiber.cancel();
+      fiber.error = new Error(reason);
+      task.callback();
+    }
+  }
+
   /**
    * Process all current tasks. This only applies to the fibers that are ready.
    * Other tasks are left unchanged.
@@ -40,28 +76,38 @@ export class Scheduler {
   flush() {
     let tasks = this.tasks;
     this.tasks = [];
-    tasks = tasks.filter(task => {
-      if (task.fiber.isCancelled) {
+    tasks = tasks.filter((task) => {
+      if (task.fiber.isCompleted) {
+        task.callback();
         return false;
       }
       if (task.fiber.counter === 0) {
+        if (!task.fiber.error) {
+          try {
+            task.fiber.complete();
+          } catch (e) {
+            task.fiber.handleError(e);
+          }
+        }
         task.callback();
         return false;
       }
       return true;
     });
     this.tasks = tasks.concat(this.tasks);
+    if (this.tasks.length === 0) {
+      this.stop();
+    }
   }
 
   scheduleTasks() {
-    this.isRunning = true;
     this.requestAnimationFrame(() => {
       this.flush();
-      if (this.tasks.length > 0) {
+      if (this.isRunning) {
         this.scheduleTasks();
-      } else {
-        this.isRunning = false;
       }
     });
   }
 }
+
+export const scheduler = new Scheduler(browser.requestAnimationFrame);

src/component/styles.ts

@@ -0,0 +1,70 @@
+/**
+ * Owl Style System
+ *
+ * This files contains the Owl code related to processing (extended) css strings
+ * and creating/adding <style> tags to the document head.
+ */
+
+export const STYLESHEETS: { [id: string]: HTMLStyleElement } = {};
+
+export function processSheet(str: string): string {
+  const tokens = str.split(/(\{|\}|;)/).map((s) => s.trim());
+  const selectorStack: string[][] = [];
+  const parts: string[] = [];
+  let rules: string[] = [];
+  function generateSelector(stackIndex: number, parentSelector?: string) {
+    const parts: string[] = [];
+    for (const selector of selectorStack[stackIndex]) {
+      let part = (parentSelector && parentSelector + " " + selector) || selector;
+      if (part.includes("&")) {
+        part = selector.replace(/&/g, parentSelector || "");
+      }
+      if (stackIndex < selectorStack.length - 1) {
+        part = generateSelector(stackIndex + 1, part);
+      }
+      parts.push(part);
+    }
+    return parts.join(", ");
+  }
+  function generateRules() {
+    if (rules.length) {
+      parts.push(generateSelector(0) + " {");
+      parts.push(...rules);
+      parts.push("}");
+      rules = [];
+    }
+  }
+  while (tokens.length) {
+    let token = tokens.shift()!;
+    if (token === "}") {
+      generateRules();
+      selectorStack.pop();
+    } else {
+      if (tokens[0] === "{") {
+        generateRules();
+        selectorStack.push(token.split(/\s*,\s*/));
+        tokens.shift();
+      }
+      if (tokens[0] === ";") {
+        rules.push("  " + token + ";");
+      }
+    }
+  }
+  return parts.join("\n");
+}
+export function registerSheet(id: string, css: string) {
+  const sheet = document.createElement("style");
+  sheet.innerHTML = processSheet(css);
+  STYLESHEETS[id] = sheet;
+}
+
+export function activateSheet(id, name) {
+  const sheet = STYLESHEETS[id];
+  if (!sheet) {
+    throw new Error(
+      `Invalid css stylesheet for component '${name}'. Did you forget to use the 'css' tag helper?`
+    );
+  }
+  sheet.setAttribute("component", name);
+  document.head.appendChild(sheet);
+}

src/config.ts

@@ -0,0 +1,40 @@
+import { QWeb } from "./qweb/index";
+
+/**
+ * This file creates and exports the OWL 'config' object, with keys:
+ *  - 'mode': 'prod' or 'dev',
+ *  - 'env': the environment to use in root components.
+ */
+
+interface Config {
+  mode: string;
+  enableTransitions: boolean;
+}
+
+export const config = {} as Config;
+
+Object.defineProperty(config, "mode", {
+  get() {
+    return QWeb.dev ? "dev" : "prod";
+  },
+  set(mode: string) {
+    QWeb.dev = mode === "dev";
+    if (QWeb.dev) {
+      const url = `https://github.com/odoo/owl/blob/master/doc/reference/config.md#mode`;
+      console.warn(
+        `Owl is running in 'dev' mode.  This is not suitable for production use. See ${url} for more information.`
+      );
+    } else {
+      console.log(`Owl is now running in 'prod' mode.`);
+    }
+  },
+});
+
+Object.defineProperty(config, "enableTransitions", {
+  get() {
+    return QWeb.enableTransitions;
+  },
+  set(value: boolean) {
+    QWeb.enableTransitions = value;
+  },
+});

src/context.ts

@@ -1,7 +1,8 @@
-import { Component, scheduler } from "./component/component";
+import { Component } from "./component/component";
+import { scheduler } from "./component/scheduler";
 import { EventBus } from "./core/event_bus";
 import { Observer } from "./core/observer";
-import { onWillUnmount } from "./hooks";
+
 /**
  * The `Context` object provides a way to share data between an arbitrary number
  * of component. Usually, data is passed from a parent to its children component,
@@ -12,6 +13,28 @@ import { onWillUnmount } from "./hooks";
  * With a `Context` object, each component can subscribe (with the `useContext`
  * hook) to its state, and will be updated whenever the context state is updated.
  */
+
+function partitionBy<T>(arr: T[], fn: (t: T) => boolean) {
+  let lastGroup: T[] | false = false;
+  let lastValue;
+  return arr.reduce((acc: T[][], cur) => {
+    let curVal = fn(cur);
+    if (lastGroup) {
+      if (curVal === lastValue) {
+        lastGroup.push(cur);
+      } else {
+        lastGroup = false;
+      }
+    }
+    if (!lastGroup) {
+      lastGroup = [cur];
+      acc.push(lastGroup);
+    }
+    lastValue = curVal;
+    return acc;
+  }, []);
+}
+
 export class Context extends EventBus {
   state: any;
   observer: Observer;
@@ -22,40 +45,52 @@ export class Context extends EventBus {
   constructor(state: Object = {}) {
     super();
     this.observer = new Observer();
-    this.observer.notifyCB = this.__notifyComponents.bind(this);
+    this.observer.notifyCB = () => {
+      // notify components in the next microtask tick to ensure that subscribers
+      // are notified only once for all changes that occur in the same micro tick
+      let rev = this.rev;
+      return Promise.resolve().then(() => {
+        if (rev === this.rev) {
+          this.__notifyComponents();
+        }
+      });
+    };
     this.state = this.observer.observe(state);
+    this.subscriptions.update = [];
   }
 
   /**
    * Instead of using trigger to emit an update event, we actually implement
    * our own function to do that.  The reason is that we need to be smarter than
    * a simple trigger function: we need to wait for parent components to be
-   * done before doing children components.  The reason is that if an update
-   * as an effect of destroying a children, we do not want to call the
-   * mapStoreToProps function of the child, nor rendering it.
+   * done before doing children components.  More precisely, if an update
+   * as an effect of destroying a children, we do not want to call any code
+   * from the child, and certainly not render it.
    *
-   * This method is not optimal if we have a bunch of asynchronous components:
-   * we wait sequentially for each component to be completed before updating the
-   * next.  However, the only things that matters is that children are updated
-   * after their parents.  So, this could be optimized by being smarter, and
-   * updating all widgets concurrently, except for parents/children.
+   * This method implements a simple grouping algorithm by depth. If we have
+   * connected components of depths [2, 4,4,4,4, 3,8,8], the Context will notify
+   * them in the following groups: [2], [4,4,4,4], [3], [8,8]. Each group will
+   * be updated sequentially, but each components in a given group will be done in
+   * parallel.
    *
-   * A potential cheap way to improve this situation is to keep track of the
-   * depth of a component in the component tree. A root component has a depth of
-   * 1, then its children of 2 and so on... Then, we can update all components
-   * with the same depth in parallel.
+   * This is a very simple algorithm, but it avoids checking if a given
+   * component is a child of another.
    */
   async __notifyComponents() {
     const rev = ++this.rev;
-    const subs = this.subscriptions.update || [];
-    for (let i = 0, iLen = subs.length; i < iLen; i++) {
-      const sub = subs[i];
-      const shouldCallback = sub.owner ? sub.owner.__owl__.isMounted : true;
-      if (shouldCallback) {
-        const render = sub.callback.call(sub.owner, rev);
-        scheduler.flush();
-        await render;
-      }
+    const subscriptions = this.subscriptions.update;
+    const groups = partitionBy(subscriptions, (s) => (s.owner ? s.owner.__owl__.depth : -1));
+    for (let group of groups) {
+      const proms = group.map((sub) => sub.callback.call(sub.owner, rev));
+      // at this point, each component in the current group has registered a
+      // top level fiber in the scheduler. It could happen that rendering these
+      // components is done (if they have no children).  This is why we manually
+      // flush the scheduler.  This will force the scheduler to check
+      // immediately if they are done, which will cause their rendering
+      // promise to resolve earlier, which means that there is a chance of
+      // processing the next group in the same frame.
+      scheduler.flush();
+      await Promise.all(proms);
     }
   }
 }
@@ -65,11 +100,11 @@ export class Context extends EventBus {
  * to context state changes. The `useContext` method returns the context state
  */
 export function useContext(ctx: Context): any {
-  const component: Component<any, any> = Component.current!;
+  const component: Component = Component.current!;
   return useContextWithCB(ctx, component, component.render.bind(component));
 }
 
-export function useContextWithCB(ctx: Context, component: Component<any, any>, method): any {
+export function useContextWithCB(ctx: Context, component: Component, method): any {
   const __owl__ = component.__owl__;
   const id = __owl__.id;
   const mapping = ctx.mapping;
@@ -80,32 +115,24 @@ export function useContextWithCB(ctx: Context, component: Component<any, any>, m
     __owl__.observer = new Observer();
     __owl__.observer.notifyCB = component.render.bind(component);
   }
-  const currentCB = __owl__.observer.notifyCB;
-  __owl__.observer.notifyCB = function () {
-      if (ctx.rev > mapping[id]) {
-          // in this case, the context has been updated since we were rendering
-          // last, and we do not need to render here with the observer. A
-          // rendering is coming anyway, with the correct props.
-          return;
-      }
-      currentCB();
-  }
 
   mapping[id] = 0;
   const renderFn = __owl__.renderFn;
-  __owl__.renderFn = function(comp, params) {
+  __owl__.renderFn = function (comp, params) {
     mapping[id] = ctx.rev;
     return renderFn(comp, params);
   };
-  ctx.on("update", component, async contextRev => {
+  ctx.on("update", component, async (contextRev) => {
     if (mapping[id] < contextRev) {
       mapping[id] = contextRev;
       await method();
     }
   });
-  onWillUnmount(() => {
+  const __destroy = component.__destroy;
+  component.__destroy = (parent) => {
     ctx.off("update", component);
     delete mapping[id];
-  });
+    __destroy.call(component, parent);
+  };
   return ctx.state;
 }

src/core/event_bus.ts

@@ -44,7 +44,7 @@ export class EventBus {
     }
     this.subscriptions[eventType].push({
       owner,
-      callback
+      callback,
     });
   }
 
@@ -54,7 +54,7 @@ export class EventBus {
   off(eventType: string, owner: any) {
     const subs = this.subscriptions[eventType];
     if (subs) {
-      this.subscriptions[eventType] = subs.filter(s => s.owner !== owner);
+      this.subscriptions[eventType] = subs.filter((s) => s.owner !== owner);
     }
   }
 

src/core/observer.ts

@@ -20,21 +20,17 @@
 export class Observer {
   rev: number = 1;
   allowMutations: boolean = true;
-  dirty: boolean = false;
   weakMap: WeakMap<any, any> = new WeakMap();
 
   notifyCB() {}
-  async notifyChange() {
-    this.dirty = true;
-    await Promise.resolve();
-    if (this.dirty) {
-      this.dirty = false;
-      this.notifyCB();
-    }
-  }
 
   observe<T>(value: T, parent?: any): T {
-    if (value === null || typeof value !== "object" || value instanceof Date) {
+    if (
+      value === null ||
+      typeof value !== "object" ||
+      value instanceof Date ||
+      value instanceof Promise
+    ) {
       // fun fact: typeof null === 'object'
       return value;
     }
@@ -46,10 +42,6 @@ export class Observer {
     const metadata = this.weakMap.get(value);
     return metadata ? metadata.rev : 0;
   }
-  deepRevNumber(value): number {
-    const metadata = this.weakMap.get(value);
-    return metadata ? metadata.deepRev : 0;
-  }
 
   _observe(value, parent) {
     var self = this;
@@ -69,7 +61,7 @@ export class Observer {
           }
           self._updateRevNumber(target);
           target[key] = newVal;
-          self.notifyChange();
+          self.notifyCB();
         }
         return true;
       },
@@ -77,18 +69,17 @@ export class Observer {
         if (key in target) {
           delete target[key];
           self._updateRevNumber(target);
-          self.notifyChange();
+          self.notifyCB();
         }
         return true;
-      }
+      },
     });
 
     const metadata = {
       value,
       proxy,
       rev: this.rev,
-      deepRev: this.rev,
-      parent
+      parent,
     };
 
     this.weakMap.set(value, metadata);
@@ -99,11 +90,10 @@ export class Observer {
   _updateRevNumber(target: any) {
     this.rev++;
     let metadata = this.weakMap.get(target);
-    metadata.rev!++;
     let parent = target;
     do {
       metadata = this.weakMap.get(parent);
-      metadata.deepRev++;
+      metadata.rev++;
     } while ((parent = metadata.parent) && parent !== target);
   }
 }

src/core/owl_event.ts

@@ -0,0 +1,15 @@
+import { Component } from "../component/component";
+
+/**
+ * We define here OwlEvent, a subclass of CustomEvent, with an additional
+ * attribute:
+ *  - originalComponent: the component that triggered the event
+ */
+
+export class OwlEvent<T> extends CustomEvent<T> {
+  originalComponent: Component;
+  constructor(component, eventType, options) {
+    super(eventType, options);
+    this.originalComponent = component;
+  }
+}

src/hooks.ts

@@ -1,4 +1,4 @@
-import { Component } from "./component/component";
+import { Component, Env } from "./component/component";
 import { Observer } from "./core/observer";
 
 /**
@@ -22,7 +22,7 @@ import { Observer } from "./core/observer";
  * trigger a rerendering of the current component.
  */
 export function useState<T>(state: T): T {
-  const component: Component<any, any> = Component.current!;
+  const component: Component = Component.current!;
   const __owl__ = component.__owl__;
   if (!__owl__.observer) {
     __owl__.observer = new Observer();
@@ -36,11 +36,11 @@ export function useState<T>(state: T): T {
 // -----------------------------------------------------------------------------
 function makeLifecycleHook(method: string, reverse: boolean = false) {
   if (reverse) {
-    return function(cb) {
-      const component: Component<any, any> = Component.current!;
+    return function (cb) {
+      const component: Component = Component.current!;
       if (component.__owl__[method]) {
         const current = component.__owl__[method];
-        component.__owl__[method] = function() {
+        component.__owl__[method] = function () {
           current.call(component);
           cb.call(component);
         };
@@ -49,11 +49,11 @@ function makeLifecycleHook(method: string, reverse: boolean = false) {
       }
     };
   } else {
-    return function(cb) {
-      const component: Component<any, any> = Component.current!;
+    return function (cb) {
+      const component: Component = Component.current!;
       if (component.__owl__[method]) {
         const current = component.__owl__[method];
-        component.__owl__[method] = function() {
+        component.__owl__[method] = function () {
           cb.call(component);
           current.call(component);
         };
@@ -65,12 +65,12 @@ function makeLifecycleHook(method: string, reverse: boolean = false) {
 }
 
 function makeAsyncHook(method: string) {
-  return function(cb) {
-    const component: Component<any, any> = Component.current!;
+  return function (cb) {
+    const component: Component = Component.current!;
     if (component.__owl__[method]) {
       const current = component.__owl__[method];
-      component.__owl__[method] = function(...args) {
-        return Promise.all[(current.call(component, ...args), cb.call(component, ...args))];
+      component.__owl__[method] = function (...args) {
+        return Promise.all([current.call(component, ...args), cb.call(component, ...args)]);
       };
     } else {
       component.__owl__[method] = cb;
@@ -94,25 +94,50 @@ export const onWillUpdateProps = makeAsyncHook("willUpdatePropsCB");
  * The purpose of this hook is to allow components to get a reference to a sub
  * html node or component.
  */
-interface Ref {
+interface Ref<C extends Component = Component> {
   el: HTMLElement | null;
-  comp: Component<any, any> | null;
+  comp: C | null;
 }
 
-export function useRef(name: string): Ref {
+export function useRef<C extends Component = Component>(name: string): Ref<C> {
   const __owl__ = Component.current!.__owl__;
   return {
     get el(): HTMLElement | null {
       const val = __owl__.refs && __owl__.refs[name];
-      return val instanceof HTMLElement ? val : null;
+      if (val instanceof HTMLElement) {
+        return val;
+      } else if (val instanceof Component) {
+        return val.el;
+      }
+      return null;
     },
-    get comp(): Component<any, any> | null {
+    get comp(): C | null {
       const val = __owl__.refs && __owl__.refs[name];
-      return val instanceof Component ? val : null;
-    }
+      return val instanceof Component ? (val as C) : null;
+    },
   };
 }
 
+// -----------------------------------------------------------------------------
+// "Builder" hooks
+// -----------------------------------------------------------------------------
+
+/**
+ * This hook is useful as a building block for some customized hooks, that may
+ * need a reference to the component calling them.
+ */
+export function useComponent<P, E extends Env>(): Component<P, E> {
+  return Component.current as any;
+}
+
+/**
+ * This hook is useful as a building block for some customized hooks, that may
+ * need a reference to the env of the component calling them.
+ */
+export function useEnv<E extends Env>(): E {
+  return Component.current.env as any;
+}
+
 // -----------------------------------------------------------------------------
 // useSubEnv
 // -----------------------------------------------------------------------------
@@ -126,3 +151,32 @@ export function useSubEnv(nextEnv) {
   const component = Component.current!;
   component.env = Object.assign(Object.create(component.env), nextEnv);
 }
+
+// -----------------------------------------------------------------------------
+// useExternalListener
+// -----------------------------------------------------------------------------
+
+/**
+ * When a component needs to listen to DOM Events on element(s) that are not
+ * part of his hierarchy, we can use the `useExternalListener` hook.
+ * It will correctly add and remove the event listener, whenever the
+ * component is mounted and unmounted.
+ *
+ * Example:
+ *  a menu needs to listen to the click on window to be closed automatically
+ *
+ * Usage:
+ *  in the constructor of the OWL component that needs to be notified,
+ *  `useExternalListener(window, 'click', this._doSomething);`
+ * */
+export function useExternalListener(
+  target: HTMLElement | typeof window,
+  eventName: string,
+  handler,
+  eventParams?
+) {
+  const boundHandler = handler.bind(Component.current);
+
+  onMounted(() => target.addEventListener(eventName, boundHandler, eventParams));
+  onWillUnmount(() => target.removeEventListener(eventName, boundHandler, eventParams));
+}

src/index.ts

@@ -7,18 +7,22 @@
 import { EventBus } from "./core/event_bus";
 import { Observer } from "./core/observer";
 import { QWeb } from "./qweb/index";
+import { config } from "./config";
 import * as _store from "./store";
 import * as _utils from "./utils";
 import * as _tags from "./tags";
-import {AsyncRoot} from "./misc/async_root";
+import { AsyncRoot } from "./misc/async_root";
+import { Portal } from "./misc/portal";
 import * as _hooks from "./hooks";
 import * as _context from "./context";
 import { Link } from "./router/link";
 import { RouteComponent } from "./router/route_component";
 import { Router } from "./router/router";
 
-export { Component } from "./component/component";
+export { Component, mount } from "./component/component";
 export { QWeb };
+export { config };
+export { browser } from "./browser";
 
 export const Context = _context.Context;
 export const useState = _hooks.useState;
@@ -27,28 +31,12 @@ export const router = { Router, RouteComponent, Link };
 export const Store = _store.Store;
 export const utils = _utils;
 export const tags = _tags;
-export const misc = { AsyncRoot};
+export const misc = { AsyncRoot, Portal };
 export const hooks = Object.assign({}, _hooks, {
   useContext: _context.useContext,
   useDispatch: _store.useDispatch,
   useGetters: _store.useGetters,
-  useStore: _store.useStore
+  useStore: _store.useStore,
 });
-export const __info__ = {};
 
-Object.defineProperty(__info__, "mode", {
-  get() {
-    return QWeb.dev ? "dev" : "prod";
-  },
-  set(mode: string) {
-    QWeb.dev = mode === "dev";
-    if (QWeb.dev) {
-      const url = `https://github.com/odoo/owl/blob/master/doc/tooling.md#development-mode`;
-      console.warn(
-        `Owl is running in 'dev' mode.  This is not suitable for production use. See ${url} for more information.`
-      );
-    } else {
-      console.log(`Owl is now running in 'prod' mode.`);
-    }
-  }
-});
+export const __info__ = {};

src/misc/async_root.ts

@@ -10,7 +10,7 @@ import { xml } from "../tags";
  * from this coordination.  This is the goal of the AsyncRoot component.
  */
 
-export class AsyncRoot extends Component<any, any> {
+export class AsyncRoot extends Component {
   static template = xml`<t t-slot="default"/>`;
 
   async __updateProps(nextProps, parentFiber) {

src/misc/portal.ts

@@ -0,0 +1,171 @@
+import { Component, portalSymbol } from "../component/component";
+import { VNode, patch } from "../vdom/index";
+import { xml } from "../tags";
+import { OwlEvent } from "../core/owl_event";
+import { useSubEnv } from "../hooks";
+
+/**
+ * Portal
+ *
+ * The Portal component allows to render a part of a component outside it's DOM.
+ * It is for example useful for dialogs: for css reasons, dialogs are in general
+ * placed in a specific spot of the DOM (e.g. directly in the body). With the
+ * Portal, a component can conditionally specify in its tempate that it contains
+ * a dialog, and where this dialog should be inserted in the DOM.
+ *
+ * The Portal component ensures that the communication between the content of
+ * the Portal and its parent properly works: business events reaching the Portal
+ * are re-triggered on an empty <portal> node located in the parent's DOM.
+ */
+
+interface Props {
+  target: string;
+}
+
+export class Portal extends Component<Props> {
+  static template = xml`<portal><t t-slot="default"/></portal>`;
+  static props = {
+    target: {
+      type: String,
+    },
+  };
+
+  // boolean to indicate whether or not we must listen to 'dom-appended' event
+  // to hook on the moment when the target is inserted into the DOM (because it
+  // is not when the portal is rendered)
+  doTargetLookUp: boolean = true;
+  // set of encountered events that need to be redirected
+  _handledEvents: Set<string> = new Set();
+  // function that will be the event's tunnel (needs to be an arrow function to
+  // avoid having to rebind `this`)
+  _handlerTunnel: (f: OwlEvent<any>) => void = (ev: OwlEvent<any>) => {
+    ev.stopPropagation();
+    this.__trigger(ev.originalComponent, ev.type, ev.detail);
+  };
+  // Storing the parent's env
+  parentEnv: any = null;
+  // represents the element that is moved somewhere else
+  portal: VNode | null = null;
+  // the target where we will move `portal`
+  target: Element | null = null;
+
+  constructor(parent, props) {
+    super(parent, props);
+    this.parentEnv = parent ? parent.env : {};
+    // put a callback in the env that is propagated to children s.t. portal can
+    // register an handler to those events just before children will trigger them
+    useSubEnv({
+      [portalSymbol]: (ev) => {
+        if (!this._handledEvents.has(ev.type)) {
+          this.portal!.elm!.addEventListener(ev.type, this._handlerTunnel);
+          this._handledEvents.add(ev.type);
+        }
+      },
+    });
+  }
+  /**
+   * Override to revert back to a classic Component's structure
+   *
+   * @override
+   */
+  __callWillUnmount() {
+    super.__callWillUnmount();
+    this.el!.appendChild(this.portal!.elm!);
+    this.doTargetLookUp = true;
+  }
+  /**
+   * At each DOM change, we must ensure that the portal contains exactly one
+   * child
+   */
+  __checkVNodeStructure(vnode: VNode) {
+    const children = vnode.children!;
+    let countRealNodes = 0;
+    for (let child of children) {
+      if ((child as VNode).sel) {
+        countRealNodes++;
+      }
+    }
+    if (countRealNodes !== 1) {
+      throw new Error(`Portal must have exactly one non-text child (has ${countRealNodes})`);
+    }
+  }
+  /**
+   * Ensure the target is still there at whichever time we render
+   */
+  __checkTargetPresence() {
+    if (!this.target || !document.contains(this.target)) {
+      throw new Error(`Could not find any match for "${this.props.target}"`);
+    }
+  }
+  /**
+   * Move the portal's element to the target
+   */
+  __deployPortal() {
+    this.__checkTargetPresence();
+    this.target!.appendChild(this.portal!.elm!);
+  }
+  /**
+   * Override to remove from the DOM the element we have teleported
+   *
+   * @override
+   */
+  __destroy(parent) {
+    if (this.portal && this.portal.elm) {
+      const displacedElm = this.portal.elm!;
+      const parent = displacedElm.parentNode;
+      if (parent) {
+        parent.removeChild(displacedElm);
+      }
+    }
+    super.__destroy(parent);
+  }
+  /**
+   * Override to patch the element that has been teleported
+   *
+   * @override
+   */
+  __patch(target, vnode) {
+    if (this.doTargetLookUp) {
+      const target = document.querySelector(this.props.target);
+      if (!target) {
+        this.env.qweb.on("dom-appended", this, () => {
+          this.doTargetLookUp = false;
+          this.env.qweb.off("dom-appended", this);
+          this.target = document.querySelector(this.props.target);
+          this.__deployPortal();
+        });
+      } else {
+        this.doTargetLookUp = false;
+        this.target = target;
+      }
+    }
+    this.__checkVNodeStructure(vnode);
+    const shouldDeploy =
+      (!this.portal || this.el!.contains(this.portal.elm!)) && !this.doTargetLookUp;
+
+    if (!this.doTargetLookUp && !shouldDeploy) {
+      // Only on pure patching, provided the
+      // this.target's parent has not been unmounted
+      this.__checkTargetPresence();
+    }
+
+    const portalPatch = this.portal ? this.portal : document.createElement(vnode.children[0].sel);
+    this.portal = patch(portalPatch, vnode.children![0] as VNode);
+    vnode.children = [];
+
+    super.__patch(target, vnode);
+
+    if (shouldDeploy) {
+      this.__deployPortal();
+    }
+  }
+  /**
+   * Override to set the env
+   */
+  __trigger(component: Component, eventType: string, payload?: any) {
+    const env = this.env;
+    this.env = this.parentEnv;
+    super.__trigger(component, eventType, payload);
+    this.env = env;
+  }
+}

src/qweb/base_directives.ts

@@ -1,7 +1,7 @@
-import { CompilationContext } from "./compilation_context";
-import { QWebExprVar } from "./expression_parser";
+import { CompilationContext, INTERP_REGEXP } from "./compilation_context";
 import { QWeb } from "./qweb";
 import { htmlToVDOM } from "../vdom/html_to_vdom";
+import { QWebVar } from "./expression_parser";
 
 /**
  * Owl QWeb Directives
@@ -20,35 +20,41 @@ import { htmlToVDOM } from "../vdom/html_to_vdom";
 //------------------------------------------------------------------------------
 // t-esc and t-raw
 //------------------------------------------------------------------------------
-QWeb.utils.getFragment = function(str: string): DocumentFragment {
-  const temp = document.createElement("template");
-  temp.innerHTML = str;
-  return temp.content;
-};
-
 QWeb.utils.htmlToVDOM = htmlToVDOM;
 
 function compileValueNode(value: any, node: Element, qweb: QWeb, ctx: CompilationContext) {
-  if (value === "0" && ctx.caller) {
-    qweb._compileNode(ctx.caller, ctx);
-    return;
-  }
-
-  if (value.xml instanceof NodeList) {
-    for (let node of Array.from(value.xml)) {
-      qweb._compileNode(<ChildNode>node, ctx);
+  ctx.rootContext.shouldDefineScope = true;
+  if (value === "0") {
+    if (ctx.parentNode) {
+      // the 'zero' magical symbol is where we can find the result of the rendering
+      // of  the body of the t-call.
+      ctx.rootContext.shouldDefineUtils = true;
+      const zeroArgs = ctx.escaping
+        ? `{text: utils.vDomToString(scope[utils.zero])}`
+        : `...scope[utils.zero]`;
+      ctx.addLine(`c${ctx.parentNode}.push(${zeroArgs});`);
     }
     return;
   }
+
   let exprID: string;
   if (typeof value === "string") {
     exprID = `_${ctx.generateID()}`;
-    ctx.addLine(`var ${exprID} = ${ctx.formatExpression(value)};`);
+    ctx.addLine(`let ${exprID} = ${ctx.formatExpression(value)};`);
   } else {
-    exprID = value.id;
+    exprID = `scope.${value.id}`;
   }
-  ctx.addIf(`${exprID} || ${exprID} === 0`);
+  ctx.addIf(`${exprID} != null`);
+
   if (ctx.escaping) {
+    let protectID;
+    if (value.hasBody) {
+      ctx.rootContext.shouldDefineUtils = true;
+      protectID = ctx.startProtectScope();
+      ctx.addLine(
+        `${exprID} = ${exprID} instanceof utils.VDomArray ? utils.vDomToString(${exprID}) : ${exprID};`
+      );
+    }
     if (ctx.parentTextNode) {
       ctx.addLine(`vn${ctx.parentTextNode}.text += ${exprID};`);
     } else if (ctx.parentNode) {
@@ -57,14 +63,24 @@ function compileValueNode(value: any, node: Element, qweb: QWeb, ctx: Compilatio
       let nodeID = ctx.generateID();
       ctx.rootContext.rootNode = nodeID;
       ctx.rootContext.parentTextNode = nodeID;
-      ctx.addLine(`var vn${nodeID} = {text: ${exprID}};`);
+      ctx.addLine(`let vn${nodeID} = {text: ${exprID}};`);
       if (ctx.rootContext.shouldDefineResult) {
         ctx.addLine(`result = vn${nodeID}`);
       }
     }
+    if (value.hasBody) {
+      ctx.stopProtectScope(protectID);
+    }
   } else {
     ctx.rootContext.shouldDefineUtils = true;
-    ctx.addLine(`c${ctx.parentNode}.push(...utils.htmlToVDOM(${exprID}));`);
+    if (value.hasBody) {
+      ctx.addLine(
+        `const vnodeArray = ${exprID} instanceof utils.VDomArray ? ${exprID} : utils.htmlToVDOM(${exprID});`
+      );
+      ctx.addLine(`c${ctx.parentNode}.push(...vnodeArray);`);
+    } else {
+      ctx.addLine(`c${ctx.parentNode}.push(...utils.htmlToVDOM(${exprID}));`);
+    }
   }
   if (node.childNodes.length) {
     ctx.addElse();
@@ -81,7 +97,7 @@ QWeb.addDirective({
     let value = ctx.getValue(node.getAttribute("t-esc")!);
     compileValueNode(value, node, qweb, ctx.subContext("escaping", true));
     return true;
-  }
+  },
 });
 
 QWeb.addDirective({
@@ -91,7 +107,7 @@ QWeb.addDirective({
     let value = ctx.getValue(node.getAttribute("t-raw")!);
     compileValueNode(value, node, qweb, ctx);
     return true;
-  }
+  },
 });
 
 //------------------------------------------------------------------------------
@@ -101,28 +117,54 @@ QWeb.addDirective({
   name: "set",
   extraNames: ["value"],
   priority: 60,
-  atNodeEncounter({ node, ctx }): boolean {
+  atNodeEncounter({ node, qweb, ctx }): boolean {
+    ctx.rootContext.shouldDefineScope = true;
     const variable = node.getAttribute("t-set")!;
     let value = node.getAttribute("t-value")!;
+    ctx.variables[variable] = ctx.variables[variable] || ({} as QWebVar);
+    let qwebvar = ctx.variables[variable];
+    const hasBody = node.hasChildNodes();
+
+    qwebvar.id = variable;
+    qwebvar.expr = `scope.${variable}`;
     if (value) {
       const formattedValue = ctx.formatExpression(value);
-      if (ctx.variables.hasOwnProperty(variable)) {
-        ctx.addLine(`${(<QWebExprVar>ctx.variables[variable]).id} = ${formattedValue}`);
-      } else {
-        const varName = `_${ctx.generateID()}`;
-        ctx.addLine(`var ${varName} = ${formattedValue};`);
-        ctx.variables[variable] = {
-          id: varName,
-          expr: formattedValue
-        };
+      let scopeExpr = `scope`;
+      if (ctx.protectedScopeNumber) {
+        ctx.rootContext.shouldDefineUtils = true;
+        scopeExpr = `utils.getScope(scope, '${variable}')`;
+      }
+      ctx.addLine(`${scopeExpr}.${variable} = ${formattedValue};`);
+      qwebvar.value = formattedValue;
+    }
+
+    if (hasBody) {
+      ctx.rootContext.shouldDefineUtils = true;
+      if (value) {
+        ctx.addIf(`!(${qwebvar.expr})`);
+      }
+      const tempParentNodeID = ctx.generateID();
+      const _parentNode = ctx.parentNode;
+      ctx.parentNode = tempParentNodeID;
+
+      ctx.addLine(`let c${tempParentNodeID} = new utils.VDomArray();`);
+      const nodeCopy = node.cloneNode(true) as Element;
+      for (let attr of ["t-set", "t-value", "t-if", "t-else", "t-elif"]) {
+        nodeCopy.removeAttribute(attr);
+      }
+      qweb._compileNode(nodeCopy, ctx);
+
+      ctx.addLine(`${qwebvar.expr} = c${tempParentNodeID}`);
+      qwebvar.value = `c${tempParentNodeID}`;
+      qwebvar.hasBody = true;
+
+      ctx.parentNode = _parentNode;
+      if (value) {
+        ctx.closeIf();
       }
-    } else {
-      ctx.variables[variable] = {
-        xml: node.childNodes
-      };
     }
     return true;
-  }
+  },
 });
 
 //------------------------------------------------------------------------------
@@ -133,12 +175,12 @@ QWeb.addDirective({
   priority: 20,
   atNodeEncounter({ node, ctx }): boolean {
     let cond = ctx.getValue(node.getAttribute("t-if")!);
-    ctx.addIf(typeof cond === "string" ? ctx.formatExpression(cond) : cond.id);
+    ctx.addIf(typeof cond === "string" ? ctx.formatExpression(cond) : `scope.${cond.id!}`);
     return false;
   },
   finalize({ ctx }) {
     ctx.closeIf();
-  }
+  },
 });
 
 QWeb.addDirective({
@@ -146,13 +188,15 @@ QWeb.addDirective({
   priority: 30,
   atNodeEncounter({ node, ctx }): boolean {
     let cond = ctx.getValue(node.getAttribute("t-elif")!);
-    ctx.addLine(`else if (${typeof cond === "string" ? ctx.formatExpression(cond) : cond.id}) {`);
+    ctx.addLine(
+      `else if (${typeof cond === "string" ? ctx.formatExpression(cond) : `scope.${cond.id}`}) {`
+    );
     ctx.indent();
     return false;
   },
   finalize({ ctx }) {
     ctx.closeIf();
-  }
+  },
 });
 
 QWeb.addDirective({
@@ -165,7 +209,7 @@ QWeb.addDirective({
   },
   finalize({ ctx }) {
     ctx.closeIf();
-  }
+  },
 });
 
 //------------------------------------------------------------------------------
@@ -175,91 +219,94 @@ QWeb.addDirective({
   name: "call",
   priority: 50,
   atNodeEncounter({ node, qweb, ctx }): boolean {
-    if (node.nodeName !== "t") {
-      throw new Error("Invalid tag for t-call directive (should be 't')");
-    }
+    // Step 1: sanity checks
+    // ------------------------------------------------
+    ctx.rootContext.shouldDefineScope = true;
+    ctx.rootContext.shouldDefineUtils = true;
     const subTemplate = node.getAttribute("t-call")!;
+    const isDynamic = INTERP_REGEXP.test(subTemplate);
     const nodeTemplate = qweb.templates[subTemplate];
-    if (!nodeTemplate) {
+    if (!isDynamic && !nodeTemplate) {
       throw new Error(`Cannot find template "${subTemplate}" (t-call)`);
     }
-    const nodeCopy = node.cloneNode(true) as Element;
-    nodeCopy.removeAttribute("t-call");
 
