[REL] bump to v0.24.1

[IMP] tests: add concurrency test
[DOC] add architecture notes on rendering pipeline
2025-10-06 19:59:41 +07:00 · 2019-10-28 14:58:52 +01:00 · 2019-10-28 14:46:21 +01:00 · 2019-10-28 14:23:02 +01:00 · 2019-10-28 14:23:02 +01:00 · 2019-10-28 13:58:44 +01:00
203 changed files with 67280 additions and 10686 deletions
@@ -1,5 +1,6 @@
 /node_modules
 /dist
+
 npm-debug.log

 # misc
@@ -14,8 +15,12 @@ yarn-debug.log*
 yarn-error.log*

 package-lock.json
+
+#ide's
 .vscode
+.idea
+
 node_modules

 # Extras temp file
-/extras/owl.js
+/tools/owl.js
@@ -0,0 +1,14 @@
+
+Most of the files are
+
+  Copyright (c) 2004-2015 Odoo S.A.
+
+Many files also contain contributions from third
+parties. In this case the original copyright of
+the contributions can be traced through the
+history of the source version control system.
+
+When that is not the case, the files contain a prominent
+notice stating the original copyright and applicable
+license, or come with their own dedicated COPYRIGHT
+and/or LICENSE file.
@@ -1,12 +1,9 @@
-
-For copyright information, please see the COPYRIGHT file.
-
-Odoo is published under the GNU LESSER GENERAL PUBLIC LICENSE, Version 3
+OWL is published under the GNU LESSER GENERAL PUBLIC LICENSE, Version 3
 (LGPLv3), as included below. Since the LGPL is a set of additional
 permissions on top of the GPL, the text of the GPL is included at the
 bottom as well.

-Some external libraries and contributions bundled with Odoo may be published
+Some external libraries and contributions bundled with OWL may be published
 under other GPL-compatible licenses. For these, please refer to the relevant
 source files and/or license files, in the source code tree.

@@ -1,19 +1,70 @@
 <h1 align="center">🦉 <a href="https://odoo.github.io/owl/">Odoo Web Library</a> 🦉</h1>

-_A web framework for structured, dynamic and maintainable applications_
+_A no nonsense web framework for structured, dynamic and maintainable applications_

 ## Project Overview

-The Odoo Web Library (OWL) is a small
-UI framework intended to be the basis for the [Odoo](https://www.odoo.com/) Web Client, and hopefully many
-other Odoo related projects. OWL's main feature is a _declarative component system_, with QWeb as a template engine, asynchronous rendering, and an underlying virtual dom.
+The Odoo Web Library (OWL) is a smallish (~18kb 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:

-**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.
+- a declarative component system,
+- a reactivity system based on hooks,
+- a store implementation (for state management),
+- a small frontend router

-## OWL's design principles
+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.
+
+Owl is currently mostly stable.  Possible future changes are explained in the
+[roadmap](roadmap.md).
+
+## Example
+
+Here is a short example to illustrate interactive components:
+
+```javascript
+const { Component, QWeb, useState } = owl;
+const { xml } = owl.tags;
+
+class Counter extends Component {
+  static template = xml`
+    <button t-on-click="state.value++">
+      Click Me! [<t t-esc="state.value"/>]
+    </button>`;
+
+  state = useState({ value: 0 });
+}
+
+class App extends Component {
+  static template = xml`
+    <div>
+      <span>Hello Owl</span>
+      <Counter />
+    </div>`;
+
+  static components = { Counter };
+}
+
+const app = new App({ qweb: new QWeb() });
+app.mount(document.body);
+```
+
+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
+[playground](https://odoo.github.io/owl/playground) application.
+
+## Design Principles

 OWL is designed to be used in highly dynamic applications where changing
-requirements are common, code needs to be maintained by large teams.
+requirements are common and code needs to be maintained by large teams.

 - **XML based**: templates are based on the XML format, which allows interesting
  applications. For example, they could be stored in a database and modified
@@ -26,17 +77,79 @@ requirements are common, code needs to be maintained by large teams.
  for various reasons (security/deployment/dynamic modules/specific assets tools),
  it is not ok to use standard web tools based on `npm`.

-Owl is not designed to be fast or small (even though it is quite good on those
-two topics). If you are interested in a comparison with React or Vue, you will
+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).
+
+If you are interested in a comparison with React or Vue, you will
 find some more information [here](doc/comparison.md).

-# Example
+## Documentation

-Here is a short example to illustrate interactive widgets:
+A complete documentation for Owl can be found here:

-```javascript
-class ClickCounter extends owl.Component {
-  inlineTemplate = `
+- [Main documentation page](doc/readme.md).
+
+The most important sections are:
+
+- [Quick Start](doc/quick_start.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
+
+If you want to use a simple `<script>` tag, the last release can be downloaded here:
+
+- [owl-0.24.1.js](https://github.com/odoo/owl/releases/download/v0.24.1/owl.js)
+- [owl-0.24.1.min.js](https://github.com/odoo/owl/releases/download/v0.24.1/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](doc/reference/qweb.md). 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>`;
@@ -45,42 +158,111 @@ class ClickCounter extends owl.Component {

  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 });
  }
 }

-const qweb = new owl.QWeb();
-const counter = new ClickCounter({ qweb });
-counter.mount(document.body);
+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++;
+  }
+}
 ```

-More interesting examples can be found on the [playground](https://odoo.github.io/owl/playground) application.
+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/reference/component.md#event-handling)
+for more details on how events work.

-## Installing/Building
-
-If you want to use a simple `<script>` tag, the last release can be downloaded here:
-
- [owl-0.9.0.js](https://github.com/odoo/owl/releases/download/v0.9.0/owl-0.9.0.js)
- [owl-0.9.0.min.js](https://github.com/odoo/owl/releases/download/v0.9.0/owl-0.9.0.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 tests                                                                   |
-| `npm run test:watch` | run all tests, and keep a watcher                                               |
-| `npm run extras`     | build extras applications, start a static server (see [here](extras/readme.md)) |
-
-## Documentation
-
-The complete documentation can be found [here](doc/readme.md). The most important sections are:
-
- [Quick Start](doc/quick_start.md)
- [Component](doc/component.md)
- [QWeb](doc/qweb.md)
+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.

 ## License

-OWL is [GPL licensed](./LICENSE).
+OWL is [LGPL licensed](./LICENSE).
@@ -1,39 +0,0 @@
-# 🦉 Animations 🦉
-
-
-Animation is a complex topic. There are many different use cases, and many
-solutions and technologies.
-
-## Simple CSS effects
-
-Sometimes, using pure CSS is enough.  For these use cases, Owl is not really
-necessary: it just needs to render a DOM element with a specific class. For
-example:
-
-
-```xml
-<button class="flash" t-on-click="doSomething">Click</button>
-```
-
-with the following CSS:
-
-```css
-.flash {
-  transition: background 0.5s;
-}
-
-.flash:active {
-  background-color: #41454a;
-  transition: background 0s;
-}
-```
-
-will produce a nice flash effect whenever the user click (or activate with the
-keyboard) the button.
-
-## CSS Transitions (single element)
-
-A more complex situation occurs when we want to transition an element in or out
-of the page.  For example, we may want a fade-in and fade-out effect.
-
-The `t-transition` directive is here to help us (see [QWeb documentation](doc/qweb.md#t-transition-directive)).
@@ -0,0 +1,34 @@
+# 🦉 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).
+
@@ -0,0 +1,18 @@
+# 🦉 VDom 🦉
+
+Owl is a declarative component system: we declare the structure of the component
+tree, and Owl will translate that to a list of imperative operations. This
+translation is done by a virtual dom. This is the low level layer of Owl, most
+developer will not need to call directly the virtual dom functions.
+
+The main idea behind a virtual dom is to keep a in-memory representation of the
+DOM (called a virtual node), and whenever some change is needed, to regenerate
+a new representation, compute the difference between the old and the new, then
+apply the changes.
+
+`vdom` exports two functions:
+
+- `h`: create a new virtual node
+- `patch`: compare two virtual nodes, and apply the difference.
+
+Note: Owl's virtual dom is a fork of [snabbdom](https://github.com/snabbdom/snabbdom).
@@ -3,30 +3,61 @@
 OWL, React and Vue have the same main feature: they allow developers to build
 declarative user interfaces. To do that, all these frameworks uses a virtual dom. However, there are still obviously many differences.

-In this page, we try to highlight some of these differences. Obviously, some
+In this page, we try to highlight some of these differences. Obviously, a lot of
 effort was done to be fair. However, if you disagree with some of the points
 discussed, feel free to open an issue/submit a PR to correct this text.

+## Content
+
 - [Size](#size)
+- [Class Based](#class-based)
 - [Tooling/Build Step](#toolingbuild-step)
 - [Templating](#templating)
 - [Asynchronous rendering](#asynchronous-rendering)
 - [Reactiveness](#reactiveness)
 - [State Management](#state-management)
+- [Hooks](#hooks)

-### Size
+## Size

 OWL is intended to be small and to work at a slightly lower level of abstraction
 than React and Vue. Also, jQuery is not the same kind of framework, but it is interesting to compare.

-| Framework                | Size (minified) | Size (minified, gzipped) |
-| ------------------------ | --------------- | ------------------------ |
-| OWL                      | 32kb            | 11kb                     |
-| Vue + VueX               |                 | 30kb                     |
-| React + ReactDOM + Redux |                 | 40kb                     |
-| jQuery                   | 86kb            | 30kb                     |
+| Framework                | Size (minified, gzipped) |
+| ------------------------ | ------------------------ |
+| OWL                      | 18kb                     |
+| Vue + VueX               | 30kb                     |
+| Vue + VueX + Vue Router  | 39kb                     |
+| React + ReactDOM + Redux | 40kb                     |
+| jQuery                   | 30kb                     |

-### Tooling/Build step
+Note that those comparisons are not entirely fair, because we do not compare
+the same exact set of features. For example, VueX and Vue Router support more
+advanced use cases.
+
+## Class Based
+
+Both React and Vue moved away from defining components with classes. They prefer
+a more functional approach, in particular, with the new `hooks` mechanisms.
+
+This has some advantages and disadvantages. But the end result is that React
+and Vue both offers multiple different ways of defining new components. In
+contrast, Owl has only one mechanism: class-based components. We believe that Owl
+components are fast enough for all our usecases, and making it as simple as
+possible for developers is more valuable (for us).
+
+Also, functions or class based components are more than just syntax. Functions
+comes with a mindset of composition and class are about inheritance. Clearly,
+both of these are important mechanisms for reusing code. Also, one does not
+exclude the other.
+
+It certainly looks like the world of UI frameworks is moving toward composition,
+for many very good reasons. Owl is still good at composition (for example,
+Owl supports slots, which is the primary mechanism to make generic reusable
+components). But it can also use inheritance (and this is very important since
+templates can also be inherited with `xpaths` transformations).
+
+## Tooling/Build step

 OWL is designed to be easy to use in a standalone way. For various reasons,
 Odoo does not want to rely on standard web tools (such as webpack), and OWL can
@@ -36,14 +67,24 @@ be used by simply adding a script tag to a page.
 <script src="owl.min.js" />
 ```

-In comparison, React encourages using JSX,
-which necessitate a build step, and most Vue applications uses single file
-components, which also necessitate a build step.
+In comparison, React encourages using JSX, which necessitate a build step, and
+most Vue applications uses single file components, which also necessitate a build step.

 On the flipside, external tooling may make it harder to use in some case, but it
 also brings a lot of benefits. And React/Vue have both a large ecosystem.

-### Templating
+Note that since Owl is not dependant on any external tool nor libraries, it is
+very easy to integrate into any build toolchain. Also, since we cannot rely on
+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`](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.
+
+## Templating

 OWL uses its own QWeb engine, which compiles templates on the
 frontend, as they are needed. This is extremely convenient for our use case, in
@@ -65,7 +106,8 @@ into javascript functions. Note that Vue has a separate build which includes the
 template compiler.

 In contrast, most React applications do not use a templating language, but write
-some JSX code, which is precompiled into plain JavaScript by a build step.
+some JSX code, which is precompiled into plain JavaScript by a build step. This
+example is done with the (kind of outdated) React class system:

 ```jsx
 class Clock extends React.Component {
@@ -84,22 +126,36 @@ This has the advantage of having the full power of Javascript, but is less
 structured than a template language. Note that the tooling is quite impressive:
 there is a syntax highlighter for jsx here on github!

-### Asynchronous rendering
+By comparison, here is the equivalent Owl component, written with the
+[`xml`](reference/tags.md#xml-tag) tag helper:
+
+```js
+class Clock extends Component {
+  static template = xml`
+      <div>
+        <h1>Hello, world!</h1>
+        <h2>It is {props.date.toLocaleTimeString()}.</h2>
+      </div>
+    `;
+}
+```
+
+## Asynchronous Rendering

 This is actually a big difference between OWL and React/Vue: components in OWL
 are totally asynchronous. They have two asynchronous hooks in their lifecycle:

- `willStart` (before the widget starts rendering)
+- `willStart` (before the component starts rendering)
 - `willUpdateProps` (before new props are set)

 Both these methods can be implemented and return a promise. The rendering will
 then wait for these promises to be completed before patching the DOM. This is
-useful for some use cases: for example, a widget may want to fetch an external
-library (a calendar widget may need a specialized calendar rendering library),
+useful for some use cases: for example, a component may want to fetch an external
+library (a calendar component may need a specialized calendar rendering library),
 in its willStart hook.

 ```javascript
-class MyCalendarWidget extends owl.Component {
+class MyCalendarComponent extends owl.Component {
    ...

    willStart() {
@@ -113,12 +169,14 @@ This may be dangerous (to stop the rendering waiting for the network), but it is
 extremely powerful as well, as demonstrated by the Odoo Web Client.

 Lazy loading static libraries can obviously be done with React/Vue, but it is
-more convoluted.
+more convoluted. For example, in Vue, you need to use a dynamic import keyword
+that needs to be transpiled at build time in order for the component to be loaded
+asynchronously (see [the documentation](https://vuejs.org/v2/guide/components-dynamic-async.html#Async-Components)).

-### Reactiveness
+## Reactiveness

 React has a simple model: whenever the state changes, it is
-replaced with a new state (via the setState method). Then, the DOM is patched.
+replaced with a new state (via the `setState` method). Then, the DOM is patched.
 This is simple, efficient, and a little bit awkward to write.

 Vue is a little bit different: it replace magically the properties in the state
@@ -126,10 +184,12 @@ by getters/setters. With that, it can notify components whenever the state that
 they read was changed.

 Owl is closer to vue: it also tracks magically the state properties, but it does
-only increment a counter whenever it changes (and a _deep_ counter for each of
-its parents). This assumes that the state is actually a tree.
+only increment an internal counter whenever it changes. Note that it is done
+with a `Proxy`, which means that it is totally transparent to the developers.
+Adding new keys is supported. Once any part of the state has been changed, a
+rendering is scheduled in the next microtask tick (promise queue).

-### State Management
+## State Management

 Managing the state of an application is a tricky issue. Many solutions have
 been proposed these last few years. It also depends on the kind of application we
@@ -188,7 +248,97 @@ keeps track of who get data, and retrigger a render when it was changed.

 **Owl**

-Owl store is a little bit like a mix of redux and vuex: it has mutations and
-actions, like VueX, it keeps track of the state changes, but it does not notify
-a component when the state changes.  Instead, components need to connect to the
-store like in redux, with a function that will listen to the relevant state.
+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](reference/store.md#connecting-a-component)).
+
+```javascript
+const actions = {
+  increment({ state }, val) {
+    state.counter.value += val;
+  }
+};
+
+const state = {
+  counter: { value: 0 }
+};
+const store = new owl.Store({ state, actions });
+
+class Counter extends Component {
+  static template = xml`
+      <button t-name="Counter" t-on-click="dispatch('increment')">
+        Click Me! [<t t-esc="counter.value"/>]
+      </button>`;
+  counter = useStore(state => state.counter);
+  dispatch = useDispatch();
+}
+
+const counter = new Counter({ store, qweb });
+```
+
+## Hooks
+
+[Hooks](https://reactjs.org/docs/hooks-intro.html#motivation) recently took over
+the React world. They solve a lot of seemingly unconnected problems: attach
+reusable behavior to a component, in a composable way, extract stateful logic
+from a component or reuse stateful logic between component, without changing your
+component hierarchy.
+
+Here is an example of the React `useState` hook:
+
+```js
+import React, { useState } from "react";
+
+function Example() {
+  // Declare a new state variable, which we'll call "count"
+  const [count, setCount] = useState(0);
+
+  return (
+    <div>
+      <p>You clicked {count} times</p>
+      <button onClick={() => setCount(count + 1)}>Click me</button>
+    </div>
+  );
+}
+```
+
+Because of the way React designed the hooks API, they only work for functional
+components. But in that case, they really are powerful. Every major React library
+is in the process of redesigning their API with hooks (for example,
+[Redux](https://react-redux.js.org/next/api/hooks)).
+
+Vue 2 does not have hooks, but the Vue project is working on its next version,
+which will feature its new [composition API](https://vue-composition-api-rfc.netlify.com/).
+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](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.
+
+Here is what the `Counter` example above look like in Owl:
+
+```js
+import { Component, Owl } from "owl";
+import { xml } from "owl/tags";
+
+class Example extends Component {
+  static template = xml`
+      <div>
+        <p>You clicked {count.value} times</p>
+        <button t-on-click="increment">Click me</button>
+      </div>`;
+
+  count = useState({ value: 0 });
+
+  increment() {
+    this.state.value++;
+  }
+}
+```
+
+Since the Owl framework had hooks from early in its life, its main APIs
+are designed to be interacted with hooks from the start. For example, the
+`Context` and `Store` abstractions.
@@ -1,316 +0,0 @@
-# 🦉 OWL Component 🦉
-
-## Content
-
- [Overview](#overview)
- [Example](#example)
- [Templates](#templates)
- [Reference](#reference)
-  - [Properties](#properties)
-  - [Methods](#methods)
-  - [Lifecycle](#lifecycle)
-
-## Overview
-
-OWL components are the building blocks for user interface. They are designed to be:
-
-1. **declarative:** the user interface should be described in term of the state
-   of the application, not as a sequence of imperative steps.
-
-2. **composable:** each widget can seamlessly be created in a parent widget by
-   a simple directive in its template.
-
-3. **asynchronous rendering:** the framework will transparently wait for each
-   subwidgets to be ready before applying the rendering. It uses native promises
-   under the hood.
-
-4. **uses QWeb as a template system:** the templates are described in XML
-   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 (either defined inline or preloaded in QWeb).
-The rendering is done by QWeb, which will generate a virtual dom representation
-of the widget, then patch the DOM to apply the changes in an efficient way.
-
-OWL components observe their states, and rerender themselves whenever it is
-changed. This is done by an [observer](observer.md).
-
-## Example
-
-Let us have a look at a simple component:
-
-```javascript
-class ClickCounter extends owl.Component {
-  template = "click-counter";
-  state = { value: 0 };
-
-  increment() {
-    this.state.value++;
-  }
-}
-```
-
-```xml
-<button t-name="click-counter" t-on-click="increment">
-  Click Me! [<t t-esc="state.value"/>]
-</button>
-```
-
-Note that this code is written in ESNext style, so it will only run on the
-latest browsers without a transpilation step.
-
-This example show how a component should be defined: it simply subclasses the
-Component class. It needs to define a template (`click-counter` here). Also,
-a state object is defined. It is not mandatory to use the state object, but it
-is certainly encouraged. The state object is [observed](observer.md), and any
-change to it will cause a rerendering.
-
-## Templates
-
-The example above shows a QWeb template with a `t-on-click` directive.  Widget
-templates are standard [QWeb](qweb.md) templates, but with an extra directive:
-`t-widget`.  With the `t-widget` directive, widget templates can declare sub
-widgets:
-
-```xml
-  <div>
-    <span>some text</span>
-    <t t-widget="MyWidget" t-props="{info: 13}">
-  </div>
-```
-
-In this example, the template create a widget MyWidget just after the span. See
-the [QWeb](qweb.md) documentation for more information on the `t-widget` directive.
-
-Note that the rendering context for the template is the widget itself.  This means
-that the template can access `state`, `props`, `env`, or any methods defined in the widget.
-
-## Reference
-
-An Owl component is a small class which represent a widget 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
-will be used to render the component template.
-
-### Properties
-
- **`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.
-
- **`template`** (string): a string, which is the name of the QWeb template that will render
-  the component.
-
- **`inlineTemplate`** (string, optional): a string that represents a xml template. If set,
-  this will be loaded into QWeb and used instead of the `template` property.
-
- **`state`** (Object): this is the location of the component's state, if there is
-  any. After the willStart method, the `state` property is observed, and each
-  change will cause the widget to rerender itself.
-
- **`props`** (Object): this is an object given (in the constructor) by the parent
-  to configure the component. It can be dynamically changed later by the parent,
-  in some case. Note that `props` are owned by the parent, not by the component.
-  As such, it should not ever be modified by the component.
-
- **`refs`** (Object): the `refs` object contains all references to sub DOM nodes
-  or sub widgets defined by a `t-ref` directive in the component's template.
-
-### Methods
-
- **`mount(target)`** (async): this is the main way a component's hierarchy is added to the
-  DOM: the root component is mounted to a target HTMLElement. 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.
-
- **`unmount()`**: in case a component need 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
-  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
-  are updated. It returns a boolean, which indicates if the widget 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.
-
- **`updateEnv(nextEnv)`**: update the environment of a component and all its
-  children. This forces a complete rerender. For example, this could be useful
-  if we have a `isMobile` key in the environment, to decide if we want a mobile
-  interface or a destkop one.
-
- **`set(target, key, value)`**. This method is necessary in some cases when we
-  need to modify the state of the component in a way that is not visible to the
-  observer (see [observer's technical limitations](observer.md#technical-limitations)).
-  For example, if we need to add a key to the state.
-
- **`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
-  framework instead.
-
-### Lifecycle
-
-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](#constructor)**                  | constructor                             |
-| **[willStart](#willStart)**                      | async, before first rendering           |
-| **[mounted](#mounted)**                          | when component is render and in 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 |
-
-Notes:
-
- hooks call order is precisely defined: `[willX]` hooks are called first on parent,
-  then on children, and `[Xed]` are called in the reverse order: first children,
-  then parent.
- no hook method should ever be called manually. They are supposed to be
-called by the owl framework whenever it is required.
-
-#### `constructor(parent, props)`
-
-The constructor is not exactly a hook, it is the regular,
-normal, constructor of the component. Since it is not a hook, you need to make
-sure that `super` is called.
-
-This is usually where you would set the initial state and the template of the
-component.
-
-```javascript
-  constructor(parent, props) {
-    super(parent, props);
-    this.state = {someValue: true};
-    this.template = 'mytemplate';
-  }
-```
-
-Note that with ESNext class fields, the constructor method does not need to be
-implemented in most cases:
-
-```javascript
-class ClickCounter extends owl.Component {
-  template = "click-counter";
-  state = { value: 0 };
-
-  ...
-}
-```
-
-#### `willStart()`
-
-willStart is an asynchronous hook that can be implemented to
-perform some action before the initial rendering of a component.
-
-It will be called exactly once before the initial rendering. It is useful
-in some cases, for example, to load external assets (such as a JS library)
-before the widget is rendered. Another use case is to load data from a server.
-
-```javascript
-  async willStart() {
-    await owl.utils.loadJS("my-awesome-lib.js");
-  }
-```
-
-At this point, the component is not yet rendered. Note that a slow `willStart` method will slow down the rendering of the user
-interface. Therefore, some care should be made to make this method as
-fast as possible.
-
-The widget rendering will take place after `willStart` is completed.
-
-#### `mounted()`
-
-`mounted` is called each time a component is attached to the
-DOM, after the initial rendering and possibly later if the component was unmounted
-and remounted. At this point, the component is considered _active_. This is a good place to add some listeners, or to interact with the
-DOM, if the component needs to perform some measure for example.
-
-It is the opposite of `willUnmount`. If a component has been mounted, it will
-always be unmounted at some point in the future.
-
-The mounted method will be called recursively on each of its children. First,
-the parent, then all its children.
-
-Note that the state is now observed. It is however allowed (but not encouraged)
-to modify the state in the `mounted` hook. Doing so will cause a rerender,
-which will not be perceptible by the user, but 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
-some record Id, fetching the record data).
-
-```javascript
-  willUpdateProps(nextProps) {
-    return this.loadData({id: nextProps.id});
-  }
-```
-
-This hook is not called during the first render (but willStart is called
-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
-information from the DOM. For example, the current position of the
-scrollbar.
-
-Note that modifying the state object 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 widget is not in the DOM (this can
-happen with widgets with `t-keepalive`).
-
-The return value of this method will be given as the first argument of the
-corresponding `patched` call.
-
-#### `patched(snapshot)`
-
-This hook is called whenever a component did actually update its DOM (most
-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 widget is
-not in the DOM (this can happen with widgets with `t-keepalive`).
-
-The `snapshot` parameter is the result of the previous `willPatch` call.
-
-Updating the widget state in this hook is possible, but not encouraged.
-One need to be careful, because updates here will cause rerender, which in
-turn will cause other calls to patched. So, we need to be particularly
-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.
-
-```javascript
-  mounted() {
-    this.env.bus.on('someevent', this, this.doSomething);
-  }
-  willUnmount() {
-    this.env.bus.off('someevent', this, this.doSomething);
-  }
-```
-
-This is the opposite method of `mounted`. The `willUnmount` method will be
-called in reverse order: first the children, then the parents.
@@ -1,54 +0,0 @@
-# 🦉 Observer 🦉
-
-Owl need to be able to react to state changes. For example, whenever the state
-of a component is changed, we need to rerender it. To help with that, we have
-an Observer class. Its job is to observe some object state, and react to any
-change. To do that, it recursively replace all keys of the observed state by
-getters and setters.
-
-For example, this code will display `update` in the console:
-
-```javascript
-const observer = new owl.Observer();
-observer.notifyCB = () => console.log("update");
-observer.observe(obj);
-
-const obj = { a: { b: 1 } };
-obj.a.b = 2;
-```
-
-## Technical Limitations
-
-Since the observer uses getters and setters, it is actually unable to react to
-changes in two situations:
-
- adding a key to an object:
-
-  ```javascript
-  const observer = new owl.Observer();
-  const obj = { a: 1 };
-  observer.observe(obj);
-  obj.b = 2; // will do nothing
-  ```
-
-  In that case, we need a way to tell the observer that something happened.
-  This can be done by using the `set` method:
-
-  ```javascript
-  observer.set(obj, "b", 2);
-  ```
-
- modifying an array by setting a new value at a given index:
-
-  ```javascript
-  const observer = new owl.Observer();
-  const obj = { todos: [{ id: 1, text: "todo" }] };
-  observer.observe(obj);
-  obj[0] = { id: 2, text: "othertodo" }; // will do nothing, and obj[0] is not observed
-  ```
-
-  In that case, the solution is the same, we can simply use the `set` method:
-
-  ```javascript
-  observer.set(obj, 0, { id: 2, text: "othertodo" });
-  ```
@@ -1,6 +1,6 @@
 # 🦉 Quick Start 🦉