-    // extract variables from nodecopy
-    const tempCtx = new CompilationContext();
-    tempCtx.nextID = ctx.rootContext.nextID;
-    tempCtx.allowMultipleRoots = true;
-    qweb._compileNode(nodeCopy, tempCtx);
-    const vars = Object.assign({}, ctx.variables, tempCtx.variables);
-    ctx.rootContext.nextID = tempCtx.nextID;
-
-    const templateMap = Object.create(ctx.templates);
-    // open new scope, if necessary
-    const hasNewVariables = Object.keys(tempCtx.variables).length > 0;
-
-    // compile sub template
-    let subCtx = ctx.subContext("caller", nodeCopy).subContext("variables", Object.create(vars));
-    subCtx = subCtx.subContext("templates", templateMap);
-
-    if (templateMap[subTemplate]) {
-      // OUCH, IT IS A RECURSIVE TEMPLATE SITUATION...
-      // This is a tricky situation... We obviously cannot inline the compiled
-      // template. So, what we need to do is to compile it, and make sure we
-      // properly transfer everything from the current scope to the sub template.
-      ctx.rootContext.shouldTrackScope = true;
-      ctx.rootContext.shouldDefineOwner = true;
-      let subTemplateName;
-      if (ctx.hasParentWidget) {
-        subTemplateName = ctx.templateName;
-      } else {
-        subTemplateName = `__${ctx.generateID()}`;
-        subCtx.variables = {};
-        let id = 0;
-        for (let v in vars) {
-          subCtx.variables[v] = vars[v];
-          (vars[v] as any).id = `_v${id++}`;
-        }
-        const subTemplateFn = qweb._compile(subTemplateName, nodeTemplate.elem, subCtx);
-        qweb.recursiveFns[subTemplateName] = subTemplateFn;
-      }
-      let varCode = `{}`;
-      if (Object.keys(vars).length) {
-        let id = 0;
-        const content = Object.values(vars)
-          .map((v: any) => `_v${id++}: ${v.expr}`)
-          .join(",");
-        varCode = `{${content}}`;
-      }
+    // Step 2: compile target template in sub templates
+    // ------------------------------------------------
+    let subIdstr: string;
+    if (isDynamic) {
+      const _id = ctx.generateID();
+      ctx.addLine(`let tname${_id} = ${ctx.interpolate(subTemplate)};`);
+      ctx.addLine(`let tid${_id} = this.subTemplates[tname${_id}];`);
+      ctx.addIf(`!tid${_id}`);
+      ctx.addLine(`tid${_id} = this.constructor.nextId++;`);
+      ctx.addLine(`this.subTemplates[tname${_id}] = tid${_id};`);
       ctx.addLine(
-        `this.recursiveFns['${subTemplateName}'].call(this, context, Object.assign({}, extra, {parentNode: c${ctx.parentNode}, fiber: {vars: ${varCode}, scope}}));`
+        `this.constructor.subTemplates[tid${_id}] = this._compile(tname${_id}, {hasParent: true, defineKey: true});`
       );
-      return true;
-    }
-    templateMap[subTemplate] = true;
-
-    if (hasNewVariables) {
-      ctx.addLine("{");
-      ctx.indent();
-      // add new variables, if any
-      for (let key in tempCtx.variables) {
-        const v = tempCtx.variables[key];
-        if ((<QWebExprVar>v).expr) {
-          ctx.addLine(`let ${(<QWebExprVar>v).id} = ${(<QWebExprVar>v).expr};`);
-        }
-        // todo: handle XML variables...
+      ctx.closeIf();
+      subIdstr = `tid${_id}`;
+    } else {
+      let subId = qweb.subTemplates[subTemplate];
+      if (!subId) {
+        subId = QWeb.nextId++;
+        qweb.subTemplates[subTemplate] = subId;
+        const subTemplateFn = qweb._compile(subTemplate, { hasParent: true, defineKey: true });
+        QWeb.subTemplates[subId] = subTemplateFn;
       }
+      subIdstr = `'${subId}'`;
     }
-    qweb._compileNode(nodeTemplate.elem, subCtx);
 
-    // close new scope
-    if (hasNewVariables) {
+    // Step 3: compile t-call body if necessary
+    // ------------------------------------------------
+    let hasBody = node.hasChildNodes();
+    const protectID = ctx.startProtectScope();
+    if (hasBody) {
+      // we add a sub scope to protect the ambient scope
+      ctx.addLine(`{`);
+      ctx.indent();
+      const nodeCopy = node.cloneNode(true) as Element;
+      for (let attr of ["t-if", "t-else", "t-elif", "t-call"]) {
+        nodeCopy.removeAttribute(attr);
+      }
+      // this local scope is intended to trap c__0
+      ctx.addLine(`{`);
+      ctx.indent();
+      ctx.addLine("let c__0 = [];");
+      qweb._compileNode(nodeCopy, ctx.subContext("parentNode", "__0"));
+      ctx.rootContext.shouldDefineUtils = true;
+      ctx.addLine("scope[utils.zero] = c__0;");
       ctx.dedent();
-      ctx.addLine("}");
+      ctx.addLine(`}`);
     }
 
+    // Step 4: add the appropriate function call to current component
+    // ------------------------------------------------
+    const parentComponent = ctx.rootContext.shouldDefineParent
+      ? `parent`
+      : `utils.getComponent(context)`;
+    const key = ctx.generateTemplateKey();
+    const parentNode = ctx.parentNode ? `c${ctx.parentNode}` : "result";
+    const extra = `Object.assign({}, extra, {parentNode: ${parentNode}, parent: ${parentComponent}, key: ${key}})`;
+    if (ctx.parentNode) {
+      ctx.addLine(`this.constructor.subTemplates[${subIdstr}].call(this, scope, ${extra});`);
+    } else {
+      // this is a t-call with no parentnode, we need to extract the result
+      ctx.rootContext.shouldDefineResult = true;
+      ctx.addLine(`result = []`);
+      ctx.addLine(`this.constructor.subTemplates[${subIdstr}].call(this, scope, ${extra});`);
+      ctx.addLine(`result = result[0]`);
+    }
+
+    // Step 5: restore previous scope
+    // ------------------------------------------------
+    if (hasBody) {
+      ctx.dedent();
+      ctx.addLine(`}`);
+    }
+    ctx.stopProtectScope(protectID);
+
     return true;
-  }
+  },
 });
 
 //------------------------------------------------------------------------------
@@ -270,55 +317,57 @@ QWeb.addDirective({
   extraNames: ["as"],
   priority: 10,
   atNodeEncounter({ node, qweb, ctx }): boolean {
-    ctx.rootContext.shouldProtectContext = true;
+    ctx.rootContext.shouldDefineScope = true;
     ctx = ctx.subContext("loopNumber", ctx.loopNumber + 1);
     const elems = node.getAttribute("t-foreach")!;
     const name = node.getAttribute("t-as")!;
     let arrayID = ctx.generateID();
-    ctx.addLine(`var _${arrayID} = ${ctx.formatExpression(elems)};`);
+    ctx.addLine(`let _${arrayID} = ${ctx.formatExpression(elems)};`);
     ctx.addLine(`if (!_${arrayID}) { throw new Error('QWeb error: Invalid loop expression')}`);
     let keysID = ctx.generateID();
     let valuesID = ctx.generateID();
-    ctx.addLine(`var _${keysID} = _${valuesID} = _${arrayID};`);
+    ctx.addLine(`let _${keysID} = _${valuesID} = _${arrayID};`);
     ctx.addIf(`!(_${arrayID} instanceof Array)`);
     ctx.addLine(`_${keysID} = Object.keys(_${arrayID});`);
     ctx.addLine(`_${valuesID} = Object.values(_${arrayID});`);
     ctx.closeIf();
-    ctx.addLine(`var _length${keysID} = _${keysID}.length;`);
+    ctx.addLine(`let _length${keysID} = _${keysID}.length;`);
+    let varsID = ctx.startProtectScope(true);
     const loopVar = `i${ctx.loopNumber}`;
     ctx.addLine(`for (let ${loopVar} = 0; ${loopVar} < _length${keysID}; ${loopVar}++) {`);
     ctx.indent();
-    ctx.addToScope(name + "_first", `${loopVar} === 0`);
-    ctx.addToScope(name + "_last", `${loopVar} === _length${keysID} - 1`);
-    ctx.addToScope(name + "_index", loopVar);
-    ctx.addToScope(name, `_${keysID}[${loopVar}]`);
-    ctx.addToScope(name + "_value", `_${valuesID}[${loopVar}]`);
+
+    ctx.addLine(`scope.${name}_first = ${loopVar} === 0`);
+    ctx.addLine(`scope.${name}_last = ${loopVar} === _length${keysID} - 1`);
+    ctx.addLine(`scope.${name}_index = ${loopVar}`);
+    ctx.addLine(`scope.${name} = _${keysID}[${loopVar}]`);
+    ctx.addLine(`scope.${name}_value = _${valuesID}[${loopVar}]`);
     const nodeCopy = <Element>node.cloneNode(true);
-    let shouldWarn = nodeCopy.tagName !== "t" && !nodeCopy.hasAttribute("t-key");
-    if (!shouldWarn && node.tagName === "t") {
-      if (node.hasAttribute("t-component") && !node.hasAttribute("t-key")) {
-        shouldWarn = true;
-      }
-      if (
-        !shouldWarn &&
-        node.children.length === 1 &&
-        node.children[0].tagName !== "t" &&
-        !node.children[0].hasAttribute("t-key")
-      ) {
-        shouldWarn = true;
-      }
-    }
+    let shouldWarn =
+      !nodeCopy.hasAttribute("t-key") &&
+      node.children.length === 1 &&
+      node.children[0].tagName !== "t" &&
+      !node.children[0].hasAttribute("t-key");
     if (shouldWarn) {
       console.warn(
         `Directive t-foreach should always be used with a t-key! (in template: '${ctx.templateName}')`
       );
     }
+    if (nodeCopy.hasAttribute("t-key")) {
+      const expr = ctx.formatExpression(nodeCopy.getAttribute("t-key")!);
+      ctx.addLine(`let key${ctx.loopNumber} = ${expr};`);
+      nodeCopy.removeAttribute("t-key");
+    } else {
+      ctx.addLine(`let key${ctx.loopNumber} = i${ctx.loopNumber};`);
+    }
+
     nodeCopy.removeAttribute("t-foreach");
     qweb._compileNode(nodeCopy, ctx);
     ctx.dedent();
     ctx.addLine("}");
+    ctx.stopProtectScope(varsID);
     return true;
-  }
+  },
 });
 
 //------------------------------------------------------------------------------
@@ -329,7 +378,7 @@ QWeb.addDirective({
   priority: 1,
   atNodeEncounter({ ctx }) {
     ctx.addLine("debugger;");
-  }
+  },
 });
 
 //------------------------------------------------------------------------------
@@ -341,5 +390,5 @@ QWeb.addDirective({
   atNodeEncounter({ ctx, value }) {
     const expr = ctx.formatExpression(value);
     ctx.addLine(`console.log(${expr})`);
-  }
+  },
 });

src/qweb/compilation_context.ts

@@ -1,4 +1,4 @@
-import { compileExpr, QWebVar, QWebExprVar } from "./expression_parser";
+import { compileExpr, compileExprToArray, QWebVar } from "./expression_parser";
 
 export const INTERP_REGEXP = /\{\{.*?\}\}/g;
 //------------------------------------------------------------------------------
@@ -6,75 +6,73 @@ export const INTERP_REGEXP = /\{\{.*?\}\}/g;
 //------------------------------------------------------------------------------
 
 export class CompilationContext {
-  nextID: number = 1;
+  static nextID: number = 1;
   code: string[] = [];
   variables: { [key: string]: QWebVar } = {};
   escaping: boolean = false;
-  parentNode: number | null = null;
+  parentNode: number | null | string = null;
   parentTextNode: number | null = null;
   rootNode: number | null = null;
   indentLevel: number = 0;
   rootContext: CompilationContext;
-  caller: Element | undefined;
-  shouldDefineOwner: boolean = false;
   shouldDefineParent: boolean = false;
+  shouldDefineScope: boolean = false;
+  protectedScopeNumber: number = 0;
   shouldDefineQWeb: boolean = false;
   shouldDefineUtils: boolean = false;
   shouldDefineRefs: boolean = false;
   shouldDefineResult: boolean = true;
-  shouldDefineSibling: boolean = true;
-  shouldProtectContext: boolean = false;
-  shouldTrackScope: boolean = false;
   loopNumber: number = 0;
   inPreTag: boolean = false;
   templateName: string;
   allowMultipleRoots: boolean = false;
   hasParentWidget: boolean = false;
-  scopeVars: any[] = [];
-  currentKey: string = "";
-  lastNodeKey: string = ""; // temp variable to communicate to previous caller
-  templates: { [key: string]: boolean } = {};
+  hasKey0: boolean = false;
+  keyStack: boolean[] = [];
 
   constructor(name?: string) {
     this.rootContext = this;
     this.templateName = name || "noname";
-    this.templates[this.templateName] = true;
-    this.addLine("var h = this.h;");
+    this.addLine("let h = this.h;");
   }
 
   generateID(): number {
-    const id = this.rootContext.nextID++;
-    return id;
+    return CompilationContext.nextID++;
+  }
+
+  /**
+   * This method generates a "template key", which is basically a unique key
+   * which depends on the currently set keys, and on the iteration numbers (if
+   * we are in a loop).
+   *
+   * Such a key is necessary when we need to associate an id to some element
+   * generated by a template (for example, a component)
+   */
+  generateTemplateKey(prefix: string = ""): string {
+    const id = this.generateID();
+    if (this.loopNumber === 0 && !this.hasKey0) {
+      return `'${prefix}__${id}__'`;
+    }
+    let key = `\`${prefix}__${id}__`;
+    let start = this.hasKey0 ? 0 : 1;
+    for (let i = start; i < this.loopNumber + 1; i++) {
+      key += `\${key${i}}__`;
+    }
+    this.addLine(`let k${id} = ${key}\`;`);
+    return `k${id}`;
   }
 
   generateCode(): string[] {
-    const shouldTrackScope = this.shouldTrackScope && this.scopeVars.length;
-    if (shouldTrackScope) {
-      // add some vars to scope if needed
-      for (let scopeVar of this.scopeVars.reverse()) {
-        let { index, key, indent } = scopeVar;
-        const prefix = new Array(indent + 2).join("    ");
-        this.code.splice(index + 1, 0, prefix + `scope.${key} = context.${key};`);
-      }
-      this.code.unshift("    const scope = Object.create(null);");
-    }
-    if (this.shouldProtectContext) {
-      this.code.unshift("    context = Object.create(context);");
-    }
     if (this.shouldDefineResult) {
       this.code.unshift("    let result;");
     }
-    if (this.shouldDefineSibling) {
-      this.code.unshift("    let sibling = null;");
+
+    if (this.shouldDefineScope) {
+      this.code.unshift("    let scope = Object.create(context);");
     }
     if (this.shouldDefineRefs) {
       this.code.unshift("    context.__owl__.refs = context.__owl__.refs || {};");
     }
-    if (this.shouldDefineOwner) {
-      // this is necessary to prevent some directives (t-forach for ex) to
-      // pollute the rendering context by adding some keys in it.
-      this.code.unshift("    let owner = context;");
-    }
     if (this.shouldDefineParent) {
       if (this.hasParentWidget) {
         this.code.unshift("    let parent = extra.parent;");
@@ -115,11 +113,11 @@ export class CompilationContext {
   }
 
   indent() {
-    this.indentLevel++;
+    this.rootContext.indentLevel++;
   }
 
   dedent() {
-    this.indentLevel--;
+    this.rootContext.indentLevel--;
   }
 
   addLine(line: string): number {
@@ -128,11 +126,6 @@ export class CompilationContext {
     return this.code.length - 1;
   }
 
-  addToScope(key: string, expr: string) {
-    const index = this.addLine(`context.${key} = ${expr};`);
-    this.rootContext.scopeVars.push({ index, key, indent: this.indentLevel });
-  }
-
   addIf(condition: string) {
     this.addLine(`if (${condition}) {`);
     this.indent();
@@ -149,7 +142,7 @@ export class CompilationContext {
     this.addLine("}");
   }
 
-  getValue(val: any): QWebExprVar | string {
+  getValue(val: any): QWebVar | string {
     return val in this.variables ? this.getValue(this.variables[val]) : val;
   }
 
@@ -160,8 +153,27 @@ export class CompilationContext {
    * - replace already defined variables by their internal name
    */
   formatExpression(expr: string): string {
+    this.rootContext.shouldDefineScope = true;
     return compileExpr(expr, this.variables);
   }
+  captureExpression(expr: string): string {
+    this.rootContext.shouldDefineScope = true;
+    const argId = this.generateID();
+    const tokens = compileExprToArray(expr, this.variables);
+    const done = new Set();
+    return tokens
+      .map((tok) => {
+        if (tok.varName) {
+          if (!done.has(tok.varName)) {
+            done.add(tok.varName);
+            this.addLine(`const ${tok.varName}_${argId} = ${tok.value};`);
+          }
+          tok.value = `${tok.varName}_${argId}`;
+        }
+        return tok.value;
+      })
+      .join("");
+  }
 
   /**
    * Perform string interpolation on the given string. Note that if the whole
@@ -177,7 +189,23 @@ export class CompilationContext {
       return `(${this.formatExpression(s.slice(2, -2))})`;
     }
 
-    let r = s.replace(/\{\{.*?\}\}/g, s => "${" + this.formatExpression(s.slice(2, -2)) + "}");
+    let r = s.replace(/\{\{.*?\}\}/g, (s) => "${" + this.formatExpression(s.slice(2, -2)) + "}");
     return "`" + r + "`";
   }
+  startProtectScope(codeBlock?: boolean): number {
+    const protectID = this.generateID();
+    this.rootContext.protectedScopeNumber++;
+    this.rootContext.shouldDefineScope = true;
+    const scopeExpr = `Object.create(scope);`;
+    this.addLine(`let _origScope${protectID} = scope;`);
+    this.addLine(`scope = ${scopeExpr}`);
+    if (!codeBlock) {
+      this.addLine(`scope.__access_mode__ = 'ro';`);
+    }
+    return protectID;
+  }
+  stopProtectScope(protectID: number) {
+    this.rootContext.protectedScopeNumber--;
+    this.addLine(`scope = _origScope${protectID};`);
+  }
 }

src/qweb/expression_parser.ts

@@ -25,30 +25,26 @@
 // Misc types, constants and helpers
 //------------------------------------------------------------------------------
 
-const RESERVED_WORDS = "true,false,NaN,null,undefined,debugger,console,window,in,instanceof,new,function,return,this,typeof,eval,void,Math,RegExp,Array,Object,Date".split(
+const RESERVED_WORDS = "true,false,NaN,null,undefined,debugger,console,window,in,instanceof,new,function,return,this,eval,void,Math,RegExp,Array,Object,Date".split(
   ","
 );
 
-const WORD_REPLACEMENT = {
+const WORD_REPLACEMENT = Object.assign(Object.create(null), {
   and: "&&",
   or: "||",
   gt: ">",
   gte: ">=",
   lt: "<",
-  lte: "<="
-};
+  lte: "<=",
+});
 
-export interface QWebExprVar {
-  id: string;
-  expr: string;
+export interface QWebVar {
+  id: string; // foo
+  expr: string; // scope.foo (local variables => only foo)
+  value?: string; // 1 + 3
+  hasBody?: boolean;
 }
 
-export interface QWebXMLVar {
-  xml: NodeList;
-}
-
-export type QWebVar = QWebExprVar | QWebXMLVar;
-
 //------------------------------------------------------------------------------
 // Tokenizer
 //------------------------------------------------------------------------------
@@ -68,10 +64,12 @@ type TKind =
 interface Token {
   type: TKind;
   value: string;
+  originalValue?: string;
   size?: number;
+  varName?: string;
 }
 
-const STATIC_TOKEN_MAP: { [key: string]: TKind } = {
+const STATIC_TOKEN_MAP: { [key: string]: TKind } = Object.assign(Object.create(null), {
   "{": "LEFT_BRACE",
   "}": "RIGHT_BRACE",
   "[": "LEFT_BRACKET",
@@ -79,14 +77,16 @@ const STATIC_TOKEN_MAP: { [key: string]: TKind } = {
   ":": "COLON",
   ",": "COMMA",
   "(": "LEFT_PAREN",
-  ")": "RIGHT_PAREN"
-};
+  ")": "RIGHT_PAREN",
+});
 
-const OPERATORS = ".,===,==,+,!==,!=,!,||,&&,>=,>,<=,<,?,-,*,/,%".split(",");
+// note that the space after typeof is relevant. It makes sure that the formatted
+// expression has a space after typeof
+const OPERATORS = "...,.,===,==,+,!==,!=,!,||,&&,>=,>,<=,<,?,-,*,/,%,typeof ,=>,=,;,in ".split(",");
 
 type Tokenizer = (expr: string) => Token | false;
 
-let tokenizeString: Tokenizer = function(expr) {
+let tokenizeString: Tokenizer = function (expr) {
   let s = expr[0];
   let start = s;
   if (s !== "'" && s !== '"') {
@@ -114,7 +114,7 @@ let tokenizeString: Tokenizer = function(expr) {
   return { type: "VALUE", value: s };
 };
 
-let tokenizeNumber: Tokenizer = function(expr) {
+let tokenizeNumber: Tokenizer = function (expr) {
   let s = expr[0];
   if (s && s.match(/[0-9]/)) {
     let i = 1;
@@ -128,7 +128,7 @@ let tokenizeNumber: Tokenizer = function(expr) {
   }
 };
 
-let tokenizeSymbol: Tokenizer = function(expr) {
+let tokenizeSymbol: Tokenizer = function (expr) {
   let s = expr[0];
   if (s && s.match(/[a-zA-Z_\$]/)) {
     let i = 1;
@@ -145,7 +145,7 @@ let tokenizeSymbol: Tokenizer = function(expr) {
   }
 };
 
-const tokenizeStatic: Tokenizer = function(expr) {
+const tokenizeStatic: Tokenizer = function (expr) {
   const char = expr[0];
   if (char && char in STATIC_TOKEN_MAP) {
     return { type: STATIC_TOKEN_MAP[char], value: char };
@@ -153,7 +153,7 @@ const tokenizeStatic: Tokenizer = function(expr) {
   return false;
 };
 
-const tokenizeOperator: Tokenizer = function(expr) {
+const tokenizeOperator: Tokenizer = function (expr) {
   for (let op of OPERATORS) {
     if (expr.startsWith(op)) {
       return { type: "OPERATOR", value: op };
@@ -165,9 +165,9 @@ const tokenizeOperator: Tokenizer = function(expr) {
 const TOKENIZERS = [
   tokenizeString,
   tokenizeNumber,
+  tokenizeOperator,
   tokenizeSymbol,
   tokenizeStatic,
-  tokenizeOperator
 ];
 
 /**
@@ -230,35 +230,60 @@ export function tokenize(expr: string): Token[] {
  * - unless the previous token is a dot (in that case, this is a property: `a.b`)
  * - or if the previous token is a left brace or a comma, and the next token is
  *   a colon (in that case, this is an object key: `{a: b}`)
+ *
+ * Some specific code is also required to support arrow functions. If we detect
+ * the arrow operator, then we add the current (or some previous tokens) token to
+ * the list of variables so it does not get replaced by a lookup in the context
  */
-export function compileExpr(expr: string, vars: { [key: string]: QWebVar }): string {
+export function compileExprToArray(expr: string, scope: { [key: string]: QWebVar }): Token[] {
+  scope = Object.create(scope);
   const tokens = tokenize(expr);
-  let result = "";
   for (let i = 0; i < tokens.length; i++) {
     let token = tokens[i];
+    let prevToken = tokens[i - 1];
+    let nextToken = tokens[i + 1];
+    let isVar = token.type === "SYMBOL" && !RESERVED_WORDS.includes(token.value);
     if (token.type === "SYMBOL" && !RESERVED_WORDS.includes(token.value)) {
-      // we need to find if it is a variable
-      let isVar = true;
-      let prevToken = tokens[i - 1];
       if (prevToken) {
         if (prevToken.type === "OPERATOR" && prevToken.value === ".") {
           isVar = false;
         } else if (prevToken.type === "LEFT_BRACE" || prevToken.type === "COMMA") {
-          let nextToken = tokens[i + 1];
           if (nextToken && nextToken.type === "COLON") {
             isVar = false;
           }
         }
       }
-      if (isVar) {
-        if (token.value in vars && "id" in vars[token.value]) {
-          token.value = (<QWebExprVar>vars[token.value]).id;
-        } else {
-          token.value = `context['${token.value}']`;
+    }
+    if (nextToken && nextToken.type === "OPERATOR" && nextToken.value === "=>") {
+      if (token.type === "RIGHT_PAREN") {
+        let j = i - 1;
+        while (j > 0 && tokens[j].type !== "LEFT_PAREN") {
+          if (tokens[j].type === "SYMBOL" && tokens[j].originalValue) {
+            tokens[j].value = tokens[j].originalValue!;
+            scope[tokens[j].value] = { id: tokens[j].value, expr: tokens[j].value };
+          }
+          j--;
         }
+      } else {
+        scope[token.value] = { id: token.value, expr: token.value };
+      }
+    }
+
+    if (isVar) {
+      token.varName = token.value;
+      if (token.value in scope && "id" in scope[token.value]) {
+        token.value = scope[token.value].expr!;
+      } else {
+        token.originalValue = token.value;
+        token.value = `scope['${token.value}']`;
       }
     }
-    result += token.value;
   }
-  return result;
+  return tokens;
+}
+
+export function compileExpr(expr: string, scope: { [key: string]: QWebVar }): string {
+  return compileExprToArray(expr, scope)
+    .map((t) => t.value)
+    .join("");
 }

src/qweb/extensions.ts

@@ -1,4 +1,6 @@
+import { STATUS } from "../component/component";
 import { VNode } from "../vdom/index";
+import { INTERP_REGEXP } from "./compilation_context";
 import { QWeb } from "./qweb";
 
 /**
@@ -23,51 +25,74 @@ import { QWeb } from "./qweb";
 export const MODS_CODE = {
   prevent: "e.preventDefault();",
   self: "if (e.target !== this.elm) {return}",
-  stop: "e.stopPropagation();"
+  stop: "e.stopPropagation();",
 };
 
+interface HandlerInfo {
+  event: string;
+  handler: string;
+}
+
+const FNAMEREGEXP = /^[$A-Z_][0-9A-Z_$]*$/i;
+
+export function makeHandlerCode(
+  ctx,
+  fullName,
+  value,
+  putInCache: boolean,
+  modcodes = MODS_CODE
+): HandlerInfo {
+  let [event, ...mods] = fullName.slice(5).split(".");
+  if (mods.includes("capture")) {
+    event = "!" + event;
+  }
+  if (!event) {
+    throw new Error("Missing event name with t-on directive");
+  }
+  let code: string;
+  // check if it is a method with no args, a method with args or an expression
+  let args: string = "";
+  const name: string = value.replace(/\(.*\)/, function (_args) {
+    args = _args.slice(1, -1);
+    return "";
+  });
+  const isMethodCall = name.match(FNAMEREGEXP);
+
+  // then generate code
+  if (isMethodCall) {
+    ctx.rootContext.shouldDefineUtils = true;
+    const comp = `utils.getComponent(context)`;
+    if (args) {
+      const argId = ctx.generateID();
+      ctx.addLine(`let args${argId} = [${ctx.formatExpression(args)}];`);
+      code = `${comp}['${name}'](...args${argId}, e);`;
+      putInCache = false;
+    } else {
+      code = `${comp}['${name}'](e);`;
+    }
+  } else {
+    // if we get here, then it is an expression
+    // we need to capture every variable in it
+    putInCache = false;
+    code = ctx.captureExpression(value);
+  }
+  const modCode = mods.map((mod) => modcodes[mod]).join("");
+  let handler = `function (e) {if (context.__owl__.status === ${STATUS.DESTROYED}){return}${modCode}${code}}`;
+  if (putInCache) {
+    const key = ctx.generateTemplateKey(event);
+    ctx.addLine(`extra.handlers[${key}] = extra.handlers[${key}] || ${handler};`);
+    handler = `extra.handlers[${key}]`;
+  }
+  return { event, handler };
+}
+
 QWeb.addDirective({
   name: "on",
   priority: 90,
   atNodeCreation({ ctx, fullName, value, nodeID }) {
-    ctx.rootContext.shouldDefineOwner = true;
-    const [eventName, ...mods] = fullName.slice(5).split(".");
-    if (!eventName) {
-      throw new Error("Missing event name with t-on directive");
-    }
-    let extraArgs;
-    let handlerName = value.replace(/\(.*\)/, function(args) {
-      extraArgs = args.slice(1, -1);
-      return "";
-    });
-    let params = extraArgs ? `owner, ${ctx.formatExpression(extraArgs)}` : "owner";
-    let handler = `function (e) {`;
-    handler += mods
-      .map(function(mod) {
-        return MODS_CODE[mod];
-      })
-      .join("");
-    if (handlerName) {
-      if (!extraArgs) {
-        handler += `const fn = context['${handlerName}'];`;
-        handler += `if (fn) { fn.call(${params}, e); } else { context.${handlerName}; }`;
-        handler += `}`;
-        ctx.addLine(
-          `extra.handlers['${eventName}' + ${nodeID}] = extra.handlers['${eventName}' + ${nodeID}] || ${handler};`
-        );
-        ctx.addLine(`p${nodeID}.on['${eventName}'] = extra.handlers['${eventName}' + ${nodeID}];`);
-      } else {
-        const handlerKey = `handler${ctx.generateID()}`;
-        ctx.addLine(`const ${handlerKey} = context['${handlerName}'] && context['${handlerName}'].bind(${params});`);
-        handler += `if (${handlerKey}) { ${handlerKey}(e); } else { context.${value}; }`;
-        handler += `}`;
-        ctx.addLine(`p${nodeID}.on['${eventName}'] = ${handler};`);
-      }
-    } else {
-      handler += "}";
-      ctx.addLine(`p${nodeID}.on['${eventName}'] = ${handler};`);
-    }
-  }
+    const { event, handler } = makeHandlerCode(ctx, fullName, value, true);
+    ctx.addLine(`p${nodeID}.on['${event}'] = ${handler};`);
+  },
 });
 
 //------------------------------------------------------------------------------
@@ -82,17 +107,17 @@ QWeb.addDirective({
     ctx.addLine(`const ${refKey} = ${ctx.interpolate(value)};`);
     addNodeHook("create", `context.__owl__.refs[${refKey}] = n.elm;`);
     addNodeHook("destroy", `delete context.__owl__.refs[${refKey}];`);
-  }
+  },
 });
 
 //------------------------------------------------------------------------------
 // t-transition
 //------------------------------------------------------------------------------
-QWeb.utils.nextFrame = function(cb: () => void) {
+QWeb.utils.nextFrame = function (cb: () => void) {
   requestAnimationFrame(() => requestAnimationFrame(cb));
 };
 
-QWeb.utils.transitionInsert = function(vn: VNode, name: string) {
+QWeb.utils.transitionInsert = function (vn: VNode, name: string) {
   const elm = <HTMLElement>vn.elm;
   // remove potential duplicated vnode that is currently being removed, to
   // prevent from having twice the same node in the DOM during an animation
@@ -103,6 +128,8 @@ QWeb.utils.transitionInsert = function(vn: VNode, name: string) {
 
   elm.classList.add(name + "-enter");
   elm.classList.add(name + "-enter-active");
+  elm.classList.remove(name + "-leave-active");
+  elm.classList.remove(name + "-leave-to");
   const finalize = () => {
     elm.classList.remove(name + "-enter-active");
     elm.classList.remove(name + "-enter-to");
@@ -114,13 +141,16 @@ QWeb.utils.transitionInsert = function(vn: VNode, name: string) {
   });
 };
 
-QWeb.utils.transitionRemove = function(vn: VNode, name: string, rm: () => void) {
+QWeb.utils.transitionRemove = function (vn: VNode, name: string, rm: () => void) {
   const elm = <HTMLElement>vn.elm;
   elm.setAttribute("data-owl-key", vn.key!);
 
   elm.classList.add(name + "-leave");
   elm.classList.add(name + "-leave-active");
   const finalize = () => {
+    if (!elm.classList.contains(name + "-leave-active")) {
+      return;
+    }
     elm.classList.remove(name + "-leave-active");
     elm.classList.remove(name + "-leave-to");
     rm();
@@ -155,6 +185,13 @@ function toMs(s: string): number {
 }
 
 function whenTransitionEnd(elm: HTMLElement, cb) {
+  if (!elm.parentNode) {
+    // if we get here, this means that the element was removed for some other
+    // reasons, and in that case, we don't want to work on animation since nothing
+    // will be displayed anyway.
+    return;
+  }
+
   const styles = window.getComputedStyle(elm);
   const delays: Array<string> = (styles.transitionDelay || "").split(", ");
   const durations: Array<string> = (styles.transitionDuration || "").split(", ");
@@ -170,16 +207,19 @@ QWeb.addDirective({
   name: "transition",
   priority: 96,
   atNodeCreation({ ctx, value, addNodeHook }) {
+    if (!QWeb.enableTransitions) {
+      return;
+    }
     ctx.rootContext.shouldDefineUtils = true;
     let name = value;
     const hooks = {
       insert: `utils.transitionInsert(vn, '${name}');`,
-      remove: `utils.transitionRemove(vn, '${name}', rm);`
+      remove: `utils.transitionRemove(vn, '${name}', rm);`,
     };
     for (let hookName in hooks) {
       addNodeHook(hookName, hooks[hookName]);
     }
-  }
+  },
 });
 
 //------------------------------------------------------------------------------
@@ -188,40 +228,49 @@ QWeb.addDirective({
 QWeb.addDirective({
   name: "slot",
   priority: 80,
-  atNodeEncounter({ ctx, value }): boolean {
+  atNodeEncounter({ ctx, value, node, qweb }): boolean {
     const slotKey = ctx.generateID();
-    ctx.rootContext.shouldDefineOwner = true;
+    const valueExpr = value.match(INTERP_REGEXP) ? ctx.interpolate(value) : `'${value}'`;
     ctx.addLine(
-      `const slot${slotKey} = this.constructor.slots[context.__owl__.slotId + '_' + '${value}'];`
+      `const slot${slotKey} = this.constructor.slots[context.__owl__.slotId + '_' + ${valueExpr}];`
     );
     ctx.addIf(`slot${slotKey}`);
     let parentNode = `c${ctx.parentNode}`;
     if (!ctx.parentNode) {
       ctx.rootContext.shouldDefineResult = true;
       ctx.rootContext.shouldDefineUtils = true;
-      parentNode = `children${ctx.nextID++}`;
+      parentNode = `children${ctx.generateID()}`;
       ctx.addLine(`let ${parentNode}= []`);
       ctx.addLine(`result = {}`);
     }
     ctx.addLine(
-      `slot${slotKey}.call(this, context.__owl__.parent, Object.assign({}, extra, {parentNode: ${parentNode}, vars: extra.vars, parent: owner}));`
+      `slot${slotKey}.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: ${parentNode}, parent: extra.parent || context}));`
     );
     if (!ctx.parentNode) {
       ctx.addLine(`utils.defineProxy(result, ${parentNode}[0]);`);
     }
+    if (node.hasChildNodes()) {
+      ctx.addElse();
+      const nodeCopy = <Element>node.cloneNode(true);
+      nodeCopy.removeAttribute("t-slot");
+      qweb._compileNode(nodeCopy, ctx);
+    }
     ctx.closeIf();
     return true;
-  }
+  },
 });
 
 //------------------------------------------------------------------------------
 // t-model
 //------------------------------------------------------------------------------
-QWeb.utils.toNumber = function(val: string): number | string {
+QWeb.utils.toNumber = function (val: string): number | string {
   const n = parseFloat(val);
   return isNaN(n) ? val : n;
 };
 
+const hasDotAtTheEnd = /\.[\w_]+\s*$/;
+const hasBracketsAtTheEnd = /\[[^\[]+\]\s*$/;
+
 QWeb.addDirective({
   name: "model",
   priority: 42,
@@ -229,7 +278,43 @@ QWeb.addDirective({
     const type = node.getAttribute("type");
     let handler;
     let event = fullName.includes(".lazy") ? "change" : "input";
-    const expr = ctx.formatExpression(value);
+
+    // First step: we need to understand the structure of the expression, and
+    // from it, extract a base expression (that we can capture, which is
+    // important because it will be used in a handler later) and a formatted
+    // expression (which uses the captured base expression)
+    //
+    // Also, we support 2 kinds of values: some.expr.value or some.expr[value]
+    // For the first one, we have:
+    // - base expression = scope[some].expr
+    // - expression = exprX.value (where exprX is the var that captures the base expr)
+    // and for the expression with brackets:
+    // - base expression = scope[some].expr
+    // - expression = exprX[keyX] (where exprX is the var that captures the base expr
+    //        and keyX captures scope[value])
+    let expr: string;
+    let baseExpr: string;
+
+    if (hasDotAtTheEnd.test(value)) {
+      // we manage the case where the expr has a dot: some.expr.value
+      const index = value.lastIndexOf(".");
+      baseExpr = value.slice(0, index);
+      ctx.addLine(`let expr${nodeID} = ${ctx.formatExpression(baseExpr)};`);
+      expr = `expr${nodeID}${value.slice(index)}`;
+    } else if (hasBracketsAtTheEnd.test(value)) {
+      // we manage here the case where the expr ends in a bracket expression:
+      //    some.expr[value]
+      const index = value.lastIndexOf("[");
+      baseExpr = value.slice(0, index);
+      ctx.addLine(`let expr${nodeID} = ${ctx.formatExpression(baseExpr)};`);
+      let exprKey = value.trimRight().slice(index + 1, -1);
+      ctx.addLine(`let exprKey${nodeID} = ${ctx.formatExpression(exprKey)};`);
+      expr = `expr${nodeID}[exprKey${nodeID}]`;
+    } else {
+      throw new Error(`Invalid t-model expression: "${value}" (it should be assignable)`);
+    }
+
+    const key = ctx.generateTemplateKey();
     if (node.tagName === "select") {
       ctx.addLine(`p${nodeID}.props = {value: ${expr}};`);
       addNodeHook("create", `n.elm.value=${expr};`);
@@ -253,9 +338,31 @@ QWeb.addDirective({
       }
       handler = `(ev) => {${expr} = ${valueCode}}`;
     }
-    ctx.addLine(
-      `extra.handlers['${event}' + ${nodeID}] = extra.handlers['${event}' + ${nodeID}] || (${handler});`
-    );
-    ctx.addLine(`p${nodeID}.on['${event}'] = extra.handlers['${event}' + ${nodeID}];`);
-  }
+    ctx.addLine(`extra.handlers[${key}] = extra.handlers[${key}] || (${handler});`);
+    ctx.addLine(`p${nodeID}.on['${event}'] = extra.handlers[${key}];`);
+  },
+});
+
+//------------------------------------------------------------------------------
+// t-key
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "key",
+  priority: 45,
+  atNodeEncounter({ ctx, value, node }) {
+    if (ctx.loopNumber === 0) {
+      ctx.keyStack.push(ctx.rootContext.hasKey0);
+      ctx.rootContext.hasKey0 = true;
+    }
+    ctx.addLine("{");
+    ctx.indent();
+    ctx.addLine(`let key${ctx.loopNumber} = ${ctx.formatExpression(value)};`);
+  },
+  finalize({ ctx }) {
+    ctx.dedent();
+    ctx.addLine("}");
+    if (ctx.loopNumber === 0) {
+      ctx.rootContext.hasKey0 = ctx.keyStack.pop() as boolean;
+    }
+  },
 });

src/qweb/qweb.ts

@@ -1,7 +1,7 @@
 import { EventBus } from "../core/event_bus";
 import { h, patch, VNode } from "../vdom/index";
 import { CompilationContext } from "./compilation_context";
-import { shallowEqual } from "../utils";
+import { shallowEqual, escape } from "../utils";
 import { addNS } from "../vdom/vdom";
 
 /**
@@ -57,20 +57,26 @@ export interface Directive {
   finalize?(info: CompilationInfo): void;
 }
 
+interface QWebConfig {
+  templates?: string;
+  translateFn?(text: string): string;
+}
+
 //------------------------------------------------------------------------------
 // Const/global stuff/helpers
 //------------------------------------------------------------------------------
 
-const DISABLED_TAGS = ["input", "textarea", "button", "select", "option", "optgroup"];
+const TRANSLATABLE_ATTRS = ["label", "title", "placeholder", "alt"];
 
 const lineBreakRE = /[\r\n]/;
 const whitespaceRE = /\s+/g;
+const translationRE = /^(\s*)([\s\S]+?)(\s*)$/;
 
 const NODE_HOOKS_PARAMS = {
   create: "(_, n)",
   insert: "vn",
   remove: "(vn, rm)",
-  destroy: "()"
+  destroy: "()",
 };
 
 interface Utils {
@@ -79,7 +85,32 @@ interface Utils {
   [key: string]: any;
 }
 
+function isComponent(obj): boolean {
+  return obj && obj.hasOwnProperty("__owl__");
+}
+
+class VDomArray extends Array {
+  toString() {
+    return vDomToString(this);
+  }
+}
+
+function vDomToString(vdom: VNode[]): string {
+  return vdom
+    .map((vnode) => {
+      if (vnode.sel) {
+        const node = document.createElement(vnode.sel);
+        const result = patch(node, vnode);
+        return (<HTMLElement>result.elm).outerHTML;
+      } else {
+        return vnode.text;
+      }
+    })
+    .join("");
+}
+
 const UTILS: Utils = {
+  zero: Symbol("zero"),
   toObj(expr) {
     if (typeof expr === "string") {
       expr = expr.trim();
@@ -98,7 +129,30 @@ const UTILS: Utils = {
   shallowEqual,
   addNameSpace(vnode) {
     addNS(vnode.data, vnode.children, vnode.sel);
-  }
+  },
+  VDomArray,
+  vDomToString,
+  getComponent(obj) {
+    while (obj && !isComponent(obj)) {
+      obj = obj.__proto__;
+    }
+    return obj;
+  },
+  getScope(obj, property: string) {
+    const obj0 = obj;
+    while (
+      obj &&
+      !obj.hasOwnProperty(property) &&
+      !(obj.hasOwnProperty("__access_mode__") && obj.__access_mode__ === "ro")
+    ) {
+      const newObj = obj.__proto__;
+      if (!newObj || isComponent(newObj)) {
+        return obj0;
+      }
+      obj = newObj;
+    }
+    return obj;
+  },
 };
 
 function parseXML(xml: string): Document {
@@ -131,9 +185,14 @@ function parseXML(xml: string): Document {
   return doc;
 }
 
+function escapeQuotes(str: string): string {
+  return str.replace(/\'/g, "\\'");
+}
+
 //------------------------------------------------------------------------------
 // QWeb rendering engine
 //------------------------------------------------------------------------------
+
 export class QWeb extends EventBus {
   templates: { [name: string]: Template };
   static utils = UTILS;
@@ -143,7 +202,8 @@ export class QWeb extends EventBus {
     name: 1,
     att: 1,
     attf: 1,
-    key: 1
+    translation: 1,
+    tag: 1,
   };
   static DIRECTIVES: Directive[] = [];
 
@@ -154,24 +214,31 @@ export class QWeb extends EventBus {
   h = h;
   // dev mode enables better error messages or more costly validations
   static dev: boolean = false;
+  static enableTransitions: boolean = true;
 
   // slots contains sub templates defined with t-set inside t-component nodes, and
   // are meant to be used by the t-slot directive.
   static slots = {};
   static nextSlotId = 1;
 
-  // recursiveTemplates contains sub templates called with t-call, but which
-  // ends up in recursive situations.  This is very similar to the slot situation,
-  // as in we need to propagate the scope.
-  recursiveFns = {};
+  // subTemplates are stored in two objects: a (local) mapping from a name to an
+  // id, and a (global) mapping from an id to the compiled function.  This is
+  // necessary to ensure that global templates can be called with more than one
+  // QWeb instance.
+  subTemplates: { [key: string]: number } = {};
+  static subTemplates: { [id: number]: Function } = {};
 
   isUpdating: boolean = false;
+  translateFn?: QWebConfig["translateFn"];
 
-  constructor(data?: string) {
+  constructor(config: QWebConfig = {}) {
     super();
     this.templates = Object.create(QWeb.TEMPLATES);
-    if (data) {
-      this.addTemplates(data);
+    if (config.templates) {
+      this.addTemplates(config.templates);
+    }
+    if (config.translateFn) {
+      this.translateFn = config.translateFn;
     }
   }
 
@@ -183,7 +250,7 @@ export class QWeb extends EventBus {
     QWeb.DIRECTIVE_NAMES[directive.name] = 1;
     QWeb.DIRECTIVES.sort((d1, d2) => d1.priority - d2.priority);
     if (directive.extraNames) {
-      directive.extraNames.forEach(n => (QWeb.DIRECTIVE_NAMES[n] = 1));
+      directive.extraNames.forEach((n) => (QWeb.DIRECTIVE_NAMES[n] = 1));
     }
   }
 
@@ -247,11 +314,11 @@ export class QWeb extends EventBus {
     this._processTemplate(elem);
     const template = {
       elem,
-      fn: function(this: QWeb, context, extra) {
-        const compiledFunction = this._compile(name, elem);
+      fn: function (this: QWeb, context, extra) {
+        const compiledFunction = this._compile(name);
         template.fn = compiledFunction;
         return compiledFunction.call(this, context, extra);
-      }
+      },
     };
     this.templates[name] = template;
   }
@@ -261,10 +328,10 @@ export class QWeb extends EventBus {
     for (let i = 0, ilen = tbranch.length; i < ilen; i++) {
       let node = tbranch[i];
       let prevElem = node.previousElementSibling!;
-      let pattr = function(name) {
+      let pattr = function (name) {
         return prevElem.getAttribute(name);
       };
-      let nattr = function(name) {
+      let nattr = function (name) {
         return +!!node.getAttribute(name);
       };
       if (prevElem && (pattr("t-if") || pattr("t-elif"))) {
@@ -274,16 +341,17 @@ export class QWeb extends EventBus {
           );
         }
         if (
-          ["t-if", "t-elif", "t-else"].map(nattr).reduce(function(a, b) {
+          ["t-if", "t-elif", "t-else"].map(nattr).reduce(function (a, b) {
             return a + b;
           }) > 1
         ) {
           throw new Error("Only one conditional branching directive is allowed per node");
         }
-        // All text nodes between branch nodes are removed
+        // All text (with only spaces) and comment nodes (nodeType 8) between
+        // branch nodes are removed
         let textNode;
         while ((textNode = node.previousSibling) !== prevElem) {
-          if (textNode.nodeValue.trim().length) {
+          if (textNode.nodeValue.trim().length && textNode.nodeType !== 8) {
             throw new Error("text is not allowed between branching directives");
           }
           textNode.remove();
@@ -321,8 +389,17 @@ export class QWeb extends EventBus {
       return vnode.text!;
     }
     const node = document.createElement(vnode.sel);
-    const result = patch(node, vnode);
-    return (<HTMLElement>result.elm).outerHTML;
+    const elem = patch(node, vnode).elm as HTMLElement;
+    function escapeTextNodes(node) {
+      if (node.nodeType === 3) {
+        node.textContent = escape(node.textContent);
+      }
+      for (let n of node.childNodes) {
+        escapeTextNodes(n);
+      }
+    }
+    escapeTextNodes(elem);
+    return elem.outerHTML;
   }
 
   /**
@@ -341,35 +418,36 @@ export class QWeb extends EventBus {
     });
   }
 
-  _compile(name: string, elem: Element, parentContext?: CompilationContext): CompiledTemplate {
+  _compile(
+    name: string,
+    options: {
+      elem?: Element;
+      hasParent?: boolean;
+      defineKey?: boolean;
+    } = {}
+  ): CompiledTemplate {
+    const elem = options.elem || this.templates[name].elem;
     const isDebug = elem.attributes.hasOwnProperty("t-debug");
     const ctx = new CompilationContext(name);
     if (elem.tagName !== "t") {
       ctx.shouldDefineResult = false;
     }
-    if (parentContext) {
-      ctx.templates = Object.create(parentContext.templates);
-      ctx.variables = Object.create(parentContext.variables);
-      ctx.nextID = parentContext.nextID + 1;
-      ctx.parentNode = parentContext.parentNode || ctx.nextID++;
+    if (options.hasParent) {
+      ctx.variables = Object.create(null);
+      ctx.parentNode = ctx.generateID();
       ctx.allowMultipleRoots = true;
+      ctx.shouldDefineParent = true;
       ctx.hasParentWidget = true;
       ctx.shouldDefineResult = false;
       ctx.addLine(`let c${ctx.parentNode} = extra.parentNode;`);
-
-      for (let v in parentContext.variables) {
-        let variable = <any>parentContext.variables[v];
-        if (variable.id) {
-          ctx.addLine(`let ${variable.id} = extra.fiber.vars.${variable.id}`);
-        }
+      if (options.defineKey) {
+        ctx.addLine(`let key0 = extra.key || "";`);
+        ctx.hasKey0 = true;
       }
     }
-    if (parentContext) {
-      ctx.addLine("    Object.assign(context, extra.fiber.scope);");
-    }
     this._compileNode(elem, ctx);
 
-    if (!parentContext) {
+    if (!options.hasParent) {
       if (ctx.shouldDefineResult) {
         ctx.addLine(`return result;`);
       } else {
@@ -381,12 +459,13 @@ export class QWeb extends EventBus {
     }
 
     let code = ctx.generateCode();
+    const templateName = ctx.templateName.replace(/`/g, "'").slice(0, 200);
+    code.unshift(`    // Template name: "${templateName}"`);
 
     let template;
     try {
-      template = new Function("context", "extra", code.join("\n")) as CompiledTemplate;
+      template = new Function("context, extra", code.join("\n")) as CompiledTemplate;
     } catch (e) {
-      const templateName = ctx.templateName.replace(/`/g, "'");
       console.groupCollapsed(`Invalid Code generated by ${templateName}`);
       console.warn(code.join("\n"));
       console.groupEnd();
@@ -418,6 +497,12 @@ export class QWeb extends EventBus {
         }
         text = text.replace(whitespaceRE, " ");
       }
+      if (this.translateFn) {
+        if ((node.parentNode as any).getAttribute("t-translation") !== "off") {
+          const match = translationRE.exec(text);
+          text = match[1] + this.translateFn(match[2]) + match[3];
+        }
+      }
       if (ctx.parentNode) {
         if (node.nodeType === 3) {
           ctx.addLine(`c${ctx.parentNode}.push({text: \`${text}\`});`);
@@ -430,7 +515,7 @@ export class QWeb extends EventBus {
         // this is an unusual situation: this text node is the result of the
         // template rendering.
         let nodeID = ctx.generateID();
-        ctx.addLine(`var vn${nodeID} = {text: \`${text}\`};`);
+        ctx.addLine(`let vn${nodeID} = {text: \`${text}\`};`);
         ctx.addLine(`result = vn${nodeID};`);
         ctx.rootContext.rootNode = nodeID;
         ctx.rootContext.parentTextNode = nodeID;
@@ -438,11 +523,22 @@ export class QWeb extends EventBus {
       return;
     }
 
+    if (node.tagName !== "t" && node.hasAttribute("t-call")) {
+      const tCallNode = document.createElement("t");
+      tCallNode.setAttribute("t-call", node.getAttribute("t-call")!);
+      node.removeAttribute("t-call");
+      node.prepend(tCallNode);
+    }
+
     const firstLetter = node.tagName[0];
     if (firstLetter === firstLetter.toUpperCase()) {
       // this is a component, we modify in place the xml document to change
-      // <SomeComponent ... /> to <t t-component="SomeComponent" ... />
+      // <SomeComponent ... /> to <SomeComponent t-component="SomeComponent" ... />
       node.setAttribute("t-component", node.tagName);
+    } else if (node.tagName !== "t" && node.hasAttribute("t-component")) {
+      throw new Error(
+        `Directive 't-component' can only be used on <t> nodes (used on a <${node.tagName}>)`
+      );
     }
     const attributes = (<Element>node).attributes;
 
@@ -509,7 +605,7 @@ export class QWeb extends EventBus {
           qweb: this,
           ctx,
           fullName,
-          value
+          value,
         });
         if (isDone) {
           for (let { directive, value, fullName } of finalizers) {
@@ -520,12 +616,11 @@ export class QWeb extends EventBus {
       }
     }
 
-    if (node.nodeName !== "t") {
+    if (node.nodeName !== "t" || node.hasAttribute("t-tag")) {
       let nodeID = this._compileGenericNode(node, ctx, withHandlers);
       ctx = ctx.withParent(nodeID);
-      ctx = ctx.subContext("currentKey", ctx.lastNodeKey);
       let nodeHooks = {};
-      let addNodeHook = function(hook, handler) {
+      let addNodeHook = function (hook, handler) {
         nodeHooks[hook] = nodeHooks[hook] || [];
         nodeHooks[hook].push(handler);
       };
@@ -539,7 +634,7 @@ export class QWeb extends EventBus {
             fullName,
             value,
             nodeID,
-            addNodeHook
+            addNodeHook,
           });
         }
       }
@@ -592,22 +687,31 @@ export class QWeb extends EventBus {
     const props: string[] = [];
     const tattrs: number[] = [];
 
-    function handleBooleanProps(key, val) {
+    function handleProperties(key, val) {
       let isProp = false;
-      if (node.nodeName === "input" && key === "checked") {
-        let type = (<Element>node).getAttribute("type");
-        if (type === "checkbox" || type === "radio") {
-          isProp = true;
-        }
-      }
-      if (node.nodeName === "option" && key === "selected") {
-        isProp = true;
-      }
-      if (key === "disabled" && DISABLED_TAGS.indexOf(node.nodeName) > -1) {
-        isProp = true;
-      }
-      if ((key === "readonly" && node.nodeName === "input") || node.nodeName === "textarea") {
-        isProp = true;
+      switch (node.nodeName) {
+        case "input":
+          let type = (<Element>node).getAttribute("type");
+          if (type === "checkbox" || type === "radio") {
+            if (key === "checked" || key === "indeterminate") {
+              isProp = true;
+            }
+          }
+          if (key === "value" || key === "readonly" || key === "disabled") {
+            isProp = true;
+          }
+          break;
+        case "option":
+          isProp = key === "selected" || key === "disabled";
+          break;
+        case "textarea":
+          isProp = key === "readonly" || key === "disabled";
+          break;
+        case "button":
+        case "select":
+        case "optgroup":
+          isProp = key === "disabled";
+          break;
       }
       if (isProp) {
         props.push(`${key}: _${val}`);
@@ -617,27 +721,36 @@ export class QWeb extends EventBus {
 
     for (let i = 0; i < attributes.length; i++) {
       let name = attributes[i].name;
-      const value = attributes[i].textContent!;
+      let value = attributes[i].textContent!;
+
+      if (this.translateFn && TRANSLATABLE_ATTRS.includes(name)) {
+        value = this.translateFn(value);
+      }
 
       // regular attributes
       if (!name.startsWith("t-") && !(<Element>node).getAttribute("t-attf-" + name)) {
         const attID = ctx.generateID();
         if (name === "class") {
-          let classDef = value
-            .trim()
-            .split(/\s+/)
-            .map(a => `'${a}':true`)
-            .join(",");
-          classObj = `_${ctx.generateID()}`;
-          ctx.addLine(`let ${classObj} = {${classDef}};`);
+          if ((value = value.trim())) {
+            let classDef = value
+              .split(/\s+/)
+              .map((a) => `'${escapeQuotes(a)}':true`)
+              .join(",");
+            if (classObj) {
+              ctx.addLine(`Object.assign(${classObj}, {${classDef}})`);
+            } else {
+              classObj = `_${ctx.generateID()}`;
+              ctx.addLine(`let ${classObj} = {${classDef}};`);
+            }
+          }
         } else {
-          ctx.addLine(`var _${attID} = '${value}';`);
+          ctx.addLine(`let _${attID} = '${escapeQuotes(value)}';`);
           if (!name.match(/^[a-zA-Z]+$/)) {
             // attribute contains 'non letters' => we want to quote it
             name = '"' + name + '"';
           }
           attrs.push(`${name}: _${attID}`);
-          handleBooleanProps(name, attID);
+          handleProperties(name, attID);
         }
       }
 
@@ -645,7 +758,7 @@ export class QWeb extends EventBus {
       if (name.startsWith("t-att-")) {
         let attName = name.slice(6);
         const v = ctx.getValue(value);
-        let formattedValue = typeof v === "string" ? ctx.formatExpression(v) : v.id;
+        let formattedValue = typeof v === "string" ? ctx.formatExpression(v) : `scope.${v.id}`;
 
         if (attName === "class") {
           ctx.rootContext.shouldDefineUtils = true;
@@ -667,14 +780,14 @@ export class QWeb extends EventBus {
           const attValue = (<Element>node).getAttribute(attName);
           if (attValue) {
             const attValueID = ctx.generateID();
-            ctx.addLine(`var _${attValueID} = ${formattedValue};`);
+            ctx.addLine(`let _${attValueID} = ${formattedValue};`);
             formattedValue = `'${attValue}' + (_${attValueID} ? ' ' + _${attValueID} : '')`;
-            const attrIndex = attrs.findIndex(att => att.startsWith(attName + ":"));
+            const attrIndex = attrs.findIndex((att) => att.startsWith(attName + ":"));
             attrs.splice(attrIndex, 1);
           }
-          ctx.addLine(`var _${attID} = ${formattedValue};`);
+          ctx.addLine(`let _${attID} = ${formattedValue};`);
           attrs.push(`${attName}: _${attID}`);
-          handleBooleanProps(attName, attID);
+          handleProperties(attName, attID);
         }
       }
 
@@ -688,9 +801,9 @@ export class QWeb extends EventBus {
         const attID = ctx.generateID();
         let staticVal = (<Element>node).getAttribute(attName);
         if (staticVal) {
-          ctx.addLine(`var _${attID} = '${staticVal} ' + ${formattedExpr};`);
+          ctx.addLine(`let _${attID} = '${staticVal} ' + ${formattedExpr};`);
         } else {
-          ctx.addLine(`var _${attID} = ${formattedExpr};`);
+          ctx.addLine(`let _${attID} = ${formattedExpr};`);
         }
         attrs.push(`${attName}: _${attID}`);
       }
@@ -698,20 +811,13 @@ export class QWeb extends EventBus {
       // t-att= attributes
       if (name === "t-att") {
         let id = ctx.generateID();
-        ctx.addLine(`var _${id} = ${ctx.formatExpression(value!)};`);
+        ctx.addLine(`let _${id} = ${ctx.formatExpression(value!)};`);
         tattrs.push(id);
       }
     }
     let nodeID = ctx.generateID();
-    let nodeKey: any = (<Element>node).getAttribute("t-key");
-    if (nodeKey) {
-      ctx.addLine(`const nodeKey${nodeID} = ${ctx.formatExpression(nodeKey)}`);
-      nodeKey = `nodeKey${nodeID}`;
-      ctx.lastNodeKey = nodeKey;
-    } else {
-      nodeKey = nodeID;
-    }
-    const parts = [`key:${nodeKey}`];
+    let key = ctx.loopNumber || ctx.hasKey0 ? `\`\${key${ctx.loopNumber}}_${nodeID}\`` : nodeID;
+    const parts = [`key:${key}`];
     if (attrs.length + tattrs.length > 0) {
       parts.push(`attrs:{${attrs.join(",")}}`);
     }
@@ -737,9 +843,19 @@ export class QWeb extends EventBus {
       ctx.addLine(`}`);
       ctx.closeIf();
     }
-    ctx.addLine(`var vn${nodeID} = h('${node.nodeName}', p${nodeID}, c${nodeID});`);
+    let nodeName = `'${node.nodeName}'`;
+    if ((<Element>node).hasAttribute("t-tag")) {
+      const tagExpr = (<Element>node).getAttribute("t-tag");
+      (<Element>node).removeAttribute("t-tag");
+      nodeName = `tag${ctx.generateID()}`;
+      ctx.addLine(`let ${nodeName} = ${ctx.formatExpression(tagExpr)};`);
+    }
+    ctx.addLine(`let vn${nodeID} = h(${nodeName}, p${nodeID}, c${nodeID});`);
     if (ctx.parentNode) {
       ctx.addLine(`c${ctx.parentNode}.push(vn${nodeID});`);
+    } else if (ctx.loopNumber || ctx.hasKey0) {
+      ctx.rootContext.shouldDefineResult = true;
+      ctx.addLine(`result = vn${nodeID};`);
     }
 
     return nodeID;

src/router/link.ts

@@ -4,7 +4,7 @@ import { Destination, RouterEnv } from "./router";
 
 type Props = Destination;
 
-export class Link<Env extends RouterEnv> extends Component<Env, Props> {
+export class Link<Env extends RouterEnv> extends Component<Props, Env> {
   static template = xml`
     <a  t-att-class="{'router-link-active': isActive }"
         t-att-href="href"

src/router/route_component.ts

@@ -1,7 +1,8 @@
 import { Component } from "../component/component";
 import { xml } from "../tags";
+import { EnvWithRouter } from "./router";
 
-export class RouteComponent extends Component<any, {}> {
+export class RouteComponent extends Component<{}, EnvWithRouter> {
   static template = xml`
     <t>
         <t

src/router/router.ts

@@ -11,6 +11,7 @@ type NavigationGuard = (info: {
 export interface Route {
   name: string;
   path: string;
+  extractionRegExp: RegExp;
   component?: any;
   redirect?: Destination;
   params: string[];
@@ -49,7 +50,12 @@ interface Options {
   mode: Router["mode"];
 }
 
+export interface EnvWithRouter extends Env {
+  router: Router;
+}
+
 const paramRegexp = /\{\{(.*?)\}\}/;
+const globalParamRegexp = new RegExp(paramRegexp.source, "g");
 
 export class Router {
   currentRoute: Route | null = null;
@@ -60,7 +66,11 @@ export class Router {
   routeIds: string[];
   env: RouterEnv;
 
-  constructor(env: Env, routes: Partial<Route>[], options: Options = { mode: "history" }) {
+  constructor(
+    env: Partial<EnvWithRouter>,
+    routes: Partial<Route>[],
+    options: Options = { mode: "history" }
+  ) {
     env.router = this;
     this.mode = options.mode;
     this.env = env as RouterEnv;
@@ -79,6 +89,7 @@ export class Router {
         this.validateDestination(partialRoute.redirect);
       }
       partialRoute.params = partialRoute.path ? findParams(partialRoute.path) : [];
+      partialRoute.extractionRegExp = makeExtractionRegExp(partialRoute.path);
       this.routes[partialRoute.name] = partialRoute as Route;
       this.routeIds.push(partialRoute.name);
     }
@@ -89,7 +100,7 @@ export class Router {
   //--------------------------------------------------------------------------
 
   async start() {
-    (this as any)._listener = ev => this._navigate(this.currentPath(), ev);
+    (this as any)._listener = (ev) => this._navigate(this.currentPath(), ev);
     window.addEventListener("popstate", (this as any)._listener);
     if (this.mode === "hash") {
       window.addEventListener("hashchange", (this as any)._listener);
@@ -148,7 +159,7 @@ export class Router {
   //--------------------------------------------------------------------------
 
   private setUrlFromPath(path: string) {
-    const separator = this.mode === "hash" ? "/" : "";
+    const separator = this.mode === "hash" ? location.pathname : "";
     const url = location.origin + separator + path;
     if (url !== window.location.href) {
       window.history.pushState({}, path, url);
@@ -162,19 +173,14 @@ export class Router {
   }
 
   private routeToPath(route: Route, params: RouteParams): string {
-    const path = route.path;
-    const parts = path.split("/");
-    const l = parts.length;
-    for (let i = 0; i < l; i++) {
-      const part = parts[i];
-      const match = part.match(paramRegexp);
-      if (match) {
-        const key = match[1].split(".")[0];
-        parts[i] = <string>params[key];
-      }
-    }
     const prefix = this.mode === "hash" ? "#" : "";
-    return prefix + parts.join("/");
+    return (
+      prefix +
+      route.path.replace(globalParamRegexp, (match, param) => {
+        const [key] = param.split(".");
+        return <string>params[key];
+      })
+    );
   }
 
   private currentPath(): string {
@@ -190,7 +196,7 @@ export class Router {
         return {
           type: "match",
           route: route,
-          params: params
+          params: params,
         };
       }
     }
@@ -215,7 +221,7 @@ export class Router {
       const result = await route.beforeRouteEnter({
         env: this.env,
         from: this.currentRoute,
-        to: route
+        to: route,
       });
       if (result === false) {
         return { type: "cancelled" };
@@ -236,40 +242,47 @@ export class Router {
     if (path.startsWith("#")) {
       path = path.slice(1);
     }
-    const descrParts = route.path.split("/");
-    const targetParts = path.split("/");
-    const l = descrParts.length;
-    if (l !== targetParts.length) {
+    const paramsMatch = path.match(route.extractionRegExp);
+    if (!paramsMatch) {
       return false;
     }
     const result = {};
-    for (let i = 0; i < l; i++) {
-      const descr = descrParts[i];
-      let target: string | number = targetParts[i];
-      const match = descr.match(paramRegexp);
-      if (match) {
-        const [key, suffix] = match[1].split(".");
-        if (suffix === "number") {
-          target = parseInt(target, 10);
-        }
-        result[key] = target;
-      } else if (descr !== target) {
-        return false;
+    route.params.forEach((param, index) => {
+      const [key, suffix] = param.split(".");
+      const paramValue = paramsMatch[index + 1];
+      if (suffix === "number") {
+        return (result[key] = parseInt(paramValue, 10));
       }
-    }
+      return (result[key] = paramValue);
+    });
     return result;
   }
 }
 
 function findParams(str: string): string[] {
-  const globalParamRegexp = /\{\{(.*?)\}\}/g;
   const result: string[] = [];
   let m;
   do {
     m = globalParamRegexp.exec(str);
     if (m) {
-      result.push(m[1].split(".")[0]);
+      result.push(m[1]);
     }
   } while (m);
   return result;
 }
+
+function escapeRegExp(str: string) {
+  return str.replace(/[-[\]{}()*+?.,\\^$|#\s]/g, "\\$&");
+}
+
+function makeExtractionRegExp(path: string) {
+  // replace param strings with capture groups so that we can build a regex to match over the path
+  const extractionString = path
+    .split(paramRegexp)
+    .map((part, index) => {
+      return index % 2 ? "(.*)" : escapeRegExp(part);
+    })
+    .join("");
+  // Example: /home/{{param1}}/{{param2}} => ^\/home\/(.*)\/(.*)$
+  return new RegExp(`^${extractionString}$`);
+}

src/store.ts

@@ -1,5 +1,4 @@
-import { Component } from "./component/component";
-import { Env } from "./component/component";
+import { Component, Env } from "./component/component";
 import { Context, useContextWithCB } from "./context";
 import { onWillUpdateProps } from "./hooks";
 
@@ -24,6 +23,10 @@ import { onWillUpdateProps } from "./hooks";
 // Store Definition
 //------------------------------------------------------------------------------
 
+export interface EnvWithStore extends Env {
+  store: Store;
+}
+
 export type Action = ({ state, dispatch, env, getters }, ...payload: any) => any;
 export type Getter = ({ state: any, getters }, payload?) => any;
 
@@ -49,7 +52,7 @@ export class Store extends Context {
     if (config.getters) {
       const firstArg = {
         state: this.state,
-        getters: this.getters
+        getters: this.getters,
       };
       for (let g in config.getters) {
         this.getters[g] = config.getters[g].bind(this, firstArg);
@@ -66,77 +69,105 @@ export class Store extends Context {
         dispatch: this.dispatch.bind(this),
         env: this.env,
         state: this.state,
-        getters: this.getters
+        getters: this.getters,
       },
       ...payload
     );
     return result;
   }
+
+  __notifyComponents(): Promise<void> {
+    this.trigger("before-update");
+    return super.__notifyComponents();
+  }
 }
 
 interface SelectorOptions {
   store?: Store;
   isEqual?: (a: any, b: any) => boolean;
+  onUpdate?: (result: any) => any;
 }
 
 const isStrictEqual = (a, b) => a === b;
 
 export function useStore(selector, options: SelectorOptions = {}): any {
-  const component: Component<any, any> = Component.current!;
+  const component = Component.current as Component<any, EnvWithStore>;
+  const componentId = component.__owl__.id;
   const store = options.store || (component.env.store as Store);
-  let result = selector(store.state, component.props);
-  const hashFn = store.observer.deepRevNumber.bind(store.observer);
-  let revNumber = hashFn(result) || result;
-  const isEqual = options.isEqual || isStrictEqual;
-  if (!store.updateFunctions[component.__owl__.id]) {
-    store.updateFunctions[component.__owl__.id] = [];
+  if (!(store instanceof Store)) {
+    throw new Error(`No store found when connecting '${component.constructor.name}'`);
   }
-  const updateFunctions = store.updateFunctions[component.__owl__.id];
-  updateFunctions.push(function(): boolean {
+  let result = selector(store.state, component.props);
+  const hashFn = store.observer.revNumber.bind(store.observer);
+  let revNumber = hashFn(result);
+  const isEqual = options.isEqual || isStrictEqual;
+  if (!store.updateFunctions[componentId]) {
+    store.updateFunctions[componentId] = [];
+  }
+  function selectCompareUpdate(state, props): boolean {
     const oldResult = result;
-    result = selector(store!.state, component.props);
+    result = selector(state, props);
     const newRevNumber = hashFn(result);
-    if (
-      (newRevNumber > 0 && revNumber !== newRevNumber) ||
-      (newRevNumber === 0 && !isEqual(oldResult, result))
-    ) {
+    if ((newRevNumber > 0 && revNumber !== newRevNumber) || !isEqual(oldResult, result)) {
       revNumber = newRevNumber;
       return true;
     }
     return false;
+  }
+  if (options.onUpdate) {
+    store.on("before-update", component, () => {
+      const newValue = selector(store!.state, component.props!);
+      options.onUpdate(newValue);
+    });
+  }
+  store.updateFunctions[componentId].push(function (): boolean {
+    return selectCompareUpdate(store!.state, component.props);
   });
 
-  useContextWithCB(store, component, function(): Promise<void> | void {
+  useContextWithCB(store, component, function (): Promise<void> | void {
     let shouldRender = false;
-    updateFunctions.forEach(function(updateFn) {
-      shouldRender = updateFn() || shouldRender;
-    });
+    for (let fn of store.updateFunctions[componentId]) {
+      shouldRender = fn() || shouldRender;
+    }
     if (shouldRender) {
       return component.render();
     }
   });
-  onWillUpdateProps(props => {
-    // FIXME: only do that if not keepalive + do it in destroy in that case
-    delete store.updateFunctions[component.__owl__.id];
-    result = selector(store.state, props);
+  onWillUpdateProps((props) => {
+    selectCompareUpdate(store.state, props);
   });
+
+  const __destroy = component.__destroy;
+  component.__destroy = (parent) => {
+    delete store.updateFunctions[componentId];
+    if (options.onUpdate) {
+      store.off("before-update", component);
+    }
+    __destroy.call(component, parent);
+  };
+
+  if (typeof result !== "object" || result === null) {
+    return result;
+  }
   return new Proxy(result, {
     get(target, k) {
       return result[k];
     },
     set(target, k, v) {
-      result[k] = v;
-      return true;
-    }
+      throw new Error("Store state should only be modified through actions");
+    },
+    has(target, k) {
+      return k in result;
+    },
   });
 }
 
 export function useDispatch(store?: Store): Store["dispatch"] {
-  store = store || (Component.current!.env.store as Store);
+  store = store || (Component.current!.env as EnvWithStore).store;
   return store.dispatch.bind(store);
 }
 
 export function useGetters(store?: Store): Store["getters"] {
-  store = store || (Component.current!.env.store as Store);
+  store = store || (Component.current!.env as EnvWithStore).store;
   return store.getters;
 }

src/tags.ts

@@ -1,4 +1,5 @@
 import { QWeb } from "./qweb/index";
+import { registerSheet } from "./component/styles";
 
 /**
  * Owl Tags
@@ -25,3 +26,19 @@ export function xml(strings, ...args) {
   QWeb.registerTemplate(name, value);
   return name;
 }
+
+/**
+ * CSS tag helper for defining inline stylesheets.  With this, one can simply define
+ * an inline stylesheet with just the following code:
+ * ```js
+ *   class A extends Component {
+ *     static style = css`.component-a { color: red; }`;
+ *   }
+ * ```
+ */
+export function css(strings, ...args) {
+  const name = `__sheet__${QWeb.nextId++}`;
+  const value = String.raw(strings, ...args);
+  registerSheet(name, value);
+  return name;
+}

src/utils.ts

@@ -10,14 +10,16 @@
  * - debounce
  */
 
+import { browser } from "./browser";
+
 export function whenReady(fn?: any) {
-  return new Promise(function(resolve) {
+  return new Promise(function (resolve) {
     if (document.readyState !== "loading") {
       resolve();
     } else {
       document.addEventListener("DOMContentLoaded", resolve, false);
     }
-  }).then(fn || function() {});
+  }).then(fn || function () {});
 }
 
 const loadedScripts: { [key: string]: Promise<void> } = {};
@@ -26,14 +28,14 @@ export function loadJS(url: string): Promise<void> {
   if (url in loadedScripts) {
     return loadedScripts[url];
   }
-  const promise: Promise<void> = new Promise(function(resolve, reject) {
+  const promise: Promise<void> = new Promise(function (resolve, reject) {
     const script = document.createElement("script");
     script.type = "text/javascript";
     script.src = url;
-    script.onload = function() {
+    script.onload = function () {
       resolve();
     };
-    script.onerror = function() {
+    script.onerror = function () {
       reject(`Error loading file '${url}'`);
     };
     const head = document.head || document.getElementsByTagName("head")[0];
@@ -44,7 +46,7 @@ export function loadJS(url: string): Promise<void> {
 }
 
 export async function loadFile(url: string): Promise<string> {
-  const result = await fetch(url);
+  const result = await browser.fetch(url);
   if (!result.ok) {
     throw new Error("Error while fetching xml templates");
   }
@@ -58,12 +60,9 @@ export function escape(str: string | number | undefined): string {
   if (typeof str === "number") {
     return String(str);
   }
-  return str
-    .replace(/&/g, "&amp;")
-    .replace(/</g, "&lt;")
-    .replace(/>/g, "&gt;")
-    .replace(/"/g, "&#x27;")
-    .replace(/`/g, "&#x60;");
+  const p = document.createElement("p");
+  p.textContent = str;
+  return p.innerHTML;
 }
 
 /**
@@ -76,7 +75,7 @@ export function escape(str: string | number | undefined): string {
  */
 export function debounce(func: Function, wait: number, immediate?: boolean): Function {
   let timeout;
-  return function(this: any) {
+  return function (this: any) {
     const context = this;
     const args = arguments;
     function later() {
@@ -86,8 +85,8 @@ export function debounce(func: Function, wait: number, immediate?: boolean): Fun
       }
     }
     const callNow = immediate && !timeout;
-    clearTimeout(timeout);
-    timeout = setTimeout(later, wait);
+    browser.clearTimeout(timeout);
+    timeout = browser.setTimeout(later, wait);
     if (callNow) {
       func.apply(context, args);
     }

src/vdom/html_to_vdom.ts

@@ -1,4 +1,4 @@
-import { VNode, h } from "./vdom";
+import { VNode, h, addNS } from "./vdom";
 
 const parser = new DOMParser();
 
@@ -13,6 +13,9 @@ export function htmlToVDOM(html: string): VNode[] {
 
 function htmlToVNode(node: ChildNode): VNode {
   if (!(node instanceof Element)) {
+    if (node instanceof Comment) {
+      return h("!", node.textContent);
+    }
     return { text: node.textContent! } as VNode;
   }
   const attrs = {};
@@ -20,10 +23,12 @@ function htmlToVNode(node: ChildNode): VNode {
     attrs[attr.name] = attr.textContent;
   }
   const children: VNode[] = [];
-  if (node.hasChildNodes) {
-    for (let c of node.childNodes) {
-      children.push(htmlToVNode(c));
-    }
+  for (let c of node.childNodes) {
+    children.push(htmlToVNode(c));
   }
-  return h((node as Element).tagName, { attrs }, children);
+  const vnode = h((node as Element).tagName, { attrs }, children);
+  if (vnode.sel === "svg") {
+    addNS(vnode.data, (vnode as any).children, vnode.sel);
+  }
+  return vnode;
 }

src/vdom/modules.ts

@@ -33,7 +33,7 @@ function updateProps(oldVnode: VNode, vnode: VNode): void {
 
 export const propsModule = {
   create: updateProps,
-  update: updateProps
+  update: updateProps,
 } as Module;
 
 //------------------------------------------------------------------------------
@@ -70,8 +70,12 @@ function handleEvent(event: Event, vnode: VNode) {
     on = (vnode.data as VNodeData).on;
 
   // call event handler(s) if exists
-  if (on && on[name]) {
-    invokeHandler(on[name], vnode, event);
+  if (on) {
+    if (on[name]) {
+      invokeHandler(on[name], vnode, event);
+    } else if (on["!" + name]) {
+      invokeHandler(on["!" + name], vnode, event);
+    }
   }
 }
 