-## Static server
+## 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.
@@ -55,29 +55,28 @@ 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 context some user session information, some
+  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 widget, which can
-  have sub widgets
+- 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 widget
- mount the root widget to a DOM element
+- 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 {
-  constructor() {
-    super(...arguments);
-    this.template = "clickcounter";
-    this.state = { value: 0 };
-  }
+  static template = "clickcounter";
+  state = useState({ value: 0 });

  increment() {
    this.state.value++;
@@ -88,9 +87,9 @@ class ClickCounter extends owl.Component {
 // Application initialization
 //------------------------------------------------------------------------------
 async function start() {
-  const templates = await owl.utils.loadTemplates("templates.xml");
+  const templates = await owl.utils.loadFile("templates.xml");
  const env = {
-    qweb: new owl.QWeb(templates)
+    qweb: new owl.QWeb({ templates })
  };
  const counter = new ClickCounter(env);
  const target = document.getElementById("main");
@@ -1,361 +0,0 @@
-# 🦉 QWeb 🦉
-
-## Content
-
- [Overview](#overview)
- [QWeb Specification](#qweb-specification)
-    - [Static html nodes](#static-html-nodes)
-    - [`t-esc` directive](#t-esc-directive)
-    - [`t-raw` directive](#t-raw-directive)
-    - [`t-set` directive](#t-set-directive)
-    - [`t-if` directive](#t-if-directive)
-    - [Expression evaluation](#expression-evaluation)
-    - [`t-att` directive (dynamic attributes)](#t-att-directive-dynamic-attributes)
- [JS/OWL Specific Extensions](#jsowl-specific-extensions)
-    - [`t-on` directive](#t-on-directive)
-    - [Component: `t-widget`, `t-props`](#component-t-widget-t-props)
-    - [`t-ref` directive](#t-ref-directive)
-    - [`t-key` directive](#t-key-directive)
-    - [`t-transition` directive](#t-transition)
-    - [Debugging (`t-debug` and `t-log`)](#debugging-t-debug-and-t-log)
-    - [White spaces](#white-spaces)
-    - [Root nodes](#root-nodes)
-
-## Overview
-
-[QWeb](https://www.odoo.com/documentation/12.0/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.
-
-The QWeb implementation in the OWL project is slightly different. It compiles
-templates into functions that output a virtual DOM instead of a string. This is
-necessary for the component system. In addition, it has a few extra directives
-(see [OWL Specific Extensions](#owlspecificextensions))
-
-
-## QWeb Specification
-
-
-### Static html nodes
-
-Normal, regular html nodes are rendered into themselves:
-
-```xml
-  <div>hello</div> <!–– rendered as itself ––>
-```
-
-### `t-esc` directive
-
-The `t-esc` directive is necessary whenever you want to add a dynamic text
-expression in a template. The text is escaped to avoid security issues.
-
-```xml
-<p><t t-esc="value"/></p>
-```
-
-rendered with the value `value` set to `42` in the rendering context yields:
-
-```html
-<p>42</p>
-```
-
-### `t-raw` directive
-
-The `t-raw` directive is almost the same as `t-esc`, but without the escaping.
-This is mostly useful to inject a raw html string somewhere. Obviously, this
-is unsafe to do in general, and should only be used for strings known to be safe.
-
-```xml
-<p><t t-esc="value"/></p>
-```
-
-rendered with the value `value` set to `<span>foo</span>` in the rendering context yields:
-
-```html
-<p><span>foo</span></p>
-```
-
-### `t-set` directive
-
-QWeb allows creating variables from within the template, to memoize a computation (to use it multiple times), give a piece of data a clearer name, ...
-
-This is done via the `t-set` directive, which takes the name of the variable to create. The value to set can be provided in two ways:
-
-1. a `t-value` attribute containing an expression, and the result of its
-   evaluation will be set:
-
-   ```xml
-   <t t-set="foo" t-value="2 + 1"/>
-   <t t-esc="foo"/>
-   ```
-
-   will print `3`. Note that the evaluation is done at rendering time, not at
-   compilte time.
-
-2. if there is no `t-value` attribute, the node’s body is saved and its value is
-   set as the variable’s value:
-
-   ```xml
-   <t t-set="foo">
-       <li>ok</li>
-   </t>
-   <t t-esc="foo"/>
-   ```
-
-   will generate `&lt;li&gt;ok&lt;/li&gt;` (the content is escaped as we used the `t-esc` directive)
-
-The `t-set` directive acts like a regular variable in most programming language.
-It is lexically scoped (inner nodes are sub scopes), can be shadowed, ...
-
-### `t-if` directive
-
-The `t-if` directive is useful to conditionally render something. It evaluates
-the expression given as attribute value, and then acts accordingly.
-
-```xml
-<div>
-    <t t-if="condition">
-        <p>ok</p>
-    </t>
-</div>
-```
-
-The element is rendered if the condition (evaluated with the current rendering
-context) is true:
-
-```xml
-<div>
-    <p>ok</p>
-</div>
-```
-
-but if the condition is false it is removed from the result:
-
-```xml
-<div>
-</div>
-```
-
-The conditional rendering applies to the bearer of the directive, which does not
-have to be `<t>`:
-
-```xml
-<div>
-    <p t-if="condition">ok</p>
-</div>
-```
-
-will give the same results as the previous example.
-
-Extra conditional branching directives `t-elif` and `t-else` are also available:
-
-```xml
-<div>
-    <p t-if="user.birthday == today()">Happy bithday!</p>
-    <p t-elif="user.login == 'root'">Welcome master!</p>
-    <p t-else="">Welcome!</p>
-</div>
-```
-
-### Expression evaluation
-
-It is useful to explain the various rules that applies on QWeb expressions. These
-expressions are strings that will be converted to a javascript expression at
-compile time.
-
-1. it should be a simple expression which returns a value. It cannot be a statement.
-
-   ```xml
-   <div><p t-if="1 + 2 === 3">ok</p></div>
-   ```
-
-   is valid, but the following is not valid:
-
-   ```xml
-   <div><p t-if="console.log(1)">NOT valid</p></div>
-   ```
-
-2. it can use anything in the rendering context:
-
-   ```xml
-   <p t-if="user.birthday == today()">Happy bithday!</p>
-   ```
-
-   is valid, and will read the `user` object from the context, and call the
-   `today` function.
-
-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` | `<=`                |
-
-   So, one can write this:
-
-   ```xml
-   <div><p t-if="10 + 2 gt 5">ok</p></div>
-   ```
-
-### `t-att` directive (dynamic attributes)
-
-One can use the `t-att-` directive to add dynamic attributes. Its main use is to
-evaluate an expression (at rendering time) and bind an attribute to its result:
-
-For example, if we have `id` set to 32 in the rendering context,
-
-```xml
-<div t-att-data-action-id="id"/>  <!-- result: <div data-action-id="32"></div> -->
-```
-
-If an expression evaluates to a falsy value, it will not be set at all:
-
-```xml
-<div t-att-foo="false"/>  <!-- result: <div></div> -->
-```
-
-## JS/OWL Specific Extensions
-
-### `t-on` directive
-
-### Component: `t-widget`, `t-props`
-
-### `t-ref` directive
-
-### `t-key` directive
-
-Even though Owl tries to be as declarative as possible, some DOM state is still
-locked inside the DOM: for example, the scrolling state, the current user selection,
-the focused element or the state of an input. 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.
-
-### `t-transition` directive
-
-To perform useful transition effects, whenever an element appears or disappears,
-it is necessary to add/remove some css style or class at some precise moment in
-the lifetime of a node.  Since this is not easy to do by hand, Owl `t-transition`
-directive is there to help.
-
-Whenever a node has a `t-transition` directive, with a `name` value, the following
-will happen:
-
-At node creation:
-
- the css classes `name-enter` and `name-enter-active` will be added before the
-  node is added to 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.
-
-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.
-
-For example, a simple fade in/out effect can be done with this:
-
-```xml
-<div>
-    <div t-if="state.flag" class="square" t-transition="fade">Hello</div>
-</div>
-```
-
-```css
-.fade-enter-active, .fade-leave-active {
-    transition: opacity .5s;
-}
-.fade-enter, .fade-leave-to {
-    opacity: 0;
-}
-```
-
-Note: you will find more information on animations in the [animation](doc/animations.md)
-documentation.
-
-### Debugging (`t-debug` and `t-log`)
-
-The javascript QWeb implementation provides two useful debugging directives:
-
-`t-debug` adds a debugger statement during template rendering:
-
-```xml
-<t t-if="a_test">
-    <t t-debug="">
-</t>
-````
-
-will stop execution if the browser dev tools are open.
-
-`t-log` takes an expression parameter, evaluates the expression during rendering and logs its result with console.log:
-
-```xml
-<t t-set="foo" t-value="42"/>
-<t t-log="foo"/>
-```
-
-will print 42 to the console
-
-
-### White spaces
-
-White spaces in a templates are handled in a special way:
-
- consecutive whitespaces are always condensed to a single whitespace
- if a whitespace-only text node contains a linebreak, it is ignored
- the previous rules do not apply if we are in a `<pre>` tag
-
-### Root nodes
-
-For many reasons, Owl QWeb templates should have a single root node.  More
-precisely, the result of a template rendering should have a single root node:
-
-```xml
-<!–– not ok: two root nodes ––>
-<t>
-    <div>foo</div>
-    <div>bar</div>
-</t>
-
-<!–– ok: result has one single root node ––>
-<t>
-    <div t-if="someCondition">foo</div>
-    <span t-else="1">bar</span>
-</t>
-```
-
-Extra root nodes will actually be ignored (even though they will be rendered
-in memory).
-
-Note: this does not apply to subtemplates (see the `t-call` directive).  In that
-case, they will be inlined in the main template, and can actually have many
-root nodes.
@@ -1,15 +1,82 @@
 # 🦉 OWL Documentation 🦉

+## Owl Content
+
+Owl is a javascript library that contains some core classes and function to help
+build applications. Here is a complete representation of its content:
+
+```
+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.

 ## Reference

- [Component](component.md)
- [QWeb](qweb.md)
- [Store](store.md)
- [Observer](observer.md)
- [Virtual DOM](vdom.md)
+- [Animations](reference/animations.md)
+- [Component](reference/component.md)
+- [Context](reference/context.md)
+- [Event Bus](reference/event_bus.md)
+- [Hooks](reference/hooks.md)
+- [Misc](reference/misc.md)
+- [Observer](reference/observer.md)
+- [QWeb](reference/qweb.md)
+- [Router](reference/router.md)
+- [Store](reference/store.md)
+- [Tags](reference/tags.md)
+- [Utils](reference/utils.md)
+
+## Learning Resources
+
+- [Quick Start](quick_start.md)