@@ -100,13 +104,17 @@ function updateEventListeners(oldVnode: VNode, vnode?: VNode): void {
     if (!on) {
       for (name in oldOn) {
         // remove listener if element was changed or existing listeners removed
-        oldElm.removeEventListener(name, oldListener, false);
+        const capture = name.charAt(0) === "!";
+        name = capture ? name.slice(1) : name;
+        oldElm.removeEventListener(name, oldListener, capture);
       }
     } else {
       for (name in oldOn) {
         // remove listener if existing listener removed
         if (!on[name]) {
-          oldElm.removeEventListener(name, oldListener, false);
+          const capture = name.charAt(0) === "!";
+          name = capture ? name.slice(1) : name;
+          oldElm.removeEventListener(name, oldListener, capture);
         }
       }
     }
@@ -123,13 +131,17 @@ function updateEventListeners(oldVnode: VNode, vnode?: VNode): void {
     if (!oldOn) {
       for (name in on) {
         // add listener if element was changed or new listeners added
-        elm.addEventListener(name, listener, false);
+        const capture = name.charAt(0) === "!";
+        name = capture ? name.slice(1) : name;
+        elm.addEventListener(name, listener, capture);
       }
     } else {
       for (name in on) {
         // add listener if new listener added
         if (!oldOn[name]) {
-          elm.addEventListener(name, listener, false);
+          const capture = name.charAt(0) === "!";
+          name = capture ? name.slice(1) : name;
+          elm.addEventListener(name, listener, capture);
         }
       }
     }
@@ -139,7 +151,7 @@ function updateEventListeners(oldVnode: VNode, vnode?: VNode): void {
 export const eventListenersModule = {
   create: updateEventListeners,
   update: updateEventListeners,
-  destroy: updateEventListeners
+  destroy: updateEventListeners,
 } as Module;
 
 //------------------------------------------------------------------------------
@@ -198,7 +210,7 @@ function updateAttrs(oldVnode: VNode, vnode: VNode): void {
 
 export const attrsModule = {
   create: updateAttrs,
-  update: updateAttrs
+  update: updateAttrs,
 } as Module;
 
 //------------------------------------------------------------------------------
@@ -219,7 +231,7 @@ function updateClass(oldVnode: VNode, vnode: VNode): void {
   elm = vnode.elm as Element;
 
   for (name in oldClass) {
-    if (!klass[name]) {
+    if (name && !klass[name]) {
       elm.classList.remove(name);
     }
   }

src/vdom/vdom.ts

@@ -101,7 +101,7 @@ function isVnode(vnode: any): vnode is VNode {
 
 type KeyToIndexMap = { [key: string]: number };
 
-type ArraysOf<T> = { [K in keyof T]: (T[K])[] };
+type ArraysOf<T> = { [K in keyof T]: T[K][] };
 
 type ModuleHooks = ArraysOf<Module>;
 
@@ -176,10 +176,12 @@ export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {
       }
       vnode.elm = api.createComment(vnode.text as string);
     } else if (sel !== undefined) {
-      const elm = (vnode.elm =
-        isDef(data) && isDef((i = (data as VNodeData).ns))
-          ? api.createElementNS(i, sel)
-          : api.createElement(sel));
+      const elm =
+        vnode.elm ||
+        (vnode.elm =
+          isDef(data) && isDef((i = (data as VNodeData).ns))
+            ? api.createElementNS(i, sel)
+            : api.createElement(sel));
       for (i = 0, iLen = cbs.create.length; i < iLen; ++i) cbs.create[i](emptyNode, vnode);
       if (array(children)) {
         for (i = 0, iLen = children.length; i < iLen; ++i) {
@@ -518,7 +520,7 @@ const htmlDomApi = {
   parentNode,
   nextSibling,
   tagName,
-  setTextContent
+  setTextContent,
 } as DOMAPI;
 
 //------------------------------------------------------------------------------

tests/__snapshots__/animations.test.ts.snap

@@ -1,103 +1,149 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`animations t-transition combined with component 1`] = `
-"function anonymous(context,extra
+"function anonymous(context, extra
 ) {
+    // Template name: \\"Parent\\"
     let utils = this.constructor.utils;
     let QWeb = this.constructor;
     let parent = context;
-    let owner = context;
-    let sibling = null;
-    var h = this.h;
+    let scope = Object.create(context);
+    let h = this.h;
     let c1 = [], p1 = {key:1};
-    var vn1 = h('div', p1, c1);
-    //COMPONENT
-    let templateId3 = \`__4__\`;
-    let w3 = templateId3 in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap[templateId3]] : false;
-    let props3 = {};
-    if (w3 && w3.__owl__.currentFiber && !w3.__owl__.vnode) {
-        w3.destroy();
-        w3 = false;
+    let vn1 = h('div', p1, c1);
+    // Component 'Child'
+    let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+    let props2 = {};
+    if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+        w2.destroy();
+        w2 = false;
     }
-    if (w3) {
-        w3.__updateProps(props3, extra.fiber, undefined, undefined, sibling);
-        let pvnode = w3.__owl__.pvnode;
+    if (w2) {
+        w2.__updateProps(props2, extra.fiber, undefined);
+        let pvnode = w2.__owl__.pvnode;
         c1.push(pvnode);
     } else {
-        let componentKey3 = \`Child\`;
-        let W3 = context.constructor.components[componentKey3] || QWeb.components[componentKey3]|| context['Child'];
-        if (!W3) {throw new Error('Cannot find the definition of component \\"' + componentKey3 + '\\"')}
-        w3 = new W3(parent, props3);
-        parent.__owl__.cmap[templateId3] = w3.__owl__.id;
-        let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
-        let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;utils.transitionInsert(vn, 'chimay');},remove() {},destroy(vn) {let finalize = () => {
-          w3.destroy();
+        let componentKey2 = \`Child\`;
+        let W2 = scope['Child'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+        if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+        w2 = new W2(parent, props2);
+        const __patch2 = w2.__patch;
+        w2.__patch = (t, vn) => {__patch2.call(w2, t, vn); if(!w2.__owl__.transitionInserted){w2.__owl__.transitionInserted = true;utils.transitionInsert(w2.__owl__.vnode, 'chimay');}};
+        parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+        let fiber = w2.__prepare(extra.fiber, undefined, () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {let finalize = () => {
+          w2.destroy();
         };
+        delete w2.__owl__.transitionInserted;
         utils.transitionRemove(vn, 'chimay', finalize);}}});
-        const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (w3.__owl__.isDestroyed) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
         c1.push(pvnode);
-        w3.__owl__.pvnode = pvnode;
+        w2.__owl__.pvnode = pvnode;
     }
-    sibling = w3.__owl__.currentFiber || sibling;
+    w2.__owl__.parentLastFiberId = extra.fiber.id;
     return vn1;
 }"
 `;
 
 exports[`animations t-transition combined with t-component and t-if 1`] = `
-"function anonymous(context,extra
+"function anonymous(context, extra
 ) {
+    // Template name: \\"Parent\\"
     let utils = this.constructor.utils;
     let QWeb = this.constructor;
     let parent = context;
-    let owner = context;
-    let sibling = null;
-    var h = this.h;
+    let scope = Object.create(context);
+    let h = this.h;
     let c1 = [], p1 = {key:1};
-    var vn1 = h('div', p1, c1);
-    if (context['state'].display) {
-        //COMPONENT
-        let templateId3 = \`__4__\`;
-        let w3 = templateId3 in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap[templateId3]] : false;
-        let props3 = {};
-        if (w3 && w3.__owl__.currentFiber && !w3.__owl__.vnode) {
-            w3.destroy();
-            w3 = false;
+    let vn1 = h('div', p1, c1);
+    if (scope['state'].display) {
+        // Component 'Child'
+        let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+        let props2 = {};
+        if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+            w2.destroy();
+            w2 = false;
         }
-        if (w3) {
-            w3.__updateProps(props3, extra.fiber, undefined, undefined, sibling);
-            let pvnode = w3.__owl__.pvnode;
+        if (w2) {
+            w2.__updateProps(props2, extra.fiber, undefined);
+            let pvnode = w2.__owl__.pvnode;
             c1.push(pvnode);
         } else {
-            let componentKey3 = \`Child\`;
-            let W3 = context.constructor.components[componentKey3] || QWeb.components[componentKey3]|| context['Child'];
-            if (!W3) {throw new Error('Cannot find the definition of component \\"' + componentKey3 + '\\"')}
-            w3 = new W3(parent, props3);
-            parent.__owl__.cmap[templateId3] = w3.__owl__.id;
-            let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
-            let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;utils.transitionInsert(vn, 'chimay');},remove() {},destroy(vn) {let finalize = () => {
-          w3.destroy();
+            let componentKey2 = \`Child\`;
+            let W2 = scope['Child'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+            if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+            w2 = new W2(parent, props2);
+            const __patch2 = w2.__patch;
+            w2.__patch = (t, vn) => {__patch2.call(w2, t, vn); if(!w2.__owl__.transitionInserted){w2.__owl__.transitionInserted = true;utils.transitionInsert(w2.__owl__.vnode, 'chimay');}};
+            parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+            let fiber = w2.__prepare(extra.fiber, undefined, () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {let finalize = () => {
+          w2.destroy();
         };
+        delete w2.__owl__.transitionInserted;
         utils.transitionRemove(vn, 'chimay', finalize);}}});
-            const fiber = w3.__owl__.currentFiber;
-            def2.then(function () {if (w3.__owl__.isDestroyed) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
             c1.push(pvnode);
-            w3.__owl__.pvnode = pvnode;
+            w2.__owl__.pvnode = pvnode;
         }
-        sibling = w3.__owl__.currentFiber || sibling;
+        w2.__owl__.parentLastFiberId = extra.fiber.id;
+    }
+    return vn1;
+}"
+`;
+
+exports[`animations t-transition combined with t-component, remove and re-add before transitionend 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__2\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    if (scope['state'].flag) {
+        // Component 'Child'
+        let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+        let props2 = {};
+        if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+            w2.destroy();
+            w2 = false;
+        }
+        if (w2) {
+            w2.__updateProps(props2, extra.fiber, undefined);
+            let pvnode = w2.__owl__.pvnode;
+            c1.push(pvnode);
+        } else {
+            let componentKey2 = \`Child\`;
+            let W2 = scope['Child'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+            if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+            w2 = new W2(parent, props2);
+            const __patch2 = w2.__patch;
+            w2.__patch = (t, vn) => {__patch2.call(w2, t, vn); if(!w2.__owl__.transitionInserted){w2.__owl__.transitionInserted = true;utils.transitionInsert(w2.__owl__.vnode, 'chimay');}};
+            parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+            let fiber = w2.__prepare(extra.fiber, undefined, () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {let finalize = () => {
+          w2.destroy();
+        };
+        delete w2.__owl__.transitionInserted;
+        utils.transitionRemove(vn, 'chimay', finalize);}}});
+            c1.push(pvnode);
+            w2.__owl__.pvnode = pvnode;
+        }
+        w2.__owl__.parentLastFiberId = extra.fiber.id;
     }
     return vn1;
 }"
 `;
 
 exports[`animations t-transition with no delay/duration 1`] = `
-"function anonymous(context,extra
+"function anonymous(context, extra
 ) {
+    // Template name: \\"test\\"
     let utils = this.constructor.utils;
-    let sibling = null;
-    var h = this.h;
+    let h = this.h;
     let c1 = [], p1 = {key:1};
-    var vn1 = h('span', p1, c1);
+    let vn1 = h('span', p1, c1);
     p1.hook = {
       insert: vn => {
         utils.transitionInsert(vn, 'jupiler');
@@ -112,13 +158,34 @@ exports[`animations t-transition with no delay/duration 1`] = `
 `;
 
 exports[`animations t-transition, on a simple node (insert) 1`] = `
-"function anonymous(context,extra
+"function anonymous(context, extra
 ) {
+    // Template name: \\"test\\"
     let utils = this.constructor.utils;
-    let sibling = null;
-    var h = this.h;
+    let h = this.h;
     let c1 = [], p1 = {key:1};
-    var vn1 = h('span', p1, c1);
+    let vn1 = h('span', p1, c1);
+    p1.hook = {
+      insert: vn => {
+        utils.transitionInsert(vn, 'chimay');
+      },
+      remove: (vn, rm) => {
+        utils.transitionRemove(vn, 'chimay', rm);
+      },
+    };
+    c1.push({text: \`blue\`});
+    return vn1;
+}"
+`;
+
+exports[`animations t-transition, on a simple node, not in the DOM 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let utils = this.constructor.utils;
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('span', p1, c1);
     p1.hook = {
       insert: vn => {
         utils.transitionInsert(vn, 'chimay');

tests/animations.test.ts

@@ -1,13 +1,15 @@
 import { Component, Env } from "../src/component/component";
+import { useRef, useState } from "../src/hooks";
 import { QWeb } from "../src/qweb/index";
-import { useState, useRef } from "../src/hooks";
+import { xml } from "../src/tags";
 import {
   makeDeferred,
-  makeTestFixture,
   makeTestEnv,
+  makeTestFixture,
+  nextFrame,
   patchNextFrame,
   renderToDOM,
-  unpatchNextFrame
+  unpatchNextFrame,
 } from "./helpers";
 
 //------------------------------------------------------------------------------
@@ -29,6 +31,7 @@ let cssEl: HTMLElement;
 beforeEach(() => {
   fixture = makeTestFixture();
   env = makeTestEnv();
+  Component.env = env;
   qweb = new QWeb();
 });
 
@@ -68,7 +71,27 @@ describe("animations", () => {
     qweb.addTemplate("test", `<span t-transition="chimay">blue</span>`);
 
     let def = makeDeferred();
-    patchNextFrame(cb => {
+    patchNextFrame((cb) => {
+      expect(node.className).toBe("chimay-enter chimay-enter-active");
+      cb();
+      expect(node.className).toBe("chimay-enter-active chimay-enter-to");
+      def.resolve();
+    });
+    let node: HTMLElement = <HTMLElement>renderToDOM(qweb, "test");
+    fixture.appendChild(node);
+
+    expect(node.className).toBe("chimay-enter chimay-enter-active");
+    await def; // wait for the mocked repaint to be done
+    node.dispatchEvent(new Event("transitionend")); // mock end of css transition
+    expect(node.className).toBe("");
+  });
+
+  test("t-transition, on a simple node, not in the DOM", async () => {
+    expect.assertions(5);
+    qweb.addTemplate("test", `<span t-transition="chimay">blue</span>`);
+
+    let def = makeDeferred();
+    patchNextFrame((cb) => {
       expect(node.className).toBe("chimay-enter chimay-enter-active");
       cb();
       expect(node.className).toBe("chimay-enter-active chimay-enter-to");
@@ -78,8 +101,10 @@ describe("animations", () => {
 
     expect(node.className).toBe("chimay-enter chimay-enter-active");
     await def; // wait for the mocked repaint to be done
-    node.dispatchEvent(new Event("transitionend")); // mock end of css transition
-    expect(node.className).toBe("");
+    node.dispatchEvent(new Event("transitionend"));
+    // we check here that the css classes have not been removed, since the
+    // element is not in the dom, we actually do not want to do anything.
+    expect(node.className).toBe("chimay-enter-active chimay-enter-to");
   });
 
   test("t-transition with no delay/duration", async () => {
@@ -87,13 +112,14 @@ describe("animations", () => {
     qweb.addTemplate("test", `<span t-transition="jupiler">blue</span>`);
 
     let def = makeDeferred();
-    patchNextFrame(cb => {
+    patchNextFrame((cb) => {
       expect(node.className).toBe("jupiler-enter jupiler-enter-active");
       cb();
       expect(node.className).toBe("");
       def.resolve();
     });
     let node: HTMLElement = <HTMLElement>renderToDOM(qweb, "test");
+    fixture.appendChild(node);
     expect(node.className).toBe("jupiler-enter jupiler-enter-active");
     await def;
   });
@@ -108,12 +134,12 @@ describe("animations", () => {
     class TestWidget extends Widget {
       state = useState({ hide: false });
     }
-    const widget = new TestWidget(env);
+    const widget = new TestWidget();
 
     // insert widget into the DOM
     let def = makeDeferred();
     var spanNode;
-    patchNextFrame(cb => {
+    patchNextFrame((cb) => {
       expect(spanNode.className).toBe("chimay-enter chimay-enter-active");
       cb();
       expect(spanNode.className).toBe("chimay-enter-active chimay-enter-to");
@@ -129,7 +155,7 @@ describe("animations", () => {
     // remove span from the DOM
     def = makeDeferred();
     widget.state.hide = true;
-    patchNextFrame(cb => {
+    patchNextFrame((cb) => {
       expect(spanNode.className).toBe("chimay-leave chimay-leave-active");
       cb();
       expect(spanNode.className).toBe("chimay-leave-active chimay-leave-to");
@@ -151,12 +177,12 @@ describe("animations", () => {
       state = useState({ hide: false });
       span = useRef("span");
     }
-    const widget = new TestWidget(env);
+    const widget = new TestWidget();
 
     // insert widget into the DOM
     let def = makeDeferred();
     var spanNode;
-    patchNextFrame(cb => {
+    patchNextFrame((cb) => {
       expect(spanNode.className).toBe("chimay-enter chimay-enter-active");
       cb();
       expect(spanNode.className).toBe("chimay-enter-active chimay-enter-to");
@@ -180,11 +206,11 @@ describe("animations", () => {
     class Parent extends Widget {
       static components = { Child: Child };
     }
-    const widget = new Parent(env);
+    const widget = new Parent();
 
     let def = makeDeferred();
     var spanNode;
-    patchNextFrame(cb => {
+    patchNextFrame((cb) => {
       expect(fixture.innerHTML).toBe(
         '<div><span class="chimay-enter chimay-enter-active">blue</span></div>'
       );
@@ -220,11 +246,11 @@ describe("animations", () => {
       static components = { Child: Child };
       state = useState({ display: true });
     }
-    const widget = new Parent(env);
+    const widget = new Parent();
 
     let def = makeDeferred();
     var spanNode;
-    patchNextFrame(cb => {
+    patchNextFrame((cb) => {
       expect(fixture.innerHTML).toBe(
         '<div><span class="chimay-enter chimay-enter-active">blue</span></div>'
       );
@@ -249,13 +275,13 @@ describe("animations", () => {
     // remove span from the DOM
     def = makeDeferred();
     widget.state.display = false;
-    patchNextFrame(cb => {
+    patchNextFrame((cb) => {
       expect(fixture.innerHTML).toBe(
-        '<div><span class="chimay-leave chimay-leave-active" data-owl-key="__4__">blue</span></div>'
+        '<div><span class="chimay-leave chimay-leave-active" data-owl-key="__3__">blue</span></div>'
       );
       cb();
       expect(fixture.innerHTML).toBe(
-        '<div><span class="chimay-leave-active chimay-leave-to" data-owl-key="__4__">blue</span></div>'
+        '<div><span class="chimay-leave-active chimay-leave-to" data-owl-key="__3__">blue</span></div>'
       );
       def.resolve();
     });
@@ -283,13 +309,13 @@ describe("animations", () => {
       }
     }
 
-    const widget = new Parent(env);
+    const widget = new Parent();
     await widget.mount(fixture);
     let button = widget.el!.querySelector("button");
 
     let def = makeDeferred();
     let phase = "enter";
-    patchNextFrame(cb => {
+    patchNextFrame((cb) => {
       let spans = fixture.querySelectorAll("span");
       expect(spans.length).toBe(1);
       expect(spans[0].className).toBe(`chimay-${phase} chimay-${phase}-active`);
@@ -320,34 +346,27 @@ describe("animations", () => {
   });
 
   test("t-transition combined with t-component, remove and re-add before transitionend", async () => {
-    expect.assertions(11);
+    expect.assertions(12);
 
-    env.qweb.addTemplates(
-      `<templates>
-        <div t-name="Parent">
-          <button t-on-click="toggle">Toggle</button>
-          <t t-if="state.flag" t-component="Child" t-transition="chimay"/>
-        </div>
-        <span t-name="Child">blue</span>
-      </templates>`
-    );
-    class Child extends Widget {}
+    class Child extends Widget {
+      static template = xml`<span>blue</span>`;
+    }
     class Parent extends Widget {
+      static template = xml`
+        <div t-name="Parent">
+          <t t-if="state.flag" t-component="Child" t-transition="chimay"/>
+        </div>`;
       static components = { Child };
       state = useState({ flag: false });
-
-      toggle() {
-        this.state.flag = !this.state.flag;
-      }
     }
 
-    const widget = new Parent(env);
+    const widget = new Parent();
     await widget.mount(fixture);
-    let button = widget.el!.querySelector("button");
+    expect(env.qweb.templates[Parent.template].fn.toString()).toMatchSnapshot();
 
     let def = makeDeferred();
     let phase = "enter";
-    patchNextFrame(cb => {
+    patchNextFrame((cb) => {
       let spans = fixture.querySelectorAll("span");
       expect(spans.length).toBe(1);
       expect(spans[0].className).toBe(`chimay-${phase} chimay-${phase}-active`);
@@ -356,24 +375,78 @@ describe("animations", () => {
       def.resolve();
     });
 
-    // click display the span
-    button!.click();
+    // display the span
+    widget.state.flag = true;
     await def; // wait for the mocked repaint to be done
     widget.el!.querySelector("span")!.dispatchEvent(new Event("transitionend")); // mock end of css transition
-    expect(fixture.innerHTML).toBe('<div><button>Toggle</button><span class="">blue</span></div>');
+    expect(fixture.innerHTML).toBe('<div><span class="">blue</span></div>');
 
     // click to remove the span, and click again to re-add it before transitionend
     def = makeDeferred();
     phase = "leave";
-    button!.click();
+
+    widget.state.flag = false;
 
     await def; // wait for the mocked repaint to be done
     def = makeDeferred();
     phase = "enter";
-    button!.click();
+    widget.state.flag = true;
 
     await def; // wait for the mocked repaint to be done
     widget.el!.querySelector("span")!.dispatchEvent(new Event("transitionend")); // mock end of css transition
-    expect(fixture.innerHTML).toBe('<div><button>Toggle</button><span class="">blue</span></div>');
+    expect(fixture.innerHTML).toBe('<div><span class="" data-owl-key="__3__">blue</span></div>');
+  });
+
+  test("transitionInsert is called the correct amount of times", async () => {
+    const oldTransitionInsert = QWeb.utils.transitionInsert;
+    QWeb.utils.transitionInsert = jest.fn(oldTransitionInsert);
+
+    class Child extends Widget {
+      static template = xml`<span>blue</span>`;
+    }
+    class Parent extends Widget {
+      static template = xml`
+        <div t-name="Parent">
+          <Child t-if="state.flag" t-transition="chimay"/>
+        </div>`;
+      static components = { Child };
+      state = useState({ flag: false });
+    }
+
+    patchNextFrame((cb) => cb());
+
+    const widget = new Parent();
+    await widget.mount(fixture);
+
+    widget.state.flag = true;
+
+    await nextFrame();
+    widget.el!.querySelector("span")!.dispatchEvent(new Event("transitionend"));
+    expect(fixture.innerHTML).toBe('<div><span class="">blue</span></div>');
+    expect(QWeb.utils.transitionInsert).toBeCalledTimes(1);
+
+    widget.state.flag = false;
+    await nextFrame();
+    expect(fixture.innerHTML).toBe(
+      '<div><span class="chimay-leave-active chimay-leave-to" data-owl-key="__3__">blue</span></div>'
+    );
+    expect(QWeb.utils.transitionInsert).toBeCalledTimes(1);
+
+    widget.state.flag = true;
+    await nextFrame();
+    expect(fixture.innerHTML).toBe(
+      '<div><span class="chimay-enter-active chimay-enter-to" data-owl-key="__3__">blue</span></div>'
+    );
+    expect(QWeb.utils.transitionInsert).toBeCalledTimes(2);
+
+    widget.state.flag = false;
+    await nextFrame();
+    widget.state.flag = true;
+    await nextFrame();
+
+    expect(QWeb.utils.transitionInsert).toBeCalledTimes(3);
+    widget.el!.querySelector("span")!.dispatchEvent(new Event("transitionend"));
+    expect(fixture.innerHTML).toBe('<div><span class="" data-owl-key="__3__">blue</span></div>');
+    QWeb.utils.transitionInsert = oldTransitionInsert;
   });
 });

tests/component/__snapshots__/class_style.test.ts.snap

@@ -0,0 +1,156 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`class and style attributes with t-component dynamic t-att-style is properly added and updated on widget root el 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"ParentWidget\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    // Component 'child'
+    const _4 = scope['state'].style;
+    let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+    let props2 = {};
+    if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+        w2.destroy();
+        w2 = false;
+    }
+    if (w2) {
+        w2.__updateProps(props2, extra.fiber, undefined).then(()=>{if (w2.__owl__.status === 5) {return};w2.el.style=_4;});;
+        let pvnode = w2.__owl__.pvnode;
+        c1.push(pvnode);
+    } else {
+        let componentKey2 = \`child\`;
+        let W2 = scope['child'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+        if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+        w2 = new W2(parent, props2);
+        parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+        let fiber = w2.__prepare(extra.fiber, undefined, () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; utils.assignHooks(vnode.data, {create(_, vn){vn.elm.style = _4;}});});
+        let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {w2.destroy();}}});
+        c1.push(pvnode);
+        w2.__owl__.pvnode = pvnode;
+    }
+    w2.__owl__.parentLastFiberId = extra.fiber.id;
+    return vn1;
+}"
+`;
+
+exports[`class and style attributes with t-component t-att-class is properly added/removed on widget root el (v2) 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"ParentWidget\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    context.__owl__.refs = context.__owl__.refs || {};
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    // Component 'Child'
+    const ref4 = \`child\`;
+    let _5 = {'a':true};
+    Object.assign(_5, {b:scope['state'].b})
+    let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+    let props2 = {};
+    if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+        w2.destroy();
+        w2 = false;
+    }
+    if (w2) {
+        w2.__updateProps(props2, extra.fiber, undefined);
+        let pvnode = w2.__owl__.pvnode;
+        c1.push(pvnode);
+    } else {
+        let componentKey2 = \`Child\`;
+        let W2 = scope['Child'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+        if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+        w2 = new W2(parent, props2);
+        parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+        let fiber = w2.__prepare(extra.fiber, undefined, () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; utils.assignHooks(vnode.data, {create(_, vn){}});});
+        let pvnode = h('dummy', {key: '__3__', hook: {insert(vn) {context.__owl__.refs[ref4] = w2;},remove() {},destroy(vn) {w2.destroy();delete context.__owl__.refs[ref4];}}});
+        c1.push(pvnode);
+        w2.__owl__.pvnode = pvnode;
+    }
+    w2.__owl__.classObj=_5;
+    w2.__owl__.parentLastFiberId = extra.fiber.id;
+    return vn1;
+}"
+`;
+
+exports[`class and style attributes with t-component t-att-class is properly added/removed on widget root el (v2) 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"Child\\"
+    let utils = this.constructor.utils;
+    let scope = Object.create(context);
+    let h = this.h;
+    let _7 = {'c':true};
+    Object.assign(_7, utils.toObj({d:scope['state'].d}))
+    let c8 = [], p8 = {key:8,class:_7};
+    let vn8 = h('span', p8, c8);
+    return vn8;
+}"
+`;
+
+exports[`class and style attributes with t-component t-att-class is properly added/removed on widget root el (v3) 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"ParentWidget\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    context.__owl__.refs = context.__owl__.refs || {};
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    // Component 'Child'
+    const ref4 = \`child\`;
+    let _5 = {'a':true};
+    Object.assign(_5, utils.toObj(scope['state'].b?'b':''))
+    let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+    let props2 = {};
+    if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+        w2.destroy();
+        w2 = false;
+    }
+    if (w2) {
+        w2.__updateProps(props2, extra.fiber, undefined);
+        let pvnode = w2.__owl__.pvnode;
+        c1.push(pvnode);
+    } else {
+        let componentKey2 = \`Child\`;
+        let W2 = scope['Child'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+        if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+        w2 = new W2(parent, props2);
+        parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+        let fiber = w2.__prepare(extra.fiber, undefined, () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; utils.assignHooks(vnode.data, {create(_, vn){}});});
+        let pvnode = h('dummy', {key: '__3__', hook: {insert(vn) {context.__owl__.refs[ref4] = w2;},remove() {},destroy(vn) {w2.destroy();delete context.__owl__.refs[ref4];}}});
+        c1.push(pvnode);
+        w2.__owl__.pvnode = pvnode;
+    }
+    w2.__owl__.classObj=_5;
+    w2.__owl__.parentLastFiberId = extra.fiber.id;
+    return vn1;
+}"
+`;
+
+exports[`class and style attributes with t-component t-att-class is properly added/removed on widget root el (v3) 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"Child\\"
+    let utils = this.constructor.utils;
+    let scope = Object.create(context);
+    let h = this.h;
+    let _7 = {'c':true};
+    Object.assign(_7, utils.toObj(scope['state'].d?'d':''))
+    let c8 = [], p8 = {key:8,class:_7};
+    let vn8 = h('span', p8, c8);
+    return vn8;
+}"
+`;

tests/component/__snapshots__/props_validation.test.ts.snap

@@ -1,43 +1,39 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`props validation props are validated in dev mode (code snapshot) 1`] = `
-"function anonymous(context,extra
+"function anonymous(context, extra
 ) {
+    // Template name: \\"App\\"
     let utils = this.constructor.utils;
     let QWeb = this.constructor;
     let parent = context;
-    let owner = context;
-    let sibling = null;
-    var h = this.h;
+    let scope = Object.create(context);
+    let h = this.h;
     let c1 = [], p1 = {key:1};
-    var vn1 = h('div', p1, c1);
-    //COMPONENT
-    let templateId3 = \`__4__\`;
-    let w3 = templateId3 in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap[templateId3]] : false;
-    let props3 = {message:1};
-    if (w3 && w3.__owl__.currentFiber && !w3.__owl__.vnode) {
-        w3.destroy();
-        w3 = false;
+    let vn1 = h('div', p1, c1);
+    // Component 'Child'
+    let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+    let props2 = {message:1};
+    if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+        w2.destroy();
+        w2 = false;
     }
-    if (w3) {
-        utils.validateProps(w3.constructor, props3)
-        w3.__updateProps(props3, extra.fiber, undefined, undefined, sibling);
-        let pvnode = w3.__owl__.pvnode;
+    if (w2) {
+        w2.__updateProps(props2, extra.fiber, undefined);
+        let pvnode = w2.__owl__.pvnode;
         c1.push(pvnode);
     } else {
-        let componentKey3 = \`Child\`;
-        let W3 = context.constructor.components[componentKey3] || QWeb.components[componentKey3]|| context['Child'];
-        if (!W3) {throw new Error('Cannot find the definition of component \\"' + componentKey3 + '\\"')}
-        w3 = new W3(parent, props3);
-        parent.__owl__.cmap[templateId3] = w3.__owl__.id;
-        let def2 = w3.__prepare(extra.fiber, undefined, undefined, sibling);
-        let pvnode = h('dummy', {key: templateId3, hook: {insert(vn) { let nvn=w3.__mount(fiber, pvnode.elm);pvnode.elm=nvn.elm;},remove() {},destroy(vn) {w3.destroy();}}});
-        const fiber = w3.__owl__.currentFiber;
-        def2.then(function () {if (w3.__owl__.isDestroyed) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        let componentKey2 = \`Child\`;
+        let W2 = scope['Child'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+        if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+        w2 = new W2(parent, props2);
+        parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+        let fiber = w2.__prepare(extra.fiber, undefined, () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {w2.destroy();}}});
         c1.push(pvnode);
-        w3.__owl__.pvnode = pvnode;
+        w2.__owl__.pvnode = pvnode;
     }
-    sibling = w3.__owl__.currentFiber || sibling;
+    w2.__owl__.parentLastFiberId = extra.fiber.id;
     return vn1;
 }"
 `;

tests/component/__snapshots__/slots.test.ts.snap

@@ -0,0 +1,627 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`t-slot directive can define and call slots 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"Parent\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    // Component 'Dialog'
+    let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+    let props2 = {};
+    if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+        w2.destroy();
+        w2 = false;
+    }
+    if (w2) {
+        w2.__updateProps(props2, extra.fiber, Object.assign(Object.create(context), scope));
+        let pvnode = w2.__owl__.pvnode;
+        c1.push(pvnode);
+    } else {
+        let componentKey2 = \`Dialog\`;
+        let W2 = scope['Dialog'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+        if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+        w2 = new W2(parent, props2);
+        parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+        w2.__owl__.slotId = 1;
+        let fiber = w2.__prepare(extra.fiber, Object.assign(Object.create(context), scope), () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {w2.destroy();}}});
+        c1.push(pvnode);
+        w2.__owl__.pvnode = pvnode;
+    }
+    w2.__owl__.parentLastFiberId = extra.fiber.id;
+    return vn1;
+}"
+`;
+
+exports[`t-slot directive can define and call slots 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"Dialog\\"
+    let h = this.h;
+    let c9 = [], p9 = {key:9};
+    let vn9 = h('div', p9, c9);
+    let c10 = [], p10 = {key:10};
+    let vn10 = h('div', p10, c10);
+    c9.push(vn10);
+    const slot11 = this.constructor.slots[context.__owl__.slotId + '_' + 'header'];
+    if (slot11) {
+        slot11.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c10, parent: extra.parent || context}));
+    }
+    let c12 = [], p12 = {key:12};
+    let vn12 = h('div', p12, c12);
+    c9.push(vn12);
+    const slot13 = this.constructor.slots[context.__owl__.slotId + '_' + 'footer'];
+    if (slot13) {
+        slot13.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c12, parent: extra.parent || context}));
+    }
+    return vn9;
+}"
+`;
+
+exports[`t-slot directive can define and call slots 3`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_header_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c4 = extra.parentNode;
+    let c5 = [], p5 = {key:5};
+    let vn5 = h('span', p5, c5);
+    c4.push(vn5);
+    c5.push({text: \`header\`});
+}"
+`;
+
+exports[`t-slot directive can define and call slots 4`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_footer_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c6 = extra.parentNode;
+    let c7 = [], p7 = {key:7};
+    let vn7 = h('span', p7, c7);
+    c6.push(vn7);
+    c7.push({text: \`footer\`});
+}"
+`;
+
+exports[`t-slot directive can define and call slots using old t-set keyword 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__2\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    // Component 'Dialog'
+    let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+    let props2 = {};
+    if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+        w2.destroy();
+        w2 = false;
+    }
+    if (w2) {
+        w2.__updateProps(props2, extra.fiber, Object.assign(Object.create(context), scope));
+        let pvnode = w2.__owl__.pvnode;
+        c1.push(pvnode);
+    } else {
+        let componentKey2 = \`Dialog\`;
+        let W2 = scope['Dialog'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+        if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+        w2 = new W2(parent, props2);
+        parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+        w2.__owl__.slotId = 1;
+        let fiber = w2.__prepare(extra.fiber, Object.assign(Object.create(context), scope), () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {w2.destroy();}}});
+        c1.push(pvnode);
+        w2.__owl__.pvnode = pvnode;
+    }
+    w2.__owl__.parentLastFiberId = extra.fiber.id;
+    return vn1;
+}"
+`;
+
+exports[`t-slot directive can define and call slots using old t-set keyword 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__1\\"
+    let h = this.h;
+    let c9 = [], p9 = {key:9};
+    let vn9 = h('div', p9, c9);
+    let c10 = [], p10 = {key:10};
+    let vn10 = h('div', p10, c10);
+    c9.push(vn10);
+    const slot11 = this.constructor.slots[context.__owl__.slotId + '_' + 'header'];
+    if (slot11) {
+        slot11.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c10, parent: extra.parent || context}));
+    }
+    let c12 = [], p12 = {key:12};
+    let vn12 = h('div', p12, c12);
+    c9.push(vn12);
+    const slot13 = this.constructor.slots[context.__owl__.slotId + '_' + 'footer'];
+    if (slot13) {
+        slot13.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c12, parent: extra.parent || context}));
+    }
+    return vn9;
+}"
+`;
+
+exports[`t-slot directive can define and call slots using old t-set keyword 3`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_header_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c4 = extra.parentNode;
+    let c5 = [], p5 = {key:5};
+    let vn5 = h('span', p5, c5);
+    c4.push(vn5);
+    c5.push({text: \`header\`});
+}"
+`;
+
+exports[`t-slot directive can define and call slots using old t-set keyword 4`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_footer_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c6 = extra.parentNode;
+    let c7 = [], p7 = {key:7};
+    let vn7 = h('span', p7, c7);
+    c6.push(vn7);
+    c7.push({text: \`footer\`});
+}"
+`;
+
+exports[`t-slot directive content is the default slot 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_default_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c4 = extra.parentNode;
+    let c5 = [], p5 = {key:5};
+    let vn5 = h('span', p5, c5);
+    c4.push(vn5);
+    c5.push({text: \`sts rocks\`});
+}"
+`;
+
+exports[`t-slot directive dafault slots can define a default content 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__1\\"
+    let h = this.h;
+    let c4 = [], p4 = {key:4};
+    let vn4 = h('span', p4, c4);
+    const slot5 = this.constructor.slots[context.__owl__.slotId + '_' + 'default'];
+    if (slot5) {
+        slot5.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c4, parent: extra.parent || context}));
+    } else {
+        c4.push({text: \`default content\`});
+    }
+    return vn4;
+}"
+`;
+
+exports[`t-slot directive default slot work with text nodes 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_default_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c4 = extra.parentNode;
+    c4.push({text: \`sts rocks\`});
+}"
+`;
+
+exports[`t-slot directive dynamic t-slot call 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__1\\"
+    let utils = this.constructor.utils;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c10 = [], p10 = {key:10,on:{}};
+    let vn10 = h('button', p10, c10);
+    extra.handlers['click__11__'] = extra.handlers['click__11__'] || function (e) {if (context.__owl__.status === 5){return}utils.getComponent(context)['toggle'](e);};
+    p10.on['click'] = extra.handlers['click__11__'];
+    const slot12 = this.constructor.slots[context.__owl__.slotId + '_' + (scope['current'].slot)];
+    if (slot12) {
+        slot12.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c10, parent: extra.parent || context}));
+    }
+    return vn10;
+}"
+`;
+
+exports[`t-slot directive multiple roots are allowed in a default slot 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_default_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c4 = extra.parentNode;
+    let c5 = [], p5 = {key:5};
+    let vn5 = h('span', p5, c5);
+    c4.push(vn5);
+    c5.push({text: \`sts\`});
+    let c6 = [], p6 = {key:6};
+    let vn6 = h('span', p6, c6);
+    c4.push(vn6);
+    c6.push({text: \`rocks\`});
+}"
+`;
+
+exports[`t-slot directive multiple roots are allowed in a named slot 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_content_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c4 = extra.parentNode;
+    let c5 = [], p5 = {key:5};
+    let vn5 = h('span', p5, c5);
+    c4.push(vn5);
+    c5.push({text: \`sts\`});
+    let c6 = [], p6 = {key:6};
+    let vn6 = h('span', p6, c6);
+    c4.push(vn6);
+    c6.push({text: \`rocks\`});
+}"
+`;
+
+exports[`t-slot directive named slots can define a default content 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__1\\"
+    let h = this.h;
+    let c4 = [], p4 = {key:4};
+    let vn4 = h('span', p4, c4);
+    const slot5 = this.constructor.slots[context.__owl__.slotId + '_' + 'header'];
+    if (slot5) {
+        slot5.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c4, parent: extra.parent || context}));
+    } else {
+        c4.push({text: \`default content\`});
+    }
+    return vn4;
+}"
+`;
+
+exports[`t-slot directive refs are properly bound in slots 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_footer_template\\"
+    let utils = this.constructor.utils;
+    let parent = extra.parent;
+    context.__owl__.refs = context.__owl__.refs || {};
+    let h = this.h;
+    let c8 = extra.parentNode;
+    let c9 = [], p9 = {key:9,on:{}};
+    let vn9 = h('button', p9, c9);
+    c8.push(vn9);
+    extra.handlers['click__10__'] = extra.handlers['click__10__'] || function (e) {if (context.__owl__.status === 5){return}utils.getComponent(context)['doSomething'](e);};
+    p9.on['click'] = extra.handlers['click__10__'];
+    const ref11 = \`myButton\`;
+    p9.hook = {
+      create: (_, n) => {
+        context.__owl__.refs[ref11] = n.elm;
+      },
+      destroy: () => {
+        delete context.__owl__.refs[ref11];
+      },
+    };
+    c9.push({text: \`do something\`});
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_footer_template\\"
+    let utils = this.constructor.utils;
+    let parent = extra.parent;
+    let h = this.h;
+    let c8 = extra.parentNode;
+    let c9 = [], p9 = {key:9,on:{}};
+    let vn9 = h('button', p9, c9);
+    c8.push(vn9);
+    extra.handlers['click__10__'] = extra.handlers['click__10__'] || function (e) {if (context.__owl__.status === 5){return}utils.getComponent(context)['doSomething'](e);};
+    p9.on['click'] = extra.handlers['click__10__'];
+    c9.push({text: \`do something\`});
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 2 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"Link\\"
+    let scope = Object.create(context);
+    let h = this.h;
+    let _12 = scope['props'].to;
+    let c13 = [], p13 = {key:13,attrs:{href: _12}};
+    let vn13 = h('a', p13, c13);
+    const slot14 = this.constructor.slots[context.__owl__.slotId + '_' + 'default'];
+    if (slot14) {
+        slot14.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c13, parent: extra.parent || context}));
+    }
+    return vn13;
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 2 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"App\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    let c2 = [], p2 = {key:2};
+    let vn2 = h('u', p2, c2);
+    c1.push(vn2);
+    let _3 = scope['state'].users;
+    if (!_3) { throw new Error('QWeb error: Invalid loop expression')}
+    let _4 = _5 = _3;
+    if (!(_3 instanceof Array)) {
+        _4 = Object.keys(_3);
+        _5 = Object.values(_3);
+    }
+    let _length4 = _4.length;
+    let _origScope6 = scope;
+    scope = Object.create(scope);
+    for (let i1 = 0; i1 < _length4; i1++) {
+        scope.user_first = i1 === 0
+        scope.user_last = i1 === _length4 - 1
+        scope.user_index = i1
+        scope.user = _4[i1]
+        scope.user_value = _5[i1]
+        let key1 = scope['user'].id;
+        let c7 = [], p7 = {key:\`\${key1}_7\`};
+        let vn7 = h('li', p7, c7);
+        c2.push(vn7);
+        // Component 'Link'
+        let k9 = \`__9__\${key1}__\`;
+        let w8 = k9 in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap[k9]] : false;
+        let props8 = {to:'/user/'+scope['user'].id};
+        if (w8 && w8.__owl__.currentFiber && !w8.__owl__.vnode) {
+            w8.destroy();
+            w8 = false;
+        }
+        if (w8) {
+            w8.__updateProps(props8, extra.fiber, Object.assign(Object.create(context), scope));
+            let pvnode = w8.__owl__.pvnode;
+            c7.push(pvnode);
+        } else {
+            let componentKey8 = \`Link\`;
+            let W8 = scope['Link'] || context.constructor.components[componentKey8] || QWeb.components[componentKey8];
+            if (!W8) {throw new Error('Cannot find the definition of component \\"' + componentKey8 + '\\"')}
+            w8 = new W8(parent, props8);
+            parent.__owl__.cmap[k9] = w8.__owl__.id;
+            w8.__owl__.slotId = 1;
+            let fiber = w8.__prepare(extra.fiber, Object.assign(Object.create(context), scope), () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            let pvnode = h('dummy', {key: k9, hook: {remove() {},destroy(vn) {w8.destroy();}}});
+            c7.push(pvnode);
+            w8.__owl__.pvnode = pvnode;
+        }
+        w8.__owl__.parentLastFiberId = extra.fiber.id;
+    }
+    scope = _origScope6;
+    return vn1;
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 2 3`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_default_template\\"
+    let parent = extra.parent;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c10 = extra.parentNode;
+    c10.push({text: \`User \`});
+    let _11 = scope['user'].name;
+    if (_11 != null) {
+        c10.push({text: _11});
+    }
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 3 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"Link\\"
+    let scope = Object.create(context);
+    let h = this.h;
+    let _12 = scope['props'].to;
+    let c13 = [], p13 = {key:13,attrs:{href: _12}};
+    let vn13 = h('a', p13, c13);
+    const slot14 = this.constructor.slots[context.__owl__.slotId + '_' + 'default'];
+    if (slot14) {
+        slot14.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c13, parent: extra.parent || context}));
+    }
+    return vn13;
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 3 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"App\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    let c2 = [], p2 = {key:2};
+    let vn2 = h('u', p2, c2);
+    c1.push(vn2);
+    let _3 = scope['state'].users;
+    if (!_3) { throw new Error('QWeb error: Invalid loop expression')}
+    let _4 = _5 = _3;
+    if (!(_3 instanceof Array)) {
+        _4 = Object.keys(_3);
+        _5 = Object.values(_3);
+    }
+    let _length4 = _4.length;
+    let _origScope6 = scope;
+    scope = Object.create(scope);
+    for (let i1 = 0; i1 < _length4; i1++) {
+        scope.user_first = i1 === 0
+        scope.user_last = i1 === _length4 - 1
+        scope.user_index = i1
+        scope.user = _4[i1]
+        scope.user_value = _5[i1]
+        let key1 = scope['user'].id;
+        let c7 = [], p7 = {key:\`\${key1}_7\`};
+        let vn7 = h('li', p7, c7);
+        c2.push(vn7);
+        utils.getScope(scope, 'userdescr').userdescr = 'User '+scope['user'].name;
+        // Component 'Link'
+        let k9 = \`__9__\${key1}__\`;
+        let w8 = k9 in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap[k9]] : false;
+        let props8 = {to:'/user/'+scope['user'].id};
+        if (w8 && w8.__owl__.currentFiber && !w8.__owl__.vnode) {
+            w8.destroy();
+            w8 = false;
+        }
+        if (w8) {
+            w8.__updateProps(props8, extra.fiber, Object.assign(Object.create(context), scope));
+            let pvnode = w8.__owl__.pvnode;
+            c7.push(pvnode);
+        } else {
+            let componentKey8 = \`Link\`;
+            let W8 = scope['Link'] || context.constructor.components[componentKey8] || QWeb.components[componentKey8];
+            if (!W8) {throw new Error('Cannot find the definition of component \\"' + componentKey8 + '\\"')}
+            w8 = new W8(parent, props8);
+            parent.__owl__.cmap[k9] = w8.__owl__.id;
+            w8.__owl__.slotId = 1;
+            let fiber = w8.__prepare(extra.fiber, Object.assign(Object.create(context), scope), () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            let pvnode = h('dummy', {key: k9, hook: {remove() {},destroy(vn) {w8.destroy();}}});
+            c7.push(pvnode);
+            w8.__owl__.pvnode = pvnode;
+        }
+        w8.__owl__.parentLastFiberId = extra.fiber.id;
+    }
+    scope = _origScope6;
+    return vn1;
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 3 3`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_default_template\\"
+    let parent = extra.parent;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c10 = extra.parentNode;
+    let _11 = scope['userdescr'];
+    if (_11 != null) {
+        c10.push({text: _11});
+    }
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 4 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"App\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    scope.userdescr = 'User '+scope['state'].user.name;
+    // Component 'Link'
+    let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+    let props2 = {to:'/user/'+scope['state'].user.id};
+    if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+        w2.destroy();
+        w2 = false;
+    }
+    if (w2) {
+        w2.__updateProps(props2, extra.fiber, Object.assign(Object.create(context), scope));
+        let pvnode = w2.__owl__.pvnode;
+        c1.push(pvnode);
+    } else {
+        let componentKey2 = \`Link\`;
+        let W2 = scope['Link'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+        if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+        w2 = new W2(parent, props2);
+        parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+        w2.__owl__.slotId = 1;
+        let fiber = w2.__prepare(extra.fiber, Object.assign(Object.create(context), scope), () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {w2.destroy();}}});
+        c1.push(pvnode);
+        w2.__owl__.pvnode = pvnode;
+    }
+    w2.__owl__.parentLastFiberId = extra.fiber.id;
+    return vn1;
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 4 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_default_template\\"
+    let parent = extra.parent;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c4 = extra.parentNode;
+    let _5 = scope['userdescr'];
+    if (_5 != null) {
+        c4.push({text: _5});
+    }
+}"
+`;
+
+exports[`t-slot directive t-set t-value in a slot 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__1\\"
+    let h = this.h;
+    let c5 = [], p5 = {key:5};
+    let vn5 = h('span', p5, c5);
+    const slot6 = this.constructor.slots[context.__owl__.slotId + '_' + 'default'];
+    if (slot6) {
+        slot6.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c5, parent: extra.parent || context}));
+    }
+    return vn5;
+}"
+`;
+
+exports[`t-slot directive template can just return a slot 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__2\\"
+    let utils = this.constructor.utils;
+    let result;
+    let h = this.h;
+    const slot7 = this.constructor.slots[context.__owl__.slotId + '_' + 'default'];
+    if (slot7) {
+        let children8= []
+        result = {}
+        slot7.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: children8, parent: extra.parent || context}));
+        utils.defineProxy(result, children8[0]);
+    }
+    return result;
+}"
+`;

tests/component/class_style.test.ts

@@ -0,0 +1,271 @@
+import { Component, Env } from "../../src/component/component";
+import { QWeb } from "../../src/qweb/qweb";
+import { xml } from "../../src/tags";
+import { useState, useRef } from "../../src/hooks";
+import { makeTestFixture, makeTestEnv, nextTick } from "../helpers";
+
+//------------------------------------------------------------------------------
+// Setup and helpers
+//------------------------------------------------------------------------------
+
+// We create before each test:
+// - fixture: a div, appended to the DOM, intended to be the target of dom
+//   manipulations.  Note that it is removed after each test.
+// - env: a WEnv, necessary to create new components
+
+let fixture: HTMLElement;
+let env: Env;
+
+beforeEach(() => {
+  fixture = makeTestFixture();
+  env = makeTestEnv();
+  Component.env = env;
+});
+
+afterEach(() => {
+  fixture.remove();
+});
+
+describe("class and style attributes with t-component", () => {
+  test("class is properly added on widget root el", async () => {
+    class Child extends Component {
+      static template = xml`<div class="c"/>`;
+    }
+    class ParentWidget extends Component {
+      static template = xml`<div><Child class="a b"/></div>`;
+      static components = { Child };
+    }
+    const widget = new ParentWidget();
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe(`<div><div class="c a b"></div></div>`);
+  });
+
+  test("empty class attribute is not added on widget root el", async () => {
+    class Child extends Component {
+      static template = xml`<span/>`;
+    }
+    class Parent extends Component {
+      static template = xml`<div><Child class=""/></div>`;
+      static components = { Child };
+    }
+    const widget = new Parent();
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe(`<div><span></span></div>`);
+  });
+
+  test("t-att-class is properly added/removed on widget root el", async () => {
+    class Child extends Component {
+      static template = xml`<div class="c"/>`;
+    }
+    class ParentWidget extends Component {
+      static template = xml`<div><Child t-att-class="{a:state.a, b:state.b}"/></div>`;
+      static components = { Child };
+      state = useState({ a: true, b: false });
+    }
+    const widget = new ParentWidget();
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe(`<div><div class="c a"></div></div>`);
+    expect(QWeb.TEMPLATES[ParentWidget.template].fn.toString());
+
+    widget.state.a = false;
+    widget.state.b = true;
+    await nextTick();
+    expect(fixture.innerHTML).toBe(`<div><div class="c b"></div></div>`);
+  });
+
+  test("class with extra whitespaces", async () => {
+    env.qweb.addTemplate(
+      "ParentWidget",
+      `<div>
+              <Child class="a  b c   d"/>
+        </div>`
+    );
+    class Child extends Component {}
+    class ParentWidget extends Component {
+      static components = { Child };
+    }
+    env.qweb.addTemplate("Child", `<div/>`);
+    const widget = new ParentWidget();
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe(`<div><div class="a b c d"></div></div>`);
+  });
+
+  test("t-att-class is properly added/removed on widget root el (v2)", async () => {
+    env.qweb.addTemplates(`
+        <templates>
+          <div t-name="ParentWidget">
+            <Child class="a" t-att-class="{ b: state.b }" t-ref="child"/>
+          </div>
+          <span t-name="Child" class="c" t-att-class="{ d: state.d }"/>
+        </templates>`);
+
+    class Child extends Component {
+      state = useState({ d: true });
+    }
+    class ParentWidget extends Component {
+      static components = { Child };
+      state = useState({ b: true });
+      child = useRef("child");
+    }
+    const widget = new ParentWidget();
+    await widget.mount(fixture);
+
+    const span = fixture.querySelector("span")!;
+    expect(span.className).toBe("c d a b");
+
+    widget.state.b = false;
+    await nextTick();
+    expect(span.className).toBe("c d a");
+
+    (widget.child.comp as Child).state.d = false;
+    await nextTick();
+    expect(span.className).toBe("c a");
+
+    widget.state.b = true;
+    await nextTick();
+    expect(span.className).toBe("c a b");
+
+    (widget.child.comp as Child).state.d = true;
+    await nextTick();
+    expect(span.className).toBe("c a b d");
+    expect(env.qweb.templates.ParentWidget.fn.toString()).toMatchSnapshot();
+    expect(env.qweb.templates.Child.fn.toString()).toMatchSnapshot();
+  });
+
+  test("t-att-class is properly added/removed on widget root el (v3)", async () => {
+    env.qweb.addTemplates(`
+        <templates>
+          <div t-name="ParentWidget">
+            <Child class="a" t-att-class="state.b ? 'b' : ''" t-ref="child"/>
+          </div>
+          <span t-name="Child" class="c" t-att-class="state.d ? 'd' : ''"/>
+        </templates>`);
+
+    class Child extends Component {
+      state = useState({ d: true });
+    }
+    class ParentWidget extends Component {
+      static components = { Child };
+      state = useState({ b: true });
+      child = useRef("child");
+    }
+    const widget = new ParentWidget();
+    await widget.mount(fixture);
+
+    const span = fixture.querySelector("span")!;
+    expect(span.className).toBe("c d a b");
+
+    widget.state.b = false;
+    await nextTick();
+    expect(span.className).toBe("c d a");
+
+    (widget.child.comp as Child).state.d = false;
+    await nextTick();
+    expect(span.className).toBe("c a");
+
+    widget.state.b = true;
+    await nextTick();
+    expect(span.className).toBe("c a b");
+
+    (widget.child.comp as Child).state.d = true;
+    await nextTick();
+    expect(span.className).toBe("c a b d");
+    expect(env.qweb.templates.ParentWidget.fn.toString()).toMatchSnapshot();
+    expect(env.qweb.templates.Child.fn.toString()).toMatchSnapshot();
+  });
+
+  test("class on components do not interfere with user defined classes", async () => {
+    env.qweb.addTemplates(`
+        <templates>
+          <div t-name="App" t-att-class="{ c: state.c }" />
+        </templates>`);
+
+    class App extends Component {
+      state = useState({ c: true });
+      mounted() {
+        this.el!.classList.add("user");
+      }
+    }
+
+    const widget = new App();
+    await widget.mount(fixture);
+
+    expect(fixture.innerHTML).toBe('<div class="c user"></div>');
+
+    widget.state.c = false;
+    await nextTick();
+
+    expect(fixture.innerHTML).toBe('<div class="user"></div>');
+  });
+
+  test("style is properly added on widget root el", async () => {
+    env.qweb.addTemplate(
+      "ParentWidget",
+      `
+          <div>
+              <t t-component="child" style="font-weight: bold;"/>
+          </div>`
+    );
+
+    class SomeComponent extends Component {
+      static template = xml`<div/>`;
+    }
+
+    class ParentWidget extends Component {
+      static components = { child: SomeComponent };
+    }
+    const widget = new ParentWidget();
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe(`<div><div style="font-weight: bold;"></div></div>`);
+  });
+
+  test("dynamic t-att-style is properly added and updated on widget root el", async () => {
+    env.qweb.addTemplate(
+      "ParentWidget",
+      `
+          <div>
+              <t t-component="child" t-att-style="state.style"/>
+          </div>`
+    );
+
+    class SomeComponent extends Component {
+      static template = xml`<div/>`;
+    }
+
+    class ParentWidget extends Component {
+      static components = { child: SomeComponent };
+      state = useState({ style: "font-size: 20px" });
+    }
+    const widget = new ParentWidget();
+    await widget.mount(fixture);
+
+    expect(env.qweb.templates.ParentWidget.fn.toString()).toMatchSnapshot();
+
+    expect(fixture.innerHTML).toBe(`<div><div style="font-size: 20px;"></div></div>`);
+
+    widget.state.style = "font-size: 30px";
+    await nextTick();
+
+    expect(fixture.innerHTML).toBe(`<div><div style="font-size: 30px;"></div></div>`);
+  });
+
+  test("error in subcomponent with class", async () => {
+    class Child extends Component {
+      static template = xml`<div t-esc="this.will.crash"/>`;
+    }
+    class ParentWidget extends Component {
+      static template = xml`<div><Child class="a"/></div>`;
+      static components = { Child };
+    }
+    const widget = new ParentWidget();
+    let error;
+    try {
+      await widget.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Cannot read property 'crash' of undefined");
+    expect(fixture.innerHTML).toBe("");
+  });
+});

tests/component/error_handling.test.ts

@@ -0,0 +1,523 @@
+import { Component, Env, STATUS } from "../../src/component/component";
+import { useState } from "../../src/hooks";
+import { xml } from "../../src/tags";
+import { makeTestEnv, makeTestFixture, nextTick } from "../helpers";
+
+//------------------------------------------------------------------------------
+// Setup and helpers
+//------------------------------------------------------------------------------
+
+// We create before each test:
+// - fixture: a div, appended to the DOM, intended to be the target of dom
+//   manipulations.  Note that it is removed after each test.
+// - env: a WEnv, necessary to create new components
+
+let fixture: HTMLElement;
+let env: Env;
+
+beforeEach(() => {
+  fixture = makeTestFixture();
+  env = makeTestEnv();
+  Component.env = env;
+});
+
+afterEach(() => {
+  fixture.remove();
+});
+
+describe("component error handling (catchError)", () => {
+  /**
+   * This test suite requires often to wait for 3 ticks. Here is why:
+   * - First tick is to let the app render and crash.
+   * - When we crash, we call the catchError handler in a setTimeout (because we
+   *   need to wait for the previous rendering to be completely stopped). So, we
+   *   need to wait for the second tick.
+   * - Then, when the handler changes the state, we need to wait for the interface
+   *   to be rerendered.
+   *  */
+
+  test("can catch an error in a component render function", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn();
+    const handler = jest.fn();
+    env.qweb.on("error", null, handler);
+    class ErrorComponent extends Component {
+      static template = xml`<div>hey<t t-esc="props.flag and state.this.will.crash"/></div>`;
+    }
+    class ErrorBoundary extends Component {
+      static template = xml`
+          <div>
+            <t t-if="state.error">Error handled</t>
+            <t t-else=""><t t-slot="default" /></t>
+          </div>`;
+      state = useState({ error: false });
+
+      catchError() {
+        this.state.error = true;
+      }
+    }
+    class App extends Component {
+      static template = xml`
+          <div>
+            <ErrorBoundary><ErrorComponent flag="state.flag"/></ErrorBoundary>
+          </div>`;
+      state = useState({ flag: false });
+      static components = { ErrorBoundary, ErrorComponent };
+    }
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div><div>heyfalse</div></div></div>");
+    app.state.flag = true;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><div>Error handled</div></div>");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+    expect(handler).toBeCalledTimes(1);
+  });
+
+  test("no component catching error lead to full app destruction", async () => {
+    expect.assertions(6);
+    const handler = jest.fn();
+    env.qweb.on("error", null, handler);
+    const consoleError = console.error;
+    console.error = jest.fn();
+
+    class ErrorComponent extends Component {
+      static template = xml`<div>hey<t t-esc="props.flag and state.this.will.crash"/></div>`;
+    }
+
+    class App extends Component {
+      static template = xml`<div><ErrorComponent flag="state.flag"/></div>`;
+      static components = { ErrorComponent };
+      state = useState({ flag: false });
+      async render() {
+        try {
+          await super.render();
+        } catch (e) {
+          expect(e.message).toBe("Cannot read property 'this' of undefined");
+        }
+      }
+    }
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>heyfalse</div></div>");
+    app.state.flag = true;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+    expect(app.__owl__.status).toBe(STATUS.DESTROYED);
+    expect(handler).toBeCalledTimes(1);
+  });
+
+  test("can catch an error in the initial call of a component render function (parent mounted)", async () => {
+    const handler = jest.fn();
+    env.qweb.on("error", null, handler);
+    const consoleError = console.error;
+    console.error = jest.fn();
+    class ErrorComponent extends Component {
+      static template = xml`<div>hey<t t-esc="state.this.will.crash"/></div>`;
+    }
+    class ErrorBoundary extends Component {
+      static template = xml`
+          <div>
+            <t t-if="state.error">Error handled</t>
+            <t t-else=""><t t-slot="default" /></t>
+          </div>`;
+      state = useState({ error: false });
+
+      catchError() {
+        this.state.error = true;
+      }
+    }
+    class App extends Component {
+      static template = xml`
+          <div>
+              <ErrorBoundary><ErrorComponent /></ErrorBoundary>
+          </div>`;
+      static components = { ErrorBoundary, ErrorComponent };
+    }
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>Error handled</div></div>");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+    expect(handler).toBeCalledTimes(1);
+  });
+
+  test("can catch an error in the initial call of a component render function (parent updated)", async () => {
+    const handler = jest.fn();
+    env.qweb.on("error", null, handler);
+    const consoleError = console.error;
+    console.error = jest.fn();
+    class ErrorComponent extends Component {
+      static template = xml`<div>hey<t t-esc="state.this.will.crash"/></div>`;
+    }
+    class ErrorBoundary extends Component {
+      static template = xml`
+          <div>
+            <t t-if="state.error">Error handled</t>
+            <t t-else=""><t t-slot="default" /></t>
+          </div>`;
+      state = useState({ error: false });
+
+      catchError() {
+        this.state.error = true;
+      }
+    }
+    class App extends Component {
+      static template = xml`
+          <div>
+              <ErrorBoundary t-if="state.flag"><ErrorComponent /></ErrorBoundary>
+          </div>`;
+      state = useState({ flag: false });
+      static components = { ErrorBoundary, ErrorComponent };
+    }
+    const app = new App();
+    await app.mount(fixture);
+    app.state.flag = true;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><div>Error handled</div></div>");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+    expect(handler).toBeCalledTimes(1);
+  });
+
+  test("can catch an error in the constructor call of a component render function", async () => {
+    const handler = jest.fn();
+    env.qweb.on("error", null, handler);
+    const consoleError = console.error;
+    console.error = jest.fn();
+    env.qweb.addTemplates(`
+        <templates>
+          <div t-name="ErrorBoundary">
+              <t t-if="state.error">Error handled</t>
+              <t t-else=""><t t-slot="default" /></t>
+          </div>
+          <div t-name="ErrorComponent">Some text</div>
+          <div t-name="App">
+              <ErrorBoundary><ErrorComponent /></ErrorBoundary>
+          </div>
+        </templates>`);
+    class ErrorComponent extends Component {
+      constructor(parent) {
+        super(parent);
+        throw new Error("NOOOOO");
+      }
+    }
+    class ErrorBoundary extends Component {
+      state = useState({ error: false });
+
+      catchError() {
+        this.state.error = true;
+      }
+    }
+    class App extends Component {
+      static components = { ErrorBoundary, ErrorComponent };
+    }
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>Error handled</div></div>");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+    expect(handler).toBeCalledTimes(1);
+  });
+
+  test("can catch an error in the willStart call", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn();
+    class ErrorComponent extends Component {
+      static template = xml`<div t-name="ErrorComponent">Some text</div>`;
+      async willStart() {
+        // we wait a little bit to be in a different stack frame
+        await nextTick();
+        throw new Error("NOOOOO");
+      }
+    }
+    class ErrorBoundary extends Component {
+      static template = xml`
+          <div>
+            <t t-if="state.error">Error handled</t>
+            <t t-else=""><t t-slot="default" /></t>
+          </div>`;
+      state = useState({ error: false });
+
+      catchError() {
+        this.state.error = true;
+      }
+    }
+    class App extends Component {
+      static template = xml`<div><ErrorBoundary><ErrorComponent /></ErrorBoundary></div>`;
+      static components = { ErrorBoundary, ErrorComponent };
+    }
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>Error handled</div></div>");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test.skip("can catch an error in the mounted call", async () => {
+    // we do not catch error in mounted anymore
+    console.error = jest.fn();
+    env.qweb.addTemplates(`
+        <templates>
+          <div t-name="ErrorBoundary">
+              <t t-if="state.error">Error handled</t>
+              <t t-else=""><t t-slot="default" /></t>
+          </div>
+          <div t-name="ErrorComponent">Some text</div>
+          <div t-name="App">
+              <ErrorBoundary><ErrorComponent /></ErrorBoundary>
+          </div>
+        </templates>`);
+    class ErrorComponent extends Component {
+      mounted() {
+        throw new Error("NOOOOO");
+      }
+    }
+    class ErrorBoundary extends Component {
+      state = useState({ error: false });
+
+      catchError() {
+        this.state.error = true;
+      }
+    }
+    class App extends Component {
+      static components = { ErrorBoundary, ErrorComponent };
+    }
+    const app = new App();
+    await app.mount(fixture);
+    await nextTick();
+    await nextTick();
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><div>Error handled</div></div>");
+  });
+
+  test.skip("can catch an error in the willPatch call", async () => {
+    // we do not catch error in willPatch anymore
+    const consoleError = console.error;
+    console.error = jest.fn();
+    class ErrorComponent extends Component {
+      static template = xml`<div><t t-esc="props.message"/></div>`;
+      willPatch() {
+        throw new Error("NOOOOO");
+      }
+    }
+    class ErrorBoundary extends Component {
+      static template = xml`
+          <div>
+            <t t-if="state.error">Error handled</t>
+            <t t-else=""><t t-slot="default" /></t>
+          </div>`;
+      state = useState({ error: false });
+
+      catchError() {
+        this.state.error = true;
+      }
+    }
+    class App extends Component {
+      static template = xml`
+          <div>
+              <span><t t-esc="state.message"/></span>
+            <ErrorBoundary><ErrorComponent message="state.message" /></ErrorBoundary>
+          </div>`;
+      state = useState({ message: "abc" });
+      static components = { ErrorBoundary, ErrorComponent };
+    }
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><span>abc</span><div><div>abc</div></div></div>");
+    app.state.message = "def";
+    await nextTick();
+    await nextTick();
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><span>def</span><div>Error handled</div></div>");
+    expect(console.error).toHaveBeenCalledTimes(1);
+    console.error = consoleError;
+  });
+
+  test("a rendering error will reject the mount promise", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+    // we do not catch error in willPatch anymore
+    class App extends Component {
+      static template = xml`<div><t t-esc="this.will.crash"/></div>`;
+    }
+
+    const app = new App();
+    let error;
+    try {
+      await app.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Cannot read property 'crash' of undefined");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test("an error in mounted call will reject the mount promise", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+
+    class App extends Component {
+      static template = xml`<div>abc</div>`;
+      mounted() {
+        throw new Error("boom");
+      }
+    }
+
+    const app = new App();
+    let error;
+    try {
+      await app.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("boom");
+    expect(fixture.innerHTML).toBe("");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test("an error in willPatch call will reject the render promise", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+
+    class App extends Component {
+      static template = xml`<div><t t-esc="val"/></div>`;
+      val = 3;
+      willPatch() {
+        throw new Error("boom");
+      }
+    }
+
+    const app = new App();
+    await app.mount(fixture);
+    app.val = 4;
+    let error;
+    try {
+      await app.render();
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("boom");
+    expect(fixture.innerHTML).toBe("");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test("an error in patched call will reject the render promise", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+
+    class App extends Component {
+      static template = xml`<div><t t-esc="val"/></div>`;
+      val = 3;
+      patched() {
+        throw new Error("boom");
+      }
+    }
+
+    const app = new App();
+    await app.mount(fixture);
+    app.val = 4;
+    let error;
+    try {
+      await app.render();
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("boom");
+    expect(fixture.innerHTML).toBe("");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test("a rendering error in a sub component will reject the mount promise", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+    // we do not catch error in willPatch anymore
+    class Child extends Component {
+      static template = xml`<div><t t-esc="this.will.crash"/></div>`;
+    }
+    class App extends Component {
+      static template = xml`<div><Child/></div>`;
+      static components = { Child };
+    }
+
+    const app = new App();
+    let error;
+    try {
+      await app.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Cannot read property 'crash' of undefined");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test("a rendering error will reject the render promise", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+    // we do not catch error in willPatch anymore
+    class App extends Component {
+      static template = xml`<div><t t-if="flag" t-esc="this.will.crash"/></div>`;
+      flag = false;
+    }
+
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div></div>");
+    app.flag = true;
+    let error;
+    try {
+      await app.render();
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Cannot read property 'crash' of undefined");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test("a rendering error will reject the render promise (with sub components)", async () => {
+    class Child extends Component {
+      static template = xml`<span></span>`;
+    }
+    class Parent extends Component {
+      static template = xml`<div><Child/><t t-esc="x.y"/></div>`;
+      static components = { Child };
+    }
+
+    let error;
+    try {
+      const parent = new Parent();
+      await parent.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Cannot read property 'y' of undefined");
+  });
+});

tests/component/props_validation.test.ts

@@ -15,6 +15,7 @@ let dev: boolean = false;
 beforeEach(() => {
   fixture = makeTestFixture();
   env = makeTestEnv();
+  Component.env = env;
   dev = QWeb.dev;
   QWeb.dev = true;
 });
@@ -24,7 +25,7 @@ afterEach(() => {
   QWeb.dev = dev;
 });
 
-class Widget extends Component<any, any> {}
+class Widget extends Component {}
 
 //------------------------------------------------------------------------------
 // Tests
@@ -35,17 +36,32 @@ describe("props validation", () => {
       static props = ["message"];
       static template = xml`<div>hey</div>`;
     }
+    class Parent extends Widget {
+      static components = { TestWidget };
+      static template = xml`<div><TestWidget /></div>`;
+    }
 
+    let error;
     QWeb.dev = true;
-    expect(() => {
-      new TestWidget(env);
-    }).toThrow();
+    try {
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe(`Missing props 'message' (component 'TestWidget')`);
+
+    error = undefined;
 
     QWeb.dev = false;
-
-    expect(() => {
-      new TestWidget(env);
-    }).not.toThrow();
+    try {
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
   });
 
   test("props: list of strings", async () => {
@@ -53,10 +69,20 @@ describe("props validation", () => {
       static props = ["message"];
       static template = xml`<div>hey</div>`;
     }
+    class Parent extends Widget {
+      static components = { TestWidget };
+      static template = xml`<div><TestWidget /></div>`;
+    }
 
-    expect(() => {
-      new TestWidget(env);
-    }).toThrow("Missing props 'message' (component 'TestWidget')");
+    let error;
+    try {
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe(`Missing props 'message' (component 'TestWidget')`);
   });
 
   test("validate simple types", async () => {
@@ -66,26 +92,53 @@ describe("props validation", () => {
       { type: String, ok: "1", ko: 1 },
       { type: Object, ok: {}, ko: "1" },
       { type: Date, ok: new Date(), ko: "1" },
-      { type: Function, ok: () => {}, ko: "1" }
+      { type: Function, ok: () => {}, ko: "1" },
     ];
 
+    let props;
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      get p() {
+        return props.p;
+      }
+    }
     for (let test of Tests) {
       let TestWidget = class extends Widget {
         static template = xml`<div>hey</div>`;
         static props = { p: test.type };
       };
+      Parent.components = { TestWidget };
 
-      expect(() => {
-        new TestWidget(env);
-      }).toThrow("Missing props 'p'");
+      let error;
+      props = {};
+      try {
+        const p = new Parent();
+        await p.mount(fixture);
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeDefined();
+      expect(error.message).toBe(`Missing props 'p' (component '_a')`);
 
-      expect(() => {
-        new TestWidget(env, { p: test.ok });
-      }).not.toThrow();
+      error = undefined;
+      props = { p: test.ok };
+      try {
+        const p = new Parent();
+        await p.mount(fixture);
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeUndefined();
 
-      expect(() => {
-        new TestWidget(env, { p: test.ko });
-      }).toThrow("Props 'p' of invalid type in component");
+      props = { p: test.ko };
+      try {
+        const p = new Parent();
+        await p.mount(fixture);
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeDefined();
+      expect(error.message).toBe("Invalid Prop 'p' in component '_a'");
     }
   });
 
@@ -96,142 +149,454 @@ describe("props validation", () => {
       { type: String, ok: "1", ko: 1 },
       { type: Object, ok: {}, ko: "1" },
       { type: Date, ok: new Date(), ko: "1" },
-      { type: Function, ok: () => {}, ko: "1" }
+      { type: Function, ok: () => {}, ko: "1" },
     ];
 
+    let props;
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      get p() {
+        return props.p;
+      }
+    }
     for (let test of Tests) {
-      let TestWidget = class extends Widget {
-        static template = xml`<div>hey</div>`;
+      let TestWidget = class extends Component {
         static props = { p: { type: test.type } };
+        static template = xml`<div>hey</div>`;
       };
+      Parent.components = { TestWidget };
 
-      expect(() => {
-        new TestWidget(env);
-      }).toThrow("Missing props 'p'");
+      let error;
+      props = {};
+      try {
+        const p = new Parent();
+        await p.mount(fixture);
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeDefined();
+      expect(error.message).toBe(`Missing props 'p' (component '_a')`);
 
-      expect(() => {
-        new TestWidget(env, { p: test.ok });
-      }).not.toThrow();
+      error = undefined;
+      props = { p: test.ok };
+      try {
+        const p = new Parent();
+        await p.mount(fixture);
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeUndefined();
 
-      expect(() => {
-        new TestWidget(env, { p: test.ko });
-      }).toThrow("Props 'p' of invalid type in component");
+      props = { p: test.ko };
+      try {
+        const p = new Parent();
+        await p.mount(fixture);
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeDefined();
+      expect(error.message).toBe("Invalid Prop 'p' in component '_a'");
     }
   });
 
   test("can validate a prop with multiple types", async () => {
-    let TestWidget = class extends Widget {
+    class TestWidget extends Component {
       static template = xml`<div>hey</div>`;
       static props = { p: [String, Boolean] };
-    };
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      static components = { TestWidget };
+      get p() {
+        return props.p;
+      }
+    }
 
-    expect(() => {
-      new TestWidget(env, { p: "string" });
-      new TestWidget(env, { p: true });
-    }).not.toThrow();
+    let error;
+    let props;
+    try {
+      props = { p: "string" };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
 
-    expect(() => {
-      new TestWidget(env, { p: 1 });
-    }).toThrow("Props 'p' of invalid type in component");
+    try {
+      props = { p: true };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: 1 };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'p' in component 'TestWidget'");
   });
 
   test("can validate an optional props", async () => {
-    let TestWidget = class extends Widget {
+    class TestWidget extends Component {
       static template = xml`<div>hey</div>`;
       static props = { p: { type: String, optional: true } };
-    };
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      static components = { TestWidget };
+      get p() {
+        return props.p;
+      }
+    }
 
-    expect(() => {
-      new TestWidget(env, { p: "hey" });
-      new TestWidget(env, {});
-    }).not.toThrow();
+    let error;
+    let props;
+    try {
+      props = { p: "key" };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
 
-    expect(() => {
-      new TestWidget(env, { p: 1 });
-    }).toThrow();
+    try {
+      props = {};
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: 1 };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'p' in component 'TestWidget'");
   });
 
   test("can validate an array with given primitive type", async () => {
-    let TestWidget = class extends Widget {
+    class TestWidget extends Component {
       static template = xml`<div>hey</div>`;
       static props = { p: { type: Array, element: String } };
-    };
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      static components = { TestWidget };
+      get p() {
+        return props.p;
+      }
+    }
 
-    expect(() => {
-      new TestWidget(env, { p: [] });
-      new TestWidget(env, { p: ["string"] });
-    }).not.toThrow();
+    let error;
+    let props;
+    try {
+      props = { p: [] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
 
-    expect(() => {
-      new TestWidget(env, { p: [1] });
-    }).toThrow();
+    try {
+      props = { p: ["string"] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
 
-    expect(() => {
-      new TestWidget(env, { p: ["string", 1] });
-    }).toThrow();
+    try {
+      props = { p: [1] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+
+    error = undefined;
+    try {
+      props = { p: ["string", 1] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
   });
 
   test("can validate an array with multiple sub element types", async () => {
-    let TestWidget = class extends Widget {
+    class TestWidget extends Component {
       static template = xml`<div>hey</div>`;
       static props = { p: { type: Array, element: [String, Boolean] } };
-    };
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      static components = { TestWidget };
+      get p() {
+        return props.p;
+      }
+    }
 
-    expect(() => {
-      new TestWidget(env, { p: [] });
-      new TestWidget(env, { p: ["string"] });
-      new TestWidget(env, { p: [false, true, "string"] });
-    }).not.toThrow();
+    let error;
+    let props;
+    try {
+      props = { p: [] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
 