 ## Miscellaneous
- [Quick Start](quick_start.md)
- [Animations](animations.md)
+
 - [Comparison with React/Vue](comparison.md)
+- [Tooling](tooling.md)
+- [Templates to start Owl applications (external link)](https://github.com/ged-odoo/owl-templates)
+
+## Architecture
+
+This section explains in more detail the inner workings of Owl. It is more
+useful for people working on Owl code.
+
+- [Virtual DOM](architecture/vdom.md)
+- [Rendering](architecture/rendering.md)
@@ -0,0 +1,95 @@
+# 🦉 Animations 🦉
+
+Animation is a complex topic. There are many different use cases, and many
+solutions and technologies. Owl only supports some basic use cases.
+
+## Simple CSS effects
+
+Sometimes, using pure CSS is enough. For these use cases, Owl is not really
+necessary: it just needs to render a DOM element with a specific class. For
+example:
+
+```xml
+<a class="btn flash" t-on-click="doSomething">Click</a>
+```
+
+with the following CSS:
+
+```css
+btn {
+  background-color: gray;
+}
+
+.flash {
+  transition: background 0.5s;
+}
+
+.flash:active {
+  background-color: #41454a;
+  transition: background 0s;
+}
+```
+
+will produce a nice flash effect whenever the user clicks (or activates with the
+keyboard) the button.
+
+## CSS Transitions
+
+A more complex situation occurs when we want to transition an element in or out
+of the page. For example, we may want a fade-in and fade-out effect.
+
+The `t-transition` directive is here to help us. It works on html elements and
+on components, by adding and removing some css classes.
+
+To perform useful transition effects, whenever an element appears or disappears,
+it is necessary to add/remove some css style or class at some precise moment in
+the lifetime of a node. Since this is not easy to do by hand, Owl `t-transition`
+directive is there to help.
+
+Whenever a node has a `t-transition` directive, with a `name` value, the following
+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,
+- 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.
+
+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.
+
+For example, a simple fade in/out effect can be done with this:
+
+```xml
+<div>
+    <div t-if="state.flag" class="square" t-transition="fade">Hello</div>
+</div>
+```
+
+```css
+.fade-enter-active,
+.fade-leave-active {
+  transition: opacity 0.5s;
+}
+.fade-enter,
+.fade-leave-to {
+  opacity: 0;
+}
+```
+
+The `t-transition` directive can be applied on a node element or on a component.
+
+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).
@@ -0,0 +1,108 @@
+# 🦉 Context 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Example](#example)
+- [Reference](#reference)
+  - [`Context`](#context)
+  - [`useContext`](#usecontext)
+
+## Overview
+
+The `Context` object provides a way to share data between an arbitrary number
+of components. Usually, data is passed from a parent to its children component,
+but when we have to deal with some mostly global information, this can be
+annoying, since each component will need to pass the information to each children,
+even though some or most of them will not use the information.
+
+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.
+
+## Example
+
+Assume that we have an application with various components which needs to render
+differently depending on the size of the device. Here is how we could proceed
+to make sure that the information is properly shared. First, let us create a
+context, and add it to the environment:
+
+```js
+const deviceContext = new Context({ isMobile: true });
+const env = {
+  qweb: new QWeb({ templates: TEMPLATES }),
+  deviceContext
+};
+```
+
+If we want to make it completely responsive, we need to update its value whenever
+the size of the screen is updated:
+
+```js
+const isMobile = () => window.innerWidth <= 768;
+window.addEventListener(
+  "resize",
+  owl.utils.debounce(() => {
+    const state = deviceContext.state;
+    if (state.isMobile !== isMobile()) {
+      state.isMobile = !state.isMobile;
+    }
+  }, 15)
+);
+```
+
+Then, each component that want can subscribe and render differently depending on the
+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>
+    `;
+  device = useContext(this.env.deviceContext);
+}
+```
+
+## Reference
+
+### `Context`
+
+A `Context` object should be created with a state object:
+
+```js
+const someContext = new Context({ some: "key" });
+```
+
+Its state is now available in the `state` key:
+
+```js
+someContext.state.some = "other key";
+```
+
+This is the way some global code (such as the responsive code above) should
+read and update the context state. However, components should not ever read the
+context state directly from the context, they should instead use the `useContext`
+hook to properly register themselves to state changes.
+
+Note that the `Context` hook is different from the React version. For example,
+there is no concept of provider/consumer. So, the `Context` feature does not
+by itself allow the use of a different context state depending on the component
+place in the component tree. However, this functionality can be obtained, if
+necessary, with the use of sub environment.
+
+### `useContext`
+
+The `useContext` hook is the normal way for a component to register themselve
+to context state changes. The `useContext` method returns the context state:
+
+```js
+device = useContext(this.env.deviceContext);
+```
+
+It is a simple observed state (with an owl `Observer`), which contains the shared
+information.
@@ -0,0 +1,27 @@
+# 🦉 Event Bus 🦉
+
+It is sometimes useful to use a `Bus` to communicate informations between various
+parts of the code. Owl has a very simple bus class, which manages subscriptions,
+triggering events, and callbacks.
+
+```js
+const bus = new owl.core.EventBus();
+
+bus.on("some-event", null, function(...args) {
+  console.log(...args);
+});
+
+bus.trigger("some-event", 1, 2, 3);
+// [1,2,3] will be logged to the console
+```
+
+Its API is:
+
+| Method                           | Description                       |
+| -------------------------------- | --------------------------------- |
+| `on(eventType, owner, callback)` | add a listener                    |
+| `off(eventType, owner)`          | remove all listeners for an owner |
+| `trigger(eventType, ...args)`    | trigger an event                  |
+| `clear`                          | remove all subscriptions          |
+
+Note that the [`Store`](store.md) is an example of an `EventBus`.
@@ -0,0 +1,425 @@
+# 🦉 Hooks 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Example: Mouse Position](#example-mouse-position)
+- [Example: Autofocus](#example-autofocus)
+- [Reference](#reference)
+  - [One Rule](#one-rule)
+  - [`useState`](#usestate)
+  - [`onMounted`](#onmounted)
+  - [`onWillUnmount`](#onwillunmount)
+  - [`onWillPatch`](#onwillpatch)
+  - [`onPatched`](#onpatched)
+  - [`onWillStart`](#onwillstart)
+  - [`onWillUpdateProps`](#onwillupdateprops)
+  - [`useContext`](#usecontext)
+  - [`useRef`](#useref)
+  - [`useSubEnv`](#usesubenv)
+  - [`useStore`](#usestore)
+  - [`useDispatch`](#usedispatch)
+  - [`useGetters`](#usegetters)
+  - [Making customized hooks](#making-customized-hooks)
+
+## Overview
+
+Hooks were popularised by React as a way to solve the following issues:
+
+- help reusing stateful logic between components
+- help organizing code by feature in complex components
+- use state in functional components, without writing a class.
+
+Owl hooks serve the same purpose, except that they work for class components
+(note: React hooks do not work on class components, and maybe because of that,
+there seems to be the misconception that hooks are in opposition to class. This
+is clearly not true, as shown by Owl hooks).
+
+Hooks work beautifully with Owl components: they solve the problems mentioned
+above, and in particular, they are the perfect way to make your component
+reactive.
+
+## Example: mouse position
+
+Here is the classical example of a non trivial hook to track the mouse position.
+
+```js
+const { useState, onMounted, onWillUnmount } = owl.hooks;
+
+// We define here a custom behaviour: this hook tracks the state of the mouse
+// position
+function useMouse() {
+  const position = useState({ x: 0, y: 0 });
+
+  function update(e) {
+    position.x = e.clientX;
+    position.y = e.clientY;
+  }
+  onMounted(() => {
+    window.addEventListener("mousemove", update);
+  });
+  onWillUnmount(() => {
+    window.removeEventListener("mousemove", update);
+  });
+
+  return position;
+}
+
+// Main root component
+class App extends owl.Component {
+  static template = xml`
+    <div t-name="App">
+      <div>Mouse: <t t-esc="mouse.x"/>, <t t-esc="mouse.y"/></div>
+    </div>`;
+
+  // this hooks is bound to the 'mouse' property.
+  mouse = useMouse();
+}
+```
+
+Note that we use the prefix `use` for hooks, just like in React. This is just
+a convention.
+
+## Example: autofocus
+
+Hooks can be combined to create the desired effect. For example, the following
+hook combines the `useRef` hook with the `onPatched` and `onMounted` functions
+to create an easy way to focus an input whenever it appears in the DOM:
+
+```js
+function useAutofocus(name) {
+  let ref = useRef(name);
+  let isInDom = false;
+  function updateFocus() {
+    if (!isInDom && ref.el) {
+      isInDom = true;
+      ref.el.focus();
+    } else if (isInDom && !ref.el) {
+      isInDom = false;
+    }
+  }
+  onPatched(updateFocus);
+  onMounted(updateFocus);
+}
+```
+
+This hook takes the name of a valid `t-ref` directive, which should be present
+in the template. It then checks whenever the component is mounted or patched if
+the reference is not valid, and in this case, it will focus the node element.
+This hook can be used like this:
+
+```js
+class SomeComponent extends Component {
+  static template = xml`
+    <div>
+        <input />
+        <input t-ref="myinput"/>
+    </div>`;
+
+  constructor(...args) {
+    super(...args);
+    useAutofocus("myinput");
+  }
+}
+```
+
+## Reference
+
+### One rule
+
+There is only one rule: every hook for a component has to be called in the
+constructor (or in class fields):
+
+```js
+// ok
+class SomeComponent extends Component {
+  state = useState({ value: 0 });
+}
+
+// also ok
+class SomeComponent extends Component {
+  constructor(...args) {
+    super(...args);
+    this.state = useState({ value: 0 });
+  }
+}
+
+// not ok: this is executed after the constructor is called
+class SomeComponent extends Component {
+  async willStart() {
+    this.state = useState({ value: 0 });
+  }
+}
+```
+
+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.
+
+### `useState`
+
+The `useState` hook is certainly the most important hook for Owl components:
+this is what allows a component to be reactive, to react to state change.
+
+The `useState` hook has to be given an object or an array, and will return
+an observed version of it (using a `Proxy`).
+
+```javascript
+const { useState } = owl.hooks;
+
+class Counter extends owl.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++;
+  }
+}
+```
+
+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
+abstractions. `onMounted` registers a callback, which will be called when the component
+is mounted (see example on top of this page).
+
+### `onWillUnmount`
+
+`onWillUnmount` is not a user hook, but is a building block designed to help make useful
+abstractions. `onWillUnmount` registers a callback, which will be called when the component
+is unmounted (see example on top of this page).
+
+### `onWillPatch`
+
+`onWillPatch` is not a user hook, but is a building block designed to help make useful
+abstractions. `onWillPatch` registers a callback, which will be called just
+before the component patched.
+
+### `onPatched`
+
+`onPatched` is not a user hook, but is a building block designed to help make useful
+abstractions. `onPatched` registers a callback, which will be called just
+after the component patched.
+
+### `onWillStart`
+
+`onWillStart` is an asynchronous hook. This means that the function registered
+in the hook will be run just before the component is first rendered and can return a
+promise, to express the fact that it is an asynchronous operation.
+
+Note that if there are more than one `onWillStart` registered callback, then they
+will all be run in parallel.
+
+It can be used to load some initial data. For example, the following hook will
+automatically load some data from the server, and return an object that will
+be ready whenever the component is rendered:
+
+```js
+function useLoader() {
+  const component = Component.current;
+  const record = useState({});
+  onWillStart(async () => {
+    const recordId = component.props.id;
+    Object.assign(record, await fetchSomeRecord(recordId));
+  });
+  return record;
+}
+```
+
+Note that this example does not update the record value whenever props are
+updated. For that situation, we need to use the `onWillUpdateProps` hook.
+
+### `onWillUpdateProps`
+
+Just like `onWillStart`, `onWillUpdateProps` is an asynchronous hook. It is
+designed to be run whenever the component props are updated. This could be
+useful to perform some asynchronous task such as fetching updated data.
+
+```js
+function useLoader() {
+  const component = Component.current;
+  const record = useState({});
+
+  async function updateRecord(id) {
+    Object.assign(record, await fetchSomeRecord(id));
+  }
+
+  onWillStart(() => updateRecord(component.props.id));
+  onWillUpdateProps(nextProps => updateRecord(nextProps.id));
+
+  return record;
+}
+```
+
+Note that if there are more than one `onWillUpdateProps` registered callback,
+then they will all be run in parallel.
+
+### `useContext`
+
+See [`useContext`](context.md#usecontext) for reference documentation.
+
+### `useRef`
+
+The `useRef` hook is useful when we need a way to interact with some inside part
+of a component, rendered by Owl. It can work either on a DOM node, or on a component,
+tagged by the `t-ref` directive:
+
+```xml
+<div>
+    <div t-ref="someDiv"/>
+    <SubComponent t-ref="someComponent"/>
+</div>
+```
+
+In this example, the component will be able to access the `div` and the component
+`SubComponent` using the `useRef` hook:
+
+```js
+class Parent extends Component {
+  subRef = useRef("someComponent");
+  divRef = useRef("someDiv");
+
+  someMethod() {
+    // 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
+  }
+}
+```
+
+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`.
+
+The `t-ref` directive also accepts dynamic values with string interpolation
+(like the [`t-attf-`](qweb.md#dynamic-attributes) and
+`t-component` directives). For example,
+
+```xml
+<div t-ref="component_{{someCondition ? '1' : '2'}}"/>
+```
+
+Here, the references need to be set like this:
+
+```js
+this.ref1 = useRef("component_1");
+this.ref2 = useRef("component_2");
+```
+
+References are only guaranteed to be active while the parent component is mounted.
+If this is not the case, accessing `el` or `comp` on it will return `null`.
+
+### `useSubEnv`
+
+The environment is sometimes useful to share some common information between
+all components. But sometimes, we want to _scope_ that knowledge to a subtree.
+
+For example, if we have a form view component, maybe we would like to make some
+`model` object available to all sub components, but not to the whole application.
+This is where the `useSubEnv` hook may be useful: it lets a component add some
+information to the environment in a way that only the component and its children
+can access it:
+
+```js
+class FormComponent extends Component {
+  constructor(...args) {
+    super(...args);
+    const model = makeModel();
+    useSubEnv({ model });
+  }
+}
+```
+
+The `useSubEnv` takes one argument: an object which contains some key/value that
+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.
+
+### `useStore`
+
+The `useStore` hook is the entry point for a component to connect to the store.
+See the [store documentation](store.md) for more information.
+
+### `useDispatch`
+
+The `useDispatch` hook is the way for components to get a reference to the store
+`dispatch` function. See the [store documentation](store.md) for more information.
+
+### `useGetters`
+
+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.
+
+### Making customized hooks
+
+Hooks are a wonderful way to organize the code of a complex component by feature
+instead of by lifecycle methods. They are like mixins, except that they can be
+easily composed together.
+
+But, like every good things in life, hooks should be used with moderation. They are
+not the solution to every problem.
+
+- they may be overkill: if your component needs to perform some action specific
+  to itself (so, the specific code does not need to be shared), there is nothing
+  wrong with a simple class method:
+
+  ```js
+  // maybe overkill
+  class A extends Component {
+    constructor(...args) {
+      super(...args);
+      useMySpecificHook();
+    }
+  }
+
+  // ok
+  class B extends Component {
+    constructor(...args) {
+      super(...args);
+      this.performSpecificTask();
+    }
+  }
+  ```
+
+  Note that the second solution is easier to extend in sub components.
+
+- they may be harder to test: if a customized hook injects some external side
+  effect dependency, then it is harder to test without doing some non obvious
+  manipulation. For example, assume that we want to give a reference to a
+  router in a `useRouter` hook. We could do this:
+
+  ```js
+  const router = new Router(...);
+
+  function useRouter() {
+      return router;
+  }
+  ```
+
+  As you can see, this does not _hook_ into the internal of the component. It
+  simply returns a global object, which is difficult to mock.
+
+  A better way would be to do something like this: get the reference from the
+  environment.
+
+  ```js
+  function useRouter() {
+    return Component.current.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.
@@ -0,0 +1,23 @@
+# 🦉 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.
@@ -0,0 +1,52 @@
+# 🦉 Observer 🦉
+
+Owl needs to be able to react to state changes. For example, whenever the state
+of a component is changed, Owl needs to rerender it. To help with that, there is
+an Observer class. Its job is to observe the state of an object (or array), and
+to react to any change. The observer is implemented with the native `Proxy`
+object. Note that this means that it will not work on older browsers.
+
+Note that the `Observer` is used by the `useState` and `useContext` hooks. This
+is the way most Owl applications will create observers. For the majority of
+use cases, there is no need to directly instantiate an observer.
+
+## Example
+
+For example, this code will display `update` in the console:
+
+```javascript
+const observer = new owl.Observer();
+observer.notifyCB = () => console.log("update");
+const obj = observer.observe({ a: { b: 1 } });
+
+obj.a.b = 2;
+```
+
+This example shows that an observer can observe nested properties.
+
+## Reference
+
+**observe** An observer can observe multiple values with the `observe` method.
+This method takes an object or an array as its argument and will return a proxy
+(which is mapped to the initial object/array). With this proxy, the observer
+can detect whenever any internal value is changed.
+
+**Registering a callback** Whenever an observer sees a state change, it will
+call its `notifyCB` method. No additional information is given to the callback.
+
+**deepRevNumber** Each observed value has an internal revision number, which
+is incremented every time the value is observed. Sometimes, it can be useful
+to obtain that number:
+
+```js
+const observer = new owl.Observer();
+const obj = observer.observe({ a: { b: 1 } });
+
+observer.deepRevNumber(obj.a); // 1
+obj.a.b = 2;
+
+observer.deepRevNumber(obj.a); // 2
+```
+
+The `deepRevNumber` can also return 0, which indicates that the value is not
+observed.
@@ -0,0 +1,612 @@
+# 🦉 QWeb 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Directives](#directives)
+- [QWeb Engine](#qweb-engine)
+- [Reference](#reference)
+  - [White Spaces](#white-spaces)
+  - [Root Nodes](#root-nodes)
+  - [Expression Evaluation](#expression-evaluation)
+  - [Static html Nodes](#static-html-nodes)
+  - [Outputting Data](#outputting-data)
+  - [Setting Variables](#setting-variables)
+  - [Conditionals](#conditionals)
+  - [Dynamic Attributes](#dynamic-attributes)
+  - [Loops](#loops)
+  - [Rendering Sub Templates](#rendering-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
+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">
+        <li t-foreach="messages" t-as="message">
+            <t t-esc="message"/>
+        </li>
+    </ul>
+</div>
+```
+
+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`, ...
+
+## Directives
+
+We present here 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-translation`                | [Disabling the translation of a node](#translations)         |
+| `t-name`                       | [Defining a template (not really a directive)](#qweb-engine) |
+
+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(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](../architecture/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).
+
+## 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:
+
+- consecutive whitespaces are always condensed to a single whitespace
+- if a whitespace-only text node contains a linebreak, it is ignored
+- the previous rules do not apply if we are in a `<pre>` tag
+
+### Root Nodes
+
+For many reasons, Owl QWeb templates should have a single root node. More
+precisely, the result of a template rendering should have a single root node:
+
+```xml
+<!–– not ok: two root nodes ––>
+<t>
+    <div>foo</div>
+    <div>bar</div>
+</t>
+
+<!–– ok: result has one single root node ––>
+<t>
+    <div t-if="someCondition">foo</div>
+    <span t-else="1">bar</span>
+</t>
+```
+
+Extra root nodes will actually be ignored (even though they will be rendered
+in memory).
+
+Note: this does not apply to subtemplates (see the `t-call` directive). In that
+case, they will be inlined in the main template, and can actually have many
+root nodes.
+
+### Expression Evaluation
+
+QWeb expressions are strings that will be processed at compile time. Each variable in
+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
+context["a"] + context["b"].c(context["d"]);
+```
+
+It is useful to explain the various rules that apply on these expressions:
+
+1. it should be a simple expression which returns a value. It cannot be a statement.
+
+   ```xml
+   <div><p t-if="1 + 2 === 3">ok</p></div>
+   ```
+
+   is valid, but the following is not valid:
+
+   ```xml
+   <div><p t-if="console.log(1)">NOT valid</p></div>
+   ```
+
+2. it can use anything in the rendering context (typically, the component):
+
+   ```xml
+   <p t-if="user.birthday === today()">Happy bithday!</p>
+   ```
+
+   is valid, and will read the `user` object from the context, and call the
+   `today` function.
+
+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  | replaced with |
+   | ----- | ------------- |
+   | `and` | `&&`          |
+   | `or`  | `\|\|`        |
+   | `gt`  | `>`           |
+   | `gte` | `>=`          |
+   | `lt`  | `<`           |
+   | `lte` | `<=`          |
+
+   So, one can write this:
+
+   ```xml
+   <div><p t-if="10 + 2 gt 5">ok</p></div>
+   ```
+
+### Static Html Nodes
+
+Normal, regular html nodes are rendered into themselves:
+
+```xml
+  <div>hello</div> <!–– rendered as itself ––>
+```
+
+### Outputting Data
+
+The `t-esc` directive is necessary whenever you want to add a dynamic text
+expression in a template. The text is escaped to avoid security issues.
+
+```xml
+<p><t t-esc="value"/></p>
+```
+
+rendered with the value `value` set to `42` in the rendering context yields:
+
+```html
+<p>42</p>
+```
+
+The `t-raw` directive is almost the same as `t-esc`, but without the escaping.
+This is mostly useful to inject a raw html string somewhere. Obviously, this
+is unsafe to do in general, and should only be used for strings known to be safe.
+
+```xml
+<p><t t-raw="value"/></p>
+```
+
+rendered with the value `value` set to `<span>foo</span>` in the rendering context yields:
+
+```html
+<p><span>foo</span></p>
+```
+
+Note that since the content of the expression is not known beforehand, the `t-raw`
+directive has to parse the html (and convert it to a virtual dom structure) for
+each rendering. So, it will be much slower than a regular template. It is
+therefore advised to limit the use of `t-raw` whenever possible.
+
+### Setting Variables
+
+QWeb allows creating variables from within the template, to memoize a computation (to use it multiple times), give a piece of data a clearer name, ...
+
+This is done via the `t-set` directive, which takes the name of the variable to create. The value to set can be provided in two ways:
+
+1. a `t-value` attribute containing an expression, and the result of its
+   evaluation will be set:
+
+   ```xml
+   <t t-set="foo" t-value="2 + 1"/>
+   <t t-esc="foo"/>
+   ```
+
+   will print `3`. Note that the evaluation is done at rendering time, not at
+   compilte time.
+
+2. if there is no `t-value` attribute, the node’s body is saved and its value is
+   set as the variable’s value:
+
+   ```xml
+   <t t-set="foo">
+       <li>ok</li>
+   </t>
+   <t t-esc="foo"/>
+   ```
+
+   will generate `&lt;li&gt;ok&lt;/li&gt;` (the content is escaped as we used the `t-esc` directive)
+
+The `t-set` directive acts like a regular variable in most programming language.
+It is lexically scoped (inner nodes are sub scopes), can be shadowed, ...
+
+### Conditionals
+
+The `t-if` directive is useful to conditionally render something. It evaluates
+the expression given as attribute value, and then acts accordingly.
+
+```xml
+<div>
+    <t t-if="condition">
+        <p>ok</p>
+    </t>
+</div>
+```
+
+The element is rendered if the condition (evaluated with the current rendering
+context) is true:
+
+```xml
+<div>
+    <p>ok</p>
+</div>
+```
+
+but if the condition is false it is removed from the result:
+
+```xml
+<div>
+</div>
+```
+
+The conditional rendering applies to the bearer of the directive, which does not
+have to be `<t>`:
+
+```xml
+<div>
+    <p t-if="condition">ok</p>
+</div>
+```
+
+will give the same results as the previous example.
+
+Extra conditional branching directives `t-elif` and `t-else` are also available:
+
+```xml
+<div>
+    <p t-if="user.birthday == today()">Happy bithday!</p>
+    <p t-elif="user.login == 'root'">Welcome master!</p>
+    <p t-else="">Welcome!</p>
+</div>
+```
+
+### Dynamic Attributes
+
+One can use the `t-att-` directive to add dynamic attributes. Its main use is to
+evaluate an expression (at rendering time) and bind an attribute to its result:
+
+For example, if we have `id` set to 32 in the rendering context,
+
+```xml
+<div t-att-data-action-id="id"/> <!-- result: <div data-action-id="32"></div> -->
+```
+
+If an expression evaluates to a falsy value, it will not be set at all:
+
+```xml
+<div t-att-foo="false"/>  <!-- result: <div></div> -->
+```
+
+It is sometimes convenient to format an attribute with string interpolation. In
+that case, the `t-attf-` directive can be used. It is useful when we need to mix
+literal and dynamic elements, such as css classes.
+
+```xml
+<div t-attf-foo="a {{value1}} is {{value2}} of {{value3}} ]"/>
+<!-- result if values are set to 1,2 and 3: <div foo="a 0 is 1 of 2 ]"></div> -->
+```
+
+If we need completely dynamic attribute names, then there is an additional
+directive: `t-att`, which takes either an object (with keys mapping to their
+values) or a pair `[key, value]`. For example:
+
+```xml
+<div t-att="{'a': 1, 'b': 2}"/> <!-- result: <div a="1" b="2"></div> -->
+
+<div t-att="['a', 'b']"/> <!-- <div a="b"></div> -->
+```
+
+### Loops
+
+QWeb has an iteration directive `t-foreach` which take an expression returning the
+collection to iterate on, and a second parameter `t-as` providing the name to use
+for the current item of the iteration:
+
+```xml
+<t t-foreach="[1, 2, 3]" t-as="i">
+    <p><t t-esc="i"/></p>
+</t>
+```
+
+will be rendered as:
+
+```xml
+<p>1</p>
+<p>2</p>
+<p>3</p>
+```
+
+Like conditions, `t-foreach` applies to the element bearing the directive’s attribute, and
+
+```xml
+<p t-foreach="[1, 2, 3]" t-as="i">
+    <t t-esc="i"/>
+</p>
+```
+
+is equivalent to the previous example.
+
+`t-foreach` can iterate on an array (the current item will be the current value)
+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: `$as` will be replaced with the name
+passed to `t-as`):
+
+- `$as_value`: the current iteration value, identical to `$as` for lists and
+  integers, but for objects, it provides the value (where `$as` provides the key)
+- `$as_index`: the current iteration index (the first item of the iteration has index 0)
+- `$as_first`: whether the current item is the first of the iteration
+  (equivalent to `$as_index == 0`)
+- `$as_last`: whether the current item is the last of the iteration
+  (equivalent to `$as_index + 1 == $as_size`), requires the iteratee’s size be
+  available
+
+These extra variables provided and all new variables created into the `t-foreach`
+are only available in the scope of the `t-foreach`. If the variable exists outside
+the context of the `t-foreach`, the value is copied at the end of the foreach
+into the global context.
+
+```xml
+<t t-set="existing_variable" t-value="false"/>
+<!-- existing_variable now False -->
+
+<p t-foreach="Array(3)" t-as="i">
+    <t t-set="existing_variable" t-value="true"/>
+    <t t-set="new_variable" t-value="true"/>
+    <!-- existing_variable and new_variable now true -->
+</p>
+
+<!-- existing_variable always true -->
+<!-- new_variable undefined -->
+```
+
+Owl QWeb is used as the template engine for components. Components are frequently
+updated, and reuse as much of the previous DOM as possible. Loops offer a specific
+problem for this usecase: how does the template engine know if two rows have
+been swapped, or if the content of these rows was changed? To help Owl with that,
+there is an additional directive: [`t-key`](component.md#t-key-directive).
+
+```xml
+<p t-foreach="state.things" t-as="thing" t-key="thing.id">
+    <t t-esc="thing.content"/>
+</p>
+```
+
+If there is no `t-key` directive, Owl will use the index as a default key.
+
+### Rendering Sub Templates
+
+QWeb templates can be used for top level rendering, but they can also be used
+from within another template (to avoid duplication or give names to parts of
+templates), using the `t-call` directive:
+
+```xml
+<div t-name="other-template">
+    <p><t t-value="var"/></p>
+</div>
+
+<div t-name="main-template">
+    <t t-set="var" t-value="owl"/>
+    <t t-call="other-template"/>
+</div>
+```
+
+will be rendered as `<div><p>owl</p></div>`. This example shows that the sub
+template is rendered with the execution context of the parent. The sub template
+is actually inlined in the main template, but in a sub scope: variables defined
+in the sub template do not escape.
+
+Sometimes, one might want to pass information to the sub template. In that case,
+the content of the body of the `t-call` directive is available as a special
+magic variable `0`:
+
+```xml
+<t t-name="other-template">
+    This template was called with content:
+    <t t-raw="0"/>
+</t>
+
+<div t-name="main-template">
+    <t t-call="other-template">
+        <em>content</em>
+    </t>
+</div>
+```
+
+will result in :
+
+```xml
+<div>
+    This template was called with content:
+    <em>content</em>
+</div>
+```
+
+### 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.
+
+### Debugging
+
+The javascript QWeb implementation provides two useful debugging directives:
+
+`t-debug` adds a debugger statement during template rendering:
+
+```xml
+<t t-if="a_test">
+    <t t-debug="">
+</t>
+```
+
+will stop execution if the browser dev tools are open.
+
+`t-log` takes an expression parameter, evaluates the expression during rendering and logs its result with console.log:
+
+```xml
+<t t-set="foo" t-value="42"/>
+<t t-log="foo"/>
+```
+
+will print 42 to the console.
@@ -0,0 +1,178 @@
+# 🦉 Router 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Example](#example)
+- [Reference](#reference)
+  - [Route Definition](#route-definition)
+  - [Router](#router)
+  - [Navigation Guards](#navigation-guards)
+  - [RouteComponent](#routecomponent)
+  - [Link](#link)
+
+## Overview
+
+It is often useful to organize an application around urls. If the application is
+a single page application, then we need a way to manage those urls in the browser.
+This is why there are many different routers for different frameworks. A generic
+router can do the job just fine, but a specialized router for Owl can give a
+better developer experience.
+
+The Owl router support the following features:
+
+- `history` or `hash` mode
+- declarative routes
+- route redirection
+- navigation guards
+- parameterized routes
+- a `<Link/>` component
+- a `<RouteComponent/>` component
+
+Note that it is still in early stage of developments, and there are probably
+still some issues.
+
+## Example
+
+To use the Owl router, there are some steps that needs to be done:
+
+- declare some routes
+- create a router
+- add it to the environment
+
+```js
+async function protectRoute({ env, to }) {
+  if (!env.session.authUser) {
+    env.session.setNextRoute(to.name);
+    return { to: "SIGN_IN" };
+  }
+  return true;
+}
+
+export const ROUTES = [
+  { name: "LANDING", path: "/", component: Landing },
+  { name: "TASK", path: "/tasks/{{id}}", component: Task },
+  { name: "SIGN_UP", path: "/signup", component: SignUp },
+  { name: "SIGN_IN", path: "/signin", component: SignIn },
+  { name: "ADMIN", path: "/admin", component: Admin, beforeRouteEnter: protectRoute },
+  { name: "ACCOUNT", path: "/account", component: Account, beforeRouteEnter: protectRoute },
+  { name: "UNKNOWN", path: "*", redirect: { to: "LANDING" } }
+];
+
+function makeEnvironment() {
+    ...
+    const env = { qweb };
+    env.session = new Session(env);
+    env.router = new owl.router.Router(env, ROUTES);
+    await env.router.start();
+    return env;
+}
+```
+
+Notice that the router needs to be started. This is an asynchronous operation
+because it needs to apply the potential navigation guards on the current route
+(which may or may not mean that the application is redirected to another route).
+
+## Reference
+
+### Route definition
+
+A route need to be defined as an object with the following keys:
+
+- `name` (optional): a (unique) string useful to identify the current route. If not
+  given, it will be assigned an automatic name,
+- `path`: a string describing the url. It can be static: `/admin` or dynamic: `/users/{{id}}`.
+  It also can be `*`, to catch all remaining routes.
+- `component` (optional): an Owl component that will be used by the `t-routecomponent`
+  directive if the route is active
+- `redirect` (optional): should be destination object (with optional keys `path`, `to` and `params`) if given, the application will be redirected to the destination whenever we match this route