-    expect(() => {
-      new TestWidget(env, { p: [true, 1] });
-    }).toThrow();
+    try {
+      props = { p: ["string"] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: [false, true, "string"] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: [true, 1] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'p' in component 'TestWidget'");
   });
 
   test("can validate an object with simple shape", async () => {
-    let TestWidget = class extends Widget {
+    class TestWidget extends Component {
       static template = xml`<div>hey</div>`;
       static props = {
-        p: { type: Object, shape: { id: Number, url: String } }
+        p: { type: Object, shape: { id: Number, url: String } },
       };
-    };
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      static components = { TestWidget };
+      get p() {
+        return props.p;
+      }
+    }
 
-    expect(() => {
-      new TestWidget(env, { p: { id: 1, url: "url" } });
-      new TestWidget(env, { p: { id: 1, url: "url", extra: true } });
-    }).not.toThrow();
+    let error;
+    let props;
+    try {
+      props = { p: { id: 1, url: "url" } };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
 
-    expect(() => {
-      new TestWidget(env, { p: { id: "1", url: "url" } });
-    }).toThrow();
+    try {
+      props = { p: { id: 1, url: "url", extra: true } };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid prop 'p' in component TestWidget (unknown prop 'extra')");
 
-    expect(() => {
-      new TestWidget(env, { p: { id: 1 } });
-    }).toThrow();
+    try {
+      props = { p: { id: "1", url: "url" } };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'p' in component 'TestWidget'");
+
+    error = undefined;
+    try {
+      props = { p: { id: 1 } };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'p' in component 'TestWidget'");
   });
 
   test("can validate recursively complicated prop def", async () => {
-    let TestWidget = class extends Widget {
+    class TestWidget extends Component {
       static template = xml`<div>hey</div>`;
       static props = {
         p: {
           type: Object,
           shape: {
             id: Number,
-            url: [Boolean, { type: Array, element: Number }]
-          }
-        }
+            url: [Boolean, { type: Array, element: Number }],
+          },
+        },
       };
-    };
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      static components = { TestWidget };
+      get p() {
+        return props.p;
+      }
+    }
 
-    expect(() => {
-      new TestWidget(env, { p: { id: 1, url: true } });
-      new TestWidget(env, { p: { id: 1, url: [12] } });
-    }).not.toThrow();
+    let error;
+    let props;
+    try {
+      props = { p: { id: 1, url: true } };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
 
-    expect(() => {
-      new TestWidget(env, { p: { id: 1, url: [12, true] } });
-    }).toThrow();
+    try {
+      props = { p: { id: 1, url: [12] } };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: { id: 1, url: [12, true] } };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'p' in component 'TestWidget'");
+  });
+
+  test("can validate optional attributes in nested sub props", () => {
+    class TestComponent extends Component {
+      static props = {
+        myprop: {
+          type: Array,
+          element: {
+            type: Object,
+            shape: {
+              num: { type: Number, optional: true },
+            },
+          },
+        },
+      };
+    }
+    let error;
+    try {
+      QWeb.utils.validateProps(TestComponent, { myprop: [{}] });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      QWeb.utils.validateProps(TestComponent, { myprop: [{ a: 1 }] });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe(
+      "Invalid prop 'myprop' in component TestComponent (unknown prop 'a')"
+    );
+  });
+
+  test("can validate with a custom validator", () => {
+    class TestComponent extends Component {
+      static props = {
+        size: {
+          validate: (e) => ["small", "medium", "large"].includes(e),
+        },
+      };
+    }
+    let error;
+    try {
+      QWeb.utils.validateProps(TestComponent, { size: "small" });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      QWeb.utils.validateProps(TestComponent, { size: "abcdef" });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'size' in component 'TestComponent'");
+  });
+
+  test("can validate with a custom validator, and a type", () => {
+    const validator = jest.fn((n) => 0 <= n && n <= 10);
+    class TestComponent extends Component {
+      static props = {
+        n: {
+          type: Number,
+          validate: validator,
+        },
+      };
+    }
+    let error;
+    try {
+      QWeb.utils.validateProps(TestComponent, { n: 3 });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+    expect(validator).toBeCalledTimes(1);
+
+    try {
+      QWeb.utils.validateProps(TestComponent, { n: "str" });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'n' in component 'TestComponent'");
+    expect(validator).toBeCalledTimes(1);
+
+    error = null;
+    try {
+      QWeb.utils.validateProps(TestComponent, { n: 100 });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'n' in component 'TestComponent'");
+    expect(validator).toBeCalledTimes(2);
   });
 
   test("props are validated in dev mode (code snapshot)", async () => {
@@ -249,7 +614,7 @@ describe("props validation", () => {
     class App extends Widget {
       static components = { Child };
     }
-    const app = new App(env);
+    const app = new App();
     await app.mount(fixture);
     expect(fixture.innerHTML).toBe("<div><div>1</div></div>");
     // need to make sure there are 2 call to update props. one at component
@@ -280,6 +645,32 @@ describe("props validation", () => {
     }).toThrow();
   });
 
+  test("props with type array, and no element", async () => {
+    class TestWidget extends Widget {
+      static props = { myprop: { type: Array } };
+    }
+
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, { myprop: [1] });
+    }).not.toThrow();
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, { myprop: 1 });
+    }).toThrow(`Invalid Prop 'myprop' in component 'TestWidget'`);
+  });
+
+  test("props with type object, and no shape", async () => {
+    class TestWidget extends Widget {
+      static props = { myprop: { type: Object } };
+    }
+
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, { myprop: { a: 3 } });
+    }).not.toThrow();
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, { myprop: false });
+    }).toThrow(`Invalid Prop 'myprop' in component 'TestWidget'`);
+  });
+
   test("props: extra props cause an error", async () => {
     class TestWidget extends Widget {
       static props = ["message"];
@@ -322,17 +713,120 @@ describe("props validation", () => {
       QWeb.utils.validateProps(TestWidget, { message: null });
     }).toThrow();
   });
+
+  test("missing required boolean prop causes an error", async () => {
+    class TestWidget extends Widget {
+      static props = ["p"];
+      static template = xml`<span><t t-if="props.p">hey</t></span>`;
+    }
+
+    class App extends Widget {
+      static template = xml`<div><TestWidget/></div>`;
+      static components = { TestWidget };
+    }
+
+    const w = new App(undefined, {});
+    let error;
+    try {
+      await w.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Missing props 'p' (component 'TestWidget')");
+  });
+
+  test("props are validated whenever component is updated", async () => {
+    let error;
+    class TestWidget extends Component {
+      static props = { p: { type: Number } };
+      static template = xml`<div><t t-esc="props.p"/></div>`;
+
+      async __updateProps() {
+        try {
+          await Component.prototype.__updateProps.apply(this, arguments);
+        } catch (e) {
+          error = e;
+        }
+      }
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="state.p"/></div>`;
+      static components = { TestWidget };
+      state: any = useState({ p: 1 });
+    }
+
+    const w = new Parent();
+    await w.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>1</div></div>");
+
+    w.state.p = undefined;
+    await nextTick();
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Missing props 'p' (component 'TestWidget')");
+  });
+
+  test("default values are applied before validating props at update", async () => {
+    class TestWidget extends Component {
+      static props = { p: { type: Number } };
+      static template = xml`<div><t t-esc="props.p"/></div>`;
+      static defaultProps = { p: 4 };
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="state.p"/></div>`;
+      static components = { TestWidget };
+      state: any = useState({ p: 1 });
+    }
+
+    const w = new Parent();
+    await w.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>1</div></div>");
+
+    w.state.p = undefined;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><div>4</div></div>");
+  });
+
+  test("mix of optional and mandatory", async () => {
+    class Child extends Component {
+      static props = {
+        optional: { type: String, optional: true },
+        mandatory: Number,
+      };
+      static template = xml` <div><t t-esc="props.mandatory"/></div>`;
+    }
+
+    class App extends Component {
+      static components = { Child };
+      static template = xml`<div><Child/></div>`;
+    }
+
+    const w = new App(undefined, {});
+    let error;
+    try {
+      await w.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Missing props 'mandatory' (component 'Child')");
+  });
 });
 
 describe("default props", () => {
   test("can set default values", async () => {
-    class TestWidget extends Widget {
+    class TestWidget extends Component {
       static defaultProps = { p: 4 };
-      static template = xml`<div>hey</div>`;
+      static template = xml`<div><t t-esc="props.p"/></div>`;
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget /></div>`;
+      static components = { TestWidget };
     }
 
-    const w = new TestWidget(env, {});
-    expect(w.props.p).toBe(4);
+    const w = new Parent();
+    await w.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>4</div></div>");
   });
 
   test("default values are also set whenever component is updated", async () => {
@@ -346,7 +840,7 @@ describe("default props", () => {
       state: any = useState({ p: 1 });
     }
 
-    const w = new Parent(env);
+    const w = new Parent();
     await w.mount(fixture);
     expect(fixture.innerHTML).toBe("<div><div>1</div></div>");
 
@@ -367,7 +861,7 @@ describe("default props", () => {
       static components = { TestWidget };
     }
 
-    const w = new App(env, {});
+    const w = new App(undefined, {});
     await w.mount(fixture);
     expect(fixture.innerHTML).toBe("<div><span>heyhey</span></div>");
   });

tests/component/styles.test.ts

@@ -0,0 +1,170 @@
+import { Component, Env } from "../../src/component/component";
+import { processSheet } from "../../src/component/styles";
+import { xml, css } from "../../src/tags";
+import { makeTestFixture, makeTestEnv } from "../helpers";
+
+//------------------------------------------------------------------------------
+// Setup and helpers
+//------------------------------------------------------------------------------
+
+// We create before each test:
+// - fixture: a div, appended to the DOM, intended to be the target of dom
+//   manipulations.  Note that it is removed after each test.
+// - env: an Env, necessary to create new components
+
+let fixture: HTMLElement;
+let env: Env;
+
+beforeEach(() => {
+  fixture = makeTestFixture();
+  env = makeTestEnv();
+  Component.env = env;
+  document.head.innerHTML = "";
+});
+
+afterEach(() => {
+  fixture.remove();
+});
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+describe("styles and component", () => {
+  test("can define an inline stylesheet", async () => {
+    class App extends Component {
+      static template = xml`<div class="app">text</div>`;
+      static style = css`
+        .app {
+          color: red;
+        }
+      `;
+    }
+    expect(document.head.innerHTML).toBe("");
+    const app = new App();
+
+    expect(document.head.innerHTML).toBe(`<style component=\"App\">.app {
+  color: red;
+}</style>`);
+
+    await app.mount(fixture);
+    const style = getComputedStyle(app.el!);
+    expect(style.color).toBe("red");
+    expect(fixture.innerHTML).toBe('<div class="app">text</div>');
+  });
+
+  test("inherited components properly apply css", async () => {
+    class App extends Component {
+      static template = xml`<div class="app">text</div>`;
+      static style = css`
+        .app {
+          color: red;
+        }
+      `;
+    }
+    class SubApp extends App {
+      static style = css`
+        .app {
+          font-weight: bold;
+        }
+      `;
+    }
+    expect(document.head.innerHTML).toBe("");
+    const app = new SubApp();
+
+    expect(document.head.innerHTML).toBe(`<style component=\"SubApp\">.app {
+  font-weight: bold;
+}</style><style component=\"App\">.app {
+  color: red;
+}</style>`);
+
+    await app.mount(fixture);
+    const style = getComputedStyle(app.el!);
+    expect(style.color).toBe("red");
+    expect(style.fontWeight).toBe("bold");
+    expect(fixture.innerHTML).toBe('<div class="app">text</div>');
+  });
+
+  test("get a meaningful error message if css helper is missing", async () => {
+    class App extends Component {
+      static template = xml`<div class="app">text</div>`;
+      static style = `.app {color: red;}`;
+    }
+    let error;
+    try {
+      new App();
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe(
+      "Invalid css stylesheet for component 'App'. Did you forget to use the 'css' tag helper?"
+    );
+  });
+
+  test("inline stylesheets are processed", async () => {
+    class App extends Component {
+      static template = xml`<div class="app">text</div>`;
+      static style = css`
+        .app {
+          color: red;
+          .some-class {
+            font-weight: bold;
+            width: 40px;
+          }
+
+          display: block;
+        }
+      `;
+    }
+    new App();
+
+    expect(document.head.querySelector("style")!.innerHTML).toBe(`.app {
+  color: red;
+}
+.app .some-class {
+  font-weight: bold;
+  width: 40px;
+}
+.app {
+  display: block;
+}`);
+  });
+
+  test("properly handle rules with commas", async () => {
+    const sheet = processSheet(`.parent-a, .parent-b {
+      .child-a, .child-b {
+        color: red;
+      }
+    }`);
+
+    expect(sheet)
+      .toBe(`.parent-a .child-a, .parent-a .child-b, .parent-b .child-a, .parent-b .child-b {
+  color: red;
+}`);
+  });
+
+  test("handle & selector", async () => {
+    let sheet = processSheet(`.btn {
+      &.danger {
+        color: red;
+      }
+    }`);
+
+    expect(sheet).toBe(`.btn.danger {
+  color: red;
+}`);
+
+    sheet = processSheet(`.some-class {
+      &.btn {
+        .other-class ~ & {
+          color: red;
+        }
+      }
+    }`);
+
+    expect(sheet).toBe(`.other-class ~ .some-class.btn {
+  color: red;
+}`);
+  });
+});

tests/component/un_mounting.test.ts

@@ -0,0 +1,732 @@
+import { Component, Env, mount } from "../../src/component/component";
+import { useState } from "../../src/hooks";
+import { xml } from "../../src/tags";
+import { makeDeferred, makeTestEnv, makeTestFixture, nextTick, nextMicroTick } from "../helpers";
+import { scheduler } from "../../src/component/scheduler";
+
+//------------------------------------------------------------------------------
+// Setup and helpers
+//------------------------------------------------------------------------------
+
+// We create before each test:
+// - fixture: a div, appended to the DOM, intended to be the target of dom
+//   manipulations.  Note that it is removed after each test.
+// - env: a WEnv, necessary to create new components
+
+let fixture: HTMLElement;
+let env: Env;
+
+beforeEach(() => {
+  fixture = makeTestFixture();
+  env = makeTestEnv();
+  Component.env = env;
+});
+
+afterEach(() => {
+  fixture.remove();
+});
+
+describe("mount targets", () => {
+  test("can attach a component to an existing node (if same tagname)", async () => {
+    class App extends Component {
+      static template = xml`<div t-att-class="state.customClass">app<p>another tag</p></div>`;
+      state = useState({ customClass: "custom" });
+    }
+    const div = document.createElement("div");
+    div.classList.add("arbitrary");
+    div.innerHTML = `<p>pre-existing</p>`;
+    fixture.appendChild(div);
+
+    const app = await mount(App, { target: div, position: "self" });
+
+    expect(fixture.innerHTML).toBe(
+      `<div class="arbitrary custom"><p>pre-existing</p>app<p>another tag</p></div>`
+    );
+    expect(div).toBe(app.el);
+
+    app.state.customClass = "custom2";
+    await nextTick();
+    expect(fixture.innerHTML).toBe(
+      `<div class="arbitrary custom2"><p>pre-existing</p>app<p>another tag</p></div>`
+    );
+    expect(div).toBe(app.el);
+
+    app.unmount();
+    // This assert is a best guess
+    // The use case it covers was not really thought through
+    // and may change in the future
+    expect(fixture.innerHTML).toBe("");
+  });
+
+  test("cannot attach a component to an existing node (if not same tagname)", async () => {
+    class App extends Component {
+      static template = xml`<span>app</span>`;
+    }
+    const div = document.createElement("div");
+    fixture.appendChild(div);
+
+    let error;
+    try {
+      await mount(App, { target: div, position: "self" });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Cannot attach 'App' to target node (not same tag name)");
+  });
+
+  test("can mount a component (with position='first-child')", async () => {
+    class App extends Component {
+      static template = xml`<div>app</div>`;
+    }
+    const span = document.createElement("span");
+    fixture.appendChild(span);
+
+    await mount(App, { target: fixture, position: "first-child" });
+    expect(fixture.innerHTML).toBe("<div>app</div><span></span>");
+  });
+
+  test("can mount a component (with position='last-child')", async () => {
+    class App extends Component {
+      static template = xml`<div>app</div>`;
+    }
+    const span = document.createElement("span");
+    fixture.appendChild(span);
+
+    await mount(App, { target: fixture, position: "last-child" });
+    expect(fixture.innerHTML).toBe("<span></span><div>app</div>");
+  });
+
+  test("default mount option is 'last-child'", async () => {
+    class App extends Component {
+      static template = xml`<div>app</div>`;
+    }
+    const span = document.createElement("span");
+    fixture.appendChild(span);
+
+    await mount(App, { target: fixture });
+    expect(fixture.innerHTML).toBe("<span></span><div>app</div>");
+  });
+});
+
+describe("unmounting and remounting", () => {
+  test("widget can be unmounted and remounted", async () => {
+    const steps: string[] = [];
+    class MyWidget extends Component {
+      static template = xml`<div>Hey</div>`;
+      async willStart() {
+        steps.push("willstart");
+      }
+      mounted() {
+        steps.push("mounted");
+      }
+      willUnmount() {
+        steps.push("willunmount");
+      }
+      patched() {
+        throw new Error("patched should not be called");
+      }
+    }
+
+    const w = await mount(MyWidget, { target: fixture });
+    expect(fixture.innerHTML).toBe("<div>Hey</div>");
+    expect(steps).toEqual(["willstart", "mounted"]);
+
+    w.unmount();
+    expect(fixture.innerHTML).toBe("");
+    expect(steps).toEqual(["willstart", "mounted", "willunmount"]);
+
+    await w.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>Hey</div>");
+    expect(steps).toEqual(["willstart", "mounted", "willunmount", "mounted"]);
+  });
+
+  test("widget can be mounted twice without ill effect", async () => {
+    const steps: string[] = [];
+    class MyWidget extends Component {
+      static template = xml`<div>Hey</div>`;
+      async willStart() {
+        steps.push("willstart");
+      }
+      mounted() {
+        steps.push("mounted");
+      }
+      willUnmount() {
+        steps.push("willunmount");
+      }
+    }
+
+    const w = await mount(MyWidget, { target: fixture });
+    await w.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>Hey</div>");
+    expect(steps).toEqual(["willstart", "mounted"]);
+  });
+
+  test("state changes in willUnmount do not trigger rerender", async () => {
+    const steps: string[] = [];
+
+    class Child extends Component {
+      static template = xml`
+          <span><t t-esc="props.val"/><t t-esc="state.n"/></span>
+        `;
+      state = useState({ n: 2 });
+      __render(f) {
+        steps.push("render");
+        return super.__render(f);
+      }
+      willPatch() {
+        steps.push("willPatch");
+      }
+      patched() {
+        steps.push("patched");
+      }
+
+      willUnmount() {
+        steps.push("willUnmount");
+        this.state.n = 3;
+      }
+    }
+    class Parent extends Component {
+      static template = xml`
+          <div>
+            <Child t-if="state.flag" val="state.val"/>
+          </div>
+        `;
+      static components = { Child };
+      state = useState({ val: 1, flag: true });
+    }
+
+    const widget = await mount(Parent, { target: fixture });
+    expect(steps).toEqual(["render"]);
+    expect(fixture.innerHTML).toBe("<div><span>12</span></div>");
+    widget.state.flag = false;
+    await nextTick();
+    // we make sure here that no call to __render is done
+    expect(steps).toEqual(["render", "willUnmount"]);
+  });
+
+  test("state changes in willUnmount will be applied on remount", async () => {
+    class TestWidget extends Component {
+      static template = xml`
+          <div><t t-esc="state.val"/></div>
+        `;
+      state = useState({ val: 1 });
+      willUnmount() {
+        this.state.val = 3;
+      }
+    }
+
+    const widget = new TestWidget();
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>1</div>");
+    widget.unmount();
+    expect(fixture.innerHTML).toBe("");
+    await nextTick(); // wait for changes to be detected before remounting
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>3</div>");
+    // we want to make sure that there are no remaining tasks left at this point.
+    expect(Component.scheduler.tasks.length).toBe(0);
+  });
+
+  test("sub component is still active after being unmounted and remounted", async () => {
+    class Child extends Component {
+      static template = xml`
+          <p t-on-click="state.value++">
+            <t t-esc="state.value"/>
+          </p>`;
+
+      state = useState({ value: 1 });
+    }
+
+    class Parent extends Component {
+      static components = { Child };
+      static template = xml`<div><Child/></div>`;
+    }
+
+    const w = new Parent();
+    await w.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><p>1</p></div>");
+
+    fixture.querySelector("p")!.click();
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><p>2</p></div>");
+    w.unmount();
+    await nextTick();
+    await w.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><p>2</p></div>");
+    fixture.querySelector("p")!.click();
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><p>3</p></div>");
+  });
+
+  test("change state just before mounting component", async () => {
+    const steps: number[] = [];
+    class TestWidget extends Component {
+      static template = xml`
+          <div><t t-esc="state.val"/></div>
+        `;
+      state = useState({ val: 1 });
+      __render(f) {
+        steps.push(this.state.val);
+        return super.__render(f);
+      }
+    }
+    TestWidget.prototype.__render = jest.fn(TestWidget.prototype.__render);
+
+    const widget = new TestWidget();
+    widget.state.val = 2;
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>2</div>");
+    expect(TestWidget.prototype.__render).toHaveBeenCalledTimes(1);
+
+    // unmount and re-mount, as in this case, willStart won't be called, so it's
+    // slightly different
+    widget.unmount();
+    widget.state.val = 3;
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>3</div>");
+    expect(TestWidget.prototype.__render).toHaveBeenCalledTimes(2);
+    expect(steps).toEqual([2, 3]);
+  });
+
+  test("change state while mounting component", async () => {
+    const steps: number[] = [];
+    class TestWidget extends Component {
+      static template = xml`
+          <div><t t-esc="state.val"/></div>
+        `;
+      state = useState({ val: 1 });
+      __render(f) {
+        steps.push(this.state.val);
+        return super.__render(f);
+      }
+    }
+    TestWidget.prototype.__render = jest.fn(TestWidget.prototype.__render);
+    TestWidget.prototype.__patch = jest.fn(TestWidget.prototype.__patch);
+
+    const widget = new TestWidget();
+    let prom = widget.mount(fixture);
+    widget.state.val = 2;
+    await prom;
+    expect(fixture.innerHTML).toBe("<div>2</div>");
+    expect(TestWidget.prototype.__render).toHaveBeenCalledTimes(1);
+
+    // unmount and re-mount, as in this case, willStart won't be called, so it's
+    // slightly different
+    widget.unmount();
+    prom = widget.mount(fixture);
+    widget.state.val = 3;
+    await prom;
+    expect(fixture.innerHTML).toBe("<div>3</div>");
+    expect(TestWidget.prototype.__render).toHaveBeenCalledTimes(3);
+    expect(TestWidget.prototype.__patch).toHaveBeenCalledTimes(2);
+    expect(steps).toEqual([2, 2, 3]);
+  });
+
+  test("change state and render while mounted in detached dom", async () => {
+    class App extends Component {
+      static template = xml`<div><t t-esc="state.val"/></div>`;
+      state = useState({ val: 1 });
+    }
+
+    const detachedDiv = document.createElement("div");
+    const app = await mount(App, { target: detachedDiv });
+
+    expect(detachedDiv.innerHTML).toBe("<div>1</div>");
+    app.state.val = 2;
+    await nextTick();
+    expect(detachedDiv.innerHTML).toBe("<div>2</div>");
+  });
+
+  test("change state and render while not mounted ", async () => {
+    class App extends Component {
+      static template = xml`<div><t t-esc="state.val"/></div>`;
+      state = useState({ val: 1 });
+    }
+
+    const app = new App(null);
+
+    app.state.val = 2; // will call the render method (before being mounted)
+    await nextTick();
+
+    await app.mount(fixture);
+
+    expect(fixture.innerHTML).toBe("<div>2</div>");
+  });
+
+  test("destroy and change state after mounted in detached dom", async () => {
+    class App extends Component {
+      static template = xml`<div><t t-esc="state.val"/></div>`;
+      state = useState({ val: 1 });
+    }
+
+    const detachedDiv = document.createElement("div");
+    const app = await mount(App, { target: detachedDiv });
+
+    expect(detachedDiv.innerHTML).toBe("<div>1</div>");
+
+    app.destroy();
+    app.state.val = 2;
+    await nextTick();
+    expect(detachedDiv.innerHTML).toBe("");
+  });
+
+  test("change state while component is unmounted", async () => {
+    let child;
+    class Child extends Component {
+      static template = xml`<span t-esc="state.val"/>`;
+      state = useState({
+        val: "C1",
+      });
+      constructor(parent, props) {
+        super(parent, props);
+        child = this;
+      }
+    }
+
+    class Parent extends Component {
+      static components = { Child };
+      static template = xml`<div><t t-esc="state.val"/><Child/></div>`;
+      state = useState({ val: "P1" });
+    }
+
+    const parent = new Parent();
+    await parent.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>P1<span>C1</span></div>");
+
+    parent.unmount();
+    expect(fixture.innerHTML).toBe("");
+
+    parent.state.val = "P2";
+    child.state.val = "C2";
+
+    await parent.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>P2<span>C2</span></div>");
+  });
+
+  test("change state while component is mounted in a fragment", async () => {
+    class Child1 extends Component {
+      static template = xml`<span>C1</span>`;
+    }
+
+    class Child2 extends Component {
+      static template = xml`<span>C2</span>`;
+    }
+
+    class Parent extends Component {
+      static components = { Child1, Child2 };
+      static template = xml`
+        <div>
+          <Child1 t-if="child == 'c1'"/>
+          <Child2 t-if="child == 'c2'"/>
+        </div>`;
+      child: string | false = false;
+    }
+
+    const fragment = document.createDocumentFragment();
+    const parent = new Parent();
+    await parent.mount(fragment);
+    expect(parent.el.outerHTML).toBe("<div></div>");
+
+    parent.child = "c1";
+    parent.render();
+    await Promise.resolve();
+
+    parent.child = "c2";
+    await parent.mount(fixture);
+
+    expect(fixture.innerHTML).toBe("<div><span>C2</span></div>");
+  });
+
+  test("unmount component during a re-rendering", async () => {
+    const def = makeDeferred();
+    class Child extends Component {
+      static template = xml`<span><t t-esc="props.val"/></span>`;
+      willUpdateProps() {
+        return def;
+      }
+    }
+    Child.prototype.__render = jest.fn(Child.prototype.__render);
+
+    class Parent extends Component {
+      static template = xml`<div><Child val="state.val"/></div>`;
+      static components = { Child };
+      state = useState({ val: 1 });
+    }
+
+    const parent = new Parent();
+    await parent.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><span>1</span></div>");
+    expect(Child.prototype.__render).toBeCalledTimes(1);
+
+    parent.state.val = 2;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><span>1</span></div>");
+
+    parent.unmount();
+    expect(fixture.innerHTML).toBe("");
+
+    def.resolve();
+    await nextTick();
+    expect(fixture.innerHTML).toBe("");
+    expect(Child.prototype.__render).toBeCalledTimes(1);
+  });
+
+  test("widget can be mounted on different target", async () => {
+    class MyWidget extends Component {
+      static template = xml`<div>Hey</div>`;
+      patched() {
+        throw new Error("patched should not be called");
+      }
+    }
+    const div = document.createElement("div");
+    const span = document.createElement("span");
+    fixture.appendChild(div);
+    fixture.appendChild(span);
+    const w = new MyWidget();
+    await w.mount(div);
+
+    expect(fixture.innerHTML).toBe("<div><div>Hey</div></div><span></span>");
+
+    await w.mount(span);
+    expect(fixture.innerHTML).toBe("<div></div><span><div>Hey</div></span>");
+  });
+
+  test("widget can be mounted on different target, another situation", async () => {
+    const def = makeDeferred();
+    const steps: string[] = [];
+
+    class MyWidget extends Component {
+      static template = xml`<div>Hey</div>`;
+      async willStart() {
+        return def;
+      }
+      patched() {
+        throw new Error("patched should not be called");
+      }
+    }
+    const div = document.createElement("div");
+    const span = document.createElement("span");
+    fixture.appendChild(div);
+    fixture.appendChild(span);
+    const w = new MyWidget();
+
+    w.mount(div).catch(() => steps.push("1 catch"));
+
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div></div><span></span>");
+
+    w.mount(span).then(() => steps.push("2 resolved"));
+
+    // we wait two microticks because this is the number of internal promises
+    // that need to be resolved/rejected, and because we want to prove here
+    // that the first mount operation is cancelled immediately, and not after
+    // one full tick.
+    await nextMicroTick();
+    await nextMicroTick();
+    expect(steps).toEqual([]);
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div></div><span></span>");
+
+    def.resolve();
+    await nextTick();
+    expect(steps).toEqual(["2 resolved"]);
+    expect(fixture.innerHTML).toBe("<div></div><span><div>Hey</div></span>");
+  });
+
+  test("component can be mounted on same target, another situation", async () => {
+    const def = makeDeferred();
+    const steps: string[] = [];
+
+    class MyWidget extends Component {
+      static template = xml`<div>Hey</div>`;
+      async willStart() {
+        return def;
+      }
+      patched() {
+        throw new Error("patched should not be called");
+      }
+    }
+    const w = new MyWidget();
+
+    w.mount(fixture).then(() => steps.push("1 resolved"));
+
+    await nextTick();
+    expect(fixture.innerHTML).toBe("");
+
+    w.mount(fixture).then(() => steps.push("2 resolved"));
+
+    await nextTick();
+    expect(steps).toEqual([]);
+    expect(fixture.innerHTML).toBe("");
+
+    def.resolve();
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div>Hey</div>");
+    expect(steps).toEqual(["1 resolved", "2 resolved"]);
+  });
+
+  test("mounting a destroyed widget", async () => {
+    class MyWidget extends Component {
+      static template = xml`<div>Hey</div>`;
+    }
+    const w = new MyWidget();
+    w.destroy(); // because, why not
+
+    let error;
+    try {
+      await w.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(scheduler.tasks.length).toBe(0);
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Cannot mount a destroyed component");
+  });
+
+  test("destroying a sub-component cleans itself from parent's vnode", async () => {
+    class C1 extends Component {
+      static template = xml`<div><div><t t-esc="props.a"/></div></div>`;
+    }
+    class P extends Component {
+      static components = { C1 };
+      static template = xml`<div><div><C1 t-props="state" t-if="state.a"/></div></div>`;
+      state = {
+        a: "first",
+      };
+    }
+    const parent = new P();
+    await parent.mount(fixture);
+    expect(fixture.textContent).toBe("first");
+    parent.unmount();
+    parent.state.a = "";
+    parent.mount(fixture);
+    parent.state.a = "fixed";
+    await parent.render();
+    expect(fixture.textContent).toBe("fixed");
+  });
+
+  test("destroying a sub-component cleans itself from parent's vnode, part 2", async () => {
+    class C1 extends Component {
+      static template = xml`<div><div><t t-esc="props.a"/></div></div>`;
+    }
+    class P extends Component {
+      static components = { C1 };
+      static template = xml`<div><div><C1 t-props="state" t-if="state.a"/>some text</div></div>`;
+      state = {
+        a: "first",
+      };
+    }
+    const parent = new P();
+    await parent.mount(fixture);
+    expect(fixture.textContent).toBe("firstsome text");
+    parent.unmount();
+    parent.state.a = "";
+    parent.mount(fixture);
+    parent.state.a = "fixed";
+    await parent.render();
+    expect(fixture.textContent).toBe("fixedsome text");
+  });
+
+  test("destroying a sub-component cleans itself from parent's vnode, part 3", async () => {
+    class C1 extends Component {
+      static template = xml`<div><div><t t-esc="props.a"/></div></div>`;
+    }
+
+    class C2 extends Component {
+      static template = xml`<C1 a="props.a"/>`;
+      static components = { C1 };
+    }
+
+    class P extends Component {
+      static components = { C2 };
+      static template = xml`<div><div><C2 t-props="state" t-if="state.a"/></div></div>`;
+      state = {
+        a: "first",
+      };
+    }
+    const parent = new P();
+    await parent.mount(fixture);
+    expect(fixture.textContent).toBe("first");
+    parent.unmount();
+    parent.state.a = "";
+    parent.mount(fixture);
+    parent.state.a = "fixed";
+    await parent.render();
+    expect(fixture.textContent).toBe("fixed");
+  });
+
+  test("destroying a sub-component cleans itself from parent's vnode, part 4", async () => {
+    class C1 extends Component {
+      static template = xml`<div><div><t t-esc="props.a"/></div></div>`;
+    }
+
+    class C2 extends Component {
+      static template = xml`<C1 a="props.a"/>`;
+      static components = { C1 };
+    }
+    class P extends Component {
+      static components = { C2 };
+      static template = xml`<div><div><C2 t-props="state" t-if="state.a"/>some text</div></div>`;
+      state = {
+        a: "first",
+      };
+    }
+    const parent = new P();
+    await parent.mount(fixture);
+    expect(fixture.textContent).toBe("firstsome text");
+    parent.unmount();
+    parent.state.a = "";
+    parent.mount(fixture);
+    parent.state.a = "fixed";
+    await parent.render();
+    expect(fixture.textContent).toBe("fixedsome text");
+  });
+
+  test("remounting component tree where a component implement shouldupdate", async () => {
+    let state: any;
+    const steps = [];
+    class Child extends Component {
+      static template = xml`<div><t t-esc="state.word"/><t t-esc="props.name"/></div>`;
+
+      state = useState({ word: "hello" });
+
+      constructor(parent, props) {
+        super(parent, props);
+        state = this.state;
+      }
+      patched() {
+        steps.push("patched");
+      }
+      mounted() {
+        steps.push("mounted");
+      }
+      willUnmount() {
+        steps.push("willUnmount");
+      }
+      shouldUpdate() {
+        return false;
+      }
+    }
+
+    class Parent extends Component {
+      static template = xml`<div><Child name="state.name"/></div>`;
+      static components = { Child };
+      state = useState({ name: "World" });
+    }
+
+    const parent = await mount(Parent, { target: fixture });
+    expect(fixture.innerHTML).toBe("<div><div>helloWorld</div></div>");
+
+    parent.unmount();
+    expect(fixture.innerHTML).toBe("");
+    await parent.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>helloWorld</div></div>");
+
+    state.word = "test";
+
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><div>testWorld</div></div>");
+    expect(steps).toEqual(["mounted", "willUnmount", "mounted", "patched"]);
+  });
+});

tests/context.test.ts

@@ -1,5 +1,5 @@
 import { makeDeferred, makeTestEnv, makeTestFixture, nextTick } from "./helpers";
-import { Component, Env } from "../src/component/component";
+import { Component } from "../src/component/component";
 import { Context, useContext } from "../src/context";
 import { xml } from "../src/tags";
 import { useState } from "../src/hooks";
@@ -11,14 +11,13 @@ import { useState } from "../src/hooks";
 // We create before each test:
 // - fixture: a div, appended to the DOM, intended to be the target of dom
 //   manipulations.  Note that it is removed after each test.
-// - env: a WEnv, necessary to create new components
+// - a test env, necessary to create components, that is set as env
 
 let fixture: HTMLElement;
-let env: Env;
 
 beforeEach(() => {
   fixture = makeTestFixture();
-  env = makeTestEnv();
+  Component.env = makeTestEnv();
 });
 
 afterEach(() => {
@@ -33,11 +32,11 @@ describe("Context", () => {
   test("very simple use, with initial value", async () => {
     const testContext = new Context({ value: 123 });
 
-    class Test extends Component<any, any> {
+    class Test extends Component {
       static template = xml`<div><t t-esc="contextObj.value"/></div>`;
       contextObj = useContext(testContext);
     }
-    const test = new Test(env);
+    const test = new Test();
     await test.mount(fixture);
     expect(fixture.innerHTML).toBe("<div>123</div>");
   });
@@ -45,11 +44,11 @@ describe("Context", () => {
   test("useContext hook is reactive, for one component", async () => {
     const testContext = new Context({ value: 123 });
 
-    class Test extends Component<any, any> {
+    class Test extends Component {
       static template = xml`<div><t t-esc="contextObj.value"/></div>`;
       contextObj = useContext(testContext);
     }
-    const test = new Test(env);
+    const test = new Test();
     await test.mount(fixture);
     expect(fixture.innerHTML).toBe("<div>123</div>");
     test.contextObj.value = 321;
@@ -60,15 +59,15 @@ describe("Context", () => {
   test("two components can subscribe to same context", async () => {
     const testContext = new Context({ value: 123 });
 
-    class Child extends Component<any, any> {
+    class Child extends Component {
       static template = xml`<span><t t-esc="contextObj.value"/></span>`;
       contextObj = useContext(testContext);
     }
-    class Parent extends Component<any, any> {
+    class Parent extends Component {
       static template = xml`<div><Child /><Child /></div>`;
       static components = { Child };
     }
-    const parent = new Parent(env);
+    const parent = new Parent();
     await parent.mount(fixture);
     expect(fixture.innerHTML).toBe("<div><span>123</span><span>123</span></div>");
     testContext.state.value = 321;
@@ -76,11 +75,98 @@ describe("Context", () => {
     expect(fixture.innerHTML).toBe("<div><span>321</span><span>321</span></div>");
   });
 