+- `beforeRouteEnter`: defines a [navigation guard](#navigation-guards).
+
+### `Router`
+
+The `Router` constructor takes three arguments:
+
+- `env`: a valid environment,
+- a list of routes,
+- an optional object (with the only key `mode` which can be `history` (default
+  value) or `hash`).
+
+`history` will use the browser [History API](https://developer.mozilla.org/en-US/docs/Web/API/History_API) as the mechanism to manage URL.\
+Example: `https://yourdomain.tld/my_custom_route`.\
+For this mechanism to work, you need a way to configure your web server accordingly.
+
+`hash` will manipulate the hash of the URL.\
+Example: `https://yourdomain.tld/index.html#/my_custom_route`.
+
+```js
+const ROUTES = [...];
+const router = new owl.router.Router(env, ROUTES, {mode: 'history'});
+```
+
+Note that the route are defined in a list, and the order matters: the router
+tries to find a match by going down the list.
+
+The router needs to be added to the environment in the `router` sub key.
+
+Once a router is created, it needs to be started. This is necessary to initialize
+its current state to the current URL (and also, to potentially apply any
+navigation guards and/or redirecting).
+
+```js
+await router.start();
+```
+
+Once started, the router will keep track of the current url and reflect its
+value in two keys:
+
+- `router.currentRoute`
+- `router.currentParams`
+
+The router also has a `navigate` method, useful to programmatically change the
+application to another state (and the url):
+
+```js
+router.navigate({ to: "USER", params: { id: 51 } });
+```
+
+### Navigation Guards
+
+Navigation guards are very useful to be able to execute some business logic/
+perform some actions or redirect to other routes whenever the application is
+entering a new route. For example, the following guard checks if there is an
+authenticated user, and if it is not the case, redirect to the sign in route.
+
+```js
+async function protectRoute({ env, to }) {
+  if (!env.session.authUser) {
+    env.session.setNextRoute(to.name);
+    return { to: "SIGN_IN" };
+  }
+  return true;
+}
+```
+
+A navigation guard is a function that returns a promise, which either resolves
+to `true` (the navigation is accepted), or to another destination object.
+
+### `RouteComponent`
+
+The `RouteComponent` component directs Owl to render the component associated
+to the currently active route (if any):
+
+```xml
+<div t-name="App">
+    <NavBar />
+    <RouteComponent />
+</div>
+```
+
+### `Link`
+
+The `Link` component is a Owl component which render as a `<a>` tag with any
+content. It will compute the proper href from its props, and allow Owl to
+properly navigate to a given url if clicked on it.
+
+```xml
+<Link to="'HOME'">Home</Link>
+```
@@ -0,0 +1,326 @@
+# 🦉 Store 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Example](#example)
+- [Reference](#reference)
+  - [Store](#store)
+  - [Actions](#actions)
+  - [Getters](#getters)
+  - [Connecting a Component](#connecting-a-component)
+  - [`useStore`](#usestore)
+  - [`useDispatch`](#usedispatch)
+  - [`useGetters`](#usegetters)
+  - [Semantics](#semantics)
+  - [Good Practices](#good-practices)
+
+## Overview
+
+Managing the state in an application is not an easy task. In some cases, the
+state of an application can be part of the component tree, in a natural way.
+However, there are situations where some parts of the state need to be displayed
+in various parts of the user interface, and then, it is not obvious which
+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.
+
+Note: Owl store is inspired by React Redux and VueX.
+
+## Example
+
+Here is what a simple store looks like:
+
+```js
+const actions = {
+  addTodo({ state }, message) {
+    state.todos.push({
+      id: state.nextId++,
+      message,
+      isCompleted: false
+    });
+  }
+};
+
+const state = {
+  todos: [],
+  nextId: 1
+};
+
+const store = new owl.Store({ state, actions });
+store.on("update", null, () => console.log(store.state));
+
+// updating the state
+store.dispatch("addTodo", "fix all bugs");
+```
+
+This example shows how a store can be defined and used. Note that in most cases,
+actions will be dispatched by connected components.
+
+## Reference
+
+### `Store`
+
+The store is a simple [`owl.EventBus`](event_bus.md) that triggers `update` events
+whenever its state is changed. Note that these events are triggered only after a
+microtask tick, so only one event will be triggered for any number of state changes in a
+call stack.
+
+Also, it is important to mention that the state is observed (with an `owl.Observer`),
+which is the reason why it is able to know if it was changed. See the
+[Observer](observer.md)'s documentation for more details.
+
+The `Store` class is quite small. It has two public methods:
+
+- its constructor
+- `dispatch`
+
+The constructor takes a configuration object with four (optional) keys:
+
+- the initial state
+- the actions
+- the getters
+- the environment
+
+```javascript
+const config = {
+  state,
+  actions,
+  getters,
+  env
+};
+const store = new Store(config);
+```
+
+### Actions
+
+Actions are used to coordinate state changes. It can be used for both synchronous
+and asynchronous logic.
+
+```js
+const actions = {
+  async login({ state }, info) {
+    state.loginState = "pending";
+    try {
+      const loginInfo = await doSomeRPC("/login/", info);
+      state.loginState = loginInfo;
+    } catch (e) {
+      state.loginState = "error";
+    }
+  }
+};
+```
+
+The first argument to an action method is an object with four keys:
+
+- `state`: the current state of the store content,
+- `dispatch`: a function that can be used to dispatch other actions,
+- `getters`: an object containing all getters defined in the store,
+- `env`: the current environment. This is useful sometimes, in particular if
+  an action needs to apply some side effects (such as performing an rpc), and
+  the `rpc` method is located in the environment.
+
+Actions are called with the `dispatch` method on the store, and can receive an
+arbitrary number of arguments.
+
+```js
+store.dispatch("login", someInfo);
+```
+
+Note that anything returned by an action will also be returned by the `dispatch`
+call.
+
+Also, it is important to be aware that we need to be careful with asynchronous
+logic. Each state change will potentially trigger a rerendering, so we need to
+make sure that we do not have a partially corrupted state. Here is an example that
+is likely not a good idea:
+
+```javascript
+const actions = {
+  async fetchSomeData({ state }, recordId) {
+    state.recordId = recordId;
+    const data = await doSomeRPC("/read/", recordId);
+    state.recordData = data;
+  }
+};
+```
+
+In the previous example, there is a period of time in which the state has a
+`recordId` which does not correspond to the `recordData`. It is more likely that
+we want an atomic update: updating the `recordId` at the same time as the `recordData`
+values:
+
+```javascript
+const actions = {
+  async fetchSomeData({ state }, recordId) {
+    const data = await doSomeRPC("/read/", recordId);
+    state.recordId = recordId;
+    state.recordData = data;
+  }
+};
+```
+
+### Getters
+
+Usually, data contained in the store will be stored in a normalized way. For
+example,
+
+```js
+{
+    posts: [{id: 11, authorId: 4, content: 'Greetings'}],
+    authors: [{id: 4, name: 'John'}]
+}
+```
+
+However, the user interface will probably need some denormalized data like
+
+```js
+{id: 11, author: {id: 4, name: 'John'}, content: 'Greetings'}
+```
+
+This is what `getters` are for: they give a centralized way to process and
+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);
+    return {
+      id,
+      author,
+      content: post.content
+    };
+  }
+};
+
+// somewhere else
+const post = store.getters.getPost(id);
+```
+
+Getters take _at most_ one argument.
+
+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:
+
+- [`useStore`](#usestore) to subscribe a component to some part of the store state,
+- [`useDispatch`](#usedispatch) to get a reference to a dispatch function,
+- [`useGetters`](#usegetters) to get a reference to the getters defined in the store.
+
+Assume we have this store:
+
+```javascript
+const actions = {
+  increment({ state }, val) {
+    state.counter.value += val;
+  }
+};
+
+const state = {
+  counter: { value: 0 }
+};
+const store = new owl.Store({ state, actions });
+```
+
+A counter component can then select this value and dispatch an action like this:
+
+```js
+class Counter extends Component {
+  counter = useStore(state => state.counter);
+  dispatch = useDispatch();
+}
+
+const counter = new Counter({ store, qweb });
+```
+
+```xml
+<button t-name="Counter" t-on-click="dispatch('increment')">
+  Click Me! [<t t-esc="counter.value"/>]
+</button>
+```
+
+### `useStore`
+
+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).
+
+If the `useStore` callback selects 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.
+
+Also, it may not be obvious, but it is crucial to remember that the selector
+function should return an object or an array.  The reason is that it needs to be
+observed, otherwise the component would not be able to react to changes.
+
+### `useDispatch`
+
+The `useDispatch` hook is useful when a component needs to be able to dispatch
+actions. It takes an optional argument, which is a store. If not given, it will
+use the store in the environment.
+
+Note that a component does not need to be connected in any other way to the store.
+For example:
+
+```js
+class DoSomethingButton extends Component {
+  static template = xml`<button t-on-click="dispatch('something')">Click</button>`;
+  dispatch = useDispatch();
+}
+```
+
+### `useGetters`
+
+The `useGetters` hook is useful when a component needs to be able to use the
+getters defined in a store. It takes an optional argument, which is a store. If
+not given, it will use the store in the environment.
+
+Note that a component does not need to be connected in any other way to the store.
+For example:
+
+```js
+class InfoButton extends Component {
+  static template = xml`<span><t t-esc="getters.somevalue()"></span>`;
+  getters = useGetters();
+}
+```
+
+### Semantics
+
+The `Store` class and the `useStore` hook try to be smart and to optimize as much
+as possible the rendering and update process. What is important to know is:
+
+- components are always updated in the order of their creation (so, parent
+  before children),
+- they are updated only if they are in the DOM,
+- if a parent is asynchronous, the system will wait for it to complete its
+  update before updating other components,
+- in general, updates are not coordinated. This is not a problem for synchronous
+  components, but if there are many asynchronous components, this could lead to
+  a situation where some part of the UI is updated and some other part of the UI is
+  not updated.
+
+### Good Practices
+
+- avoid asynchronous components as much as possible. Asynchronous components
+  lead to situations where parts of the UI is not updated immediately,
+- do not be afraid to connect many components, parent or children if needed. For
+  example, a `MessageList` component could get a list of ids in its `useStore`
+  call and a `Message` component could get the data of its own
+  message,
+- since the `useStore` function is called for each connected component,
+  for each state update, it is important to make sure that these functions are
+  as fast as possible.
@@ -0,0 +1,54 @@
+# 🦉 Tags 🦉
+
+## Content
+
+- [Overview](#overview)
+- [`xml` tag](#xml-tag)
+
+## Overview
+
+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](../tooling.md#single-file-component).
+
+## 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
+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>
+    `;
+
+    ...
+}
+```
@@ -0,0 +1,148 @@
+# 🦉 Utils 🦉
+
+Owl export a few useful utility functions, to help with common issues. Those
+functions are all available in the `owl.utils` namespace.
+
+## Content
+
+- [`whenReady`](#whenready): executing code when DOM is ready
+- [`loadJS`](#loadjs): loading script files
+- [`loadFile`](#loadfile): loading a file (useful for templates)
+- [`escape`](#escape): sanitizing strings
+- [`debounce`](#debounce): limiting rate of function calls
+- [`shallowEqual`](#shallowequal): shallow object comparison
+
+## `whenReady`
+
+The function `whenReady` returns a `Promise` resolved when the DOM is ready (if
+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);
+});
+```
+
+or alternatively:
+
+```js
+owl.utils.whenReady(function() {
+  const qweb = new owl.QWeb();
+  const app = new App({ qweb });
+  app.mount(document.body);
+});
+```
+
+## `loadJS`
+
+`loadJS` takes a url (string) for a javascript resource, and loads it (by adding
+a script tag in the document head). It returns a promise, so the caller can
+properly reacts when it is ready. Also, it is smart: it maintains a list of urls
+previously loaded (or currently being loaded), and prevent doing twice the work.
+
+For example, it is useful for lazy loading external libraries:
+
+```js
+class MyComponent extends owl.Component {
+  willStart() {
+    return owl.utils.loadJS("/static/libs/someLib.js");
+  }
+}
+```
+
+## `loadFile`
+
+`loadFile` is a helper function to fetch a file. It simply
+performs a `GET` request and returns the resulting string in a promise. The
+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 });
+  return { qweb };
+}
+```
+
+Note that unlike `loadJS`, this function returns the content of the file as a
+string. It does not add a `script` tag or any other side effect.
+
+## `escape`
+
+Sometimes, we need to display dynamic data (for example user-generated data) in
+the user interface. If this is done by a `QWeb` template, it is not an issue:
+
+```xml
+    <div><t t-esc="user.data"/></div>
+```
+
+The `QWeb` engine will create a `div` node and add the content of the `user.data`
+string as a text node, so the web browser will not parse it as html. However,
+it may be a problem if this is done with some javascript code like this:
+
+```js
+class BadComponent extends Component {
+  // some template with a ref to a div
+  // some code ...
+
+  mounted() {
+    this.divRef.el.innerHTML = this.state.value;
+  }
+}
+```
+
+In this case, the content of the `div` will be parsed as html, which may inject
+unwanted behaviour. To fix this, the `escape` function will simply transform a
+string into an escaped version of the same string, which will be properly displayed
+by the browser, but which will not be parsed as html (for example, `"<ok>"` is
+escaped to the string: `"&lt;ok&gt;"`). So, the bad example above can be fixed
+with the following change:
+
+```js
+this.divRef.el.innerHTML = owl.utils.escape(this.state.value);
+```
+
+## `debounce`
+
+The `debounce` function is useful when we want to limit the number of times some
+function/action is perfomed. For example, this may be useful to prevent issue
+with people double clicking on a button.
+
+It takes three arguments:
+
+- `func` (function): this is the function that will be rate limited
+- `wait` (number): this is the number of milliseconds that we want to use to
+  rate limit the function `func`
+- `immediate` (optional, boolean, default=false): if `immediate` is true, the
+  function will be triggered immediately (leading edge of the interval). If false,
+  the function will be triggered at the end (trailing edge).
+
+It returns a function. For example:
+
+```js
+const debounce = owl.utils.debounce;
+window.addEventListener("mousemove", debounce(doSomething, 100));
+```
+
+As this example shows, it is usualy useful for event handlers which are triggered
+very quickly, such as `scroll` or `mousemove` events.
+
+## `shallowEqual`
+
+This function checks if two objects have the same values assigned to each keys:
+
+```js
+shallowEqual({ a: 1, b: 2 }, { a: 1, b: 2 }); // true
+shallowEqual({ a: 1, b: 2 }, { a: 1, b: 3 }); // false
+```
+
+However, for performance reasons, it assumes that the two objects have the same
+keys. If we are in a situation where this is not guaranteed, the following code
+will work:
+
+```js
+const completeShallowEqual = (a, b) => shallowEqual(a, b) && shallowEqual(b, a);
+```
@@ -1,8 +0,0 @@
-# 🦉 Store 🦉
-
-Managing the state in an application is not an easy task. Many different
-architectures/designs/systems/... have been created. We propose here to use
-the idea of a central store.
-
- Store
- connect
@@ -0,0 +1,101 @@
+# 🦉 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
+
+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 currently has a small helper that makes it easy to define a
+template inside a javascript (or typescript) file: the [`xml`](reference/tags.md#xml-tag)
+helper. With this, a template is automatically registered to [QWeb](reference/qweb.md).
+
+This means that the template and the javascript code can be defined in the same
+file. It is not currently possible to add css to the same file, but Owl may
+get a `css` tag helper later.
+
+```js
+const { Component } = owl;
+const { xml } = owl.tags;
+
+// -----------------------------------------------------------------------------
+// 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...
+}
+```
+
+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.
@@ -1,3 +0,0 @@
-# 🦉 VDom 🦉
-
-Owl's virtual dom is a fork of [snabbdom](https://github.com/snabbdom/snabbdom).
@@ -1,30 +0,0 @@
-<templates>
-    <div class="main" t-name="root">
-        <div class="left-thing">
-            <div class="message_count">
-                Number of msg: 0
-            </div>
-            <button class="o_btn_msg 100">Add 100 messages</button>
-            <button class="o_btn_msg 1000">Add 1000 messages</button>
-            <button class="o_btn_msg 10000">Add 10000 messages</button>
-            <button class="o_btn_msg 50000">Add 50000 messages</button>
-            <button class="updateSomeMessages">Update every 10th message</button>
-            <button class="clear">Clear</button>
-        </div>
-        <div class="right-thing">
-            <div class="content">
-            </div>
-        </div>
-    </div>
-
-    <div t-name="message" class="message">
-        <span class="author"><t t-esc="widget.author"/></span>
-        <span class="msg"><t t-esc="widget.msg"/></span>
-        <button class="remove" >Remove</button>
-    </div>
-
-  <div t-name="counter">
-    <button class="o_increment"></button>
-  </div>
-
-</templates>
@@ -1,30 +0,0 @@
-<templates>
-    <div class="main" t-name="root">
-        <div class="left-thing">
-            <div class="message_count">
-                Number of msg: 0
-            </div>
-            <button class="o_btn_msg 100">Add 100 messages</button>
-            <button class="o_btn_msg 1000">Add 1000 messages</button>
-            <button class="o_btn_msg 10000">Add 10000 messages</button>
-            <button class="o_btn_msg 50000">Add 50000 messages</button>
-            <button class="updateSomeMessages">Update every 10th message</button>
-            <button class="clear">Clear</button>
-        </div>
-        <div class="right-thing">
-            <div class="content">
-            </div>
-        </div>
-    </div>
-
-    <div t-name="message" class="message">
-        <span class="author"><t t-esc="widget.author"/></span>
-        <span class="msg"><t t-esc="widget.msg"/></span>
-        <button class="remove" >Remove</button>
-    </div>
-
-  <div t-name="counter">
-    <button class="o_increment"></button>
-  </div>
-
-</templates>
@@ -1,85 +0,0 @@
-import { buildData, startMeasure, stopMeasure } from "../shared/utils.js";
-
-//------------------------------------------------------------------------------
-// Likes Counter Widget
-//------------------------------------------------------------------------------
-class Counter extends owl.Component {
-  template = "counter";
-  state = { counter: 0 };
-
-  increment() {
-    this.state.counter++;
-  }
-}
-
-//------------------------------------------------------------------------------
-// Message Widget
-//------------------------------------------------------------------------------
-class Message extends owl.Component {
-  template = "message";
-  widgets = { Counter };
-
-  shouldUpdate(nextProps) {
-    return nextProps !== this.props;
-  }
-
-  removeMessage() {
-    this.trigger("remove_message", {
-      id: this.props.id
-    });
-  }
-}
-
-//------------------------------------------------------------------------------
-// Root Widget
-//------------------------------------------------------------------------------
-class App extends owl.Component {
-  template = "root";
-  widgets = { Message };
-  state = { messages: [] };
-
-  addMessages(n) {
-    startMeasure("add " + n);
-    const newMessages = buildData(n);
-    this.state.messages.push.apply(this.state.messages, newMessages);
-    stopMeasure();
-  }
-
-  clear() {
-    startMeasure("clear");
-    this.state.messages = [];
-    stopMeasure();
-  }
-
-  updateSomeMessages() {
-    startMeasure("update every 10th");
-    const messages = this.state.messages;
-    for (let i = 0; i < this.state.messages.length; i += 10) {
-      const msg = Object.assign({}, messages[i]);
-      msg.author += '!!!';
-      this.set(messages, i, msg);
-    }
-    stopMeasure();
-  }
-
-  removeMessage(data) {
-    startMeasure('remove message');
-    const index = this.state.messages.findIndex(m => m.id === data.id);
-    this.state.messages.splice(index, 1);
-    stopMeasure();
-  }
-}
-
-//------------------------------------------------------------------------------
-// Application initialization
-//------------------------------------------------------------------------------
-async function start() {
-  const templates = await owl.utils.loadTemplates("templates.xml");
-  const env = {
-    qweb: new owl.QWeb(templates)
-  };
-  const app = new App(env);
-  app.mount(document.body);
-}
-
-start();
@@ -1,32 +0,0 @@
-<templates>
-  <div t-name="root" class="main">
-      <div class="left-thing">
-          <div>Number of msg: <t t-esc="state.messages.length"/></div>
-          <button t-on-click="addMessages(100)">Add 100 messages</button>
-          <button t-on-click="addMessages(1000)">Add 1000 messages</button>
-          <button t-on-click="addMessages(10000)">Add 10000 messages</button>
-          <button t-on-click="addMessages(50000)">Add 50000 messages</button>
-          <button t-on-click="updateSomeMessages">Update every 10th message</button>
-          <button t-on-click="clear">Clear</button>
-      </div>
-      <div class="right-thing">
-          <div class="content">
-              <t t-foreach="state.messages" t-as="message">
-                  <t t-widget="Message" t-key="message.id" t-props="message" t-on-remove_message="removeMessage"/>
-              </t>
-          </div>
-      </div>
-  </div>
-
-  <div t-name="message" class="message">
-    <span class="author"><t t-esc="props.author"/></span>
-    <span class="msg"><t t-esc="props.msg"/></span>
-    <button class="remove" t-on-click="removeMessage">Remove</button>
-    <t t-widget="Counter"/>
-  </div>
-
-  <div t-name="counter">
-    <button t-on-click="increment">Value: <t t-esc="state.counter"/></button>
-  </div>
-
-</templates>
@@ -1,84 +0,0 @@
-import { buildData, startMeasure, stopMeasure } from "../shared/utils.js";
-
-//------------------------------------------------------------------------------
-// Likes Counter Widget
-//------------------------------------------------------------------------------
-class Counter extends owl.Component {
-  template = "counter";
-  state = { counter: 0 };
-
-  increment() {
-    this.state.counter++;
-  }
-}
-
-//------------------------------------------------------------------------------
-// Message Widget
-//------------------------------------------------------------------------------
-class Message extends owl.Component {
-  template = "message";
-  widgets = { Counter };
-
-  shouldUpdate(nextProps) {
-    return nextProps !== this.props;
-  }
-  removeMessage() {
-    this.trigger("remove_message", {
-      id: this.props.id
-    });
-  }
-}
-
-//------------------------------------------------------------------------------
-// Root Widget
-//------------------------------------------------------------------------------
-class App extends owl.Component {
-  template = "root";
-  widgets = { Message };
-  state = { messages: [] };
-
-  addMessages(n) {
-    startMeasure("add " + n);
-    const newMessages = buildData(n);
-    this.state.messages.push.apply(this.state.messages, newMessages);
-    stopMeasure();
-  }
-
-  clear() {
-    startMeasure("clear");
-    this.state.messages = [];
-    stopMeasure();
-  }
-
-  updateSomeMessages() {
-    startMeasure("update every 10th");
-    const messages = this.state.messages;
-    for (let i = 0; i < this.state.messages.length; i += 10) {
-      const msg = Object.assign({}, messages[i]);
-      msg.author += '!!!';
-      this.set(messages, i, msg);
-    }
-    stopMeasure();
-  }
-
-  removeMessage(data) {
-    startMeasure("remove message");
-    const index = this.state.messages.findIndex(m => m.id === data.id);
-    this.state.messages.splice(index, 1);
-    stopMeasure();
-  }
-}
-
-//------------------------------------------------------------------------------
-// Application initialization
-//------------------------------------------------------------------------------
-async function start() {
-  const templates = await owl.utils.loadTemplates("templates.xml");
-  const env = {
-    qweb: new owl.QWeb(templates)
-  };
-  const app = new App(env);
-  app.mount(document.body);
-}
-
-start();
@@ -1,32 +0,0 @@
-<templates>
-  <div t-name="root" class="main">
-      <div class="left-thing">
-          <div>Number of msg: <t t-esc="state.messages.length"/></div>
-          <button t-on-click="addMessages(100)">Add 100 messages</button>
-          <button t-on-click="addMessages(1000)">Add 1000 messages</button>
-          <button t-on-click="addMessages(10000)">Add 10000 messages</button>
-          <button t-on-click="addMessages(50000)">Add 50000 messages</button>
-          <button t-on-click="updateSomeMessages">Update every 10th message</button>
-          <button t-on-click="clear">Clear</button>
-      </div>
-      <div class="right-thing">
-          <div class="content">
-              <t t-foreach="state.messages" t-as="message">
-                  <t t-widget="Message" t-key="message.id" t-props="message" t-on-remove_message="removeMessage"/>
-              </t>
-          </div>
-      </div>
-  </div>
-
-  <div t-name="message" class="message">
-    <span class="author"><t t-esc="props.author"/></span>
-    <span class="msg"><t t-esc="props.msg"/></span>
-    <button class="remove" t-on-click="removeMessage">Remove</button>
-    <t t-widget="Counter"/>
-  </div>
-
-  <div t-name="counter">
-    <button t-on-click="increment">Value: <t t-esc="state.counter"/></button>
-  </div>
-
-</templates>
@@ -1,84 +0,0 @@
-import { buildData, startMeasure, stopMeasure } from "../shared/utils.js";
-
-//------------------------------------------------------------------------------
-// Likes Counter Widget
-//------------------------------------------------------------------------------
-class Counter extends owl.Component {
-  template = "counter";
-  state = { counter: 0 };
-
-  increment() {
-    this.state.counter++;
-  }
-}
-
-//------------------------------------------------------------------------------
-// Message Widget
-//------------------------------------------------------------------------------
-class Message extends owl.Component {
-  template = "message";
-  widgets = { Counter };
-
-  shouldUpdate(nextProps) {
-    return nextProps !== this.props;
-  }
-  removeMessage() {
-    this.trigger("remove_message", {
-      id: this.props.id
-    });
-  }
-}
-
-//------------------------------------------------------------------------------
-// Root Widget
-//------------------------------------------------------------------------------
-class App extends owl.Component {
-  template = "root";
-  widgets = { Message };
-  state = { messages: [] };
-
-  addMessages(n) {
-    startMeasure("add " + n);
-    const newMessages = buildData(n);
-    this.state.messages.push.apply(this.state.messages, newMessages);
-    stopMeasure();
-  }
-
-  clear() {
-    startMeasure("clear");
-    this.state.messages = [];
-    stopMeasure();
-  }
-
-  updateSomeMessages() {
-    startMeasure("update every 10th");
-    const messages = this.state.messages;
-    for (let i = 0; i < this.state.messages.length; i += 10) {
-      const msg = Object.assign({}, messages[i]);
-      msg.author += '!!!';
-      this.set(messages, i, msg);
-    }
-    stopMeasure();
-  }
-
-  removeMessage(data) {
-    startMeasure("remove message");
-    const index = this.state.messages.findIndex(m => m.id === data.id);
-    this.state.messages.splice(index, 1);
-    stopMeasure();
-  }
-}
-
-//------------------------------------------------------------------------------
-// Application initialization
-//------------------------------------------------------------------------------
-async function start() {
-  const templates = await owl.utils.loadTemplates("templates.xml");
-  const env = {
-    qweb: new owl.QWeb(templates)
-  };
-  const app = new App(env);
-  app.mount(document.body);
-}
-
-start();
@@ -1,32 +0,0 @@
-<templates>
-  <div t-name="root" class="main">
-      <div class="left-thing">
-          <div>Number of msg: <t t-esc="state.messages.length"/></div>
-          <button t-on-click="addMessages(100)">Add 100 messages</button>
-          <button t-on-click="addMessages(1000)">Add 1000 messages</button>
-          <button t-on-click="addMessages(10000)">Add 10000 messages</button>
-          <button t-on-click="addMessages(50000)">Add 50000 messages</button>
-          <button t-on-click="updateSomeMessages">Update every 10th message</button>
-          <button t-on-click="clear">Clear</button>
-      </div>
-      <div class="right-thing">
-          <div class="content">
-              <t t-foreach="state.messages" t-as="message">
-                  <t t-widget="Message" t-key="message.id" t-props="message" t-on-remove_message="removeMessage"/>
-              </t>
-          </div>
-      </div>
-  </div>
-
-  <div t-name="message" class="message">
-    <span class="author"><t t-esc="props.author"/></span>
-    <span class="msg"><t t-esc="props.msg"/></span>
-    <button class="remove" t-on-click="removeMessage">Remove</button>
-    <t t-widget="Counter"/>
-  </div>
-
-  <div t-name="counter">
-    <button t-on-click="increment">Value: <t t-esc="state.counter"/></button>
-  </div>
-
-</templates>
@@ -1,221 +0,0 @@
-import { buildData, startMeasure, stopMeasure } from "../shared/utils.js";
-
-//------------------------------------------------------------------------------
-// Counter Widget
-//------------------------------------------------------------------------------
-class Counter extends React.Component {
-  constructor(props) {
-    super(props);
-    this.state = {
-      counter: 0
-    };
-    this.increment = this.increment.bind(this);
-  }
-
-  render() {
-    return React.createElement(
-      "div",
-      null,
-      React.createElement(
-        "button",
-        {
-          onClick: this.increment
-        },
-        "Value: ",
-        this.state.counter
-      )
-    );
-  }
-
-  increment() {
-    this.setState({
-      counter: this.state.counter + 1
-    });
-  }
-}
-//------------------------------------------------------------------------------
-// Message Widget
-//------------------------------------------------------------------------------
-class Message extends React.Component {
-  constructor(props) {
-    super(props);
-    this.removeMessage = this.removeMessage.bind(this);
-  }
-
-  render() {
-    return React.createElement(
-      "div",
-      {
-        className: "message"
-      },
-      React.createElement(
-        "span",
-        {
-          className: "author"
-        },
-        this.props.message.author
-      ),
-      React.createElement(
-        "span",
-        {
-          className: "msg"
-        },
-        this.props.message.msg
-      ),
-      React.createElement(
-        "button",
-        {
-          className: "remove",
-          onClick: this.removeMessage
-        },
-        "Remove"
-      ),
-      React.createElement(Counter, null)
-    );
-  }
-
-  removeMessage() {
-    this.props.removeCB(this.props.message.id);
-  }
-}
-
-//------------------------------------------------------------------------------
-// Root Widget
-//------------------------------------------------------------------------------
-class Main extends React.Component {
-  constructor(props) {
-    super(props);
-    this.state = {
-      messages: []
-    };
-    this.removeMessage = this.removeMessage.bind(this);
-  }
-
-  render() {
-    const msgList = this.state.messages.map(m =>
-      React.createElement(Message, {
-        key: m.id,
-        message: m,
-        removeCB: this.removeMessage
-      })
-    );
-    return React.createElement(
-      "div",
-      {
-        className: "main"
-      },
-      React.createElement(
-        "div",
-        {
-          className: "left-thing"
-        },
-        React.createElement(
-          "div",
-          null,
-          "Number of msg: ",
-          this.state.messages.length
-        ),
-        React.createElement(
-          "button",
-          {
-            onClick: _ => this.addMessages(100)
-          },
-          "Add 100 messages"
-        ),
-        React.createElement(
-          "button",
-          {
-            onClick: _ => this.addMessages(1000)
-          },
-          "Add 1000 messages"
-        ),
-        React.createElement(
-          "button",
-          {
-            onClick: _ => this.addMessages(10000)
-          },
-          "Add 10000 messages"
-        ),
-        React.createElement(
-          "button",
-          {
-            onClick: _ => this.addMessages(50000)
-          },
-          "Add 50000 messages"
-        ),
-        React.createElement(
-          "button",
-          {
-            onClick: _ => this.updateSomeMessages()
-          },
-          "Update every 10th messags"
-        ),
-        React.createElement(
-          "button",
-          {
-            onClick: _ => this.clear()
-          },
-          "Clear"
-        )
-      ),
-      React.createElement(
-        "div",
-        {
-          className: "right-thing"
-        },
-        React.createElement(
-          "div",
-          {
-            className: "content"
-          },
-          msgList
-        )
-      )
-    );
-  }
-
-  addMessages(n) {
-    startMeasure("add " + n);
-    const newMessages = this.state.messages.concat(buildData(n));
-    this.setState({
-      messages: newMessages
-    });
-    stopMeasure();
-  }
-
-  clear() {