+  test("two async components are updated in parallel", async () => {
+    const testContext = new Context({ value: 123 });
+    const def = makeDeferred();
+    const steps: string[] = [];
+
+    class Child extends Component {
+      static template = xml`<span><t t-esc="contextObj.value"/></span>`;
+      contextObj = useContext(testContext);
+      async render() {
+        steps.push("render");
+        await def;
+        return super.render();
+      }
+    }
+
+    class Parent extends Component {
+      static template = xml`<div><Child /><Child /></div>`;
+      static components = { Child };
+    }
+    const parent = new Parent();
+    await parent.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><span>123</span><span>123</span></div>");
+    testContext.state.value = 321;
+    await nextTick();
+    expect(steps).toEqual(["render", "render"]);
+    expect(fixture.innerHTML).toBe("<div><span>123</span><span>123</span></div>");
+    def.resolve();
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><span>321</span><span>321</span></div>");
+  });
+
+  test("two async components on two levels are updated (mostly) in parallel", async () => {
+    const testContext = new Context({ value: 123 });
+    const def = makeDeferred();
+    const steps: string[] = [];
+
+    class SlowComp extends Component {
+      static template = xml`<p><t t-esc="props.value"/></p>`;
+      willUpdateProps() {
+        return def;
+      }
+    }
+    class Child extends Component {
+      static template = xml`<span><SlowComp value="contextObj.value"/></span>`;
+      static components = { SlowComp };
+      contextObj = useContext(testContext);
+
+      render() {
+        steps.push("render");
+        return super.render();
+      }
+    }
+
+    class Parent extends Component {
+      static template = xml`<div><Child /><Child /></div>`;
+      static components = { Child };
+    }
+
+    class App extends Component {
+      static template = xml`<div><Child /><Parent /></div>`;
+      static components = { Child, Parent };
+    }
+
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe(
+      "<div><span><p>123</p></span><div><span><p>123</p></span><span><p>123</p></span></div></div>"
+    );
+    testContext.state.value = 321;
+    await nextTick();
+    expect(steps).toEqual(["render"]);
+    expect(fixture.innerHTML).toBe(
+      "<div><span><p>123</p></span><div><span><p>123</p></span><span><p>123</p></span></div></div>"
+    );
+    def.resolve();
+    await nextTick();
+    // we need to wait for an extra tick because it could happen (even though it
+    // is rare) that the second batch of renderings is not done yet, because
+    // the initial promise has been given to the macrotask queue, so a small
+    // delay happens.
+    await nextTick();
+    expect(steps).toEqual(["render", "render", "render"]);
+    expect(fixture.innerHTML).toBe(
+      "<div><span><p>321</p></span><div><span><p>321</p></span><span><p>321</p></span></div></div>"
+    );
+  });
+
   test("one components can subscribe twice to same context", async () => {
     const testContext = new Context({ a: 1, b: 2 });
     const steps: string[] = [];
 
-    class Child extends Component<any, any> {
+    class Child extends Component {
       static template = xml`<span><t t-esc="contextObj1.a"/><t t-esc="contextObj2.b"/></span>`;
       contextObj1 = useContext(testContext);
       contextObj2 = useContext(testContext);
@@ -89,11 +175,11 @@ describe("Context", () => {
         return super.__render(fiber);
       }
     }
-    class Parent extends Component<any, any> {
+    class Parent extends Component {
       static template = xml`<div><Child /></div>`;
       static components = { Child };
     }
-    const parent = new Parent(env);
+    const parent = new Parent();
     await parent.mount(fixture);
     expect(fixture.innerHTML).toBe("<div><span>12</span></div>");
     expect(steps).toEqual(["child"]);
@@ -107,7 +193,7 @@ describe("Context", () => {
     const testContext = new Context({ a: 123, b: 321 });
     const steps: string[] = [];
 
-    class Child extends Component<any, any> {
+    class Child extends Component {
       static template = xml`<span><t t-esc="contextObj.a"/></span>`;
       contextObj = useContext(testContext);
       __render(fiber) {
@@ -115,7 +201,7 @@ describe("Context", () => {
         return super.__render(fiber);
       }
     }
-    class Parent extends Component<any, any> {
+    class Parent extends Component {
       static template = xml`<div><Child /><t t-esc="contextObj.b"/></div>`;
       static components = { Child };
       contextObj = useContext(testContext);
@@ -124,7 +210,7 @@ describe("Context", () => {
         return super.__render(fiber);
       }
     }
-    const parent = new Parent(env);
+    const parent = new Parent();
     await parent.mount(fixture);
     expect(fixture.innerHTML).toBe("<div><span>123</span>321</div>");
     expect(steps).toEqual(["parent", "child"]);
@@ -141,7 +227,7 @@ describe("Context", () => {
     const testContext = new Context({ a: 123 });
     const steps: string[] = [];
 
-    class Child extends Component<any, any> {
+    class Child extends Component {
       static template = xml`<span><t t-esc="contextObj.a"/></span>`;
       contextObj = useContext(testContext);
       __render(fiber) {
@@ -149,7 +235,7 @@ describe("Context", () => {
         return super.__render(fiber);
       }
     }
-    class Parent extends Component<any, any> {
+    class Parent extends Component {
       static template = xml`<div><Child t-if="state.flag"/></div>`;
       static components = { Child };
       state = useState({ flag: true });
@@ -158,7 +244,7 @@ describe("Context", () => {
         return super.__render(fiber);
       }
     }
-    const parent = new Parent(env);
+    const parent = new Parent();
     await parent.mount(fixture);
     expect(fixture.innerHTML).toBe("<div><span>123</span></div>");
     expect(steps).toEqual(["parent", "child"]);
@@ -174,11 +260,59 @@ describe("Context", () => {
     expect(testContext.subscriptions.update.length).toBe(0);
   });
 
-  test("concurrent renderings", async () => {
+  test("destroyed component before being mounted is inactive", async () => {
+    const testContext = new Context({ a: 123 });
+
+    class Child extends Component {
+      static template = xml`<span><t t-esc="contextObj.a"/></span>`;
+      contextObj = useContext(testContext);
+      willStart() {
+        return makeDeferred();
+      }
+    }
+    class Parent extends Component {
+      static template = xml`<div><Child t-if="state.flag"/></div>`;
+      static components = { Child };
+      state = useState({ flag: true });
+    }
+
+    const parent = new Parent();
+    const prom = parent.mount(fixture);
+    await nextTick(); // wait for Child to be instantiated
+    expect(testContext.subscriptions.update.length).toBe(1);
+    parent.state.flag = false;
+    await prom;
+    expect(fixture.innerHTML).toBe("<div></div>");
+    // kind of whitebox...
+    // we make sure we do not have any pending subscriptions to the 'update'
+    // event
+    expect(testContext.subscriptions.update.length).toBe(0);
+  });
+
+  test.skip("concurrent renderings", async () => {
+    /**
+     * Note: this test is interesting, but sadly just an incomplete attempt at
+     * protecting users against themselves.  With the context API, it is not
+     * possible for the framework to protect completely against crashes.  Maybe
+     * like in this case, when a component is in a simple hierarchy where all
+     * renderings come from the context changes, but in a real case, where some
+     * code can trigger a rendering independently, it is insufficient.
+     *
+     * The main problem is that the sub component depends on some external state,
+     * which may be modified, and then incompatible with the component actual
+     * state (for example, if the sub component has an id key related to some
+     * object that has been removed from the context).
+     *
+     * For now, sadly, the only solution is that components that depends on external
+     * state should guarantee their own integrity themselves. Then maybe this
+     * could be solved at the level of a state management solution that has a
+     * more advanced API, to let components determine if they should be updated
+     * or not (so, something slightly more advanced that the useStore hook).
+     */
     const testContext = new Context({ x: { n: 1 }, key: "x" });
     const def = makeDeferred();
     let stateC;
-    class ComponentC extends Component<any, any> {
+    class ComponentC extends Component {
       static template = xml`<span><t t-esc="context[props.key].n"/><t t-esc="state.x"/></span>`;
       context = useContext(testContext);
       state = useState({ x: "a" });
@@ -188,7 +322,7 @@ describe("Context", () => {
         stateC = this.state;
       }
     }
-    class ComponentB extends Component<any, any> {
+    class ComponentB extends Component {
       static components = { ComponentC };
       static template = xml`<p><ComponentC key="props.key"/></p>`;
 
@@ -196,18 +330,18 @@ describe("Context", () => {
         return def;
       }
     }
-    class ComponentA extends Component<any, any> {
+    class ComponentA extends Component {
       static components = { ComponentB };
       static template = xml`<div><ComponentB key="context.key"/></div>`;
       context = useContext(testContext);
     }
 
-    const component = new ComponentA(env);
+    const component = new ComponentA();
     await component.mount(fixture);
 
     expect(fixture.innerHTML).toBe("<div><p><span>1a</span></p></div>");
     testContext.state.key = "y";
-    testContext.state.y = {n: 2};
+    testContext.state.y = { n: 2 };
     delete testContext.state.x;
     await nextTick();
 

tests/core/event_bus.test.ts

@@ -14,7 +14,7 @@ describe("event bus behaviour", () => {
     expect.assertions(1);
     const bus = new EventBus();
     const owner = {};
-    bus.on("event", owner, function(this: any) {
+    bus.on("event", owner, function (this: any) {
       expect(this).toBe(owner);
     });
     bus.trigger("event");

tests/core/observer.test.ts

@@ -8,13 +8,11 @@ describe("observer", () => {
 
     expect(typeof obj).toBe("object");
     expect(observer.revNumber(obj)).toBe(1);
-    expect(observer.deepRevNumber(obj)).toBe(1);
     expect(observer.rev).toBe(1);
 
     const obj2: any = observer.observe({ a: 1 });
     expect(observer.revNumber(obj2)).toBe(1);
     expect(observer.revNumber(obj)).toBe(1);
-    expect(observer.deepRevNumber(obj)).toBe(1);
     expect(observer.rev).toBe(1);
 
     obj2.a = 2;
@@ -24,7 +22,7 @@ describe("observer", () => {
     expect(observer.rev).toBe(2);
 
     expect(obj2).toEqual({
-      a: 2
+      a: 2,
     });
   });
 
@@ -33,27 +31,23 @@ describe("observer", () => {
     const obj: any = observer.observe({ a: null, b: undefined });
 
     expect(observer.revNumber(obj)).toBe(1);
-    expect(observer.deepRevNumber(obj)).toBe(1);
     expect(observer.rev).toBe(1);
 
     obj.a = 3;
     expect(observer.revNumber(obj)).toBe(2);
-    expect(observer.deepRevNumber(obj)).toBe(2);
     expect(observer.rev).toBe(2);
 
     obj.b = 5;
     expect(observer.revNumber(obj)).toBe(3);
-    expect(observer.deepRevNumber(obj)).toBe(3);
     expect(observer.rev).toBe(3);
 
     obj.a = null;
     obj.b = undefined;
     expect(observer.revNumber(obj)).toBe(5);
-    expect(observer.deepRevNumber(obj)).toBe(5);
     expect(observer.rev).toBe(5);
     expect(obj).toEqual({
       a: null,
-      b: undefined
+      b: undefined,
     });
   });
 
@@ -63,7 +57,6 @@ describe("observer", () => {
     const obj: any = observer.observe({ date });
 
     expect(observer.revNumber(obj)).toBe(1);
-    expect(observer.deepRevNumber(obj)).toBe(1);
     expect(observer.rev).toBe(1);
     expect(typeof obj.date.getFullYear()).toBe("number");
     expect(obj.date).toBe(date);
@@ -71,25 +64,38 @@ describe("observer", () => {
     obj.date = new Date();
 
     expect(observer.revNumber(obj)).toBe(2);
-    expect(observer.deepRevNumber(obj)).toBe(2);
     expect(observer.rev).toBe(2);
     expect(obj.date).not.toBe(date);
   });
 
+  test("properly handle promises (i.e.: treat them like primitive values", async () => {
+    const observer = new Observer();
+    let resolved = false;
+    const prom = new Promise((r) => r());
+    const obj: any = observer.observe({ prom });
+    expect(obj.prom).toBeInstanceOf(Promise);
+
+    obj.prom.then(() => (resolved = true));
+
+    expect(observer.revNumber(obj)).toBe(1);
+
+    expect(resolved).toBe(false);
+    await Promise.resolve();
+    expect(resolved).toBe(true);
+    expect(observer.revNumber(obj)).toBe(1);
+  });
+
   test("can change values in array", () => {
     const observer = new Observer();
     const obj: any = observer.observe({ arr: [1, 2] });
 
     expect(Array.isArray(obj.arr)).toBe(true);
     expect(observer.revNumber(obj.arr)).toBe(1);
-    expect(observer.deepRevNumber(obj.arr)).toBe(1);
     expect(observer.rev).toBe(1);
 
     obj.arr[0] = "nope";
     expect(observer.revNumber(obj.arr)).toBe(2);
-    expect(observer.deepRevNumber(obj.arr)).toBe(2);
-    expect(observer.revNumber(obj)).toBe(1);
-    expect(observer.deepRevNumber(obj)).toBe(2);
+    expect(observer.revNumber(obj)).toBe(2);
     expect(observer.rev).toBe(2);
   });
 
@@ -98,24 +104,20 @@ describe("observer", () => {
     const obj: any = observer.observe({ a: 1 });
 
     expect(observer.revNumber(obj)).toBe(1);
-    expect(observer.deepRevNumber(obj)).toBe(1);
     expect(observer.rev).toBe(1);
 
     obj.a = 2;
 
     expect(observer.revNumber(obj)).toBe(2);
-    expect(observer.deepRevNumber(obj)).toBe(2);
     expect(observer.rev).toBe(2);
 
     // same value again
     obj.a = 2;
     expect(observer.revNumber(obj)).toBe(2);
-    expect(observer.deepRevNumber(obj)).toBe(2);
     expect(observer.rev).toBe(2);
 
     obj.a = 3;
     expect(observer.revNumber(obj)).toBe(3);
-    expect(observer.deepRevNumber(obj)).toBe(3);
     expect(observer.rev).toBe(3);
   });
 
@@ -126,19 +128,16 @@ describe("observer", () => {
     expect(Array.isArray(arr)).toBe(true);
     expect(arr.length).toBe(0);
     expect(observer.revNumber(arr)).toBe(1);
-    expect(observer.deepRevNumber(arr)).toBe(1);
     expect(observer.rev).toBe(1);
 
     arr.push(1);
     expect(observer.revNumber(arr)).toBe(2);
-    expect(observer.deepRevNumber(arr)).toBe(2);
     expect(observer.rev).toBe(2);
     expect(arr.length).toBe(1);
     expect(arr).toEqual([1]);
 
     arr.splice(1, 0, "hey");
     expect(observer.revNumber(arr)).toBe(3);
-    expect(observer.deepRevNumber(arr)).toBe(3);
     expect(observer.rev).toBe(3);
     expect(arr).toEqual([1, "hey"]);
     expect(arr.length).toBe(2);
@@ -146,7 +145,6 @@ describe("observer", () => {
     arr.unshift("lindemans");
     //it generates 3 primitive operations
     expect(observer.revNumber(arr)).toBe(6);
-    expect(observer.deepRevNumber(arr)).toBe(6);
     expect(observer.rev).toBe(6);
     expect(arr).toEqual(["lindemans", 1, "hey"]);
     expect(arr.length).toBe(3);
@@ -154,21 +152,18 @@ describe("observer", () => {
     arr.reverse();
     //it generates 2 primitive operations
     expect(observer.revNumber(arr)).toBe(8);
-    expect(observer.deepRevNumber(arr)).toBe(8);
     expect(observer.rev).toBe(8);
     expect(arr).toEqual(["hey", 1, "lindemans"]);
     expect(arr.length).toBe(3);
 
     arr.pop(); // one set, one delete
     expect(observer.revNumber(arr)).toBe(10);
-    expect(observer.deepRevNumber(arr)).toBe(10);
     expect(observer.rev).toBe(10);
     expect(arr).toEqual(["hey", 1]);
     expect(arr.length).toBe(2);
 
     arr.shift(); // 2 sets, 1 delete
     expect(observer.revNumber(arr)).toBe(13);
-    expect(observer.deepRevNumber(arr)).toBe(13);
     expect(observer.rev).toBe(13);
     expect(arr).toEqual([1]);
     expect(arr.length).toBe(1);
@@ -187,8 +182,7 @@ describe("observer", () => {
     arr[0].kriek = 6;
 
     expect(observer.rev).toBe(3);
-    expect(observer.revNumber(arr)).toBe(2);
-    expect(observer.deepRevNumber(arr)).toBe(3);
+    expect(observer.revNumber(arr)).toBe(3);
     expect(observer.revNumber(arr[0])).toBe(3);
   });
 
@@ -238,7 +232,6 @@ describe("observer", () => {
 
     expect(observer.rev).toBe(1);
     expect(observer.revNumber(state)).toBe(1);
-    expect(observer.deepRevNumber(state)).toBe(1);
     expect(observer.notifyCB).toBeCalledTimes(0);
 
     state[1] = "b";
@@ -247,7 +240,6 @@ describe("observer", () => {
 
     expect(observer.rev).toBe(2);
     expect(observer.revNumber(state)).toBe(2);
-    expect(observer.deepRevNumber(state)).toBe(2);
     expect(observer.notifyCB).toBeCalledTimes(1);
 
     expect(state).toEqual(["a", "b"]);
@@ -259,13 +251,11 @@ describe("observer", () => {
 
     expect(observer.rev).toBe(1);
     expect(observer.revNumber(state.arr)).toBe(1);
-    expect(observer.deepRevNumber(state.arr)).toBe(1);
     expect(state.arr.length).toBe(0);
 
     state.arr.push(1);
     expect(observer.rev).toBe(2);
     expect(observer.revNumber(state.arr)).toBe(2);
-    expect(observer.deepRevNumber(state.arr)).toBe(2);
     expect(state.arr.length).toBe(1);
   });
 
@@ -280,7 +270,7 @@ describe("observer", () => {
 
     state.arr[0].something = 2;
     expect(observer.rev).toBe(2);
-    expect(observer.revNumber(state.arr)).toBe(1);
+    expect(observer.revNumber(state.arr)).toBe(2);
     expect(observer.revNumber(state.arr[0])).toBe(2);
   });
 
@@ -294,7 +284,7 @@ describe("observer", () => {
 
     state.a.b = 2;
     expect(observer.rev).toBe(2);
-    expect(observer.revNumber(state)).toBe(1);
+    expect(observer.revNumber(state)).toBe(2);
     expect(observer.revNumber(state.a)).toBe(2);
   });
 
@@ -312,7 +302,7 @@ describe("observer", () => {
     expect(observer.revNumber(obj.a)).toBe(2);
     obj.a.b = 3;
     expect(observer.rev).toBe(3);
-    expect(observer.revNumber(obj)).toBe(2);
+    expect(observer.revNumber(obj)).toBe(3);
     expect(observer.revNumber(obj.a)).toBe(3);
   });
 
@@ -320,22 +310,18 @@ describe("observer", () => {
     const observer = new Observer();
     const state: any = observer.observe({ o: { a: 1 }, arr: [1], n: 13 });
     expect(observer.revNumber(state)).toBe(1);
-    expect(observer.deepRevNumber(state)).toBe(1);
 
     state.o.a = 2;
     expect(observer.rev).toBe(2);
-    expect(observer.revNumber(state)).toBe(1);
-    expect(observer.deepRevNumber(state)).toBe(2);
+    expect(observer.revNumber(state)).toBe(2);
 
     state.arr.push(2);
     expect(observer.rev).toBe(3);
-    expect(observer.revNumber(state)).toBe(1);
-    expect(observer.deepRevNumber(state)).toBe(3);
+    expect(observer.revNumber(state)).toBe(3);
 
     state.n = 155;
     expect(observer.rev).toBe(4);
-    expect(observer.revNumber(state)).toBe(2);
-    expect(observer.deepRevNumber(state)).toBe(4);
+    expect(observer.revNumber(state)).toBe(4);
   });
 
   test("properly handle already observed state", () => {
@@ -361,18 +347,15 @@ describe("observer", () => {
     const obj: any = observer.observe({});
 
     expect(observer.revNumber(obj)).toBe(1);
-    expect(observer.deepRevNumber(obj)).toBe(1);
     expect(observer.rev).toBe(1);
 
     obj.aku = "always finds annoying problems";
     expect(observer.revNumber(obj)).toBe(2);
-    expect(observer.deepRevNumber(obj)).toBe(2);
     expect(observer.rev).toBe(2);
 
     obj.aku = "always finds good problems";
 
     expect(observer.revNumber(obj)).toBe(3);
-    expect(observer.deepRevNumber(obj)).toBe(3);
     expect(observer.rev).toBe(3);
   });
 
@@ -416,7 +399,7 @@ describe("observer", () => {
     expect(observer.revNumber(obj2)).toBe(1);
 
     obj2.key = 3;
-    expect(observer.revNumber(obj1)).toBe(1);
+    expect(observer.revNumber(obj1)).toBe(2);
     expect(observer.revNumber(obj2)).toBe(2);
   });
 
@@ -442,7 +425,7 @@ describe("observer", () => {
     obj.a = 111;
     obj.f = 222;
     await nextMicroTick();
-    expect(observer.notifyCB).toBeCalledTimes(4);
+    expect(observer.notifyCB).toBeCalledTimes(5);
   });
 
   test("throw error when state is mutated in object if allowMutation=false", async () => {

tests/doc_link_checker.test.ts

@@ -1,131 +0,0 @@
-/**
- * Doc Link Checker
- *
- * We define here a test to make sure that there are no dead link in the Owl
- * documentation.
- */
-import * as fs from "fs";
-
-const LINK_REGEXP = /\[([^\[]+)\]\(([^\)]+)\)/g;
-const HEADING_REGEXP = /\n(#+\s*)(.*)/g;
-
-// files to be checked
-function getFiles(): string[] {
-  const DOCFILES = fs.readdirSync("doc").map(f => `doc/${f}`);
-  const MAINREADME = "README.md";
-  DOCFILES.push("roadmap.md", MAINREADME);
-  return DOCFILES;
-}
-
-test("All markdown links work", () => {
-  let linkNumber = 0;
-  let invalidLinkNumber = 0;
-  const files = getFiles();
-  const data = readDocData(files);
-  for (let file of data) {
-    for (let link of file.links) {
-      // DEBUG: uncomment next line
-      // console.warn(`Checking "${link.name}" in "${file.name}"`);
-      linkNumber++;
-      if (!isLinkValid(link, file, data)) {
-        console.warn(`Invalid Link: "${link.name}" in "${file.name}"`);
-        invalidLinkNumber++;
-      }
-    }
-  }
-  expect(invalidLinkNumber).toBe(0);
-  expect(linkNumber).toBeGreaterThan(10);
-});
-
-interface MarkDownLink {
-  name: string;
-  link: string;
-}
-
-interface MarkDownSection {
-  name: string;
-  slug: string;
-}
-
-interface FileData {
-  name: string;
-  links: MarkDownLink[];
-  sections: MarkDownSection[];
-}
-
-function isLinkValid(link: MarkDownLink, current: FileData, files: FileData[]): boolean {
-  if (link.link.startsWith("http")) {
-    // no check on external links
-    return true;
-  }
-  const parts = link.link.split("#");
-  const currentParts = current.name.split("/");
-  const path = currentParts.length > 1 ? currentParts[0] + "/" : "";
-  const fullName = path + parts[0];
-  if (parts.length === 1) {
-    // no # in url
-    if (parts[0].endsWith(".md")) {
-      // it is a local md file
-      if (!files.find(f => f.name === fullName)) {
-        return false;
-      }
-    }
-  } else {
-    const file = parts[0] === "" ? current : files.find(f => f.name === fullName);
-    if (!file) {
-      return false;
-    }
-    if (!file.sections.find(s => s.slug === parts[1])) {
-      return false;
-    }
-  }
-  return true;
-}
-// adapted from https://medium.com/@mhagemann/the-ultimate-way-to-slugify-a-url-string-in-javascript-b8e4a0d849e1
-function slugify(str) {
-  const a = "àáäâãåăæçèéëêǵḧìíïîḿńǹñòóöôœøṕŕßśșțùúüûǘẃẍÿź·_,:;";
-  const b = "aaaaaaaaceeeeghiiiimnnnooooooprssstuuuuuwxyz-----";
-  const p = new RegExp(a.split("").join("|"), "g");
-  return str
-    .toString()
-    .toLowerCase()
-    .replace(/\//g, "") // remove /
-    .replace(/\s+/g, "-") // Replace spaces with -
-    .replace(p, c => b.charAt(a.indexOf(c))) // Replace special characters
-    .replace(/&/g, "-and-") // Replace & with ‘and’
-    .replace(/[^\w\-]+/g, "") // Remove all non-word characters
-    .replace(/\-\-+/g, "-") // Replace multiple - with single -
-    .replace(/^-+/, "") // Trim - from start of text
-    .replace(/-+$/, ""); // Trim - from end of text
-}
-
-function readDocData(files: string[]): FileData[] {
-  const result: FileData[] = [];
-
-  for (let file of files) {
-    const fileData: FileData = {
-      name: file,
-      links: [],
-      sections: []
-    };
-    const content = fs.readFileSync(file, { encoding: "utf8" });
-    let m;
-    // get links info
-    do {
-      m = LINK_REGEXP.exec(content);
-      if (m) {
-        fileData.links.push({ name: m[0], link: m[2] });
-      }
-    } while (m);
-    // get sections info
-    do {
-      m = HEADING_REGEXP.exec(content);
-      if (m) {
-        fileData.sections.push({ name: m[0], slug: slugify(m[2]) });
-      }
-    } while (m);
-
-    result.push(fileData);
-  }
-  return result;
-}

tests/helpers.ts

@@ -1,15 +1,12 @@
-import { Env, scheduler } from "../src/component/component";
+import { Env, Component, STATUS } from "../src/component/component";
+import { scheduler } from "../src/component/scheduler";
 import { EvalContext, QWeb } from "../src/qweb/qweb";
+import { CompilationContext } from "../src/qweb/compilation_context";
 import { patch } from "../src/vdom";
 import "../src/qweb/base_directives";
 import "../src/qweb/extensions";
 import "../src/component/directive";
-
-// modifies scheduler to make it faster to test components
-scheduler.requestAnimationFrame = function(callback: FrameRequestCallback) {
-  setTimeout(callback, 1);
-  return 1;
-};
+import { browser } from "../src/browser";
 
 // Some static cleanup
 let nextSlotId;
@@ -19,9 +16,11 @@ let TEMPLATES;
 
 beforeEach(() => {
   nextSlotId = QWeb.nextSlotId;
+  CompilationContext.nextID = 1;
   slots = Object.assign({}, QWeb.slots);
   nextId = QWeb.nextId;
   TEMPLATES = Object.assign({}, QWeb.TEMPLATES);
+  Component.scheduler.tasks = [];
 });
 
 afterEach(() => {
@@ -29,6 +28,7 @@ afterEach(() => {
   QWeb.slots = slots;
   QWeb.nextId = nextId;
   QWeb.TEMPLATES = TEMPLATES;
+  Component.scheduler.tasks = [];
 });
 
 // helpers
@@ -37,9 +37,13 @@ export function nextMicroTick(): Promise<void> {
 }
 
 export async function nextTick(): Promise<void> {
-  return new Promise(function(resolve) {
-    setTimeout(() => scheduler.requestAnimationFrame(() => resolve()));
-  });
+  await new Promise((resolve) => setTimeout(resolve));
+  await new Promise((resolve) => scheduler.requestAnimationFrame(resolve));
+}
+
+export async function nextFrame(): Promise<void> {
+  await new Promise((resolve) => scheduler.requestAnimationFrame(resolve));
+  await new Promise((resolve) => scheduler.requestAnimationFrame(resolve));
 }
 
 export function makeTestFixture() {
@@ -70,7 +74,8 @@ export function makeDeferred(): Deferred {
 
 export function makeTestEnv(): Env {
   return {
-    qweb: new QWeb()
+    qweb: new QWeb(),
+    browser: browser,
   };
 }
 
@@ -84,6 +89,11 @@ export function renderToDOM(
   context: EvalContext = {},
   extra?: any
 ): HTMLElement | Text {
+  if (!context.__owl__) {
+    // we add `__owl__` to better simulate a component as context.  This is
+    // particularly important for event handlers added with the `t-on` directive.
+    context.__owl__ = { status: STATUS.MOUNTED };
+  }
   const vnode = qweb.render(template, context, extra);
 
   // we snapshot here the compiled code. This is useful to prevent unwanted code
@@ -113,11 +123,8 @@ export function renderToString(
   context: EvalContext = {},
   extra?: any
 ): string {
-  const node = renderToDOM(qweb, t, context, extra);
-  const result = node instanceof Text ? node.textContent! : node.outerHTML;
-  if (result !== qweb.renderToString(t, context, extra)) {
-    throw new Error("HTML string returned by renderToString helper does not match QWeb render");
-  }
+  const result = qweb.renderToString(t, context, extra);
+  expect(qweb.templates[t].fn.toString()).toMatchSnapshot();
   return result;
 }
 
@@ -125,7 +132,7 @@ export function renderToString(
 // is useful for animations tests, as we hook before repaints to trigger
 // animations (thanks to requestAnimationFrame). Patching nextFrame allows to
 // simulate calls to this hook. One must not forget to unpatch afterwards.
-let nextFrame = QWeb.utils.nextFrame;
+let _nextFrame = QWeb.utils.nextFrame;
 export function patchNextFrame(f: Function) {
   QWeb.utils.nextFrame = (cb: () => void) => {
     setTimeout(() => f(cb));
@@ -133,7 +140,7 @@ export function patchNextFrame(f: Function) {
 }
 
 export function unpatchNextFrame() {
-  QWeb.utils.nextFrame = nextFrame;
+  QWeb.utils.nextFrame = _nextFrame;
 }
 
 export async function editInput(input: HTMLInputElement | HTMLTextAreaElement, value: string) {

tests/hooks.test.ts

@@ -9,7 +9,10 @@ import {
   onWillPatch,
   onWillStart,
   onWillUpdateProps,
-  useSubEnv
+  useEnv,
+  useSubEnv,
+  useExternalListener,
+  useComponent,
 } from "../src/hooks";
 import { xml } from "../src/tags";
 
@@ -28,6 +31,7 @@ let env: Env;
 beforeEach(() => {
   fixture = makeTestFixture();
   env = makeTestEnv();
+  Component.env = env;
 });
 
 afterEach(() => {
@@ -40,11 +44,11 @@ afterEach(() => {
 
 describe("hooks", () => {
   test("can use a state hook", async () => {
-    class Counter extends Component<any, any> {
+    class Counter extends Component {
       static template = xml`<div><t t-esc="counter.value"/></div>`;
       counter = useState({ value: 42 });
     }
-    const counter = new Counter(env);
+    const counter = new Counter();
     await counter.mount(fixture);
     expect(fixture.innerHTML).toBe("<div>42</div>");
     counter.counter.value = 3;
@@ -62,14 +66,14 @@ describe("hooks", () => {
         steps.push("willunmount");
       });
     }
-    class MyComponent extends Component<any, any> {
+    class MyComponent extends Component {
       static template = xml`<div>hey</div>`;
-      constructor(env) {
-        super(env);
+      constructor() {
+        super();
         useMyHook();
       }
     }
-    const component = new MyComponent(env);
+    const component = new MyComponent();
     await component.mount(fixture);
     expect(component).not.toHaveProperty("mounted");
     expect(component).not.toHaveProperty("willUnmount");
@@ -90,20 +94,20 @@ describe("hooks", () => {
         steps.push("willunmount");
       });
     }
-    class MyComponent extends Component<any, any> {
+    class MyComponent extends Component {
       static template = xml`<div>hey</div>`;
-      constructor(env) {
-        super(env);
+      constructor(parent, props) {
+        super(parent, props);
         useMyHook();
       }
     }
 
-    class Parent extends Component<any, any> {
+    class Parent extends Component {
       static template = xml`<div><MyComponent t-if="state.flag"/></div>`;
       static components = { MyComponent };
       state = useState({ flag: true });
     }
-    const parent = new Parent(env);
+    const parent = new Parent();
     await parent.mount(fixture);
     expect(fixture.innerHTML).toBe("<div><div>hey</div></div>");
     expect(steps).toEqual(["mounted"]);
@@ -124,10 +128,10 @@ describe("hooks", () => {
         steps.push("hook:willunmount");
       });
     }
-    class MyComponent extends Component<any, any> {
+    class MyComponent extends Component {
       static template = xml`<div>hey</div>`;
-      constructor(env) {
-        super(env);
+      constructor() {
+        super();
         useMyHook();
       }
       mounted() {
@@ -137,7 +141,7 @@ describe("hooks", () => {
         steps.push("comp:willunmount");
       }
     }
-    const component = new MyComponent(env);
+    const component = new MyComponent();
     await component.mount(fixture);
     expect(fixture.innerHTML).toBe("<div>hey</div>");
     component.unmount();
@@ -155,10 +159,10 @@ describe("hooks", () => {
         steps.push("hook:willunmount");
       });
     }
-    class MyComponent extends Component<any, any> {
+    class MyComponent extends Component {
       static template = xml`<div>hey</div>`;
-      constructor(env) {
-        super(env);
+      constructor(parent, props) {
+        super(parent, props);
         useMyHook();
       }
       mounted() {
@@ -169,13 +173,13 @@ describe("hooks", () => {
       }
     }
 
-    class Parent extends Component<any, any> {
+    class Parent extends Component {
       static template = xml`<div><MyComponent t-if="state.flag"/></div>`;
       static components = { MyComponent };
       state = useState({ flag: true });
     }
 
-    const parent = new Parent(env);
+    const parent = new Parent();
     await parent.mount(fixture);
     expect(fixture.innerHTML).toBe("<div><div>hey</div></div>");
     parent.state.flag = false;
@@ -195,15 +199,15 @@ describe("hooks", () => {
         steps.push("hook:willunmount" + i);
       });
     }
-    class MyComponent extends Component<any, any> {
+    class MyComponent extends Component {
       static template = xml`<div>hey</div>`;
-      constructor(env) {
-        super(env);
+      constructor() {
+        super();
         useMyHook(1);
         useMyHook(2);
       }
     }
-    const component = new MyComponent(env);
+    const component = new MyComponent();
     await component.mount(fixture);
     expect(fixture.innerHTML).toBe("<div>hey</div>");
     component.unmount();
@@ -212,12 +216,12 @@ describe("hooks", () => {
       "hook:mounted1",
       "hook:mounted2",
       "hook:willunmount2",
-      "hook:willunmount1"
+      "hook:willunmount1",
     ]);
   });
 
   test("useRef hook", async () => {
-    class Counter extends Component<any, any> {
+    class Counter extends Component {
       static template = xml`<div><button t-ref="button"><t t-esc="value"/></button></div>`;
       button = useRef("button");
       value = 0;
@@ -226,9 +230,12 @@ describe("hooks", () => {
         (this.button.el as HTMLButtonElement).innerHTML = String(this.value);
       }
     }
-    const counter = new Counter(env);
+    const counter = new Counter();
+    expect(counter.button.el).toBe(null);
     await counter.mount(fixture);
     expect(fixture.innerHTML).toBe("<div><button>0</button></div>");
+    expect(counter.button.el).not.toBe(null);
+    expect(counter.button.el).toBe(fixture.querySelector("button"));
     counter.increment();
     await nextTick();
     expect(fixture.innerHTML).toBe("<div><button>1</button></div>");
@@ -236,7 +243,7 @@ describe("hooks", () => {
 
   test("useRef hook is null if ref is removed ", async () => {
     expect.assertions(4);
-    class TestRef extends Component<any, any> {
+    class TestRef extends Component {
       static template = xml`<div><span t-if="state.flag" t-ref="span">owl</span></div>`;
       spanRef = useRef("span");
       state = useState({ flag: true });
@@ -247,7 +254,7 @@ describe("hooks", () => {
         expect(this.spanRef.el).toBeNull();
       }
     }
-    const component = new TestRef(env);
+    const component = new TestRef();
     await component.mount(fixture);
     expect(fixture.innerHTML).toBe("<div><span>owl</span></div>");
     component.state.flag = false;
@@ -255,6 +262,104 @@ describe("hooks", () => {
     expect(fixture.innerHTML).toBe("<div></div>");
   });
 
+  test("t-refs on widget are components", async () => {
+    class WidgetB extends Component {
+      static template = xml`<div>b</div>`;
+    }
+    class WidgetC extends Component {
+      static template = xml`<div class="outer-div">Hello<WidgetB t-ref="mywidgetb" /></div>`;
+      static components = { WidgetB };
+      ref = useRef<WidgetB>("mywidgetb");
+    }
+
+    const widget = new WidgetC();
+    expect(widget.ref.comp).toBe(null);
+    expect(widget.ref.el).toBe(null);
+    await widget.mount(fixture);
+    expect(widget.ref.comp).toBeInstanceOf(WidgetB);
+    expect(widget.ref.el).toEqual(fixture.querySelector(".outer-div > div"));
+  });
+
+  test("t-refs are bound at proper timing", async () => {
+    expect.assertions(2);
+    class Widget extends Component {
+      static template = xml`<div>widget</div>`;
+    }
+
+    class ParentWidget extends Component {
+      static template = xml`
+        <div>
+          <t t-foreach="state.list" t-as="elem" t-ref="child" t-key="elem" t-component="Widget"/>
+        </div>
+      `;
+      static components = { Widget };
+      state = useState({ list: <any>[] });
+      child = useRef("child");
+      willPatch() {
+        expect(this.child.comp).toBeNull();
+      }
+      patched() {
+        expect(this.child.comp).not.toBeNull();
+      }
+    }
+
+    const parent = new ParentWidget();
+    await parent.mount(fixture);
+    parent.state.list.push(1);
+    await nextTick();
+  });
+
+  test("t-refs are bound at proper timing (2)", async () => {
+    expect.assertions(10);
+    class Widget extends Component {
+      static template = xml`<div>widget</div>`;
+    }
+    class ParentWidget extends Component {
+      static template = xml`
+        <div>
+          <t t-if="state.child1" t-ref="child1" t-component="Widget"/>
+          <t t-if="state.child2" t-ref="child2" t-component="Widget"/>
+        </div>`;
+      static components = { Widget };
+      state = useState({ child1: true, child2: false });
+      child1 = useRef("child1");
+      child2 = useRef("child2");
+      count = 0;
+      mounted() {
+        expect(this.child1.comp).toBeDefined();
+        expect(this.child2.comp).toBeNull();
+      }
+      willPatch() {
+        if (this.count === 0) {
+          expect(this.child1.comp).toBeDefined();
+          expect(this.child2.comp).toBeNull();
+        }
+        if (this.count === 1) {
+          expect(this.child1.comp).toBeDefined();
+          expect(this.child2.comp).toBeDefined();
+        }
+      }
+      patched() {
+        if (this.count === 0) {
+          expect(this.child1.comp).toBeDefined();
+          expect(this.child2.comp).toBeDefined();
+        }
+        if (this.count === 1) {
+          expect(this.child1.comp).toBeNull();
+          expect(this.child2.comp).toBeDefined();
+        }
+        this.count++;
+      }
+    }
+
+    const parent = new ParentWidget();
+    await parent.mount(fixture);
+    parent.state.child2 = true;
+    await nextTick();
+    parent.state.child1 = false;
+    await nextTick();
+  });
+
   test("can use onPatched, onWillPatch", async () => {
     const steps: string[] = [];
     function useMyHook() {
@@ -266,17 +371,17 @@ describe("hooks", () => {
       });
     }
 
-    class MyComponent extends Component<any, any> {
+    class MyComponent extends Component {
       static template = xml`<div><t t-if="state.flag">hey</t></div>`;
       state = useState({ flag: true });
 
-      constructor(env) {
-        super(env);
+      constructor() {
+        super();
         useMyHook();
       }
     }
 
-    const component = new MyComponent(env);
+    const component = new MyComponent();
     await component.mount(fixture);
     expect(component).not.toHaveProperty("patched");
     expect(component).not.toHaveProperty("willPatch");
@@ -300,12 +405,12 @@ describe("hooks", () => {
         steps.push("hook:willPatch");
       });
     }
-    class MyComponent extends Component<any, any> {
+    class MyComponent extends Component {
       static template = xml`<div><t t-if="state.flag">hey</t></div>`;
       state = useState({ flag: true });
 
-      constructor(env) {
-        super(env);
+      constructor() {
+        super();
         useMyHook();
       }
       willPatch() {
@@ -315,7 +420,7 @@ describe("hooks", () => {
         steps.push("comp:patched");
       }
     }
-    const component = new MyComponent(env);
+    const component = new MyComponent();
     await component.mount(fixture);
     expect(fixture.innerHTML).toBe("<div>hey</div>");
     component.state.flag = false;
@@ -334,16 +439,16 @@ describe("hooks", () => {
         steps.push("hook:willPatch" + i);
       });
     }
-    class MyComponent extends Component<any, any> {
+    class MyComponent extends Component {
       static template = xml`<div>hey<t t-esc="state.value"/></div>`;
       state = useState({ value: 1 });
-      constructor(env) {
-        super(env);
+      constructor() {
+        super();
         useMyHook(1);
         useMyHook(2);
       }
     }
-    const component = new MyComponent(env);
+    const component = new MyComponent();
     await component.mount(fixture);
     expect(fixture.innerHTML).toBe("<div>hey1</div>");
     component.state.value++;
@@ -370,20 +475,20 @@ describe("hooks", () => {
     }
 
     test("simple input", async () => {
-      class SomeComponent extends Component<any, any> {
+      class SomeComponent extends Component {
         static template = xml`
             <div>
                 <input t-ref="input1"/>
                 <input t-ref="input2"/>
             </div>`;
 
-        constructor(env) {
-          super(env);
+        constructor() {
+          super();
           useAutofocus("input2");
         }
       }
 
-      const component = new SomeComponent(env);
+      const component = new SomeComponent();
       await component.mount(fixture);
       expect(fixture.innerHTML).toBe("<div><input><input></div>");
       const input2 = fixture.querySelectorAll("input")[1];
@@ -391,7 +496,7 @@ describe("hooks", () => {
     });
 
     test("input in a t-if", async () => {
-      class SomeComponent extends Component<any, any> {
+      class SomeComponent extends Component {
         static template = xml`
             <div>
                 <input t-ref="input1"/>
@@ -399,13 +504,13 @@ describe("hooks", () => {
             </div>`;
 
         state = useState({ flag: false });
-        constructor(env) {
-          super(env);
+        constructor() {
+          super();
           useAutofocus("input2");
         }
       }
 
-      const component = new SomeComponent(env);
+      const component = new SomeComponent();
       await component.mount(fixture);
       expect(fixture.innerHTML).toBe("<div><input></div>");
       expect(document.activeElement).toBe(document.body);
@@ -417,77 +522,171 @@ describe("hooks", () => {
     });
   });
 
-  test("can use sub env", async () => {
-    class TestComponent extends Component<any, any> {
+  test("can use useEnv", async () => {
+    expect.assertions(1);
+    class TestComponent extends Component {
       static template = xml`<div><t t-esc="env.val"/></div>`;
-      constructor(env) {
-        super(env);
+      constructor() {
+        super();
+        expect(useEnv()).toBe(env);
+      }
+    }
+    const component = new TestComponent();
+    await component.mount(fixture);
+  });
+
+  test("can use sub env", async () => {
+    class TestComponent extends Component {
+      static template = xml`<div><t t-esc="env.val"/></div>`;
+      constructor() {
+        super();
         useSubEnv({ val: 3 });
       }
     }
-    const component = new TestComponent(env);
+    const component = new TestComponent();
     await component.mount(fixture);
     expect(fixture.innerHTML).toBe("<div>3</div>");
     expect(env).not.toHaveProperty("val");
     expect(component.env).toHaveProperty("val");
   });
 
+  test("can use useComponent", async () => {
+    expect.assertions(1);
+    class TestComponent extends Component {
+      static template = xml`<div></div>`;
+      constructor() {
+        super();
+        expect(useComponent()).toBe(this);
+      }
+    }
+    const component = new TestComponent();
+    await component.mount(fixture);
+  });
+
   test("parent and child env", async () => {
-    class Child extends Component<any, any> {
+    class Child extends Component {
       static template = xml`<div><t t-esc="env.val"/></div>`;
-      constructor(env) {
-        super(env);
+      constructor(parent, props) {
+        super(parent, props);
         useSubEnv({ val: 5 });
       }
     }
 
-    class Parent extends Component<any, any> {
+    class Parent extends Component {
       static template = xml`<div><t t-esc="env.val"/><Child/></div>`;
       static components = { Child };
-      constructor(env) {
-        super(env);
+      constructor() {
+        super();
         useSubEnv({ val: 3 });
       }
     }
-    const component = new Parent(env);
+    const component = new Parent();
     await component.mount(fixture);
     expect(fixture.innerHTML).toBe("<div>3<div>5</div></div>");
   });
 
   test("can use onWillStart, onWillUpdateProps", async () => {
     const steps: string[] = [];
+    async function slow(): Promise<string> {
+      return new Promise((resolve) => {
+        setTimeout(() => {
+          resolve("slow");
+        }, 0);
+      });
+    }
     function useMyHook() {
-      onWillStart(() => {
+      onWillStart(async () => {
+        steps.push(await slow());
         steps.push("onWillStart");
       });
-      onWillUpdateProps(nextProps => {
+      onWillUpdateProps(async (nextProps) => {
         expect(nextProps).toEqual({ value: 2 });
+        steps.push(await slow());
         steps.push("onWillUpdateProps");
       });
     }
-    class MyComponent extends Component<any, any> {
+    function use2ndHook() {
+      onWillStart(() => {
+        steps.push("on2ndStart");
+      });
+      onWillUpdateProps((nextProps) => {
+        expect(nextProps).toEqual({ value: 2 });
+        steps.push("on2ndUpdate");
+      });
+    }
+    class MyComponent extends Component {
       static template = xml`<span><t t-esc="props.value"/></span>`;
       constructor(parent, props) {
         super(parent, props);
         useMyHook();
+        use2ndHook();
       }
     }
-    class App extends Component<any, any> {
+    class App extends Component {
       static template = xml`<div><MyComponent value="state.value"/></div>`;
       static components = { MyComponent };
       state = useState({ value: 1 });
     }
 
-    const app = new App(env);
+    const app = new App();
     await app.mount(fixture);
     expect(app).not.toHaveProperty("willStart");
     expect(app).not.toHaveProperty("willUpdateProps");
     expect(fixture.innerHTML).toBe("<div><span>1</span></div>");
-    expect(steps).toEqual(["onWillStart"]);
+
+    // NOTE: 'on2ndStart' appears first in the list even though
+    // the 'use2ndHook' is declared after 'useMyHook'. This is
+    // because Promise.all is used to call the callbacks specified
+    // in the hooks, which runs them simultaneously.
+    // Additionally, 'slow' should be listed before 'onWillStart'
+    // because call to `slow` is awaited.
+    expect(steps).toEqual(["on2ndStart", "slow", "onWillStart"]);
 
     app.state.value = 2;
     await nextTick();
     expect(fixture.innerHTML).toBe("<div><span>2</span></div>");
-    expect(steps).toEqual(["onWillStart", "onWillUpdateProps"]);
+    expect(steps).toEqual([
+      "on2ndStart",
+      "slow",
+      "onWillStart",
+      "on2ndUpdate",
+      "slow",
+      "onWillUpdateProps",
+    ]);
+  });
+
+  test("useExternalListener", async () => {
+    let n = 0;
+
+    class MyComponent extends Component {
+      static template = xml`<span><t t-esc="props.value"/></span>`;
+      constructor(parent, props) {
+        super(parent, props);
+        useExternalListener(window as any, "click", this.increment);
+      }
+      increment() {
+        n++;
+      }
+    }
+    class App extends Component {
+      static template = xml`<div><MyComponent t-if="state.flag"/></div>`;
+      static components = { MyComponent };
+      state = useState({ flag: false });
+    }
+
+    const app = new App();
+    await app.mount(fixture);
+
+    expect(n).toBe(0);
+    window.dispatchEvent(new Event("click"));
+    expect(n).toBe(0);
+    app.state.flag = true;
+    await nextTick();
+    window.dispatchEvent(new Event("click"));
+    expect(n).toBe(1);
+    app.state.flag = false;
+    await nextTick();
+    window.dispatchEvent(new Event("click"));
+    expect(n).toBe(1);
   });
 });

tests/misc/async_root.test.ts

@@ -2,7 +2,7 @@ import { AsyncRoot } from "../../src/misc/async_root";
 import { useState } from "../../src/hooks";
 import { xml } from "../../src/tags";
 import { makeDeferred, makeTestFixture, makeTestEnv, nextTick } from "../helpers";
-import { Env, Component } from "../../src/component/component";
+import { Component } from "../../src/component/component";
 
 //------------------------------------------------------------------------------
 // Setup and helpers
@@ -11,14 +11,13 @@ import { Env, Component } from "../../src/component/component";
 // We create before each test:
 // - fixture: a div, appended to the DOM, intended to be the target of dom
 //   manipulations.  Note that it is removed after each test.
-// - env: a WEnv, necessary to create new components
+// - a test env, necessary to create components, that is set as env
 
 let fixture: HTMLElement;
-let env: Env;
 
 beforeEach(() => {
   fixture = makeTestFixture();
-  env = makeTestEnv();
+  Component.env = makeTestEnv();
 });
 
 afterEach(() => {
@@ -28,7 +27,7 @@ afterEach(() => {
 describe("Asyncroot", () => {
   test("delayed component with AsyncRoot component", async () => {
     let def;
-    class Child extends Component<any, any> {
+    class Child extends Component {
       static template = xml`<span><t t-esc="props.val"/></span>`;
     }
     class AsyncChild extends Child {
@@ -36,7 +35,7 @@ describe("Asyncroot", () => {
         return def;
       }
     }
-    class Parent extends Component<any, any> {
+    class Parent extends Component {
       static template = xml`
           <div>
             <button t-on-click="updateApp">Update App State</button>
@@ -55,7 +54,7 @@ describe("Asyncroot", () => {
       }
     }
 
-    const parent = new Parent(env);
+    const parent = new Parent();
     await parent.mount(fixture);
 
     expect(fixture.querySelector(".children")!.innerHTML).toBe("<span>0</span><span>0</span>");
@@ -75,7 +74,7 @@ describe("Asyncroot", () => {
 
   test("fast component with AsyncRoot", async () => {
     let def;
-    class Child extends Component<any, any> {
+    class Child extends Component {
       static template = xml`<span><t t-esc="props.val"/></span>`;
     }
     class AsyncChild extends Child {
@@ -84,7 +83,7 @@ describe("Asyncroot", () => {
       }
     }
 
-    class Parent extends Component<any, any> {
+    class Parent extends Component {
       static template = xml`
           <div>
             <button t-on-click="updateApp">Update App State</button>
@@ -103,7 +102,7 @@ describe("Asyncroot", () => {
       }
     }
 
-    const parent = new Parent(env);
+    const parent = new Parent();
     await parent.mount(fixture);
 
     expect(fixture.querySelector(".children")!.innerHTML).toBe("<span>0</span><span>0</span>");
@@ -123,7 +122,7 @@ describe("Asyncroot", () => {
 
   test("asyncroot component: mixed re-renderings", async () => {
     let def;
-    class Child extends Component<any, any> {
+    class Child extends Component {
       static template = xml`
         <span t-on-click="increment">
           <t t-esc="state.val"/>/<t t-esc="props.val"/>
@@ -139,7 +138,7 @@ describe("Asyncroot", () => {
         return def;
       }
     }
-    class Parent extends Component<any, any> {
+    class Parent extends Component {
       static template = xml`
         <div>
           <button t-on-click="updateApp">Update App State</button>
@@ -158,7 +157,7 @@ describe("Asyncroot", () => {
       }
     }
 
-    const parent = new Parent(env);
+    const parent = new Parent();
     await parent.mount(fixture);
 
     expect(fixture.querySelector(".children")!.innerHTML).toBe("<span>0/0</span><span>0/0</span>");

tests/misc/portal.test.ts

@@ -0,0 +1,890 @@
+import { Portal } from "../../src/misc/portal";
+import { xml } from "../../src/tags";
+import { makeTestFixture, makeTestEnv, nextTick } from "../helpers";
+import { Component } from "../../src/component/component";
+import { useState } from "../../src/hooks";
+import { QWeb } from "../../src/qweb";
+
+//------------------------------------------------------------------------------
+// Setup and helpers
+//------------------------------------------------------------------------------
+
+// We create before each test:
+// - fixture: a div, appended to the DOM, intended to be the target of dom
+//   manipulations.  Note that it is removed after each test.
+// - outside: a div with id #outside appended into fixture, meant to be used as
+//   target by Portal component
+// - a test env, necessary to create components, that is set on Component
+
+let fixture: HTMLElement;
+let outside: HTMLElement;
+
+beforeEach(() => {
+  fixture = makeTestFixture();
+  outside = document.createElement("div");
+  outside.setAttribute("id", "outside");
+  fixture.appendChild(outside);
+
+  Component.env = makeTestEnv();
+});
+
+afterEach(() => {
+  fixture.remove();
+});
+
+describe("Portal: Props validation", () => {
+  test("target is mandatory", async () => {
+    const dev = QWeb.dev;
+    QWeb.dev = true;
+    class Parent extends Component {
+      static components = { Portal };
+      static template = xml`
+        <div>
+          <Portal>
+            <div>2</div>
+          </Portal>
+        </div>`;
+    }
+    let error;
+    try {
+      const parent = new Parent();
+      await parent.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe(`Missing props 'target' (component 'Portal')`);
+
+    QWeb.dev = dev;
+  });
+
+  test("target is not list", async () => {
+    const dev = QWeb.dev;
+    QWeb.dev = true;
+    class Parent extends Component {
+      static components = { Portal };
+      static template = xml`
+        <div>
+          <Portal target="['body']">
+            <div>2</div>
+          </Portal>
+        </div>`;
+    }
+    let error;
+    try {
+      const parent = new Parent();
+      await parent.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe(`Invalid Prop 'target' in component 'Portal'`);
+
+    QWeb.dev = dev;
+  });
+});
+
+describe("Portal: Basic use and DOM placement", () => {
+  test("basic use of portal", async () => {
+    const dev = QWeb.dev;
+    QWeb.dev = true;
+    class Parent extends Component {
+      static components = { Portal };
+      static template = xml`
+        <div>
+          <span>1</span>
+          <Portal target="'#outside'">
+            <div>2</div>
+          </Portal>
+        </div>`;
+    }
+    let error;
+    let parent;
+    try {
+      parent = new Parent();
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+    await parent.mount(fixture);
+    expect(outside.innerHTML).toBe("<div>2</div>");
+    expect(parent.el!.outerHTML).toBe("<div><span>1</span><portal></portal></div>");
+    QWeb.dev = dev;
+  });
+
+  test("conditional use of Portal", async () => {
+    class Parent extends Component {
+      static components = { Portal };
+      static template = xml`
+        <div>
+          <span>1</span>
+          <Portal target="'#outside'" t-if="state.hasPortal">
+            <div>2</div>
+          </Portal>
+        </div>`;
+
+      state = useState({ hasPortal: false });
+    }
+
+    const parent = new Parent();
+    await parent.mount(fixture);
+    expect(outside.innerHTML).toBe("");
+    expect(parent.el!.outerHTML).toBe("<div><span>1</span></div>");
+
+    parent.state.hasPortal = true;
+    await nextTick();
+    expect(outside.innerHTML).toBe("<div>2</div>");
+    expect(parent.el!.outerHTML).toBe("<div><span>1</span><portal></portal></div>");
+
+    parent.state.hasPortal = false;
+    await nextTick();
+    expect(outside.innerHTML).toBe("");
+    expect(parent.el!.outerHTML).toBe("<div><span>1</span></div>");
+
+    parent.state.hasPortal = true;
+    await nextTick();
+    expect(outside.innerHTML).toBe("<div>2</div>");
+    expect(parent.el!.outerHTML).toBe("<div><span>1</span><portal></portal></div>");
+  });
+
+  test("conditional use of Portal (with sub Component)", async () => {
+    class Child extends Component {
+      static template = xml`<div><t t-esc="props.val"/></div>`;
+    }
+    class Parent extends Component {
+      static components = { Portal, Child };
+      static template = xml`
+        <div>
+          <span>1</span>
+          <Portal t-if="state.hasPortal" target="'#outside'">
+            <Child val="state.val"/>
+          </Portal>
+        </div>`;
+      state = useState({ hasPortal: false, val: 1 });
+    }
+
+    const parent = new Parent();
+    await parent.mount(fixture);
+    expect(outside.innerHTML).toBe("");
+    expect(parent.el!.outerHTML).toBe("<div><span>1</span></div>");
+
+    parent.state.hasPortal = true;
+    await nextTick();
+    expect(outside.innerHTML).toBe("<div>1</div>");
+    expect(parent.el!.outerHTML).toBe("<div><span>1</span><portal></portal></div>");
+
+    parent.state.hasPortal = false;
+    await nextTick();
+    expect(outside.innerHTML).toBe("");
+    expect(parent.el!.outerHTML).toBe("<div><span>1</span></div>");
+
+    parent.state.val = 2;
+    await nextTick();
+    expect(outside.innerHTML).toBe("");
+    expect(parent.el!.outerHTML).toBe("<div><span>1</span></div>");
+
+    parent.state.hasPortal = true;
+    await nextTick();
+    expect(outside.innerHTML).toBe("<div>2</div>");
+    expect(parent.el!.outerHTML).toBe("<div><span>1</span><portal></portal></div>");
+  });
+
+  test("with target in template (before portal)", async () => {
+    class Parent extends Component {
+      static components = { Portal };
+      static template = xml`
+        <div>
+          <div id="local-target"></div>
+          <span>1</span>
+          <Portal target="'#local-target'">
+            <p>2</p>
+          </Portal>
+        </div>`;
+    }
+
+    const parent = new Parent();
+    await parent.mount(fixture);
+    expect(parent.el!.innerHTML).toBe(
+      '<div id="local-target"><p>2</p></div><span>1</span><portal></portal>'
+    );
+  });
+
+  test("with target in template (after portal)", async () => {
+    class Parent extends Component {
+      static components = { Portal };
+      static template = xml`
+        <div>
+          <span>1</span>
+          <Portal target="'#local-target'">
+            <p>2</p>
+          </Portal>
+          <div id="local-target"></div>
+        </div>`;
+    }
+
+    const parent = new Parent();
+    await parent.mount(fixture);
+    expect(parent.el!.innerHTML).toBe(
+      '<span>1</span><portal></portal><div id="local-target"><p>2</p></div>'
+    );
+  });
+
+  test("portal with target not in dom", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+
+    class Parent extends Component {
+      static components = { Portal };
+      static template = xml`
+        <div>
+          <Portal target="'#does-not-exist'">
+            <div>2</div>
+          </Portal>
+        </div>`;
+    }
+
+    const parent = new Parent();
+    let error;
+    try {
+      await parent.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+
+    expect(error).toBeDefined();
+    expect(error.message).toBe('Could not find any match for "#does-not-exist"');
+    expect(console.error).toBeCalledTimes(0);
+    expect(fixture.innerHTML).toBe(`<div id="outside"></div>`);
+    console.error = consoleError;
+  });
+
+  test("portal with child and props", async () => {
+    const steps: string[] = [];
+    class Child extends Component {
+      static template = xml`<span><t t-esc="props.val"/></span>`;
+      mounted() {
+        steps.push("mounted");
+        expect(outside.innerHTML).toBe("<span>1</span>");
+      }
+      patched() {
+        steps.push("patched");
+        expect(outside.innerHTML).toBe("<span>2</span>");
+      }
+    }
+    class Parent extends Component {
+      static components = { Portal, Child };
+      static template = xml`
+        <div>
+          <Portal target="'#outside'">
+            <Child val="state.val"/>
+          </Portal>
+        </div>`;
+      state = useState({ val: 1 });
+    }
+
+    const parent = new Parent();
+    await parent.mount(fixture);
+    expect(outside.innerHTML).toBe("<span>1</span>");
+    expect(parent.el!.innerHTML).toBe("<portal></portal>");
+
+    parent.state.val = 2;
+    await nextTick();
+    expect(outside.innerHTML).toBe("<span>2</span>");
+    expect(parent.el!.innerHTML).toBe("<portal></portal>");
+    expect(steps).toEqual(["mounted", "patched"]);
+  });
+
+  test("portal with only text as content", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+
+    class Parent extends Component {
+      static components = { Portal };
+      static template = xml`
+        <div>
+          <Portal target="'#outside'">
+            <t t-esc="'only text'"/>
+          </Portal>
+        </div>`;
+    }
+
+    const parent = new Parent();
+    let error;
+    try {
+      await parent.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Portal must have exactly one non-text child (has 0)");
+    expect(console.error).toBeCalledTimes(0);
+    expect(fixture.innerHTML).toBe(`<div id="outside"></div>`);
+    console.error = consoleError;
+  });
+
+  test("portal with no content", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+
+    class Parent extends Component {
+      static components = { Portal };
+      static template = xml`
+        <div>
+          <Portal target="'#outside'">
+            <t t-if="false" t-esc="'ABC'"/>
+          </Portal>
+        </div>`;
+    }
+
+    const parent = new Parent();
+    let error;
+    try {
+      await parent.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Portal must have exactly one non-text child (has 0)");
+    expect(console.error).toBeCalledTimes(0);
+    expect(fixture.innerHTML).toBe(`<div id="outside"></div>`);
+    console.error = consoleError;
+  });
+
+  test("portal with many children", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+
+    class Parent extends Component {
+      static components = { Portal };
+      static template = xml`
+        <div>
+          <Portal target="'#outside'">
+            <div>1</div>
+            <p>2</p>
+          </Portal>
+        </div>`;
+    }
+    const parent = new Parent();
+    let error;
+    try {
+      await parent.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Portal must have exactly one non-text child (has 2)");
+    expect(console.error).toBeCalledTimes(0);
+    expect(fixture.innerHTML).toBe(`<div id="outside"></div>`);
+    console.error = consoleError;
+  });
+
+  test("portal with dynamic body", async () => {
+    class Parent extends Component {
+      static components = { Portal };
+      static template = xml`
+        <div>
+          <Portal target="'#outside'">
+            <span t-if="state.val" t-esc="state.val"/>
+            <div t-else=""/>
+          </Portal>
+        </div>`;
+      state = useState({ val: "ab" });
+    }
+
+    const parent = new Parent();
+    await parent.mount(fixture);
+
+    expect(outside.innerHTML).toBe(`<span>ab</span>`);
+
+    parent.state.val = "";
+    await nextTick();
+    expect(outside.innerHTML).toBe(`<div></div>`);
+  });
+
+  test("portal could have dynamically no content", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+
+    class Parent extends Component {
+      static components = { Portal };
+      static template = xml`
+        <div>
+          <Portal target="'#outside'">
+            <span t-if="state.val" t-esc="state.val"/>
+          </Portal>
+        </div>`;
+      state = { val: "ab" };
+    }
+    const parent = new Parent();
+    await parent.mount(fixture);
+
+    expect(outside.innerHTML).toBe(`<span>ab</span>`);
+
+    let error;
+    try {
+      parent.state.val = "";
+      await parent.render();
+    } catch (e) {
+      error = e;
+    }
+    expect(outside.innerHTML).toBe(``);
+
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Portal must have exactly one non-text child (has 0)");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test("lifecycle hooks of portal sub component are properly called", async () => {
+    const steps: any[] = [];
+
+    class Child extends Component {
+      static template = xml`<span t-esc="props.val"/>`;
+      mounted() {
+        steps.push("child:mounted");
+      }
+      willPatch() {
+        steps.push("child:willPatch");
+      }
+      patched() {
+        steps.push("child:patched");
+      }
+      willUnmount() {
+        steps.push("child:willUnmount");
+      }
+    }
+    class Parent extends Component {
+      static components = { Portal, Child };
+      static template = xml`
+        <div>
+          <Portal t-if="state.hasChild" target="'#outside'">
+            <Child val="state.val"/>
+          </Portal>
+        </div>`;
+      state = useState({ hasChild: false, val: 1 });
+      mounted() {
+        steps.push("parent:mounted");
+      }
+      willPatch() {
+        steps.push("parent:willPatch");
+      }
+      patched() {
+        steps.push("parent:patched");
+      }
+      willUnmount() {
+        steps.push("parent:willUnmount");
+      }
+    }
+    const parent = new Parent();
+    await parent.mount(fixture);
+    expect(steps).toEqual(["parent:mounted"]);
+
+    parent.state.hasChild = true;
+    await nextTick();
+    expect(steps).toEqual([
+      "parent:mounted",
+      "parent:willPatch",
+      "child:mounted",
+      "parent:patched",
+    ]);
+
+    parent.state.val = 2;
+    await nextTick();
+    expect(steps).toEqual([
+      "parent:mounted",
+      "parent:willPatch",
+      "child:mounted",
+      "parent:patched",
+      "parent:willPatch",
+      "child:willPatch",
+      "child:patched",
+      "parent:patched",
+    ]);
+
+    parent.state.hasChild = false;
+    await nextTick();
+    expect(steps).toEqual([
+      "parent:mounted",
+      "parent:willPatch",
+      "child:mounted",
+      "parent:patched",
+      "parent:willPatch",
+      "child:willPatch",
+      "child:patched",
+      "parent:patched",
+      "parent:willPatch",
+      "child:willUnmount",
+      "parent:patched",
+    ]);
+  });
+
+  test("portal destroys on crash", async () => {
+    class Child extends Component {
+      static template = xml`<span t-esc="props.error and this.will.crash" />`;
+      state = {};
+    }
+    class Parent extends Component {
+      static components = { Portal, Child };
+      static template = xml`
+        <div>
+          <Portal target="'#outside'" >
+            <Child error="state.error"/>
+          </Portal>
+        </div>`;
+      state = { error: false };
+    }
+
+    const parent = new Parent();
+    await parent.mount(fixture);
+    parent.state.error = true;
+
+    let error;
+    try {
+      await parent.render();
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Cannot read property 'crash' of undefined");
+  });
+
+  test("portal manual unmount", async () => {
+    class Parent extends Component {
+      static components = { Portal };
+      static template = xml`
+        <div>
+          <Portal target="'#outside'">
+            <span>gloria</span>
+          </Portal>
+        </div>`;
+    }
+
+    const parent = new Parent();
+    await parent.mount(fixture);
+
+    expect(outside.innerHTML).toBe("<span>gloria</span>");
+    expect(parent.el!.innerHTML).toBe("<portal></portal>");
+
+    parent.unmount();
+    expect(outside.innerHTML).toBe("");
+    expect(parent.el!.innerHTML).toBe("<portal><span>gloria</span></portal>");
+
+    await parent.mount(fixture);
+    expect(outside.innerHTML).toBe("<span>gloria</span>");
+    expect(parent.el!.innerHTML).toBe("<portal></portal>");
+  });
+
+  test("portal manual unmount with subcomponent", async () => {
+    expect.assertions(9);
+    class Child extends Component {
+      static template = xml`<span>gloria</span>`;
+      mounted() {
+        expect(outside.contains(this.el)).toBeTruthy();
+      }
+      willUnmount() {
+        expect(outside.contains(this.el)).toBeTruthy();
+      }
+    }
+    class Parent extends Component {
+      static components = { Portal, Child };
+      static template = xml`
+        <div>
+          <Portal target="'#outside'">
+            <Child />
+          </Portal>
+        </div>`;
+    }
+
+    const parent = new Parent();
+    await parent.mount(fixture);
+
+    expect(outside.innerHTML).toBe("<span>gloria</span>");
+    expect(parent.el!.innerHTML).toBe("<portal></portal>");
+
+    parent.unmount();
+    expect(outside.innerHTML).toBe("");
+    expect(parent.el!.innerHTML).toBe("<portal><span>gloria</span></portal>");
+
+    await parent.mount(fixture);
+    expect(outside.innerHTML).toBe("<span>gloria</span>");
+    expect(parent.el!.innerHTML).toBe("<portal></portal>");
+  });
+});
+
+describe("Portal: Events handling", () => {
+  test("events triggered on movable pure node are handled", async () => {
+    class Parent extends Component {
+      static components = { Portal };
+      static template = xml`
+        <div>
+          <Portal target="'#outside'">
+            <span id="trigger-me" t-on-custom="_onCustom" t-esc="state.val"/>
+          </Portal>
+        </div>`;
+      state = useState({ val: "ab" });
+
+      _onCustom() {
+        this.state.val = "triggered";
+      }
+    }
+    const parent = new Parent();
+    await parent.mount(fixture);
+
+    expect(outside.innerHTML).toBe(`<span id="trigger-me">ab</span>`);
+    outside.querySelector("#trigger-me")!.dispatchEvent(new Event("custom"));
+    await nextTick();
+    expect(outside.innerHTML).toBe(`<span id="trigger-me">triggered</span>`);
+  });
+
+  test("events triggered on movable owl components are redirected", async () => {
+    let childInst: Component | null = null;
+    class Child extends Component {
+      static template = xml`
+         <span t-on-custom="_onCustom" t-esc="props.val"/>`;
+
+      constructor(parent, props) {
+        super(parent, props);
+        childInst = this;
+      }
+
+      _onCustom() {
+        this.trigger("custom-portal");
+      }
+    }
+    class Parent extends Component {
+      static components = { Portal, Child };
+      static template = xml`
+        <div t-on-custom-portal="_onCustomPortal">
+          <Portal target="'#outside'">
+            <Child val="state.val"/>
+          </Portal>
+        </div>`;
+      state = useState({ val: "ab" });
+
+      _onCustomPortal() {
+        this.state.val = "triggered";
+      }
+    }
+    const parent = new Parent();
+    await parent.mount(fixture);
+
+    expect(outside.innerHTML).toBe(`<span>ab</span>`);
+    childInst!.trigger("custom");
+    await nextTick();
+    expect(outside.innerHTML).toBe(`<span>triggered</span>`);
+  });
+
+  test("events triggered on contained movable owl components are redirected", async () => {
+    const steps: string[] = [];
+    let childInst: Component | null = null;
+    class Child extends Component {
+      static template = xml`
+         <span t-on-custom="_onCustom"/>`;
+
+      constructor(parent, props) {
+        super(parent, props);
+        childInst = this;
+      }
+
+      _onCustom() {
+        this.trigger("custom-portal");
+      }
+    }
+    class Parent extends Component {
+      static components = { Portal, Child };
+      static template = xml`
+        <div t-on-custom="_handled" t-on-custom-portal="_handled">
+          <Portal target="'#outside'">
+            <div>
+              <Child/>
+            </div>
+          </Portal>
+        </div>`;
+
+      _handled(ev) {
+        steps.push(ev.type);
+      }
+    }
+    const parent = new Parent();
+    await parent.mount(fixture);
+
+    childInst!.trigger("custom");
+    await nextTick();
+
+    // This is expected because trigger is synchronous
+    expect(steps).toMatchObject(["custom-portal", "custom"]);
+  });
+
+  test("Dom events are not mapped", async () => {
+    let childInst: Component | null = null;
+    const steps: string[] = [];
+    class Child extends Component {
+      static template = xml`
+        <button>child</button>`;
+
+      constructor(parent, props) {
+        super(parent, props);
+        childInst = this;
+      }
+    }
+    class Parent extends Component {
+      static components = { Portal, Child };
+      static template = xml`
+        <div t-on-click="_handled">
+          <Portal target="'#outside'">
+            <Child />
+          </Portal>
+        </div>`;
+
+      _handled(ev) {
+        steps.push(ev.type as string);
+      }
+    }
+    const bodyListener = (ev) => {
+      steps.push(`body: ${ev.type}`);
+    };
+    document.body.addEventListener("click", bodyListener);
+
+    const parent = new Parent();
+    await parent.mount(fixture);
+    childInst!.el!.click();
+
+    expect(steps).toEqual(["body: click"]);
+    document.body.removeEventListener("click", bodyListener);
+  });
+
+  test("Nested portals event propagation", async () => {
+    const outside2 = document.createElement("div");
+    outside2.setAttribute("id", "outside2");
+    fixture.appendChild(outside2);
+
+    const steps: Array<string> = [];
+    let childInst: Component | null = null;
+    class Child2 extends Component {
+      static template = xml`<div>child2</div>`;
+      constructor(parent, props) {
+        super(parent, props);
+        childInst = this;
+      }
+    }
+    class Child extends Component {
+      static components = { Portal, Child2 };
+      static template = xml`
+        <Portal target="'#outside2'">
+          <Child2 />
+        </Portal>`;
+    }
+    class Parent extends Component {
+      static components = { Portal, Child };
+      static template = xml`
+        <div t-on-custom='_handled'>
+          <Portal target="'#outside'">
+            <Child/>
+          </Portal>
+        </div>`;
+
+      _handled(ev) {
+        steps.push(`${ev.type} from ${ev.originalComponent.constructor.name}`);
+      }
+    }
+
+    const parent = new Parent();
+    await parent.mount(fixture);
+
+    childInst!.trigger("custom");
+    expect(steps).toEqual(["custom from Child2"]);
+  });
+
+  test("portal's parent's env is not polluted", async () => {
+    class Child extends Component {
+      static template = xml`
+        <button>child</button>`;
+    }
+    class Parent extends Component {
+      static components = { Portal, Child };
+      static template = xml`
+        <div>
+          <Portal target="'#outside'">
+            <Child />
+          </Portal>
+        </div>`;
+    }
+    const parent = new Parent();
+    const parentEnv = Object.assign({}, parent.env);
+    await parent.mount(fixture);
+    expect(parentEnv).toStrictEqual(parent.env);
+  });
+
+  test("Portal composed with t-slot", async () => {
+    const steps: Array<string> = [];
+    let childInst: Component | null = null;
+    class Child2 extends Component {
+      static template = xml`<div>child2</div>`;
+      constructor(parent, props) {
+        super(parent, props);
+        childInst = this;
+      }
+    }
+    class Child extends Component {
+      static components = { Portal, Child2 };
+      static template = xml`
+        <Portal target="'#outside'">
+          <t t-slot="default"/>
+        </Portal>`;
+    }
+    class Parent extends Component {
+      static components = { Child, Child2 };
+      static template = xml`
+        <div t-on-custom='_handled'>
+          <Child>
+            <Child2/>
+          </Child>
+        </div>`;
+
+      _handled(ev) {
+        steps.push(ev.type as string);
+      }
+    }
+
+    const parent = new Parent();
+    await parent.mount(fixture);
+
+    childInst!.trigger("custom");
+    expect(steps).toEqual(["custom"]);
+  });
+});
+
+describe("Portal: UI/UX", () => {
+  test("focus is kept across re-renders", async () => {
+    class Child extends Component {
+      static template = xml`
+        <input id="target-me" t-att-placeholder="props.val"/>`;
+    }
+    class Parent extends Component {
+      static components = { Portal, Child };
+      static template = xml`
+        <div>
+          <Portal target="'#outside'">
+            <Child val="state.val"/>
+          </Portal>
+        </div>`;
+      state = useState({ val: "ab" });
+    }
+    const parent = new Parent();
+    await parent.mount(fixture);
+    const input = document.querySelector("#target-me");
+    expect(input!.nodeName).toBe("INPUT");
+    expect((input as HTMLInputElement).placeholder).toBe("ab");
+
+    (input as HTMLInputElement).focus();
+    expect(document.activeElement === input).toBeTruthy();
+
+    parent.state.val = "bc";
+    await nextTick();
+    const inputReRendered = document.querySelector("#target-me");
+    expect(inputReRendered!.nodeName).toBe("INPUT");
+    expect((inputReRendered as HTMLInputElement).placeholder).toBe("bc");
+    expect(document.activeElement === inputReRendered).toBeTruthy();
+  });
+});

tests/qweb/__snapshots__/qweb_t_tag.test.ts.snap

@@ -0,0 +1,71 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`qweb t-tag simple usecases 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let scope = Object.create(context);
+    let result;
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let tag2 = 'div';
+    let vn1 = h(tag2, p1, c1);
+    result = vn1;
+    return result;
+}"
+`;
+
+exports[`qweb t-tag simple usecases 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let scope = Object.create(context);
+    let result;
+    let h = this.h;
+    let c3 = [], p3 = {key:3};
+    let tag4 = scope['tag'];
+    let vn3 = h(tag4, p3, c3);
+    result = vn3;
+    c3.push({text: \`text\`});
+    return result;
+}"
+`;
+
+exports[`qweb t-tag with multiple attributes 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let scope = Object.create(context);
+    let result;
+    let h = this.h;
+    let _2 = {'blueberry':true};
+    let _3 = 'raspberry';
+    let c4 = [], p4 = {key:4,attrs:{taste: _3},class:_2};
+    let tag5 = scope['tag'];
+    let vn4 = h(tag5, p4, c4);
+    result = vn4;
+    c4.push({text: \`gooseberry\`});
+    return result;
+}"
+`;
+
+exports[`qweb t-tag with multiple child nodes 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let scope = Object.create(context);
+    let result;
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let tag2 = scope['tag'];
+    let vn1 = h(tag2, p1, c1);
+    result = vn1;
+    c1.push({text: \` pear \`});
+    let c3 = [], p3 = {key:3};
+    let vn3 = h('span', p3, c3);
+    c1.push(vn3);
+    c3.push({text: \`apple\`});
+    c1.push({text: \` strawberry \`});
+    return result;
+}"
+`;