-    startMeasure("clear");
-    this.setState({
-      messages: []
-    });
-    stopMeasure();
-  }
-
-  updateSomeMessages() {
-    startMeasure("update every 10th");
-    const messages = this.state.messages;
-    for (let i = 0; i < messages.length; i += 10) {
-      messages[i].author += "!!!";
-    }
-    this.forceUpdate();
-    stopMeasure();
-  }
-
-  removeMessage(id) {
-    startMeasure("remove message");
-    const index = this.state.messages.findIndex(m => m.id === id);
-    const messages = this.state.messages.slice();
-    messages.splice(index, 1);
-    this.setState({
-      messages
-    });
-    stopMeasure();
-  }
-} //-----------------------------
-// INIT
-//-----------------------------
-
-ReactDOM.render(
-  React.createElement(Main, null),
-  document.getElementById("main")
-);
@@ -1,42 +0,0 @@
-.main {
-  position: absolute;
-  left: 0;
-  right: 0;
-  top: 0;
-  bottom: 0;
-
-  display: grid;
-  grid-template-columns: 220px 1fr;
-}
-
-.left-thing {
-  background-color: gray;
-  padding: 20px;
-  color: white;
-}
-
-.left-thing button {
-  width: 100%;
-}
-
-.right-thing {
-  padding: 20px;
-  overflow: auto;
-}
-
-/* Message widget */
-.message .author {
-  font-weight: bold;
-}
-
-.message {
-  width: 400px;
-  background-color: lightblue;
-  margin: 10px 5px;
-  border-radius: 5px;
-  padding: 5px;
-}
-
-.remove {
-  float: right;
-}
@@ -1,106 +0,0 @@
-import { buildData, startMeasure, stopMeasure } from "../shared/utils.js";
-
-//------------------------------------------------------------------------------
-// Counter Widget
-//------------------------------------------------------------------------------
-Vue.component("likes-counter", {
-  data: function() {
-    return {
-      counter: 0
-    };
-  },
-  methods: {
-    increment() {
-      this.counter++;
-    }
-  },
-  template: `
-    <div>
-      <button @click="increment">Value: {{counter}}</button>
-    </div>`
-});
-
-//------------------------------------------------------------------------------
-// Message Widget
-//------------------------------------------------------------------------------
-Vue.component("my-message", {
-  props: ["msg"],
-  methods: {
-    removeMessage() {
-      this.$emit("removeMessage", this.msg.id);
-    }
-  },
-  template: `
-    <div class="message">
-        <span class="author">{{msg.author}}</span>
-        <span class="msg">{{msg.msg}}</span>
-        <button class="remove" @click="removeMessage">Remove</button>
-        <likes-counter></likes-counter>
-    </div>`
-});
-
-//------------------------------------------------------------------------------
-// Root Widget
-//------------------------------------------------------------------------------
-const App = {
-  name: "App",
-  data() {
-    return { messages: [] };
-  },
-  methods: {
-    addMessages(n) {
-      startMeasure("add " + n);
-      const newMessages = buildData(n);
-      this.messages.push.apply(this.messages, newMessages);
-      stopMeasure();
-    },
-
-    clear() {
-      startMeasure("clear");
-      this.messages = [];
-      stopMeasure();
-    },
-
-    updateSomeMessages() {
-      startMeasure("update every 10th");
-      const messages = this.messages;
-      for (let i = 0; i < this.messages.length; i += 10) {
-        messages[i].author += "!!!";
-      }
-      stopMeasure();
-    },
-
-    removeMessage(id) {
-      startMeasure("remove message");
-      const index = this.messages.findIndex(m => m.id === id);
-      this.messages.splice(index, 1);
-      stopMeasure();
-    }
-  },
-  template: `
-    <div class="main">
-        <div class="left-thing">
-            <div>Number of msg: {{messages.length}}</div>
-            <button @click="addMessages(100)">Add 100 messages</button>
-            <button @click="addMessages(1000)">Add 1000 messages</button>
-            <button @click="addMessages(10000)">Add 10000 messages</button>
-            <button @click="addMessages(50000)">Add 50000 messages</button>
-            <button @click="updateSomeMessages">Update every 10th message</button>
-            <button @click="clear">Clear</button>
-        </div>
-        <div class="right-thing">
-            <div class="content">
-                <my-message v-for="msg in messages" v-bind:key="msg.id" v-bind:msg="msg" @removeMessage="removeMessage"></my-message>
-            </div>
-        </div>
-    </div>
-  `
-};
-
-//------------------------------------------------------------------------------
-// Application initialization
-//------------------------------------------------------------------------------
-
-new Vue({
-  render: h => h(App)
-}).$mount(`#main`);
@@ -1,27 +0,0 @@
-<!DOCTYPE html>
-<html lang="en">
-<head>
-  <meta charset="UTF-8">
-  <title>OWL Extras</title>
-</head>
-<body>
-  <h1>🦉 OWL Extra Stuff 🦉</h1>
-
-
-  <h2>Benchmarks</h2>
-  <p>The goal is to compare some operations on large lists</p>
-
-  <ul>
-    <li><a href="benchmarks/odoo-widgets-12.0">Odoo Widgets (12.0)</a></li>
-    <li><a href="benchmarks/odoo-widgets-12.3">Odoo Widgets (12.3)</a></li>
-    <li><a href="benchmarks/owl-0.7.0">OWL 0.7.0</a></li>
-    <li><a href="benchmarks/owl-0.8.0">OWL 0.8.0</a></li>
-    <li><a href="benchmarks/owl-master">OWL Master</a></li>
-    <li><a href="benchmarks/vue">Vue</a></li>
-    <li><a href="benchmarks/react">React</a></li>
-  </ul>
-
-  <h2>Playground</h2>
-  <a href="playground">Playground</a>
-</body>
-</html>
@@ -1,325 +0,0 @@
-import { SAMPLES } from "./samples.js";
-
-let owlJS;
-
-async function owlSourceCode() {
-  if (owlJS) {
-    return owlJS;
-  }
-  const result = await fetch("../owl.js");
-  owlJS = await result.text();
-  return owlJS;
-}
-
-const MODES = {
-  js: "ace/mode/javascript",
-  css: "ace/mode/css",
-  xml: "ace/mode/xml"
-};
-
-const DEFAULT_XML = `<templates>
-</templates>`;
-
-const DEFAULT_HTML = `<!DOCTYPE html>
-<html lang="en">
-  <head>
-    <meta charset="utf-8">
-    <title>OWL App</title>
-    <link rel="icon" href="data:,">
-
-    <script src="owl.js"></script>
-    <link rel="stylesheet" href="app.css">
-    <script src="app.js"></script>
-  </head>
-  <body>
-  </body>
-</html>
-`;
-
-const APP_PY = `import sys
-import thread
-import webbrowser
-import time
-
-import BaseHTTPServer, SimpleHTTPServer
-
-def start_server():
-    httpd = BaseHTTPServer.HTTPServer(('127.0.0.1', 3600), SimpleHTTPServer.SimpleHTTPRequestHandler)
-    httpd.serve_forever()
-
-thread.start_new_thread(start_server,())
-url = 'http://127.0.0.1:3600'
-webbrowser.open_new(url)
-
-while True:
-    try:
-        time.sleep(1)
-    except KeyboardInterrupt:
-        sys.exit(0)
-`;
-
-//------------------------------------------------------------------------------
-// Tabbed editor
-//------------------------------------------------------------------------------
-class TabbedEditor extends owl.Component {
-  constructor() {
-    super(...arguments);
-    this.template = "tabbed-editor";
-    this.state = {
-      currentTab: this.props.display.split("|")[0]
-    };
-    this.tabs = {
-      js: this.props.display.includes("js"),
-      xml: this.props.display.includes("xml"),
-      css: this.props.display.includes("css")
-    };
-  }
-
-  mounted() {
-    this.editor = ace.edit(this.refs.editor);
-
-    // remove this for xml/css (?)
-    this.editor.session.setOption("useWorker", false);
-    this.editor.setValue(this.props[this.state.currentTab], -1);
-    this.editor.setFontSize("13px");
-    this.editor.setTheme("ace/theme/monokai");
-    this.editor.session.setMode(MODES[this.state.currentTab]);
-    const tabSize = this.state.currentTab === "xml" ? 2 : 4;
-    this.editor.session.setOption("tabSize", tabSize);
-    this.editor.on("blur", () => {
-      const editorValue = this.editor.getValue();
-      const propsValue = this.props[this.state.currentTab];
-      if (editorValue !== propsValue) {
-        this.trigger("updateCode", {
-          type: this.state.currentTab,
-          value: editorValue
-        });
-      }
-    });
-  }
-
-  patched() {
-    if (this.editor) {
-      window.dispatchEvent(new Event("resize"));
-      this.editor.setValue(this.props[this.state.currentTab], -1);
-    }
-  }
-
-  willUnmount() {
-    this.editor.destroy();
-    delete this.editor;
-  }
-
-  setTab(tab) {
-    this.editor.setValue(this.props[tab], -1);
-
-    const mode = MODES[tab];
-    this.editor.session.setMode(mode);
-    const tabSize = tab === "xml" ? 2 : 4;
-    this.editor.session.setOption("tabSize", tabSize);
-    this.state.currentTab = tab;
-  }
-
-  onMouseDown(ev) {
-    if (ev.target.tagName === "DIV") {
-      let y = ev.clientY;
-      const resizer = ev => {
-        const delta = ev.clientY - y;
-        y = ev.clientY;
-        this.trigger("updatePanelHeight", { delta });
-      };
-      document.body.addEventListener("mousemove", resizer);
-      document.body.addEventListener("mouseup", () => {
-        document.body.removeEventListener("mousemove", resizer);
-      });
-    }
-  }
-}
-
-//------------------------------------------------------------------------------
-// MAIN APP
-//------------------------------------------------------------------------------
-class App extends owl.Component {
-  constructor(...args) {
-    super(...args);
-    this.template = "playground";
-    this.version = owl._version;
-    this.SAMPLES = SAMPLES;
-    this.widgets = { TabbedEditor };
-
-    this.state = {
-      js: SAMPLES[0].code,
-      css: SAMPLES[0].css || "",
-      xml: SAMPLES[0].xml || DEFAULT_XML,
-      error: false,
-      displayWelcome: true,
-      splitLayout: true,
-      leftPaneWidth: Math.ceil(window.innerWidth / 2),
-      topPanelHeight: null
-    };
-  }
-
-  displayError(error) {
-    this.state.error = error;
-    if (error) {
-      setTimeout(() => {
-        this.refs.content.innerHTML = "";
-      });
-      return;
-    }
-  }
-
-  async runCode() {
-    this.state.displayWelcome = false;
-    // check templates
-    var qweb = new owl.QWeb();
-    var error = false;
-    const sanitizedXML = this.state.xml.replace(/<!--[\s\S]*?-->/g, "");
-    try {
-      qweb.loadTemplates(sanitizedXML);
-    } catch (e) {
-      error = e;
-    }
-
-    if (error) {
-      this.displayError(error.message);
-      return;
-    } else {
-      this.state.error = false;
-    }
-
-    // create iframe
-    const iframe = document.createElement("iframe");
-
-    iframe.onload = () => {
-      const doc = iframe.contentDocument;
-      // inject js
-      const owlScript = doc.createElement("script");
-      owlScript.type = "text/javascript";
-      owlScript.src = "../owl.js";
-      owlScript.addEventListener("load", () => {
-        const script = doc.createElement("script");
-        script.type = "text/javascript";
-        const content = `window.TEMPLATES = \`${sanitizedXML}\`\n${
-          this.state.js
-        }`;
-        script.innerHTML = content;
-        const errorHandler = e => this.displayError(e.message);
-        iframe.contentWindow.addEventListener("error", errorHandler);
-        setTimeout(function() {
-          if (iframe.contentWindow) {
-            iframe.contentWindow.removeEventListener("error", errorHandler);
-          }
-        }, 100);
-        doc.body.appendChild(script);
-      });
-      doc.head.appendChild(owlScript);
-
-      // inject css
-      const style = document.createElement("style");
-      style.innerHTML = this.state.css;
-      doc.head.appendChild(style);
-    };
-    this.refs.content.innerHTML = "";
-    this.refs.content.appendChild(iframe);
-  }
-
-  setSample(ev) {
-    const sample = SAMPLES.find(s => s.description === ev.target.value);
-    this.state.js = sample.code;
-    this.state.css = sample.css || "";
-    this.state.xml = sample.xml || DEFAULT_XML;
-  }
-
-  get leftPaneStyle() {
-    return `width:${this.state.leftPaneWidth}px`;
-  }
-
-  get rightPaneStyle() {
-    return `width:${window.innerWidth - 6 - this.state.leftPaneWidth}px`;
-  }
-
-  get topEditorStyle() {
-    return `flex: 0 0 ${this.state.topPanelHeight}px`;
-  }
-
-  onMouseDown() {
-    const resizer = ev => {
-      this.state.leftPaneWidth = ev.clientX;
-    };
-
-    document.body.addEventListener("mousemove", resizer);
-    for (let iframe of document.getElementsByTagName("iframe")) {
-      iframe.classList.add("disabled");
-    }
-
-    document.body.addEventListener("mouseup", () => {
-      document.body.removeEventListener("mousemove", resizer);
-      for (let iframe of document.getElementsByTagName("iframe")) {
-        iframe.classList.remove("disabled");
-      }
-    });
-  }
-  updateCode(ev) {
-    this.state[ev.type] = ev.value;
-  }
-  toggleLayout() {
-    this.state.splitLayout = !this.state.splitLayout;
-  }
-  updatePanelHeight(ev) {
-    if (!ev.delta) {
-      return;
-    }
-    let height = this.state.topPanelHeight;
-    if (!height) {
-      height = document.getElementsByClassName("tabbed-editor")[0].clientHeight;
-    }
-    this.state.topPanelHeight = height + ev.delta;
-  }
-
-  async downloadCode() {
-    await owl.utils.loadJS("libs/FileSaver.min.js");
-    await owl.utils.loadJS("libs/jszip.min.js");
-
-    const zip = new JSZip();
-
-    const JS = `async function startApp() {
-  // Loading templates
-  let TEMPLATES;
-  try {
-    TEMPLATES = await owl.utils.loadTemplates('app.xml');
-  } catch(e) {
-    document.write(\`This app requires a static server.  If you have python installed, try 'python app.py'\`);
-    return;
-  }
-
-  // Application code
-${this.state.js.split('\n').map(l => l === '' ? '' : '  ' + l).join('\n')}
-}
-
-// wait for DOM ready before starting
-owl.utils.whenReady(startApp);`;
-
-    zip.file("app.js", JS);
-    zip.file("app.css", this.state.css);
-    zip.file("app.py", APP_PY);
-    zip.file("app.xml", this.state.xml);
-    zip.file("index.html", DEFAULT_HTML);
-    zip.file("owl.js", owlSourceCode());
-    zip.generateAsync({ type: "blob" }).then(function(content) {
-      saveAs(content, "app.zip");
-    });
-  }
-}
-
-//------------------------------------------------------------------------------
-// Application initialization
-//------------------------------------------------------------------------------
-document.title = `${document.title} (v${owl._version})`;
-document.addEventListener("DOMContentLoaded", async function() {
-  const templates = await owl.utils.loadTemplates("templates.xml");
-  const qweb = new owl.QWeb(templates);
-  const env = { qweb };
-  const app = new App(env);
-  app.mount(document.body);
-});
@@ -1,46 +0,0 @@
-<templates>
-  <div t-name="tabbed-editor" class="tabbed-editor" t-att-style="props.style">
-    <div class="tabBar" t-att-class="{resizeable: props.resizeable}" t-on-mousedown="onMouseDown">
-      <a t-if="tabs.js" class="tab flash" t-att-class="{active: state.currentTab==='js'}" t-on-click="setTab('js')">JS</a>
-      <a t-if="tabs.xml" class="tab flash" t-att-class="{active: state.currentTab==='xml'}" t-on-click="setTab('xml')">XML</a>
-      <a t-if="tabs.css" class="tab flash" t-att-class="{active: state.currentTab==='css'}" t-on-click="setTab('css')">CSS</a>
-    </div>
-    <div class="code-editor" t-ref="'editor'"></div>
-  </div>
-
-  <div t-name="playground" class="playground">
-      <div class="left-bar" t-att-style="leftPaneStyle" t-att-class="{split: state.splitLayout}">
-        <div class="menubar">
-          <a class="btn run-code flash" t-on-click="runCode" title="Execute this Code">▶ Run</a>
-          <select t-on-change="setSample">
-            <option t-foreach="SAMPLES" t-as="sample" t-key="sample_index">
-              <t t-esc="sample.description"/>
-            </option>
-          </select>
-          <a class="btn flash" t-on-click="downloadCode" title="Download a Zip with this Code"><i class="fas fa-download"></i></a>
-          <a class="layout-selector flash" t-on-click="toggleLayout" title="Toggle Layout"><i class="fas"  t-att-class="state.splitLayout ?  'fa-toggle-on' : 'fa-toggle-off'"></i></a>
-        </div>
-        <t t-if="!state.splitLayout">
-          <t t-widget="TabbedEditor" t-props="{js:state.js, css:state.css, xml: state.xml, display: 'js|xml|css'}" t-on-updateCode="updateCode"/>
-        </t>
-        <t t-else="1">
-          <t t-widget="TabbedEditor" t-props="{js:state.js, css:state.css, xml: state.xml, display: 'js', style:topEditorStyle}" t-on-updateCode="updateCode"/>
-          <div class="separator horizontal"/>
-          <t t-widget="TabbedEditor" t-keepalive="1" t-props="{js:state.js, css:state.css, xml: state.xml, display: 'xml|css', resizeable: true}" t-on-updateCode="updateCode" t-on-updatePanelHeight="updatePanelHeight"/>
-        </t>
-      </div>
-      <div class="separator vertical" t-on-mousedown="onMouseDown"/>
-      <div class="right-pane"  t-att-style="rightPaneStyle">
-        <div class="welcome" t-if="state.displayWelcome">
-          <div>🦉 Odoo Web Library 🦉</div>
-          <div>v<t t-esc="version"/></div>
-          <div class="url"><a href="https://github.com/odoo/owl">https://github.com/odoo/owl</a></div>
-          <div class="note">Note: these examples require a recent browser to work without a transpilation step. </div>
-        </div>
-        <div t-if="state.error" class="error">
-          <t t-esc="state.error"/>
-        </div>
-        <div class="content" t-ref="'content'"/>
-      </div>
-  </div>
-</templates>
@@ -1,6 +0,0 @@
-# 🦉 Extra Stuff 🦉
-
-To help work/improve/learn with OWL, we have here:
-
- a benchmarks application
- a playground application
@@ -1,34 +0,0 @@
-import sys
-import thread
-import webbrowser
-import time
-
-import BaseHTTPServer
-import SimpleHTTPServer
-
-HOST = '127.0.0.1'
-PORT = 8000
-
-
-class OWLHandler(SimpleHTTPServer.SimpleHTTPRequestHandler):
-    def do_GET(self):
-        if self.path == '/extras/owl.js':
-            self.path = '/dist/owl.js'
-        return SimpleHTTPServer.SimpleHTTPRequestHandler.do_GET(self)
-
-
-def start_server():
-    httpd = BaseHTTPServer.HTTPServer((HOST, PORT), OWLHandler)
-    httpd.serve_forever()
-
-
-if __name__ == "__main__":
-    thread.start_new_thread(start_server, ())
-    url = 'http://{0}:{1}/extras'.format(HOST, PORT)
-    webbrowser.open_new(url)
-
-    while True:
-        try:
-            time.sleep(1)
-        except KeyboardInterrupt:
-            sys.exit(0)
@@ -1,51 +1,52 @@
 {
-  "name": "owl",
-  "version": "0.9.0",
+  "name": "owl-framework",
+  "version": "0.24.1",
  "description": "Odoo Web Library (OWL)",
  "main": "src/index.ts",
+  "engines": {
+    "node": ">=10.15.3"
+  },
  "scripts": {
-    "build:js": "tsc --target esnext --module es6 --outDir dist/owl src/*",
-    "build:js:es5": "tsc --target es5 --module es6 --outDir dist/owl src/*",
+    "build:js": "tsc --target esnext --module es6 --outDir dist/owl",
    "build:bundle": "rollup -c",
    "build": "npm run build:js && npm run build:bundle",
-    "build:es5": "npm run build:js:es5 && 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",
-    "dev": "npm-run-all --parallel \"build:* -- --watch\"",
    "test": "jest",
    "test:watch": "jest --watch",
-    "preextras": "npm run build",
-    "extras": "python extras/server.py"
+    "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"
  },
  "repository": {
    "type": "git",
    "url": "git+https://github.com/odoo/owl.git"
  },
  "author": "Odoo",
-  "license": "GPL-3.0-or-later",
+  "license": "LGPL",
  "bugs": {
    "url": "https://github.com/odoo/owl/issues"
  },
  "homepage": "https://github.com/odoo/owl#readme",
+  "dependencies": {},
  "devDependencies": {
    "@types/jest": "^23.3.12",
    "cpx": "^1.5.0",
    "git-rev-sync": "^1.12.0",
    "jest": "^23.6.0",
+    "jest-environment-jsdom": "^24.7.1",
    "live-server": "^1.2.1",
    "npm-run-all": "^4.1.5",
    "rollup": "^1.6.0",
    "rollup-plugin-typescript2": "^0.20.1",
    "sass": "^1.16.1",
-    "snabbdom-to-html": "^5.1.1",
    "source-map-support": "^0.5.10",
    "ts-jest": "^23.10.5",
-    "typescript": "^3.2.2",
+    "typescript": "^3.6.4",
    "uglify-es": "^3.3.9"
  },
-  "dependencies": {
-    "jest-environment-jsdom": "^24.7.1",
-    "snabbdom": "^0.7.3"
-  },
  "jest": {
    "roots": [
      "<rootDir>/src",
@@ -64,5 +65,8 @@
      "json",
      "node"
    ]
+  },
+  "prettier": {
+    "printWidth": 100
  }
 }
@@ -0,0 +1,46 @@
+# 🦉 OWL Roadmap 🦉
+
+- Current version: 0.24.1
+- Status: mostly 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?)
+
+Maybe:
+
+- reimplement vdom to use *block* system, like Vue 3,
+- refactor `QWeb` to use an intermediate representation (some kind of AST) to
+  allow additional optimisations.
+
+
@@ -9,6 +9,6 @@ export default {
    format: "iife",
    name: "owl",
    extend: true,
-    outro: `exports._version = '${version}';\nexports._date = '${new Date().toISOString()}';\nexports._hash = '${git.short()}';\nexports._url = 'https://github.com/odoo/owl';`
+    outro: `exports.__info__.version = '${version}';\nexports.__info__.date = '${new Date().toISOString()}';\nexports.__info__.hash = '${git.short()}';\nexports.__info__.url = 'https://github.com/odoo/owl';`
  }
 };
@@ -1,436 +0,0 @@
-import { EventBus } from "./event_bus";
-import { Observer } from "./observer";
-import { QWeb, CompiledTemplate } from "./qweb";
-import { h, patch, VNode } from "./vdom";
-
-//------------------------------------------------------------------------------
-// Types/helpers
-//------------------------------------------------------------------------------
-
-export interface Env {
-  qweb: QWeb;
-}
-
-interface Meta<T extends Env, Props> {
-  readonly id: number;
-  vnode: VNode | null;
-  isStarted: boolean;
-  isMounted: boolean;
-  isDestroyed: boolean;
-  parent: Component<T, any, any> | null;
-  children: { [key: number]: Component<T, any, any> };
-  // children mapping: from templateID to widgetID
-  // should it be a map number => Widget?
-  cmap: { [key: number]: number };
-
-  renderId: number;
-  renderProps: Props | null;
-  renderPromise: Promise<VNode> | null;
-  boundHandlers: { [key: number]: any };
-  observer?: Observer;
-  render?: CompiledTemplate;
-}
-
-//------------------------------------------------------------------------------
-// Widget
-//------------------------------------------------------------------------------
-let nextId = 1;
-
-export class Component<
-  T extends Env,
-  Props extends {},
-  State extends {}
-> extends EventBus {
-  readonly __owl__: Meta<Env, Props>;
-  template: string = "default";
-  inlineTemplate: string | null = null;
-
-  get el(): HTMLElement | null {
-    return this.__owl__.vnode ? (<any>this).__owl__.vnode.elm : null;
-  }
-
-  env: T;
-  state?: State;
-  props: Props;
-  refs: {
-    [key: string]: Component<T, any, any> | HTMLElement | undefined;
-  } = {};
-
-  //--------------------------------------------------------------------------
-  // Lifecycle
-  //--------------------------------------------------------------------------
-
-  /**
-   * Creates an instance of Component.
-   *
-   * The root widget of a component tree needs an environment:
-   *
-   * ```javascript
-   *   const root = new RootWidget(env, props);
-   * ```
-   *
-   * Every other widget simply needs a reference to its parent:
-   *
-   * ```javascript
-   *   const child = new SomeWidget(parent, props);
-   * ```
-   *
-   * Note that most of the time, only the root widget needs to be created by
-   * hand.  Other widgets should be created automatically by the framework (with
-   * the t-widget directive in a template)
-   */
-  constructor(parent: Component<T, any, any> | T, props?: Props) {
-    super();
-
-    // is this a good idea?
-    //   Pro: if props is empty, we can create easily a widget
-    //   Con: this is not really safe
-    //   Pro: but creating widget (by a template) is always unsafe anyway
-    this.props = <Props>props || <Props>{};
-    let id: number = nextId++;
-    let p: Component<T, any, any> | null = null;
-    if (parent instanceof Component) {
-      p = parent;
-      this.env = parent.env;
-      parent.__owl__.children[id] = this;
-    } else {
-      this.env = parent;
-    }
-    this.__owl__ = {
-      id: id,
-      vnode: null,
-      isStarted: false,
-      isMounted: false,
-      isDestroyed: false,
-      parent: p,
-      children: {},
-      cmap: {},
-      renderId: 1,
-      renderPromise: null,
-      renderProps: props || null,
-      boundHandlers: {}
-    };
-  }
-
-  /**
-   * willStart is an asynchronous hook that can be implemented to perform some
-   * action before the initial rendering of a component.
-   *
-   * It will be called exactly once before the initial rendering. It is useful
-   * in some cases, for example, to load external assets (such as a JS library)
-   * before the widget is rendered.
-   *
-   * Note that a slow willStart method will slow down the rendering of the user
-   * interface.  Therefore, some effort should be made to make this method as
-   * fast as possible.
-   *
-   * Note: this method should not be called manually.
-   */
-  async willStart() {}
-
-  /**
-   * mounted is a hook that is called each time a component is attached to the
-   * DOM. This is a good place to add some listeners, or to interact with the
-   * DOM, if the component needs to perform some measure for example.
-   *
-   * Note: this method should not be called manually.
-   *
-   * @see willUnmount
-   */
-  mounted() {}
-
-  /**
-   * 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
-   * some record Id, fetching the record data).
-   *
-   * This hook is not called during the first render (but willStart is called
-   * and performs a similar job).
-   */
-  async willUpdateProps(nextProps: Props) {}
-
-  /**
-   * The willPatch hook is called just before the DOM patching process starts.
-   * It is not called on the initial render.  This is useful to get some
-   * information which are in the DOM.  For example, the current position of the
-   * scrollbar
-   *
-   * The return value of willPatch will be given to the patched function.
-   */
-  willPatch(): any {}
-
-  /**
-   * This hook is called whenever a component did actually update its props,
-   * state or env.
-   *
-   * 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 updated.
-   *
-   * Updating the widget state in this hook is possible, but not encouraged.
-   * One need to be careful, because updates here will cause rerender, which in
-   * turn will cause other calls to updated. So, we need to be particularly
-   * careful at avoiding endless cycles.
-   *
-   * The snapshot parameter is the result of the call to willPatch.
-   */
-  patched(snapshot: any) {}
-
-  /**
-   * 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.
-   *
-   * Note: this method should not be called manually.
-   *
-   * @see mounted
-   */
-  willUnmount() {}
-
-  //--------------------------------------------------------------------------
-  // Public
-  //--------------------------------------------------------------------------
-
-  async mount(target: HTMLElement): Promise<void> {
-    const vnode = await this._prepare();
-    if (this.__owl__.isDestroyed) {
-      // widget was destroyed before we get here...
-      return;
-    }
-    this._patch(vnode);
-    target.appendChild(this.el!);
-
-    if (document.body.contains(target)) {
-      this._callMounted();
-    }
-  }
-
-  _callMounted() {
-    const children = this.__owl__.children;
-    for (let id in children) {
-      const comp = children[id];
-      if (!comp.__owl__.isMounted && this.el!.contains(comp.el)) {
-        comp._callMounted();
-      }
-    }
-    this.__owl__.isMounted = true;
-    this.mounted();
-  }
-
-  _callWillUnmount() {
-    this.willUnmount();
-    this.__owl__.isMounted = false;
-    const children = this.__owl__.children;
-    for (let id in children) {
-      const comp = children[id];
-      if (comp.__owl__.isMounted) {
-        comp._callWillUnmount();
-      }
-    }
-  }
-
-  unmount() {
-    if (this.__owl__.isMounted) {
-      this._callWillUnmount();
-      this.el!.remove();
-    }
-  }
-
-  async render(force: boolean = false, patchQueue?: any[]): Promise<void> {
-    if (this.__owl__.isDestroyed) {
-      return;
-    }
-    const shouldCallPatchHooks: boolean = !patchQueue;
-    if (shouldCallPatchHooks) {
-      patchQueue = [];
-    }
-    const renderVDom = this._render(force, patchQueue);
-    const renderId = this.__owl__.renderId;
-    const vnode = await renderVDom;
-    if (renderId === this.__owl__.renderId) {
-      // we only update the vnode and the actual DOM if no other rendering
-      // occurred between now and when the render method was initially called.
-      if (shouldCallPatchHooks) {
-        for (let i = 0; i < patchQueue!.length; i++) {
-          const c = patchQueue![i];
-          c.__owl__.willPatchVal = c.willPatch();
-        }
-      }
-      this._patch(vnode);
-      if (shouldCallPatchHooks) {
-        for (let i = patchQueue!.length - 1; i >= 0; i--) {
-          const c = patchQueue![i];
-          c.patched(c.__owl__.willPatchVal);
-        }
-      }
-    }
-  }
-
-  destroy() {
-    if (!this.__owl__.isDestroyed) {
-      const el = this.el;
-      this._destroy(this.__owl__.parent);
-      if (el) {
-        el.remove();
-      }
-    }
-  }
-
-  _destroy(parent) {
-    const isMounted = this.__owl__.isMounted;
-    if (isMounted) {
-      this.willUnmount();
-      this.__owl__.isMounted = false;
-    }
-    const children = Object.values(this.__owl__.children);
-    for (let child of children) {
-      child._destroy(this);
-    }
-    if (parent) {
-      let id = this.__owl__.id;
-      delete parent.__owl__.children[id];
-      this.__owl__.parent = null;
-    }
-    this.clear();
-    this.__owl__.isDestroyed = true;
-    delete this.__owl__.vnode;
-  }
-
-  shouldUpdate(nextProps: Props): boolean {
-    return true;
-  }
-
-  /**
-   * This method is the correct way to update the environment of a widget. Doing
-   * this will cause a full rerender of the widget and its children, so this is
-   * an operation that should not be done frequently.
-   *
-   * A good usecase for updating the environment would be to update some mostly
-   * static config keys, such as a boolean to determine if we are in mobile
-   * mode or not.
-   */
-  async updateEnv(nextEnv: Partial<T>): Promise<void> {
-    if (this.__owl__.parent && this.__owl__.parent.env === this.env) {
-      this.env = Object.create(this.env);
-    }
-    Object.assign(this.env, nextEnv);
-    if (this.__owl__.isMounted) {
-      await this.render(true);
-    }
-  }
-
-  set(target: any, key: string | number, value: any) {
-    this.__owl__.observer!.set(target, key, value);
-  }
-
-  //--------------------------------------------------------------------------
-  // Private
-  //--------------------------------------------------------------------------
-
-  async _updateProps(
-    nextProps: Props,
-    forceUpdate: boolean = false,
-    patchQueue: any[]
-  ): Promise<void> {
-    const shouldUpdate = forceUpdate || this.shouldUpdate(nextProps);
-    if (shouldUpdate) {
-      await this.willUpdateProps(nextProps);
-      this.props = nextProps;
-      await this.render(false, patchQueue);
-    }
-  }
-
-  _patch(vnode) {
-    this.__owl__.renderPromise = null;
-    if (this.__owl__.vnode) {
-      this.__owl__.vnode = patch(this.__owl__.vnode, vnode);
-    } else {
-      this.__owl__.vnode = patch(document.createElement(vnode.sel!), vnode);
-    }
-  }
-  _prepare(): Promise<VNode> {
-    this.__owl__.renderProps = this.props;
-    this.__owl__.renderPromise = this._prepareAndRender();
-    return this.__owl__.renderPromise;
-  }
-
-  async _prepareAndRender(): Promise<VNode> {
-    await this.willStart();
-    if (this.__owl__.isDestroyed) {
-      return Promise.resolve(h("div"));
-    }
-    this.__owl__.isStarted = true;
-    if (this.inlineTemplate) {
-      this.env.qweb.addTemplate(this.inlineTemplate, this.inlineTemplate, true);
-    }
-    this.__owl__.render = this.env.qweb.render.bind(
-      this.env.qweb,
-      this.inlineTemplate || this.template
-    );
-    this._observeState();
-    return this._render();
-  }
-  async _render(
-    force: boolean = false,
-    patchQueue: any[] = []
-  ): Promise<VNode> {
-    if (this.__owl__.isMounted) {
-      patchQueue.push(this);
-    }
-    this.__owl__.renderId++;
-    const promises: Promise<void>[] = [];
-    if (this.__owl__.observer) {
-      this.__owl__.observer.allowMutations = false;
-    }
-    let vnode = this.__owl__.render!(this, {
-      promises,
-      handlers: this.__owl__.boundHandlers,
-      forceUpdate: force,
-      patchQueue
-    });
-    if (this.__owl__.observer) {
-      this.__owl__.observer.allowMutations = true;
-    }
-
-    // this part is critical for the patching process to be done correctly. The
-    // tricky part is that a child widget can be rerendered on its own, which
-    // will update its own vnode representation without the knowledge of the
-    // parent widget.  With this, we make sure that the parent widget will be
-    // able to patch itself properly after
-    vnode.key = this.__owl__.id;
-    this.__owl__.renderProps = this.props;
-    this.__owl__.renderPromise = Promise.all(promises).then(() => vnode);
-    return this.__owl__.renderPromise;
-  }
-
-  /**
-   * Only called by qweb t-widget directive
-   */
-  _mount(vnode: VNode, elm: HTMLElement): VNode {
-    this.__owl__.vnode = patch(elm, vnode);
-    if (
-      this.__owl__.parent &&
-      this.__owl__.parent.__owl__.isMounted &&
-      !this.__owl__.isMounted
-    ) {
-      this._callMounted();
-    }
-    return this.__owl__.vnode;
-  }
-
-  __mount() {
-    if (!this.__owl__.isMounted) {
-      this.__owl__.isMounted = true;
-      this.mounted();
-    }
-  }
-
-  _observeState() {
-    if (this.state) {
-      this.__owl__.observer = new Observer();
-      this.__owl__.observer.observe(this.state);
-      this.__owl__.observer.notifyCB = this.render.bind(this);
-    }
-  }
-}
@@ -0,0 +1,664 @@
+import { Observer } from "../core/observer";
+import { CompiledTemplate, QWeb } from "../qweb/index";
+import { h, patch, VNode } from "../vdom/index";
+import "./directive";
+import { Fiber } from "./fiber";
+import "./props_validation";
+import { Scheduler } from "./scheduler";
+
+/**
+ * Owl Component System
+ *
+ * This file introduces a declarative and composable component system. It
+ * contains:
+ *
+ * - the Env interface (generic type for the environment)
+ * - the Internal interface (the owl specific metadata attached to a component)
+ * - the Component class
+ */
+
+//------------------------------------------------------------------------------
+// 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
+ * components of an Owl application.  It is the location which should contain
+ * the qweb instance necessary to render all components.
+ *
+ * Note that it is totally fine to extend the environment with application
+ * specific keys/objects/whatever.  For example, a key `isMobile` (to declare
+ * if we are in "mobile" mode), or a shared bus could be useful.
+ */
+export interface Env {
+  qweb: QWeb;
+  [key: string]: any;
+}
+
+/**
+ * This is mostly an internal detail of implementation. The Meta interface is
+ * useful to typecheck and describe the internal keys used by Owl to manage the
+ * component tree.
+ */
+interface Internal<T extends Env, Props> {
+  // each component has a unique id, useful mostly to handle parent/child
+  // relationships
+  readonly id: number;
+  vnode: VNode | null;
+  pvnode: VNode | null;
+  isMounted: boolean;
+  isDestroyed: boolean;
+
+  // parent and children keys are obviously useful to setup the parent-children
+  // relationship.
+  parent: Component<T, any> | null;
+  children: { [key: number]: Component<T, any> };
+  // 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;
+
+  boundHandlers: { [key: number]: any };
+  observer: Observer | null;
+  renderFn: CompiledTemplate;
+  mountedCB: Function | null;
+  willUnmountCB: Function | null;
+  willPatchCB: Function | null;
+  patchedCB: Function | null;
+  willStartCB: Function | null;
+  willUpdatePropsCB: Function | null;
+  classObj: { [key: string]: boolean } | null;
+  refs: { [key: string]: Component<T, any> | HTMLElement | undefined } | null;
+}
+
+//------------------------------------------------------------------------------
+// Component
+//------------------------------------------------------------------------------
+let nextId = 1;
+
+export class Component<T extends Env, Props extends {}> {
+  readonly __owl__: Internal<Env, Props>;
+  static template?: string | null = null;
+  static _template?: string | null = null;
+  static current: Component<any, any> | null = null;
+  static components = {};
+  static props?: any;
+  static defaultProps?: any;
+
+  /**
+   * The `el` is the root element of the component.  Note that it could be null:
+   * this is the case if the component is not mounted yet, or is destroyed.
+   */
+  get el(): HTMLElement | null {
+    return this.__owl__.vnode ? (<any>this).__owl__.vnode.elm : null;
+  }
+
+  env: T;
+  props: Props;
+
+  //--------------------------------------------------------------------------
+  // Lifecycle
+  //--------------------------------------------------------------------------
+
+  /**
+   * 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;
+    Component.current = this;
+    if (defaultProps) {
+      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>{};
+    if (QWeb.dev) {
+      QWeb.utils.validateProps(this.constructor, this.props);
+    }
+    let id: number = nextId++;
+    let p: Component<T, any> | null = null;
+    if (parent instanceof Component) {
+      p = parent;
+      this.env = parent.env;
+      parent.__owl__.children[id] = this;
+    } else {
+      this.env = parent;
+      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);
+        }
+      });
+    }
+    const qweb = this.env.qweb;
+
+    this.__owl__ = {
+      id: id,
+      vnode: null,
+      pvnode: null,
+      isMounted: false,
+      isDestroyed: false,
+      parent: p,
+      children: {},
+      cmap: {},
+      currentFiber: null,
+      boundHandlers: {},
+      mountedCB: null,
+      willUnmountCB: null,
+      willPatchCB: null,
+      patchedCB: null,
+      willStartCB: null,
+      willUpdatePropsCB: null,
+      observer: null,
+      renderFn: qweb.render.bind(qweb, this.__getTemplate(qweb)),
+      classObj: null,
+      refs: null
+    };
+  }
+
+  /**
+   * willStart is an asynchronous hook that can be implemented to perform some
+   * action before the initial rendering of a component.
+   *
+   * It will be called exactly once before the initial rendering. It is useful
+   * in some cases, for example, to load external assets (such as a JS library)
+   * before the component is rendered.
+   *
+   * Note that a slow willStart method will slow down the rendering of the user
+   * interface.  Therefore, some effort should be made to make this method as
+   * fast as possible.
+   *
+   * Note: this method should not be called manually.
+   */
+  async willStart() {}
+
+  /**
+   * mounted is a hook that is called each time a component is attached to the
+   * DOM. This is a good place to add some listeners, or to interact with the
+   * DOM, if the component needs to perform some measure for example.
+   *
+   * Note: this method should not be called manually.
+   *
+   * @see willUnmount
+   */
+  mounted() {}
+
+  /**
+   * 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
+   * some record Id, fetching the record data).
+   *
+   * This hook is not called during the first render (but willStart is called
+   * and performs a similar job).
+   */
+  async willUpdateProps(nextProps: Props) {}
+
+  /**
+   * The willPatch hook is called just before the DOM patching process starts.
+   * It is not called on the initial render.  This is useful to get some
+   * information which are in the DOM.  For example, the current position of the
+   * scrollbar
+   */
+  willPatch(): any {}
+
+  /**
+   * This hook is called whenever a component did actually update its props,
+   * state or env.
+   *
+   * 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 updated.
+   *
+   * Updating the component state in this hook is possible, but not encouraged.
+   * One need to be careful, because updates here will cause rerender, which in
+   * turn will cause other calls to updated. So, we need to be particularly
+   * careful at avoiding endless cycles.
+   */
+  patched() {}
+
+  /**
+   * 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.
+   *
+   * Note: this method should not be called manually.
+   *
+   * @see mounted
+   */
+  willUnmount() {}
+
+  /**
+   * 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;
+
+  //--------------------------------------------------------------------------
+  // Public
+  //--------------------------------------------------------------------------
+
+  /**
+   * Mount the component to a target element.
+   *
+   * This should only be done if the component was created manually. Components
+   * created declaratively in templates are managed by the Owl system.
+   *
+   * Note that a component can be mounted an unmounted several times
+   */
+  async mount(target: HTMLElement, renderBeforeRemount: boolean = false): Promise<void> {
+    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();
+      }
+      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, reject) => {
+      scheduler.addFiber(fiber, err => {
+        if (err) {
+          reject(err);
+          return;
+        }
+        if (!__owl__.isDestroyed) {
+          this.__patch(fiber.vnode);
+          target.appendChild(this.el!);
+          if (document.body.contains(target)) {
+            this.__callMounted();
+          }
+        }
+        resolve();
+      });
+    });
+  }
+
+  /**
+   * The unmount method is the opposite of the mount method.  It is useful
+   * to call willUnmount calls and remove the component from the DOM.
+   */
+  unmount() {
+    if (this.__owl__.isMounted) {
+      this.__callWillUnmount();
+      this.el!.remove();
+    }
+  }
+
+  /**
+   * The render method is the main entry point to render a component (once it
+   * is ready. This method is not initially called when the component is
+   * rendered the first time).
+   *
+   * This method will cause all its sub components to potentially rerender
+   * themselves.  Note that `render` is not called if a component is updated via
+   * its props.
+   */
+  async render(force: boolean = false): Promise<void> {
+    const __owl__ = this.__owl__;
+    if (
+      (!__owl__.isMounted && !__owl__.currentFiber) ||
+      (__owl__.currentFiber && !__owl__.currentFiber.isRendered)
+    ) {
+      return;
+    }
+    const fiber = new Fiber(null, this, this.props, undefined, undefined, force);
+    this.__render(fiber);
+    return new Promise((resolve, reject) => {
+      scheduler.addFiber(fiber.root, err => {
+        if (err) {
+          reject(err);
+          return;
+        }
+        if (__owl__.isMounted && fiber === fiber.root) {
+          fiber.patchComponents();
+        }
+        resolve();
+      });
+    });
+  }
+
+  /**
+   * Destroy the component.  This operation is quite complex:
+   *  - it recursively destroy all children
+   *  - call the willUnmount hooks if necessary
+   *  - remove the dom node from the dom
+   *
+   * This should only be called manually if you created the component.  Most
+   * components will be automatically destroyed.
+   */
+  destroy() {
+    const __owl__ = this.__owl__;
+    if (!__owl__.isDestroyed) {
+      const el = this.el;
+      this.__destroy(__owl__.parent);
+      if (el) {
+        el.remove();
+      }
+    }
+  }
+
+  /**
+   * This method is called by the component system whenever its props are
+   * updated. If it returns true, then the component will be rendered.
+   * Otherwise, it will skip the rendering (also, its props will not be updated)
+   */
+  shouldUpdate(nextProps: Props): boolean {
+    return true;
+  }
+
+  /**
+   * Emit a custom event of type 'eventType' with the given 'payload' on the
+   * component's el, if it exists. However, note that the event will only bubble
+   * 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);
+    }
+  }
+
+  //--------------------------------------------------------------------------
+  // Private
+  //--------------------------------------------------------------------------
+
+  /**
+   * Private helper to perform a full destroy, from the point of view of an Owl
+   * component. It does not remove the el (this is done only once on the top
+   * level destroyed component, for performance reasons).
+   *
+   * The job of this method is mostly to call willUnmount hooks, and to perform
+   * all necessary internal cleanup.
+   *
+   * Note that it does not call the __callWillUnmount method to avoid visiting
+   * all children many times.
+   */
+  __destroy(parent: Component<any, any> | null) {
+    const __owl__ = this.__owl__;
+    const isMounted = __owl__.isMounted;
+    if (isMounted) {
+      if (__owl__.willUnmountCB) {
+        __owl__.willUnmountCB();
+      }
+      this.willUnmount();
+      __owl__.isMounted = false;
+    }
+    const children = __owl__.children;
+    for (let key in children) {
+      children[key].__destroy(this);
+    }
+    if (parent) {
+      let id = __owl__.id;
+      delete parent.__owl__.children[id];
+      __owl__.parent = null;
+    }
+    __owl__.isDestroyed = true;
+    delete __owl__.vnode;
+  }
+
+  __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
+    }
+  }
+
+  __callWillUnmount() {
+    const __owl__ = this.__owl__;
+    if (__owl__.willUnmountCB) {
+      __owl__.willUnmountCB();
+    }
+    this.willUnmount();
+    __owl__.isMounted = false;
+    const children = __owl__.children;
+    for (let id in children) {
+      const comp = children[id];
+      if (comp.__owl__.isMounted) {
+        comp.__callWillUnmount();
+      }
+    }
+  }
+
+  /**
+   * 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> {
+    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);
+      if (!parentFiber.child) {
+        parentFiber.child = fiber;
+      } else {
+        previousSibling!.sibling = fiber;
+      }
+
+      const defaultProps = (<any>this.constructor).defaultProps;
+      if (defaultProps) {
+        nextProps = this.__applyDefaultProps(nextProps, defaultProps);
+      }
+      if (QWeb.dev) {
+        QWeb.utils.validateProps(this.constructor, nextProps);
+      }
+      await Promise.all([
+        this.willUpdateProps(nextProps),
+        __owl__.willUpdatePropsCB && __owl__.willUpdatePropsCB(nextProps)
+      ]);
+      if (fiber.isCancelled) {
+        return;
+      }
+      this.props = nextProps;
+
+      this.__render(fiber);
+    }
+  }
+
+  /**
+   * 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;
+  }
+
+  /**
+   * 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
+   * parent template.
+   */
+  __prepare(parentFiber: Fiber, scope: any, vars: any, previousSibling?: Fiber | null) {
+    const fiber = new Fiber(parentFiber, this, this.props, scope, vars, parentFiber.force);
+    fiber.shouldPatch = false;
+    if (!parentFiber.child) {
+      parentFiber.child = fiber;
+    } else {
+      previousSibling!.sibling = fiber;
+    }
+    return this.__prepareAndRender(fiber);
+  }
+
+  __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).
+
+        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;
+        }
+      }
+    }
+    return p._template;
+  }
+  async __prepareAndRender(fiber: Fiber) {
+    try {
+      await Promise.all([this.willStart(), this.__owl__.willStartCB && this.__owl__.willStartCB()]);
+    } catch (e) {
+      fiber.handleError(e);
+      fiber.vnode = h("div"); // -> we render this div at the end
+      return Promise.resolve();
+    }
+    if (this.__owl__.isDestroyed) {
+      return Promise.resolve();
+    }
+    if (!fiber.isCancelled) {
+      this.__render(fiber);
+    }
+  }
+
+  __render(fiber: Fiber) {
+    const __owl__ = this.__owl__;
+    if (__owl__.observer) {
+      __owl__.observer.allowMutations = false;
+    }
+    let vnode;
+    try {
+      vnode = __owl__.renderFn!(this, {
+        handlers: __owl__.boundHandlers,
+        fiber: fiber
+      });
+    } catch (e) {
+      vnode = __owl__.vnode || h("div");
+      fiber.handleError(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();
+    }
+  }
+
+  /**
+   * Apply default props (only top level).
+   *
+   * Note that this method does not modify in place the props, it returns a new
+   * prop object
+   */
+  __applyDefaultProps(props: Object | undefined, defaultProps: Object): Props {
+    props = props ? Object.assign({}, props) : {};
+    for (let propName in defaultProps) {
+      if (props![propName] === undefined) {
+        props![propName] = defaultProps[propName];
+      }
+    }
+    return <Props>props;
+  }
+}
@@ -0,0 +1,497 @@
+import { QWeb } from "../qweb/index";
+import { INTERP_REGEXP } from "../qweb/compilation_context";
+import { MODS_CODE } from "../qweb/extensions";
+
+//------------------------------------------------------------------------------
+// t-component
+//------------------------------------------------------------------------------
+
+const T_COMPONENT_MODS_CODE = Object.assign({}, MODS_CODE, {
+  self: "if (e.target !== vn.elm) {return}"
+});
+
+QWeb.utils.defineProxy = function defineProxy(target, source) {
+  for (let k in source) {
+    Object.defineProperty(target, k, {
+      get() {
+        return source[k];
+      },
+      set(val) {
+        source[k] = val;
+      }
+    });
+  }
+};
+
+/**
+ * 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
+ * you this advice: Good luck...
+ *
+ * Since it is not 'direct' code, but rather code that generates other code, it
+ * is not easy to understand.  To help you, here  is a detailed and commented
+ * explanation of the code generated by the t-component directive for the following
+ * situation:
+ * ```xml
+ *   <Child
+ *      t-key="'somestring'"
+ *      flag="state.flag"
+ *      t-transition="fade"/>
+ * ```
+ *
+ * ```js
+ * // we assign utils on top of the function because it will be useful for
+ * // each components
+ * let utils = this.utils;
+ *
+ * // this is the virtual node representing the parent div
+ * let c1 = [], p1 = { key: 1 };
+ * var vn1 = h("div", p1, c1);
+ *
+ * // t-component directive: we start by evaluating the expression given by t-key:
+ * let key5 = "somestring";
+ *
+ * // def3 is the promise that will contain later either the new component
+ * // creation, or the props update...
+ * let def3;
+ *
+ * // this is kind of tricky: we need here to find if the component was already
+ * // created by a previous rendering.  This is done by checking the internal
+ * // `cmap` (children map) of the parent component: it maps keys to component ids,
+ * // and, then, if there is an id, we look into the children list to get the
+ * // instance
+ * let w4 =
+ *   key5 in context.__owl__.cmap
+ *   ? context.__owl__.children[context.__owl__.cmap[key5]]
+ *   : false;
+ *
+ * // We keep the index of the position of the component in the closure.  We push
+ * // null to reserve the slot, and will replace it later by the component vnode,
+ * // when it will be ready (do not forget that preparing/rendering a component is
+ * // asynchronous)
+ * let _2_index = c1.length;
+ * c1.push(null);
+ *
+ * // we evaluate here the props given to the component. It is done here to be
+ * // able to easily reference it later, and also, it might be an expensive
+ * // computation, so it is certainly better to do it only once
+ * let props4 = { flag: context["state"].flag };
+ *
+ * // If we have a component, currently rendering, but not ready yet, we do not want
+ * // to wait for it to be ready if we can avoid it
+ * if (w4 && w4.__owl__.renderPromise && !w4.__owl__.vnode) {
+ *   // we check if the props are the same.  In that case, we can simply reuse
+ *   // the previous rendering and skip all useless work
+ *   if (utils.shallowEqual(props4, w4.__owl__.renderProps)) {
+ *     def3 = w4.__owl__.renderPromise;
+ *   } else {
+ *     // if the props are not the same, we destroy the component and starts anew.
+ *     // this will be faster than waiting for its rendering, then updating it
+ *     w4.destroy();
+ *     w4 = false;
+ *   }
+ * }
+ *
+ * if (!w4) {
+ *   // in this situation, we need to create a new component.  First step is
+ *   // to get a reference to the class, then create an instance with
+ *   // current context as parent, and the props.
+ *   let W4 = context.component && context.components[componentKey4] || QWeb.component[componentKey4];
+
+ *   if (!W4) {
+ *     throw new Error("Cannot find the definition of component 'child'");
+ *   }
+ *   w4 = new W4(owner, props4);
+ *
+ *   // Whenever we rerender the parent component, we need to be sure that we
+ *   // are able to find the component instance. To do that, we register it to
+ *   // the parent cmap (children map).  Note that the 'template' key is
+ *   // used here, since this is what identify the component from the template
+ *   // perspective.
+ *   context.__owl__.cmap[key5] = w4.__owl__.id;
+ *
+ *   // __prepare is called, to basically call willStart, then render the
+ *   // component
+ *   def3 = w4.__prepare();
+ *
+ *   def3 = def3.then(vnode => {
+ *     // we create here a virtual node for the parent (NOT the component). This
+ *     // means that the vdom of the parent will be stopped here, and from
+ *     // the parent's perspective, it simply is a vnode with no children.
+ *     // However, it shares the same dom element with the component root
+ *     // vnode.
+ *     let pvnode = h(vnode.sel, { key: key5 });
+ *
+ *     // we add hooks to the parent vnode so we can interact with the new
+ *     // component at the proper time
+ *     pvnode.data.hook = {
+ *       insert(vn) {
+ *         // the __mount method will patch the component vdom into the elm vn.elm,
+ *         // then call the mounted hooks. However, suprisingly, the snabbdom
+ *         // patch method actually replace the elm by a new elm, so we need
+ *         // to synchronise the pvnode elm with the resulting elm
+ *         let nvn = w4.__mount(vnode, vn.elm);
+ *         pvnode.elm = nvn.elm;
+ *         // what follows is only present if there are animations on the component
+ *         utils.transitionInsert(vn, "fade");
+ *       },
+ *       remove() {
+ *         // override with empty function to prevent from removing the node
+ *         // directly. It will be removed when destroy is called anyway, which
+ *         // delays the removal if there are animations.
+ *       },
+ *       destroy() {
+ *         // if there are animations, we delay the call to destroy on the
+ *         // component, if not, we call it directly.
+ *         let finalize = () => {
+ *           w4.destroy();
+ *         };
+ *         utils.transitionRemove(vn, "fade", finalize);
+ *       }
+ *     };
+ *     // the pvnode is inserted at the correct position in the div's children
+ *     c1[_2_index] = pvnode;
+ *
+ *     // we keep here a reference to the parent vnode (representing the
+ *     // component, so we can reuse it later whenever we update the component
+ *     w4.__owl__.pvnode = pvnode;
+ *   });
+ * } else {
+ *   // this is the 'update' path of the directive.
+ *   // the call to __updateProps is the actual component update
+ *   // Note that we only update the props if we cannot reuse the previous
+ *   // rendering work (in the case it was rendered with the same props)
+ *   def3 = def3 || w4.__updateProps(props4, extra.forceUpdate, extra.patchQueue);
+ *   def3 = def3.then(() => {
+ *     // if component was destroyed in the meantime, we do nothing (so, this
+ *     // means that the parent's element children list will have a null in
+ *     // the component's position, which will cause the pvnode to be removed
+ *     // when it is patched.
+ *     if (w4.__owl__.isDestroyed) {
+ *       return;
+ *     }
+ *     // like above, we register the pvnode to the children list, so it
+ *     // will not be patched out of the dom.
+ *     let pvnode = w4.__owl__.pvnode;
+ *     c1[_2_index] = pvnode;
+ *   });
+ * }
+ *
+ * // we register the deferred here so the parent can coordinate its patch operation
+ * // with all the children.
+ * extra.promises.push(def3);
+ * return vn1;
+ * ```
+ */
+
+QWeb.addDirective({
+  name: "component",
+  extraNames: ["props", "keepalive"],
+  priority: 100,
+  atNodeEncounter({ ctx, value, node, qweb }): boolean {
+    ctx.addLine("//COMPONENT");
+    ctx.rootContext.shouldDefineOwner = true;
+    ctx.rootContext.shouldDefineQWeb = true;
+    ctx.rootContext.shouldDefineParent = true;
+    ctx.rootContext.shouldDefineUtils = true;
+    let keepAlive = node.getAttribute("t-keepalive") ? true : false;
+    let hasDynamicProps = node.getAttribute("t-props") ? true : false;
+
+    // t-on- events and t-transition
+    const events: [string, string[], string, string][] = [];
+    let transition: string = "";
+    const attributes = (<Element>node).attributes;
+    const props: { [key: string]: string } = {};
+    for (let i = 0; i < attributes.length; i++) {
+      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]);
+      } else if (name === "t-transition") {
+        transition = value;
+      } else if (!name.startsWith("t-")) {
+        if (name !== "class" && name !== "style") {
+          // this is a prop!
+          props[name] = ctx.formatExpression(value);
+        }
+      }
+    }
+
+    // computing the props string representing the props object
+    let propStr = Object.keys(props)
+      .map(k => k + ":" + props[k])
+      .join(",");
+    let defID = ctx.generateID();
+    let componentID = ctx.generateID();
+
+    let locationExpr = `\`__${ctx.generateID()}__`;
+    for (let i = 0; i < ctx.loopNumber - 1; i++) {
+      locationExpr += `\${i${i + 1}}__`;
+    }
+    if (ctx.lastNodeKey || ctx.currentKey) {
+      const k = ctx.lastNodeKey || 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}`;
+
+    let ref = node.getAttribute("t-ref");
+    let refExpr = "";
+    let refKey: string = "";
+    if (ref) {
+      ctx.rootContext.shouldDefineRefs = true;
+      refKey = `ref${ctx.generateID()}`;
+      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) {
+      finalizeComponentCode += `delete context.__owl__.refs[${refKey}];`;
+    }
+    if (transition) {
+      finalizeComponentCode = `let finalize = () => {
+          ${finalizeComponentCode}
+        };
+        utils.transitionRemove(vn, '${transition}', finalize);`;
+    }
+
+    let createHook = "";
+    let classAttr = node.getAttribute("class");
+    let tattClass = node.getAttribute("t-att-class");
+    let styleAttr = node.getAttribute("style");
+    let tattStyle = node.getAttribute("t-att-style");
+    if (tattStyle) {
+      const attVar = `_${ctx.generateID()}`;
+      ctx.addLine(`const ${attVar} = ${ctx.formatExpression(tattStyle)};`);
+      tattStyle = attVar;
+    }
+    let classObj = "";
+    if (classAttr || tattClass || styleAttr || tattStyle || events.length) {
+      if (classAttr) {
+        let classDef = classAttr
+          .trim()
+          .split(/\s+/)
+          .map(a => `'${a}':true`)
+          .join(",");
+        classObj = `_${ctx.generateID()}`;
+        ctx.addLine(`let ${classObj} = {${classDef}};`);
+      }
+      if (tattClass) {
+        let tattExpr = ctx.formatExpression(tattClass);
+        if (tattExpr[0] !== "{" || tattExpr[tattExpr.length - 1] !== "}") {
+          tattExpr = `utils.toObj(${tattExpr})`;
+        }
+        if (classAttr) {
+          ctx.addLine(`Object.assign(${classObj}, ${tattExpr})`);
+        } else {
+          classObj = `_${ctx.generateID()}`;
+          ctx.addLine(`let ${classObj} = ${tattExpr};`);
+        }
+      }
+      let eventsCode = events
+        .map(function([eventName, mods, handlerValue, extraArgs]) {
+          let params = "owner";
+          if (extraArgs) {
+            if (ctx.loopNumber) {
+              let argId = ctx.generateID();
+              // we need to evaluate the arguments now, because the handler will
+              // be set asynchronously later when the widget is ready, and the
+              // context might be different.
+              ctx.addLine(`let arg${argId} = ${ctx.formatExpression(extraArgs)};`);
+              params = `owner, arg${argId}`;
+            } else {
+              params = `owner, ${ctx.formatExpression(extraArgs)}`;
+            }
+          }
+          let handler = `function (e) {`;
+          handler += mods
+            .map(function(mod) {
+              return T_COMPONENT_MODS_CODE[mod];
+            })
+            .join("");
+          if (handlerValue) {
+            handler += `const fn = owner['${handlerValue}'];`;
+            handler += `if (fn) { fn.call(${params}, e); } else { owner.${handlerValue}; }`;
+          }
+          handler += `}`;
+          return `vn.elm.addEventListener('${eventName}', ${handler});`;
+        })
+        .join("");
+      const styleExpr = tattStyle || (styleAttr ? `'${styleAttr}'` : false);
+      const styleCode = styleExpr ? `vn.elm.style = ${styleExpr};` : "";
+      createHook = `vnode.data.hook = {create(_, vn){${styleCode}${eventsCode}}};`;
+    }
+
+    ctx.addLine(
+      `let w${componentID} = ${templateId} in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap[${templateId}]] : false;`
+    );
+    let shouldProxy = !ctx.parentNode;
+    if (keepAlive) {
+      ctx.addLine(
+        `const fiber${componentID} = Object.assign(Object.create(extra.fiber), {patchQueue: []});`
+      );
+    }
+    if (shouldProxy) {
+      let id = ctx.generateID();
+      ctx.rootContext.rootNode = id;
+      shouldProxy = true;
+      ctx.rootContext.shouldDefineResult = true;
+      ctx.addLine(`let vn${id} = {};`);
+      ctx.addLine(`result = vn${id};`);
+    }
+    if (hasDynamicProps) {
+      const dynamicProp = ctx.formatExpression(node.getAttribute("t-props")!);
+      ctx.addLine(`let props${componentID} = Object.assign({${propStr}}, ${dynamicProp});`);
+    } else {
+      ctx.addLine(`let props${componentID} = {${propStr}};`);
+    }
+    ctx.addIf(
+      `w${componentID} && w${componentID}.__owl__.currentFiber && !w${componentID}.__owl__.vnode`
+    );
+    ctx.addLine(`w${componentID}.destroy();`);
+    ctx.addLine(`w${componentID} = false;`);
+    ctx.closeIf();
+
+    let registerCode = "";
+    if (shouldProxy) {
+      registerCode = `utils.defineProxy(vn${ctx.rootNode}, pvnode);`;
+    }
+
+    // SLOTS
+    const varDefs: string[] = [];
+    const hasSlots = node.childNodes.length;
+    if (hasSlots) {
+      ctx.rootContext.shouldTrackScope = true;
+      for (let v of Object.values(ctx.variables)) {
+        if (v["id"]) {
+          varDefs.push(v["id"]);
+        }
+      }
+    }
+
+    let scopeVars;
+    if (hasSlots) {
+      let scope = ctx.scopeVars.length ? `Object.assign({}, scope)` : `{}`;
+      let vars = varDefs.length ? `{${varDefs.join(",")}}` : "undefined";
+      scopeVars = `${scope}, ${vars}`;
+    } else {
+      scopeVars = "undefined, undefined";
+    }
+
+    ctx.addIf(`w${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${componentID}`;
+    }
+    let styleCode = "";
+    if (tattStyle) {
+      styleCode = `.then(()=>{if (w${componentID}.__owl__.isDestroyed) {return};w${componentID}.el.style=${tattStyle};});`;
+    }
+    ctx.addLine(
+      `w${componentID}.__updateProps(props${componentID}, ${patchQueueCode}${scopeVars &&
+        ", " + scopeVars}, sibling)${styleCode};`
+    );
+    ctx.addLine(`let pvnode = w${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${componentID}.__remount();};`;
+      ctx.addLine(keepAliveCode);
+    }
+    if (registerCode) {
+      ctx.addLine(registerCode);
+    }
+    if (ctx.parentNode) {
+      ctx.addLine(`c${ctx.parentNode}.push(pvnode);`);
+    }
+
+    ctx.addElse();
+
+    // new component
+    let dynamicFallback = "";
+    if (!value.match(INTERP_REGEXP)) {
+      dynamicFallback = `|| ${ctx.formatExpression(value)}`;
+    }
+    const interpValue = ctx.interpolate(value);
+    ctx.addLine(`let componentKey${componentID} = ${interpValue};`);
+    ctx.addLine(
+      `let W${componentID} = context.constructor.components[componentKey${componentID}] || QWeb.components[componentKey${componentID}]${dynamicFallback};`
+    );
+
+    // maybe only do this in dev mode...
+    ctx.addLine(
+      `if (!W${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 (hasSlots) {
+      const clone = <Element>node.cloneNode(true);
+      const slotNodes = clone.querySelectorAll("[t-set]");
+      const slotId = QWeb.nextSlotId++;
+      ctx.addLine(`w${componentID}.__owl__.slotId = ${slotId};`);
+      if (slotNodes.length) {
+        for (let i = 0, length = slotNodes.length; i < length; i++) {
+          const slotNode = slotNodes[i];
+          slotNode.parentElement!.removeChild(slotNode);
+          const key = slotNode.getAttribute("t-set")!;
+          slotNode.removeAttribute("t-set");
+          const slotFn = qweb._compile(`slot_${key}_template`, slotNode, ctx);
+          QWeb.slots[`${slotId}_${key}`] = slotFn;
+        }
+      }
+      if (clone.childNodes.length) {
+        const t = clone.ownerDocument!.createElement("t");
+        for (let child of Object.values(clone.childNodes)) {
+          t.appendChild(child);
+        }
+        const slotFn = qweb._compile(`slot_default_template`, t, ctx);
+        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) {${finalizeComponentCode}}}});`
+    );
+    ctx.addLine(`const fiber = w${componentID}.__owl__.currentFiber;`);
+    ctx.addLine(
+      `def${defID}.then(function () {if (w${componentID}.__owl__.isDestroyed) {return;} const vnode = fiber.vnode; pvnode.sel = vnode.sel; ${createHook}});`
+    );
+    if (registerCode) {
+      ctx.addLine(registerCode);
+    }
+    if (ctx.parentNode) {
+      ctx.addLine(`c${ctx.parentNode}.push(pvnode);`);
+    }
+    ctx.addLine(`w${componentID}.__owl__.pvnode = pvnode;`);
+
+    ctx.closeIf();
+
+    if (classObj) {
+      ctx.addLine(`w${componentID}.__owl__.classObj=${classObj};`);
+    }
+
+    ctx.addLine(`sibling = w${componentID}.__owl__.currentFiber || sibling;`);
+
+    return true;
+  }
+});
@@ -0,0 +1,223 @@
+import { VNode } from "../vdom/index";
+import { Component } from "./component";
+
+/**
+ * Owl Fiber Class
+ *
+ * Fibers are small abstractions designed to contain all the internal state
+ * associated with a "rendering work unit", relative to a specific component.
+ *
+ * A rendering will cause the creation of a fiber for each impacted components.
+ *
+ * Fibers capture all that necessary information, which is critical to owl
+ * asynchronous rendering pipeline. Fibers can be cancelled, can be in different
+ * states and in general determine the state of the rendering.
+ */
+
+export class Fiber {
+  // 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;
+
+  // the fibers corresponding to component updates (updateProps) need to call
+  // the willPatch and patched hooks from the corresponding component. However,
+  // fibers corresponding to a new component do not need to do that. So, the
+  // shouldPatch hook is the boolean that we check whenever we need to apply
+  // a patch.
+  shouldPatch: boolean = true;
+
+  // isRendered is the last state of a fiber. If true, this means that it has
+  // been rendered and is inert (so, it should not be taken into account when
+  // counting the number of active fibers).
+  isRendered: boolean = false;
+
+  // the counter number is a critical information. It is only necessary for a
+  // root fiber.  For that fiber, this number counts the number of active sub
+  // fibers.  When that number reaches 0, the fiber can be applied by the
+  // scheduler.
+  counter: number = 0;
+
+  scope: any;
+  vars: any;
+  props: any;
+
+  component: Component<any, any>;
+  vnode: VNode | null = null;
+
+  root: Fiber;
+  child: Fiber | null = null;
+  sibling: Fiber | null = null;
+  parent: Fiber | null = null;
+
+  error?: Error;
+
+  constructor(parent: Fiber | null, component: Component<any, any>, props, scope, vars, force) {
+    this.force = force;
+    this.scope = scope;
+    this.vars = vars;
+    this.props = props;
+    this.component = component;
+
+    this.root = parent ? parent.root : this;
+    this.parent = parent;
+
+    let oldFiber = component.__owl__.currentFiber;
+    if (oldFiber && !oldFiber.isCancelled) {
+      this._remapFiber(oldFiber);
+    }
+
+    this.root.counter++;
+
+    component.__owl__.currentFiber = this;
+  }
+
+  /**
+   * In some cases, a rendering initiated at some component can detect that it
+   * should be part of a larger rendering initiated somewhere up the component
+   * tree.  In that case, it needs to cancel the previous rendering and
+   * remap itself as a part of the current parent rendering.
+   */
+  _remapFiber(oldFiber: Fiber) {
+    oldFiber.cancel();
+    if (oldFiber === oldFiber.root) {
+      oldFiber.root.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.child === oldFiber) {
+        this.parent.child = this;
+      } else {
+        let current = this.parent.child!;
+        while (true) {
+          if (current.sibling === oldFiber) {
+            current.sibling = this;
+            break;
+          }
+          current = current.sibling!;
+        }
+      }
+    }
+  }
+
+  /**
+   * This function has been taken from
+   * https://medium.com/react-in-depth/the-how-and-why-on-reacts-usage-of-linked-list-in-fiber-67f1014d0eb7
+   */
+  _walk(doWork: (f: Fiber) => Fiber | null) {
+    let root = this;
+    let current: Fiber = this;
+    while (true) {
+      const child = doWork(current);
+      if (child) {
+        current = child;
+        continue;
+      }
+      if (current === root) {
+        return;
+      }
+      while (!current.sibling) {
+        if (!current.parent || current.parent === root) {
+          return;
+        }
+        current = current.parent;
+      }
+      current = current.sibling;
+    }
+  }
+
+  /**
+   * 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
+   */
+  patchComponents() {
+    const patchQueue: Fiber[] = [];
+    const doWork: (Fiber) => Fiber | null = function(f) {
+      if (f.shouldPatch) {
+        patchQueue.push(f);
+      }
+      return f.child;
+    };
+    this._walk(doWork);
+    let component: Component<any, any> = this.component;
+    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);
+    }
+    for (let i = 0; i < patchLen; i++) {
+      const fiber = patchQueue[i];
+      component = fiber.component;
+      component.__patch(fiber.vnode);
+    }
+    try {
+      for (let i = patchLen - 1; i >= 0; i--) {
+        component = patchQueue[i].component;
+        component.patched();
+        if (component.__owl__.patchedCB) {
+          component.__owl__.patchedCB();
+        }
+      }
+    } catch (e) {
+      console.error(e);
+    }
+  }
+
+  /**
+   * Cancel a fiber and all its children.
+   */
+  cancel() {
+    this._walk(f => {
+      if (!f.isRendered) {
+        f.root.counter--;
+      }
+      f.isCancelled = true;
+      return f.child;
+    });
+  }
+
+  /**
+   * 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 canCatch = false;
+    let component = this.component;
+    let qweb = component.env.qweb;
+    let root = component;
+    while (component && !(canCatch = !!component.catchError)) {
+      root = component;
+      component = component.__owl__.parent!;
+    }
+    qweb.trigger("error", error);
+
+    if (canCatch) {
+      setTimeout(() => {
+        console.error(error);
+        component.catchError!(error);
+      });
+    } else {
+      this.root.error = error;
+      root.destroy();
+    }
+  }
+}
@@ -0,0 +1,96 @@
+import { QWeb } from "../qweb/index";
+
+//------------------------------------------------------------------------------
+// Prop validation helper
+//------------------------------------------------------------------------------
+
+/**
+ * Validate the component props (or next props) against the (static) props
+ * description.  This is potentially an expensive operation: it may needs to
+ * visit recursively the props and all the children to check if they are valid.
+ * This is why it is only done in 'dev' mode.
+ */
+
+QWeb.utils.validateProps = function(Widget, props: Object) {
+  const propsDef = (<any>Widget).props;
+  if (propsDef instanceof Array) {
+    // list of strings (prop names)
+    for (let i = 0, l = propsDef.length; i < l; i++) {
+      const propName = propsDef[i];
+      if (propName[propName.length - 1] === "?") {
+        // optional prop
+        break;
+      }
+      if (!(propName in props)) {
+        throw new Error(`Missing props '${propsDef[i]}' (component '${Widget.name}')`);
+      }
+    }
+    for (let key in props) {
+      if (!propsDef.includes(key) && !propsDef.includes(key + "?")) {
+        throw new Error(`Unknown prop '${key}' given to component '${Widget.name}'`);
+      }
+    }
+  } else if (propsDef) {
+    // propsDef is an object now
+    for (let propName in propsDef) {
+      if (props[propName] === undefined) {
+        if (propsDef[propName] && !propsDef[propName].optional) {
+          throw new Error(`Missing props '${propName}' (component '${Widget.name}')`);
+        } else {
+          break;
+        }
+      }
+      let isValid = isValidProp(props[propName], propsDef[propName]);
+      if (!isValid) {
+        throw new Error(`Props '${propName}' of invalid type in component '${Widget.name}'`);
+      }
+    }
+    for (let propName in props) {
+      if (!(propName in propsDef)) {
+        throw new Error(`Unknown prop '${propName}' given to component '${Widget.name}'`);
+      }
+    }
+  }
+};
+
+/**
+ * Check if an invidual prop value matches its (static) prop definition
+ */
+function isValidProp(prop, propDef): boolean {
+  if (propDef === true) {
+    return true;
+  }
+  if (typeof propDef === "function") {
+    // Check if a value is constructed by some Constructor.  Note that there is a
+    // slight abuse of language: we want to consider primitive values as well.
+    //
+    // So, even though 1 is not an instance of Number, we want to consider that
+    // it is valid.
+    if (typeof prop === "object") {
+      return prop instanceof propDef;
+    }
+    return typeof prop === propDef.name.toLowerCase();
+  } else if (propDef instanceof Array) {
+    // If this code is executed, this means that we want to check if a prop
+    // matches at least one of its descriptor.
+    let result = false;
+    for (let i = 0, iLen = propDef.length; i < iLen; i++) {
+      result = result || isValidProp(prop, propDef[i]);
+    }
+    return result;
+  }
+  // propsDef is an object
+  let result = isValidProp(prop, propDef.type);
+  if (propDef.type === Array) {
+    for (let i = 0, iLen = prop.length; i < iLen; i++) {
+      result = result && isValidProp(prop[i], propDef.element);
+    }
+  }
+  if (propDef.type === Object) {
+    const shape = propDef.shape;
+    for (let key in shape) {
+      result = result && isValidProp(prop[key], shape[key]);
+    }
+  }
+  return result;
+}
@@ -0,0 +1,67 @@
+import { Fiber } from "./fiber";
+
+/**
+ * Owl Scheduler Class
+ *
+ * The scheduler is the part of Owl that will effectively apply a rendering
+ * whenever a fiber is ready.
+ *
+ * Briefly, it can be used to register root fibers.  Whenever there is an
+ * active root fiber, it will poll continuously each animation frame (so, about
+ * once every 16ms) and whenever a root fiber is ready, it will apply it.
+ */
+
+interface Task {
+  fiber: Fiber;
+  callback: (err?: Error) => void;
+}
+
+export class Scheduler {
+  tasks: Task[] = [];
+  isRunning: boolean = false;
+  requestAnimationFrame: typeof window.requestAnimationFrame;
+
+  constructor(requestAnimationFrame) {
+    this.requestAnimationFrame = requestAnimationFrame;
+  }
+
+  addFiber(fiber, callback) {
+    this.tasks.push({ fiber, callback });
+    if (this.isRunning) {
+      return;
+    }
+    this.scheduleTasks();
+  }
+
+  /**
+   * Process all current tasks. This only applies to the fibers that are ready.
+   * Other tasks are left unchanged.
+   */
+  flush() {
+    let tasks = this.tasks;
+    this.tasks = [];
+    tasks = tasks.filter(task => {
+      if (task.fiber.isCancelled) {
+        return false;
+      }
+      if (task.fiber.counter === 0) {
+        task.callback(task.fiber.error);
+        return false;
+      }
+      return true;
+    });
+    this.tasks = tasks.concat(this.tasks);
+  }
+
+  scheduleTasks() {
+    this.isRunning = true;
+    this.requestAnimationFrame(() => {
+      this.flush();
+      if (this.tasks.length > 0) {
+        this.scheduleTasks();
+      } else {
+        this.isRunning = false;
+      }
+    });
+  }
+}
@@ -0,0 +1,111 @@
+import { Component, scheduler } from "./component/component";
+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,
+ * but when we have to deal with some mostly global information, this can be
+ * annoying, since each component will need to pass the information to each
+ * children, even though some or most of them will not use the information.
+ *
+ * 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.
+ */
+export class Context extends EventBus {
+  state: any;
+  observer: Observer;
+  rev: number = 1;
+  // mapping from component id to last observed context id
+  mapping: { [componentId: number]: number } = {};
+
+  constructor(state: Object = {}) {
+    super();
+    this.observer = new Observer();
+    this.observer.notifyCB = this.__notifyComponents.bind(this);
+    this.state = this.observer.observe(state);
+  }
+
+  /**
+   * 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.
+   *
+   * 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.
+   *
+   * 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.
+   */
+  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;
+      }
+    }
+  }
+}
+
+/**
+ * The`useContext` hook is the normal way for a component to register themselve
+ * to context state changes. The `useContext` method returns the context state
+ */
+export function useContext(ctx: Context): any {
+  const component: Component<any, any> = Component.current!;
+  return useContextWithCB(ctx, component, component.render.bind(component));
+}
+
+export function useContextWithCB(ctx: Context, component: Component<any, any>, method): any {
+  const __owl__ = component.__owl__;
+  const id = __owl__.id;
+  const mapping = ctx.mapping;
+  if (id in mapping) {
+    return ctx.state;
+  }
+  if (!__owl__.observer) {
+    __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) {
+    mapping[id] = ctx.rev;
+    return renderFn(comp, params);
+  };
+  ctx.on("update", component, async contextRev => {
+    if (mapping[id] < contextRev) {
+      mapping[id] = contextRev;
+      await method();
+    }
+  });
+  onWillUnmount(() => {
+    ctx.off("update", component);
+    delete mapping[id];
+  });
+  return ctx.state;
+}
@@ -3,7 +3,8 @@
 * - emit events
 * - add/remove listeners.
 *
- * This is a useful pattern of communication in some cases.
+ * This is a useful pattern of communication in many cases.  For OWL, each
+ * components and stores are event buses.
 */

 //------------------------------------------------------------------------------
@@ -28,7 +29,7 @@ export class EventBus {
   * Add a listener for the 'eventType' events.
   *
   * Note that the 'owner' of this event can be anything, but will more likely
-   * be a widget or a class. The idea is that the callback will be called with
+   * be a component or a class. The idea is that the callback will be called with
   * the proper owner bound.
   *
   * Also, the owner should be kind of unique. This will be used to remove the
@@ -63,7 +64,8 @@ export class EventBus {
   */
  trigger(eventType: string, ...args: any[]) {
    const subs = this.subscriptions[eventType] || [];
-    for (let sub of subs) {
+    for (let i = 0, iLen = subs.length; i < iLen; i++) {
+      const sub = subs[i];
      sub.callback.call(sub.owner, ...args);
    }
  }
@@ -0,0 +1,109 @@
+/**
+ * Owl Observer
+ *
+ * This code contains the logic that allows Owl to observe and react to state
+ * changes.
+ *
+ * This is a Observer class that can observe any JS values.  The way it works
+ * can be summarized thusly:
+ * - primitive values are not observed at all
+ * - Objects and arrays are observed by replacing them with a Proxy
+ * - each object/array metadata are tracked in a weakmap, and keep a revision
+ *   number
+ *
+ * Note that this code is loosely inspired by Vue.
+ */
+
+//------------------------------------------------------------------------------
+// Observer
+//------------------------------------------------------------------------------
+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) {
+      // fun fact: typeof null === 'object'
+      return value;
+    }
+    let metadata = this.weakMap.get(value) || this._observe(value, parent);
+    return metadata.proxy;
+  }
+
+  revNumber(value): number {
+    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;
+
+    const proxy = new Proxy(value, {
+      get(target, k) {
+        const targetValue = target[k];
+        return self.observe(targetValue, value);
+      },
+      set(target, key: string, newVal): boolean {
+        const value = target[key];
+        if (newVal !== value) {
+          if (!self.allowMutations) {
+            throw new Error(
+              `Observed state cannot be changed here! (key: "${key}", val: "${newVal}")`
+            );
+          }
+          self._updateRevNumber(target);
+          target[key] = newVal;
+          self.notifyChange();
+        }
+        return true;
+      },
+      deleteProperty(target, key) {
+        if (key in target) {
+          delete target[key];
+          self._updateRevNumber(target);
+          self.notifyChange();
+        }
+        return true;
+      }
+    });
+
+    const metadata = {
+      value,
+      proxy,
+      rev: this.rev,
+      deepRev: this.rev,
+      parent
+    };
+
+    this.weakMap.set(value, metadata);
+    this.weakMap.set(metadata.proxy, metadata);
+    return metadata;
+  }
+
+  _updateRevNumber(target: any) {
+    this.rev++;
+    let metadata = this.weakMap.get(target);
+    metadata.rev!++;
+    let parent = target;
+    do {
+      metadata = this.weakMap.get(parent);
+      metadata.deepRev++;
+    } while ((parent = metadata.parent) && parent !== target);
+  }
+}
@@ -0,0 +1,128 @@
+import { Component } from "./component/component";
+import { Observer } from "./core/observer";
+
+/**
+ * Owl Hook System
+ *
+ * This file introduces the concept of hooks, similar to React or Vue hooks.
+ * We have currently an implementation of:
+ * - useState (reactive state)
+ * - onMounted
+ * - onWillUnmount
+ * - useRef
+ */
+
+// -----------------------------------------------------------------------------
+// useState
+// -----------------------------------------------------------------------------
+
+/**
+ * This is the main way a component can be made reactive.  The useState hook
+ * will return an observed object (or array).  Changes to that value will then
+ * trigger a rerendering of the current component.
+ */
+export function useState<T>(state: T): T {
+  const component: Component<any, any> = Component.current!;
+  const __owl__ = component.__owl__;
+  if (!__owl__.observer) {
+    __owl__.observer = new Observer();
+    __owl__.observer.notifyCB = component.render.bind(component);
+  }
+  return __owl__.observer.observe(state);
+}
+
+// -----------------------------------------------------------------------------
+// Life cycle hooks
+// -----------------------------------------------------------------------------
+function makeLifecycleHook(method: string, reverse: boolean = false) {
+  if (reverse) {
+    return function(cb) {
+      const component: Component<any, any> = Component.current!;
+      if (component.__owl__[method]) {
+        const current = component.__owl__[method];
+        component.__owl__[method] = function() {
+          current.call(component);
+          cb.call(component);
+        };
+      } else {
+        component.__owl__[method] = cb;
+      }
+    };
+  } else {
+    return function(cb) {
+      const component: Component<any, any> = Component.current!;
+      if (component.__owl__[method]) {
+        const current = component.__owl__[method];
+        component.__owl__[method] = function() {
+          cb.call(component);
+          current.call(component);
+        };
+      } else {
+        component.__owl__[method] = cb;
+      }
+    };
+  }
+}
+
+function makeAsyncHook(method: string) {
+  return function(cb) {
+    const component: Component<any, any> = 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))];
+      };
+    } else {
+      component.__owl__[method] = cb;
+    }
+  };
+}
+
+export const onMounted = makeLifecycleHook("mountedCB", true);
+export const onWillUnmount = makeLifecycleHook("willUnmountCB");
+export const onWillPatch = makeLifecycleHook("willPatchCB");
+export const onPatched = makeLifecycleHook("patchedCB", true);
+
+export const onWillStart = makeAsyncHook("willStartCB");
+export const onWillUpdateProps = makeAsyncHook("willUpdatePropsCB");
+
+// -----------------------------------------------------------------------------
+// useRef
+// -----------------------------------------------------------------------------
+
+/**
+ * The purpose of this hook is to allow components to get a reference to a sub
+ * html node or component.
+ */
+interface Ref {
+  el: HTMLElement | null;
+  comp: Component<any, any> | null;
+}
+
+export function useRef(name: string): Ref {
+  const __owl__ = Component.current!.__owl__;
+  return {
+    get el(): HTMLElement | null {
+      const val = __owl__.refs && __owl__.refs[name];
+      return val instanceof HTMLElement ? val : null;
+    },
+    get comp(): Component<any, any> | null {
+      const val = __owl__.refs && __owl__.refs[name];
+      return val instanceof Component ? val : null;
+    }
+  };
+}
+
+// -----------------------------------------------------------------------------
+// useSubEnv
+// -----------------------------------------------------------------------------
+
+/**
+ * This hook is a simple way to let components use a sub environment.  Note that
+ * like for all hooks, it is important that this is only called in the
+ * constructor method.
+ */
+export function useSubEnv(nextEnv) {
+  const component = Component.current!;
+  component.env = Object.assign(Object.create(component.env), nextEnv);
+}
@@ -1,8 +1,54 @@
-export { Component } from "./component";
-export { EventBus } from "./event_bus";
-export { Observer } from "./observer";
-export { QWeb } from "./qweb";
-export { connect, Store } from "./store";
+/**
+ * This file is the main file packaged by rollup (see rollup.config.js).  From
+ * this file, we export all public owl elements.
+ *
+ * Note that dynamic values, such as a date or a commit hash are added by rollup
+ */
+import { EventBus } from "./core/event_bus";
+import { Observer } from "./core/observer";
+import { QWeb } from "./qweb/index";
+import * as _store from "./store";
 import * as _utils from "./utils";
+import * as _tags from "./tags";
+import { AsyncRoot } from "./misc/async_root";
+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 { QWeb };
+
+export const Context = _context.Context;
+export const useState = _hooks.useState;
+export const core = { EventBus, Observer };
+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 hooks = Object.assign({}, _hooks, {
+  useContext: _context.useContext,
+  useDispatch: _store.useDispatch,
+  useGetters: _store.useGetters,
+  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.`);
+    }
+  }
+});
@@ -0,0 +1,19 @@
+import { Component } from "../component/component";
+import { xml } from "../tags";
+
+/**
+ * AsyncRoot
+ *
+ * Owl is by default asynchronous, and the user interface will wait for all its
+ * subcomponents to be rendered before updating the DOM. This is most of the
+ * time what we want, but in some cases, it makes sense to "detach" a component
+ * from this coordination.  This is the goal of the AsyncRoot component.
+ */
+
+export class AsyncRoot extends Component<any, any> {
+  static template = xml`<t t-slot="default"/>`;
+
+  async __updateProps(nextProps, parentFiber) {
+    this.render(parentFiber.force);
+  }
+}
@@ -1,142 +0,0 @@
-//------------------------------------------------------------------------------
-// Observer
-//------------------------------------------------------------------------------
-
-const methodsToPatch = [
-  "push",
-  "pop",
-  "shift",
-  "unshift",
-  "splice",
-  "sort",
-  "reverse"
-];
-
-const ArrayProto = Array.prototype;
-const ModifiedArrayProto = Object.create(ArrayProto);
-
-for (let method of methodsToPatch) {
-  const initialMethod = ArrayProto[method];
-  ModifiedArrayProto[method] = function(...args) {
-    if (!this.__observer__.allowMutations) {
-      throw new Error(`Array cannot be changed here")`);
-    }
-    this.__observer__.notifyChange();
-    this.__owl__.rev++;
-    let parent = this;
-    do {
-      parent.__owl__.deepRev++;
-    } while ((parent = parent.__owl__.parent));
-    let inserted;
-    switch (method) {
-      case "push":
-      case "unshift":
-        inserted = args;
-        break;
-      case "splice":
-        inserted = args.slice(2);
-        break;
-    }
-    if (inserted) {
-      for (let elem of inserted) {
-        this.__observer__.observe(elem, this);
-      }
-    }
-    return initialMethod.call(this, ...args);
-  };
-}
-
-export class Observer {
-  rev: number = 1;
-  allowMutations: boolean = true;
-  dirty: boolean = false;
-
-  notifyCB() {}
-  notifyChange() {
-    this.rev++;
-    this.dirty = true;
-    Promise.resolve().then(() => {
-      if (this.dirty) {
-        this.dirty = false;
-        this.notifyCB();
-      }
-    });
-  }
-
-  observe(value: any, parent?: any) {
-    if (value === null) {
-      // fun fact: typeof null === 'object'
-      return;
-    }
-    if (typeof value !== "object") {
-      return;
-    }
-    if ("__owl__" in value) {
-      // already observed
-      value.__owl__.parent = parent;
-      return;
-    }
-    if (Array.isArray(value)) {
-      this._observeArr(value, parent);
-    } else {
-      this._observeObj(value, parent);
-    }
-  }
-
-  set(target: any, key: number | string, value: any) {
-    this._addProp(target, key, value);
-    target.__owl__.rev++;
-    this.notifyChange();
-  }
-
-  _observeObj<T extends { __owl__?: any }>(obj: T, parent?: any) {
-    const keys = Object.keys(obj);
-    obj.__owl__ = { rev: 1, deepRev: 1, parent };
-    Object.defineProperty(obj, "__owl__", { enumerable: false });
-    for (let key of keys) {
-      this._addProp(obj, key, obj[key]);
-    }
-  }
-
-  _observeArr(arr: Array<any>, parent?: any) {
-    (<any>arr).__owl__ = { rev: 1, deepRev: 1, parent };
-    Object.defineProperty(arr, "__owl__", { enumerable: false });
-    (<any>arr).__proto__ = Object.create(ModifiedArrayProto);
-    (<any>arr).__proto__.__observer__ = this;
-    for (let i = 0; i < arr.length; i++) {
-      this.observe(arr[i], arr);
-    }
-  }
-
-  _addProp<T extends { __owl__?: any }>(
-    obj: T,
-    key: string | number,
-    value: any
-  ) {
-    var self = this;
-    Object.defineProperty(obj, key, {
-      enumerable: true,
-      get() {
-        return value;
-      },
-      set(newVal) {
-        if (newVal !== value) {
-          if (!self.allowMutations) {
-            throw new Error(
-              `Observed state cannot be changed here! (key: "${key}", val: "${newVal}")`
-            );
-          }
-          value = newVal;
-          self.observe(newVal, obj);
-          obj.__owl__.rev!++;
-          let parent = obj;
-          do {
-            parent.__owl__.deepRev++;
-          } while ((parent = parent.__owl__.parent) && parent !== obj);
-          self.notifyChange();
-        }
-      }
-    });
-    this.observe(value, obj);
-  }
-}
@@ -0,0 +1,337 @@
+import { CompilationContext } from "./compilation_context";
+import { QWebExprVar } from "./expression_parser";
+import { QWeb } from "./qweb";
+import { htmlToVDOM } from "../vdom/html_to_vdom";
+
+/**
+ * Owl QWeb Directives
+ *
+ * This file contains the implementation of most standard QWeb directives:
+ * - t-esc
+ * - t-raw
+ * - t-set/t-value
+ * - t-if/t-elif/t-else
+ * - t-call
+ * - t-foreach/t-as
+ * - t-debug
+ * - t-log
+ */
+
+//------------------------------------------------------------------------------
+// t-esc and t-raw
+//------------------------------------------------------------------------------
+QWeb.utils.getFragment = function(str: string): DocumentFragment {
+  const temp = document.createElement("template");
+  temp.innerHTML = str;
+  return temp.content;
+};
+
+QWeb.utils.htmlToVDOM = htmlToVDOM;
+
+function compileValueNode(value: any, node: Element, qweb: QWeb, ctx: CompilationContext) {
+  if (value === "0" && ctx.caller) {
+    qweb._compileNode(ctx.caller, ctx);
+    return;
+  }
+
+  if (value.xml instanceof NodeList) {
+    for (let node of Array.from(value.xml)) {
+      qweb._compileNode(<ChildNode>node, ctx);
+    }
+    return;
+  }
+  let exprID: string;
+  if (typeof value === "string") {
+    exprID = `_${ctx.generateID()}`;
+    ctx.addLine(`var ${exprID} = ${ctx.formatExpression(value)};`);
+  } else {
+    exprID = value.id;
+  }
+  ctx.addIf(`${exprID} || ${exprID} === 0`);
+  if (ctx.escaping) {
+    if (ctx.parentTextNode) {
+      ctx.addLine(`vn${ctx.parentTextNode}.text += ${exprID};`);
+    } else if (ctx.parentNode) {
+      ctx.addLine(`c${ctx.parentNode}.push({text: ${exprID}});`);
+    } else {
+      let nodeID = ctx.generateID();
+      ctx.rootContext.rootNode = nodeID;
+      ctx.rootContext.parentTextNode = nodeID;
+      ctx.addLine(`var vn${nodeID} = {text: ${exprID}};`);
+      if (ctx.rootContext.shouldDefineResult) {
+        ctx.addLine(`result = vn${nodeID}`);
+      }
+    }
+  } else {
+    ctx.rootContext.shouldDefineUtils = true;
+    ctx.addLine(`c${ctx.parentNode}.push(...utils.htmlToVDOM(${exprID}));`);
+  }
+  if (node.childNodes.length) {
+    ctx.addElse();
+    qweb._compileChildren(node, ctx);
+  }
+
+  ctx.closeIf();
+}
+
+QWeb.addDirective({
+  name: "esc",
+  priority: 70,
+  atNodeEncounter({ node, qweb, ctx }): boolean {
+    let value = ctx.getValue(node.getAttribute("t-esc")!);
+    compileValueNode(value, node, qweb, ctx.subContext("escaping", true));
+    return true;
+  }
+});
+
+QWeb.addDirective({
+  name: "raw",
+  priority: 80,
+  atNodeEncounter({ node, qweb, ctx }): boolean {
+    let value = ctx.getValue(node.getAttribute("t-raw")!);
+    compileValueNode(value, node, qweb, ctx);
+    return true;
+  }
+});
+
+//------------------------------------------------------------------------------
+// t-set
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "set",
+  extraNames: ["value"],
+  priority: 60,
+  atNodeEncounter({ node, ctx }): boolean {
+    const variable = node.getAttribute("t-set")!;
+    let value = node.getAttribute("t-value")!;
+    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} = ${formattedValue};`);
+        ctx.variables[variable] = {
+          id: varName,
+          expr: formattedValue
+        };
+      }
+    } else {
+      ctx.variables[variable] = {
+        xml: node.childNodes
+      };
+    }
+    return true;
+  }
+});
+
+//------------------------------------------------------------------------------
+// t-if, t-elif, t-else
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "if",
+  priority: 20,
+  atNodeEncounter({ node, ctx }): boolean {
+    let cond = ctx.getValue(node.getAttribute("t-if")!);
+    ctx.addIf(typeof cond === "string" ? ctx.formatExpression(cond) : cond.id);
+    return false;
+  },
+  finalize({ ctx }) {
+    ctx.closeIf();
+  }
+});
+
+QWeb.addDirective({
+  name: "elif",
+  priority: 30,
+  atNodeEncounter({ node, ctx }): boolean {
+    let cond = ctx.getValue(node.getAttribute("t-elif")!);
+    ctx.addLine(`else if (${typeof cond === "string" ? ctx.formatExpression(cond) : cond.id}) {`);
+    ctx.indent();
+    return false;
+  },
+  finalize({ ctx }) {
+    ctx.closeIf();
+  }
+});
+
+QWeb.addDirective({
+  name: "else",
+  priority: 40,
+  atNodeEncounter({ ctx }): boolean {
+    ctx.addLine(`else {`);
+    ctx.indent();
+    return false;
+  },
+  finalize({ ctx }) {
+    ctx.closeIf();
+  }
+});
+
+//------------------------------------------------------------------------------
+// t-call
+//------------------------------------------------------------------------------
+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')");
+    }
+    const subTemplate = node.getAttribute("t-call")!;
+    const nodeTemplate = qweb.templates[subTemplate];
+    if (!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}}`;
+      }
+      ctx.addLine(
+        `this.recursiveFns['${subTemplateName}'].call(this, context, Object.assign({}, extra, {parentNode: c${ctx.parentNode}, fiber: {vars: ${varCode}, scope}}));`
+      );
+      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} = ${(<QWebExprVar>v).expr};`);
+        }
+        // todo: handle XML variables...
+      }
+    }
+    qweb._compileNode(nodeTemplate.elem, subCtx);
+
+    // close new scope
+    if (hasNewVariables) {
+      ctx.dedent();
+      ctx.addLine("}");
+    }
+
+    return true;
+  }
+});
+
+//------------------------------------------------------------------------------
+// t-foreach
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "foreach",
+  extraNames: ["as"],
+  priority: 10,
+  atNodeEncounter({ node, qweb, ctx }): boolean {
+    ctx.rootContext.shouldProtectContext = true;
+    ctx = ctx.subContext("loopNumber", ctx.loopNumber + 1);
+    const elems = node.getAttribute("t-foreach")!;
+    const name = node.getAttribute("t-as")!;
+    let arrayID = ctx.generateID();
+    ctx.addLine(`var _${arrayID} = ${ctx.formatExpression(elems)};`);
+    ctx.addLine(`if (!_${arrayID}) { throw new Error('QWeb error: Invalid loop expression')}`);
+    let keysID = ctx.generateID();
+    let valuesID = ctx.generateID();
+    ctx.addLine(`var _${keysID} = _${valuesID} = _${arrayID};`);
+    ctx.addIf(`!(_${arrayID} instanceof Array)`);
+    ctx.addLine(`_${keysID} = Object.keys(_${arrayID});`);
+    ctx.addLine(`_${valuesID} = Object.values(_${arrayID});`);
+    ctx.closeIf();
+    ctx.addLine(`var _length${keysID} = _${keysID}.length;`);
+    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}]`);
+    const nodeCopy = <Element>node.cloneNode(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: '${ctx.templateName}')`
+      );
+    }
+
+    nodeCopy.removeAttribute("t-foreach");
+    qweb._compileNode(nodeCopy, ctx);
+    ctx.dedent();
+    ctx.addLine("}");
+    return true;
+  }
+});
+
+//------------------------------------------------------------------------------
+// t-debug
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "debug",
+  priority: 1,
+  atNodeEncounter({ ctx }) {
+    ctx.addLine("debugger;");
+  }
+});
+
+//------------------------------------------------------------------------------
+// t-log
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "log",
+  priority: 1,
+  atNodeEncounter({ ctx, value }) {
+    const expr = ctx.formatExpression(value);
+    ctx.addLine(`console.log(${expr})`);
+  }
+});
@@ -0,0 +1,183 @@
+import { compileExpr, QWebVar, QWebExprVar } from "./expression_parser";
+
+export const INTERP_REGEXP = /\{\{.*?\}\}/g;
+//------------------------------------------------------------------------------
+// Compilation Context
+//------------------------------------------------------------------------------
+
+export class CompilationContext {
+  nextID: number = 1;
+  code: string[] = [];
+  variables: { [key: string]: QWebVar } = {};
+  escaping: boolean = false;
+  parentNode: number | null = null;
+  parentTextNode: number | null = null;
+  rootNode: number | null = null;
+  indentLevel: number = 0;
+  rootContext: CompilationContext;
+  caller: Element | undefined;
+  shouldDefineOwner: boolean = false;
+  shouldDefineParent: boolean = false;
+  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 } = {};
+
+  constructor(name?: string) {
+    this.rootContext = this;
+    this.templateName = name || "noname";
+    this.templates[this.templateName] = true;
+    this.addLine("var h = this.h;");
+  }
+
+  generateID(): number {
+    const id = this.rootContext.nextID++;
+    return 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.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;");
+      } else {
+        this.code.unshift("    let parent = context;");
+      }
+    }
+    if (this.shouldDefineQWeb) {
+      this.code.unshift("    let QWeb = this.constructor;");
+    }
+    if (this.shouldDefineUtils) {
+      this.code.unshift("    let utils = this.constructor.utils;");
+    }
+    return this.code;
+  }
+
+  withParent(node: number): CompilationContext {
+    if (
+      !this.allowMultipleRoots &&
+      this === this.rootContext &&
+      (this.parentNode || this.parentTextNode)
+    ) {
+      throw new Error("A template should not have more than one root node");
+    }
+    if (!this.rootContext.rootNode) {
+      this.rootContext.rootNode = node;
+    }
+    if (!this.parentNode && this.rootContext.shouldDefineResult) {
+      this.addLine(`result = vn${node};`);
+    }
+    return this.subContext("parentNode", node);
+  }
+
+  subContext(key: keyof CompilationContext, value: any): CompilationContext {
+    const newContext = Object.create(this);
+    newContext[key] = value;
+    return newContext;
+  }
+
+  indent() {
+    this.indentLevel++;
+  }
+
+  dedent() {
+    this.indentLevel--;
+  }
+
+  addLine(line: string): number {
+    const prefix = new Array(this.indentLevel + 2).join("    ");
+    this.code.push(prefix + line);
+    return this.code.length - 1;
+  }
+
+  addToScope(key: string, expr: string) {
+    const index = this.addLine(`context.${key} = ${expr};`);
+    this.rootContext.scopeVars.push({ index, key, indent: this.indentLevel });
+  }
+
+  addIf(condition: string) {
+    this.addLine(`if (${condition}) {`);
+    this.indent();
+  }
+
+  addElse() {
+    this.dedent();
+    this.addLine("} else {");
+    this.indent();
+  }
+
+  closeIf() {
+    this.dedent();
+    this.addLine("}");
+  }
+
+  getValue(val: any): QWebExprVar | string {
+    return val in this.variables ? this.getValue(this.variables[val]) : val;
+  }
+
+  /**
+   * Prepare an expression for being consumed at render time.  Its main job
+   * is to
+   * - replace unknown variables by a lookup in the context
+   * - replace already defined variables by their internal name
+   */
+  formatExpression(expr: string): string {
+    return compileExpr(expr, this.variables);
+  }
+
+  /**
+   * Perform string interpolation on the given string. Note that if the whole
+   * string is an expression, it simply returns it (formatted and enclosed in
+   * parentheses).
+   * For instance:
+   *   'Hello {{x}}!' -> `Hello ${x}`
+   *   '{{x ? 'a': 'b'}}' -> (x ? 'a' : 'b')
+   */
+  interpolate(s: string): string {
+    let matches = s.match(INTERP_REGEXP);
+    if (matches && matches[0].length === s.length) {
+      return `(${this.formatExpression(s.slice(2, -2))})`;
+    }
+
+    let r = s.replace(/\{\{.*?\}\}/g, s => "${" + this.formatExpression(s.slice(2, -2)) + "}");
+    return "`" + r + "`";
+  }
+}
@@ -0,0 +1,264 @@
+/**
+ * Owl QWeb Expression Parser
+ *
+ * Owl needs in various contexts to be able to understand the structure of a
+ * string representing a javascript expression.  The usual goal is to be able
+ * to rewrite some variables.  For example, if a template has
+ *
+ *  ```xml
+ *  <t t-if="computeSomething({val: state.val})">...</t>
+ * ```
+ *
+ * this needs to be translated in something like this:
+ *
+ * ```js
+ *   if (context["computeSomething"]({val: context["state"].val})) { ... }
+ * ```
+ *
+ * This file contains the implementation of an extremely naive tokenizer/parser
+ * and evaluator for javascript expressions.  The supported grammar is basically
+ * only expressive enough to understand the shape of objects, of arrays, and
+ * various operators.
+ */
+
+//------------------------------------------------------------------------------
+// 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 WORD_REPLACEMENT = {
+  and: "&&",
+  or: "||",
+  gt: ">",
+  gte: ">=",
+  lt: "<",
+  lte: "<="
+};
+
+export interface QWebExprVar {
+  id: string;
+  expr: string;
+}
+
+export interface QWebXMLVar {
+  xml: NodeList;
+}
+
+export type QWebVar = QWebExprVar | QWebXMLVar;
+
+//------------------------------------------------------------------------------
+// Tokenizer
+//------------------------------------------------------------------------------
+type TKind =
+  | "LEFT_BRACE"
+  | "RIGHT_BRACE"
+  | "LEFT_BRACKET"
+  | "RIGHT_BRACKET"
+  | "LEFT_PAREN"
+  | "RIGHT_PAREN"
+  | "COMMA"
+  | "VALUE"
+  | "SYMBOL"
+  | "OPERATOR"
+  | "COLON";
+
+interface Token {
+  type: TKind;
+  value: string;
+  size?: number;
+}
+
+const STATIC_TOKEN_MAP: { [key: string]: TKind } = {
+  "{": "LEFT_BRACE",
+  "}": "RIGHT_BRACE",
+  "[": "LEFT_BRACKET",
+  "]": "RIGHT_BRACKET",
+  ":": "COLON",
+  ",": "COMMA",
+  "(": "LEFT_PAREN",
+  ")": "RIGHT_PAREN"
+};
+
+const OPERATORS = ".,===,==,+,!==,!=,!,||,&&,>=,>,<=,<,?,-,*,/,%".split(",");
+
+type Tokenizer = (expr: string) => Token | false;
+
+let tokenizeString: Tokenizer = function(expr) {
+  let s = expr[0];
+  let start = s;
+  if (s !== "'" && s !== '"') {
+    return false;
+  }
+  let i = 1;
+  let cur;
+  while (expr[i] && expr[i] !== start) {
+    cur = expr[i];
+    s += cur;
+    if (cur === "\\") {
+      i++;
+      cur = expr[i];
+      if (!cur) {
+        throw new Error("Invalid expression");
+      }
+      s += cur;
+    }
+    i++;
+  }
+  if (expr[i] !== start) {
+    throw new Error("Invalid expression");
+  }
+  s += start;
+  return { type: "VALUE", value: s };
+};
+
+let tokenizeNumber: Tokenizer = function(expr) {
+  let s = expr[0];
+  if (s && s.match(/[0-9]/)) {
+    let i = 1;
+    while (expr[i] && expr[i].match(/[0-9]|\./)) {
+      s += expr[i];
+      i++;
+    }
+    return { type: "VALUE", value: s };
+  } else {
+    return false;
+  }
+};
+
+let tokenizeSymbol: Tokenizer = function(expr) {
+  let s = expr[0];
+  if (s && s.match(/[a-zA-Z_\$]/)) {
+    let i = 1;
+    while (expr[i] && expr[i].match(/\w/)) {
+      s += expr[i];
+      i++;
+    }
+    if (s in WORD_REPLACEMENT) {
+      return { type: "OPERATOR", value: WORD_REPLACEMENT[s], size: s.length };
+    }
+    return { type: "SYMBOL", value: s };
+  } else {
+    return false;
+  }
+};
+
+const tokenizeStatic: Tokenizer = function(expr) {
+  const char = expr[0];
+  if (char && char in STATIC_TOKEN_MAP) {
+    return { type: STATIC_TOKEN_MAP[char], value: char };
+  }
+  return false;
+};
+
+const tokenizeOperator: Tokenizer = function(expr) {
+  for (let op of OPERATORS) {
+    if (expr.startsWith(op)) {
+      return { type: "OPERATOR", value: op };
+    }
+  }
+  return false;
+};
+
+const TOKENIZERS = [
+  tokenizeString,
+  tokenizeNumber,
+  tokenizeSymbol,
+  tokenizeStatic,
+  tokenizeOperator
+];
+
+/**
+ * Convert a javascript expression (as a string) into a list of tokens. For
+ * example: `tokenize("1 + b")` will return:
+ * ```js
+ *  [
+ *   {type: "VALUE", value: "1"},
+ *   {type: "OPERATOR", value: "+"},
+ *   {type: "SYMBOL", value: "b"}
+ * ]
+ * ```
+ */
+export function tokenize(expr: string): Token[] {
+  const result: Token[] = [];
+  let token: boolean | Token = true;
+
+  while (token) {
+    expr = expr.trim();
+    if (expr) {
+      for (let tokenizer of TOKENIZERS) {
+        token = tokenizer(expr);
+        if (token) {
+          result.push(token);
+          expr = expr.slice(token.size || token.value.length);
+          break;
+        }
+      }
+    } else {
+      token = false;
+    }
+  }
+  if (expr.length) {
+    throw new Error(`Tokenizer error: could not tokenize "${expr}"`);
+  }
+  return result;
+}
+
+//------------------------------------------------------------------------------
+// Expression "evaluator"
+//------------------------------------------------------------------------------
+
+/**
+ * This is the main function exported by this file. This is the code that will
+ * process an expression (given as a string) and returns another expression with
+ * proper lookups in the context.
+ *
+ * Usually, this kind of code would be very simple to do if we had an AST (so,
+ * if we had a javascript parser), since then, we would only need to find the
+ * variables and replace them.  However, a parser is more complicated, and there
+ * are no standard builtin parser API.
+ *
+ * Since this method is applied to simple javasript expressions, and the work to
+ * be done is actually quite simple, we actually can get away with not using a
+ * parser, which helps with the code size.
+ *
+ * Here is the heuristic used by this method to determine if a token is a
+ * variable:
+ * - by default, all symbols are considered a variable
+ * - 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}`)
+ */
+export function compileExpr(expr: string, vars: { [key: string]: QWebVar }): string {
+  const tokens = tokenize(expr);
+  let result = "";
+  for (let i = 0; i < tokens.length; i++) {
+    let token = tokens[i];
+    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}']`;
+        }
+      }
+    }
+    result += token.value;
+  }
+  return result;
+}
@@ -0,0 +1,276 @@
+import { VNode } from "../vdom/index";
+import { QWeb } from "./qweb";
+
+/**
+ * Owl QWeb Extensions
+ *
+ * This file contains the implementation of non standard QWeb directives, added
+ * by Owl and that will only work on Owl projects:
+ *
+ * - t-on
+ * - t-ref
+ * - t-transition
+ * - t-mounted
+ * - t-slot
+ * - t-model
+ */
+
+//------------------------------------------------------------------------------
+// t-on
+//------------------------------------------------------------------------------
+// these are pieces of code that will be injected into the event handler if
+// modifiers are specified
+export const MODS_CODE = {
+  prevent: "e.preventDefault();",
+  self: "if (e.target !== this.elm) {return}",
+  stop: "e.stopPropagation();"
+};
+
+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}'] = ${handler};`);
+    }
+  }
+});
+
+//------------------------------------------------------------------------------
+// t-ref
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "ref",
+  priority: 95,
+  atNodeCreation({ ctx, value, addNodeHook }) {
+    ctx.rootContext.shouldDefineRefs = true;
+    const refKey = `ref${ctx.generateID()}`;
+    ctx.addLine(`const ${refKey} = ${ctx.interpolate(value)};`);
+    addNodeHook("create", `context.__owl__.refs[${refKey}] = n.elm;`);
+    addNodeHook("destroy", `delete context.__owl__.refs[${refKey}];`);
+  }
+});
+
+//------------------------------------------------------------------------------
+// t-transition
+//------------------------------------------------------------------------------
+QWeb.utils.nextFrame = function(cb: () => void) {
+  requestAnimationFrame(() => requestAnimationFrame(cb));
+};
+
+QWeb.utils.transitionInsert = function(vn: VNode, name: string) {
+  const elm = <HTMLElement>vn.elm;
+  // remove potential duplicated vnode that is currently being removed, to
+  // prevent from having twice the same node in the DOM during an animation
+  const dup = elm.parentElement && elm.parentElement!.querySelector(`*[data-owl-key='${vn.key}']`);
+  if (dup) {
+    dup.remove();
+  }
+
+  elm.classList.add(name + "-enter");
+  elm.classList.add(name + "-enter-active");
+  const finalize = () => {
+    elm.classList.remove(name + "-enter-active");
+    elm.classList.remove(name + "-enter-to");
+  };
+  this.nextFrame(() => {
+    elm.classList.remove(name + "-enter");
+    elm.classList.add(name + "-enter-to");
+    whenTransitionEnd(elm, finalize);
+  });
+};
+
+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 = () => {
+    elm.classList.remove(name + "-leave-active");
+    elm.classList.remove(name + "-leave-to");
+    rm();
+  };
+  this.nextFrame(() => {
+    elm.classList.remove(name + "-leave");
+    elm.classList.add(name + "-leave-to");
+    whenTransitionEnd(elm, finalize);
+  });
+};
+
+function getTimeout(delays: Array<string>, durations: Array<string>): number {
+  /* istanbul ignore next */
+  while (delays.length < durations.length) {
+    delays = delays.concat(delays);
+  }
+
+  return Math.max.apply(
+    null,
+    durations.map((d, i) => {
+      return toMs(d) + toMs(delays[i]);
+    })
+  );
+}
+
+// Old versions of Chromium (below 61.0.3163.100) formats floating pointer numbers
+// in a locale-dependent way, using a comma instead of a dot.
+// If comma is not replaced with a dot, the input will be rounded down (i.e. acting
+// as a floor function) causing unexpected behaviors
+function toMs(s: string): number {
+  return Number(s.slice(0, -1).replace(",", ".")) * 1000;
+}
+
+function whenTransitionEnd(elm: HTMLElement, cb) {
+  const styles = window.getComputedStyle(elm);
+  const delays: Array<string> = (styles.transitionDelay || "").split(", ");
+  const durations: Array<string> = (styles.transitionDuration || "").split(", ");
+  const timeout: number = getTimeout(delays, durations);
+  if (timeout > 0) {
+    elm.addEventListener("transitionend", cb, { once: true });
+  } else {
+    cb();
+  }
+}
+
+QWeb.addDirective({
+  name: "transition",
+  priority: 96,
+  atNodeCreation({ ctx, value, addNodeHook }) {
+    ctx.rootContext.shouldDefineUtils = true;
+    let name = value;
+    const hooks = {
+      insert: `utils.transitionInsert(vn, '${name}');`,
+      remove: `utils.transitionRemove(vn, '${name}', rm);`
+    };
+    for (let hookName in hooks) {
+      addNodeHook(hookName, hooks[hookName]);
+    }
+  }
+});
+
+//------------------------------------------------------------------------------
+// t-slot
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "slot",
+  priority: 80,
+  atNodeEncounter({ ctx, value }): boolean {
+    const slotKey = ctx.generateID();
+    ctx.rootContext.shouldDefineOwner = true;
+    ctx.addLine(
+      `const slot${slotKey} = this.constructor.slots[context.__owl__.slotId + '_' + '${value}'];`
+    );
+    ctx.addIf(`slot${slotKey}`);
+    let parentNode = `c${ctx.parentNode}`;
+    if (!ctx.parentNode) {
+      ctx.rootContext.shouldDefineResult = true;
+      ctx.rootContext.shouldDefineUtils = true;
+      parentNode = `children${ctx.nextID++}`;
+      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}));`
+    );
+    if (!ctx.parentNode) {
+      ctx.addLine(`utils.defineProxy(result, ${parentNode}[0]);`);
+    }
+    ctx.closeIf();
+    return true;
+  }
+});
+
+//------------------------------------------------------------------------------
+// t-model
+//------------------------------------------------------------------------------
+QWeb.utils.toNumber = function(val: string): number | string {
+  const n = parseFloat(val);
+  return isNaN(n) ? val : n;
+};
+
+QWeb.addDirective({
+  name: "model",
+  priority: 42,
+  atNodeCreation({ ctx, nodeID, value, node, fullName, addNodeHook }) {
+    const type = node.getAttribute("type");
+    let handler;
+    let event = fullName.includes(".lazy") ? "change" : "input";
+    const expr = ctx.formatExpression(value);
+    if (node.tagName === "select") {
+      ctx.addLine(`p${nodeID}.props = {value: ${expr}};`);
+      addNodeHook("create", `n.elm.value=${expr};`);
+      event = "change";
+      handler = `(ev) => {${expr} = ev.target.value}`;
+    } else if (type === "checkbox") {
+      ctx.addLine(`p${nodeID}.props = {checked: ${expr}};`);
+      handler = `(ev) => {${expr} = ev.target.checked}`;
+    } else if (type === "radio") {
+      const nodeValue = node.getAttribute("value")!;
+      ctx.addLine(`p${nodeID}.props = {checked:${expr} === '${nodeValue}'};`);
+      handler = `(ev) => {${expr} = ev.target.value}`;
+      event = "click";
+    } else {
+      ctx.addLine(`p${nodeID}.props = {value: ${expr}};`);
+      const trimCode = fullName.includes(".trim") ? ".trim()" : "";
+      let valueCode = `ev.target.value${trimCode}`;
+      if (fullName.includes(".number")) {
+        ctx.rootContext.shouldDefineUtils = true;
+        valueCode = `utils.toNumber(${valueCode})`;
+      }
+      handler = `(ev) => {${expr} = ${valueCode}}`;
+    }
+    ctx.addLine(
+      `extra.handlers['${event}' + ${nodeID}] = extra.handlers['${event}' + ${nodeID}] || (${handler});`
+    );
+    ctx.addLine(`p${nodeID}.on['${event}'] = extra.handlers['${event}' + ${nodeID}];`);
+  }
+});
+
+//------------------------------------------------------------------------------
+// t-key
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "key",
+  priority: 45,
+  atNodeEncounter({ ctx, value }) {
+    let id = ctx.generateID();
+    ctx.addLine(`const nodeKey${id} = ${ctx.formatExpression(value)};`);
+    ctx.lastNodeKey = `nodeKey${id}`;
+  }
+});
@@ -0,0 +1,4 @@
+import "./base_directives";
+import "./extensions";
+
+export { CompiledTemplate, QWeb } from "./qweb";
@@ -0,0 +1,769 @@
+import { EventBus } from "../core/event_bus";
+import { h, patch, VNode } from "../vdom/index";
+import { CompilationContext } from "./compilation_context";
+import { shallowEqual } from "../utils";
+import { addNS } from "../vdom/vdom";
+
+/**
+ * Owl QWeb Engine
+ *
+ * In this file, you will find a QWeb engine/template compiler.  It is the core
+ * of how Owl component works.
+ *
+ * Briefly, Owl QWeb compiles XML templates into functions that output a virtual
+ * DOM representation.
+ *
+ * We have here:
+ * - a CompilationContext class, which is an internal object that contains all
+ *   compilation specific information, while a template is being compiled.
+ * - a QWeb class: this is the code of the QWeb compiler.
+ *
+ * Note that this file does not contain the implementation of the QWeb
+ * directives (see qweb_directives.ts and qweb_extensions.ts).
+ */
+
+//------------------------------------------------------------------------------
+// Types
+//------------------------------------------------------------------------------
+export type EvalContext = { [key: string]: any };
+export type CompiledTemplate = (context: EvalContext, extra: any) => VNode;
+
+interface Template {
+  elem: Element;
+  fn: CompiledTemplate;
+}
+
+interface CompilationInfo {
+  node: Element;
+  qweb: QWeb;
+  ctx: CompilationContext;
+  fullName: string;
+  value: string;
+}
+
+interface NodeCreationCompilationInfo extends CompilationInfo {
+  nodeID: number;
+  addNodeHook: Function;
+}
+
+export interface Directive {
+  name: string;
+  extraNames?: string[];
+  priority: number;
+  // if return true, then directive is fully applied and there is no need to
+  // keep processing node. Otherwise, we keep going.
+  atNodeEncounter?(info: CompilationInfo): boolean | void;
+  atNodeCreation?(info: NodeCreationCompilationInfo): void;
+  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 NODE_HOOKS_PARAMS = {
+  create: "(_, n)",
+  insert: "vn",
+  remove: "(vn, rm)",
+  destroy: "()"
+};
+
+interface Utils {
+  toObj(expr: any): Object;
+  shallowEqual(p1: Object, p2: Object): boolean;
+  [key: string]: any;
+}
+
+const UTILS: Utils = {
+  toObj(expr) {
+    if (typeof expr === "string") {
+      expr = expr.trim();
+      if (!expr) {
+        return {};
+      }
+      let words = expr.split(/\s+/);
+      let result = {};
+      for (let i = 0; i < words.length; i++) {
+        result[words[i]] = true;
+      }
+      return result;
+    }
+    return expr;
+  },
+  shallowEqual,
+  addNameSpace(vnode) {
+    addNS(vnode.data, vnode.children, vnode.sel);
+  }
+};
+
+function parseXML(xml: string): Document {
+  const parser = new DOMParser();
+
+  const doc = parser.parseFromString(xml, "text/xml");
+  if (doc.getElementsByTagName("parsererror").length) {
+    let msg = "Invalid XML in template.";
+    const parsererrorText = doc.getElementsByTagName("parsererror")[0].textContent;
+    if (parsererrorText) {
+      msg += "\nThe parser has produced the following error message:\n" + parsererrorText;
+      const re = /\d+/g;
+      const firstMatch = re.exec(parsererrorText);
+      if (firstMatch) {
+        const lineNumber = Number(firstMatch[0]);
+        const line = xml.split("\n")[lineNumber - 1];
+        const secondMatch = re.exec(parsererrorText);
+        if (line && secondMatch) {
+          const columnIndex = Number(secondMatch[0]) - 1;
+          if (line[columnIndex]) {
+            msg +=
+              `\nThe error might be located at xml line ${lineNumber} column ${columnIndex}\n` +
+              `${line}\n${"-".repeat(columnIndex - 1)}^`;
+          }
+        }
+      }
+    }
+    throw new Error(msg);
+  }
+  return doc;
+}
+
+//------------------------------------------------------------------------------
+// QWeb rendering engine
+//------------------------------------------------------------------------------
+
+export class QWeb extends EventBus {
+  templates: { [name: string]: Template };
+  static utils = UTILS;
+  static components = Object.create(null);
+
+  static DIRECTIVE_NAMES: { [key: string]: 1 } = {
+    name: 1,
+    att: 1,
+    attf: 1,
+    translation: 1
+  };
+  static DIRECTIVES: Directive[] = [];
+
+  static TEMPLATES: { [name: string]: Template } = {};
+
+  static nextId: number = 1;
+
+  h = h;
+  // dev mode enables better error messages or more costly validations
+  static dev: boolean = false;
+
+  // slots contains sub templates defined with t-set inside t-component nodes, and
+  // are meant to be used by the t-slot directive.
+  static slots = {};
+  static nextSlotId = 1;
+
+  // recursiveTemplates contains sub templates called with t-call, but which
+  // ends up in recursive situations.  This is very similar to the slot situation,
+  // as in we need to propagate the scope.
+  recursiveFns = {};
+
+  isUpdating: boolean = false;
+  translateFn?: QWebConfig["translateFn"];
+
+  constructor(config: QWebConfig = {}) {
+    super();
+    this.templates = Object.create(QWeb.TEMPLATES);
+    if (config.templates) {
+      this.addTemplates(config.templates);
+    }
+    if (config.translateFn) {
+      this.translateFn = config.translateFn;
+    }
+  }
+
+  static addDirective(directive: Directive) {
+    if (directive.name in QWeb.DIRECTIVE_NAMES) {
+      throw new Error(`Directive "${directive.name} already registered`);
+    }
+    QWeb.DIRECTIVES.push(directive);
+    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));
+    }
+  }
+
+  static registerComponent(name: string, Component: any) {
+    if (QWeb.components[name]) {
+      throw new Error(`Component '${name}' has already been registered`);
+    }
+    QWeb.components[name] = Component;
+  }
+
+  /**
+   * Register globally a template.  All QWeb instances will obtain their
+   * templates from their own template map, and then, from the global static
+   * TEMPLATES property.
+   */
+  static registerTemplate(name: string, template: string) {
+    if (QWeb.TEMPLATES[name]) {
+      throw new Error(`Template '${name}' has already been registered`);
+    }
+    const qweb = new QWeb();
+    qweb.addTemplate(name, template);
+    QWeb.TEMPLATES[name] = qweb.templates[name];
+  }
+
+  /**
+   * Add a template to the internal template map.  Note that it is not
+   * immediately compiled.
+   */
+  addTemplate(name: string, xmlString: string, allowDuplicate?: boolean) {
+    if (allowDuplicate && name in this.templates) {
+      return;
+    }
+    const doc = parseXML(xmlString);
+    if (!doc.firstChild) {
+      throw new Error("Invalid template (should not be empty)");
+    }
+    this._addTemplate(name, <Element>doc.firstChild);
+  }
+
+  /**
+   * Load templates from a xml (as a string or xml document).  This will look up
+   * for the first <templates> tag, and will consider each child of this as a
+   * template, with the name given by the t-name attribute.
+   */
+  addTemplates(xmlstr: string | Document) {
+    const doc = typeof xmlstr === "string" ? parseXML(xmlstr) : xmlstr;
+    const templates = doc.getElementsByTagName("templates")[0];
+    if (!templates) {
+      return;
+    }
+    for (let elem of <any>templates.children) {
+      const name = elem.getAttribute("t-name");
+      this._addTemplate(name, elem);
+    }
+  }
+
+  _addTemplate(name: string, elem: Element) {
+    if (name in this.templates) {
+      throw new Error(`Template ${name} already defined`);
+    }
+    this._processTemplate(elem);
+    const template = {
+      elem,
+      fn: function(this: QWeb, context, extra) {
+        const compiledFunction = this._compile(name, elem);
+        template.fn = compiledFunction;
+        return compiledFunction.call(this, context, extra);
+      }
+    };
+    this.templates[name] = template;
+  }
+
+  _processTemplate(elem: Element) {
+    let tbranch = elem.querySelectorAll("[t-elif], [t-else]");
+    for (let i = 0, ilen = tbranch.length; i < ilen; i++) {
+      let node = tbranch[i];
+      let prevElem = node.previousElementSibling!;
+      let pattr = function(name) {
+        return prevElem.getAttribute(name);
+      };
+      let nattr = function(name) {
+        return +!!node.getAttribute(name);
+      };
+      if (prevElem && (pattr("t-if") || pattr("t-elif"))) {
+        if (pattr("t-foreach")) {
+          throw new Error(
+            "t-if cannot stay at the same level as t-foreach when using t-elif or t-else"
+          );
+        }
+        if (
+          ["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
+        let textNode;
+        while ((textNode = node.previousSibling) !== prevElem) {
+          if (textNode.nodeValue.trim().length) {
+            throw new Error("text is not allowed between branching directives");
+          }
+          textNode.remove();
+        }
+      } else {
+        throw new Error(
+          "t-elif and t-else directives must be preceded by a t-if or t-elif directive"
+        );
+      }
+    }
+  }
+  /**
+   * Render a template
+   *
+   * @param {string} name the template should already have been added
+   */
+  render(name: string, context: EvalContext = {}, extra: any = null): VNode {
+    const template = this.templates[name];
+    if (!template) {
+      throw new Error(`Template ${name} does not exist`);
+    }
+    return template.fn.call(this, context, extra);
+  }
+
+  /**
+   * Render a template to a html string.
+   *
+   * Note that this is more limited than the `render` method: it is not suitable
+   * to render a full component tree, since this is an asynchronous operation.
+   * This method can only render templates without components.
+   */
+  renderToString(name: string, context: EvalContext = {}, extra?: any): string {
+    const vnode = this.render(name, context, extra);
+    if (vnode.sel === undefined) {
+      return vnode.text!;
+    }
+    const node = document.createElement(vnode.sel);
+    const result = patch(node, vnode);
+    return (<HTMLElement>result.elm).outerHTML;
+  }
+
+  /**
+   * Force all widgets connected to this QWeb instance to rerender themselves.
+   *
+   * This method is mostly useful for external code that want to modify the
+   * application in some cases.  For example, a router plugin.
+   */
+  forceUpdate() {
+    this.isUpdating = true;
+    Promise.resolve().then(() => {
+      if (this.isUpdating) {
+        this.isUpdating = false;
+        this.trigger("update");
+      }
+    });
+  }
+
+  _compile(name: string, elem: Element, parentContext?: CompilationContext): CompiledTemplate {
+    const isDebug = elem.attributes.hasOwnProperty("t-debug");
+    const ctx = new CompilationContext(name);
+    if (elem.tagName !== "t") {
+      ctx.shouldDefineResult = false;
+    }
+    if (parentContext) {
+      ctx.templates = Object.create(parentContext.templates);
+      ctx.variables = Object.create(parentContext.variables);
+      ctx.nextID = parentContext.nextID + 1;
+      ctx.parentNode = parentContext.parentNode || ctx.nextID++;
+      ctx.allowMultipleRoots = true;
+      ctx.hasParentWidget = true;
+      ctx.shouldDefineResult = false;
+      ctx.addLine(`let c${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 (parentContext) {
+      ctx.addLine("    Object.assign(context, extra.fiber.scope);");
+    }
+    this._compileNode(elem, ctx);
+
+    if (!parentContext) {
+      if (ctx.shouldDefineResult) {
+        ctx.addLine(`return result;`);
+      } else {
+        if (!ctx.rootNode) {
+          throw new Error(`A template should have one root node (${ctx.templateName})`);
+        }
+        ctx.addLine(`return vn${ctx.rootNode};`);
+      }
+    }
+
+    let code = ctx.generateCode();
+
+    let template;
+    try {
+      template = new Function("context", "extra", code.join("\n")) as CompiledTemplate;
+    } catch (e) {
+      const templateName = ctx.templateName.replace(/`/g, "'");
+      console.groupCollapsed(`Invalid Code generated by ${templateName}`);
+      console.warn(code.join("\n"));
+      console.groupEnd();
+      throw new Error(
+        `Invalid generated code while compiling template '${templateName}': ${e.message}`
+      );
+    }
+    if (isDebug) {
+      const tpl = this.templates[name];
+      if (tpl) {
+        const msg = `Template: ${tpl.elem.outerHTML}\nCompiled code:\n${template.toString()}`;
+        console.log(msg);
+      }
+    }
+    return template;
+  }
+
+  /**
+   * Generate code from an xml node
+   *
+   */
+  _compileNode(node: ChildNode, ctx: CompilationContext) {
+    if (!(node instanceof Element)) {
+      // this is a text node, there are no directive to apply
+      let text = node.textContent!;
+      if (!ctx.inPreTag) {
+        if (lineBreakRE.test(text) && !text.trim()) {
+          return;
+        }
+        text = text.replace(whitespaceRE, " ");
+      }
+      if (this.translateFn) {
+        if ((node.parentNode as any).getAttribute("t-translation") !== "off") {
+          text = this.translateFn(text);
+        }
+      }
+      if (ctx.parentNode) {
+        if (node.nodeType === 3) {
+          ctx.addLine(`c${ctx.parentNode}.push({text: \`${text}\`});`);
+        } else if (node.nodeType === 8) {
+          ctx.addLine(`c${ctx.parentNode}.push(h('!', \`${text}\`));`);
+        }
+      } else if (ctx.parentTextNode) {
+        ctx.addLine(`vn${ctx.parentTextNode}.text += \`${text}\`;`);
+      } else {
+        // 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(`result = vn${nodeID};`);
+        ctx.rootContext.rootNode = nodeID;
+        ctx.rootContext.parentTextNode = nodeID;
+      }
+      return;
+    }
+
+    const firstLetter = node.tagName[0];
+    if (firstLetter === firstLetter.toUpperCase()) {
+      // this is a component, we modify in place the xml document to change
+      // <SomeComponent ... /> to <t t-component="SomeComponent" ... />
+      node.setAttribute("t-component", node.tagName);
+    }
+    const attributes = (<Element>node).attributes;
+
+    const validDirectives: {
+      directive: Directive;
+      value: string;
+      fullName: string;
+    }[] = [];
+
+    const finalizers: typeof validDirectives = [];
+
+    // maybe this is not optimal: we iterate on all attributes here, and again
+    // just after for each directive.
+    for (let i = 0; i < attributes.length; i++) {
+      let attrName = attributes[i].name;
+      if (attrName.startsWith("t-")) {
+        let dName = attrName.slice(2).split(/-|\./)[0];
+        if (!(dName in QWeb.DIRECTIVE_NAMES)) {
+          throw new Error(`Unknown QWeb directive: '${attrName}'`);
+        }
+        if (node.tagName !== "t" && (attrName === "t-esc" || attrName === "t-raw")) {
+          const tNode = document.createElement("t");
+          tNode.setAttribute(attrName, node.getAttribute(attrName)!);
+          for (let child of Array.from(node.childNodes)) {
+            tNode.appendChild(child);
+          }
+          node.appendChild(tNode);
+          node.removeAttribute(attrName);
+        }
+      }
+    }
+
+    const DIR_N = QWeb.DIRECTIVES.length;
+    const ATTR_N = attributes.length;
+    let withHandlers = false;
+    for (let i = 0; i < DIR_N; i++) {
+      let directive = QWeb.DIRECTIVES[i];
+      let fullName;
+      let value;
+      for (let j = 0; j < ATTR_N; j++) {
+        const name = attributes[j].name;
+        if (
+          name === "t-" + directive.name ||
+          name.startsWith("t-" + directive.name + "-") ||
+          name.startsWith("t-" + directive.name + ".")
+        ) {
+          fullName = name;
+          value = attributes[j].textContent;
+          validDirectives.push({ directive, value, fullName });
+          if (directive.name === "on" || directive.name === "model") {
+            withHandlers = true;
+          }
+        }
+      }
+    }
+
+    for (let { directive, value, fullName } of validDirectives) {
+      if (directive.finalize) {
+        finalizers.push({ directive, value, fullName });
+      }
+      if (directive.atNodeEncounter) {
+        const isDone = directive.atNodeEncounter({
+          node,
+          qweb: this,
+          ctx,
+          fullName,
+          value
+        });
+        if (isDone) {
+          for (let { directive, value, fullName } of finalizers) {
+            directive.finalize!({ node, qweb: this, ctx, fullName, value });
+          }
+          return;
+        }
+      }
+    }
+
+    if (node.nodeName !== "t") {
+      let nodeID = this._compileGenericNode(node, ctx, withHandlers);
+      ctx = ctx.withParent(nodeID);
+      ctx = ctx.subContext("currentKey", ctx.lastNodeKey);
+      let nodeHooks = {};
+      let addNodeHook = function(hook, handler) {
+        nodeHooks[hook] = nodeHooks[hook] || [];
+        nodeHooks[hook].push(handler);
+      };
+
+      for (let { directive, value, fullName } of validDirectives) {
+        if (directive.atNodeCreation) {
+          directive.atNodeCreation({
+            node,
+            qweb: this,
+            ctx,
+            fullName,
+            value,
+            nodeID,
+            addNodeHook
+          });
+        }
+      }
+
+      if (Object.keys(nodeHooks).length) {
+        ctx.addLine(`p${nodeID}.hook = {`);
+        for (let hook in nodeHooks) {
+          ctx.addLine(`  ${hook}: ${NODE_HOOKS_PARAMS[hook]} => {`);
+          for (let handler of nodeHooks[hook]) {
+            ctx.addLine(`    ${handler}`);
+          }
+          ctx.addLine(`  },`);
+        }
+        ctx.addLine(`};`);
+      }
+    }
+    if (node.nodeName === "pre") {
+      ctx = ctx.subContext("inPreTag", true);
+    }
+
+    this._compileChildren(node, ctx);
+    // svg support
+    // we hadd svg namespace if it is a svg or if it is a g, but only if it is
+    // the root node.  This is the easiest way to support svg sub components:
+    // they need to have a g tag as root. Otherwise, we would need a complete
+    // list of allowed svg tags.
+    const shouldAddNS =
+      node.nodeName === "svg" || (node.nodeName === "g" && ctx.rootNode === ctx.parentNode);
+    if (shouldAddNS) {
+      ctx.rootContext.shouldDefineUtils = true;
+      ctx.addLine(`utils.addNameSpace(vn${ctx.parentNode});`);
+    }
+
+    for (let { directive, value, fullName } of finalizers) {
+      directive.finalize!({ node, qweb: this, ctx, fullName, value });
+    }
+  }
+
+  _compileGenericNode(
+    node: ChildNode,
+    ctx: CompilationContext,
+    withHandlers: boolean = true
+  ): number {
+    // nodeType 1 is generic tag
+    if (node.nodeType !== 1) {
+      throw new Error("unsupported node type");
+    }
+    const attributes = (<Element>node).attributes;
+    const attrs: string[] = [];
+    const props: string[] = [];
+    const tattrs: number[] = [];
+
+    function handleBooleanProps(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;
+      }
+      if (isProp) {
+        props.push(`${key}: _${val}`);
+      }
+    }
+    let classObj = "";
+
+    for (let i = 0; i < attributes.length; i++) {
+      let name = attributes[i].name;
+      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}};`);
+        } else {
+          ctx.addLine(`var _${attID} = '${value}';`);
+          if (!name.match(/^[a-zA-Z]+$/)) {
+            // attribute contains 'non letters' => we want to quote it
+            name = '"' + name + '"';
+          }
+          attrs.push(`${name}: _${attID}`);
+          handleBooleanProps(name, attID);
+        }
+      }
+
+      // dynamic attributes
+      if (name.startsWith("t-att-")) {
+        let attName = name.slice(6);
+        const v = ctx.getValue(value);
+        let formattedValue = typeof v === "string" ? ctx.formatExpression(v) : v.id;
+
+        if (attName === "class") {
+          ctx.rootContext.shouldDefineUtils = true;
+          formattedValue = `utils.toObj(${formattedValue})`;
+          if (classObj) {
+            ctx.addLine(`Object.assign(${classObj}, ${formattedValue})`);
+          } else {
+            classObj = `_${ctx.generateID()}`;
+            ctx.addLine(`let ${classObj} = ${formattedValue};`);
+          }
+        } else {
+          const attID = ctx.generateID();
+          if (!attName.match(/^[a-zA-Z]+$/)) {
+            // attribute contains 'non letters' => we want to quote it
+            attName = '"' + attName + '"';
+          }
+          // we need to combine dynamic with non dynamic attributes:
+          // class="a" t-att-class="'yop'" should be rendered as class="a yop"
+          const attValue = (<Element>node).getAttribute(attName);
+          if (attValue) {
+            const attValueID = ctx.generateID();
+            ctx.addLine(`var _${attValueID} = ${formattedValue};`);
+            formattedValue = `'${attValue}' + (_${attValueID} ? ' ' + _${attValueID} : '')`;
+            const attrIndex = attrs.findIndex(att => att.startsWith(attName + ":"));
+            attrs.splice(attrIndex, 1);
+          }
+          ctx.addLine(`var _${attID} = ${formattedValue};`);
+          attrs.push(`${attName}: _${attID}`);
+          handleBooleanProps(attName, attID);
+        }
+      }
+
+      if (name.startsWith("t-attf-")) {
+        let attName = name.slice(7);
+        if (!attName.match(/^[a-zA-Z]+$/)) {
+          // attribute contains 'non letters' => we want to quote it
+          attName = '"' + attName + '"';
+        }
+        const formattedExpr = ctx.interpolate(value);
+        const attID = ctx.generateID();
+        let staticVal = (<Element>node).getAttribute(attName);
+        if (staticVal) {
+          ctx.addLine(`var _${attID} = '${staticVal} ' + ${formattedExpr};`);
+        } else {
+          ctx.addLine(`var _${attID} = ${formattedExpr};`);
+        }
+        attrs.push(`${attName}: _${attID}`);
+      }
+
+      // t-att= attributes
+      if (name === "t-att") {
+        let id = ctx.generateID();
+        ctx.addLine(`var _${id} = ${ctx.formatExpression(value!)};`);
+        tattrs.push(id);
+      }
+    }
+    let nodeID = ctx.generateID();
+    let nodeKey = ctx.lastNodeKey || nodeID;
+    const parts = [`key:${nodeKey}`];
+    if (attrs.length + tattrs.length > 0) {
+      parts.push(`attrs:{${attrs.join(",")}}`);
+    }
+    if (props.length > 0) {
+      parts.push(`props:{${props.join(",")}}`);
+    }
+    if (classObj) {
+      parts.push(`class:${classObj}`);
+    }
+    if (withHandlers) {
+      parts.push(`on:{}`);
+    }
+
+    ctx.addLine(`let c${nodeID} = [], p${nodeID} = {${parts.join(",")}};`);
+    for (let id of tattrs) {
+      ctx.addIf(`_${id} instanceof Array`);
+      ctx.addLine(`p${nodeID}.attrs[_${id}[0]] = _${id}[1];`);
+      ctx.addElse();
+      ctx.addLine(`for (let key in _${id}) {`);
+      ctx.indent();
+      ctx.addLine(`p${nodeID}.attrs[key] = _${id}[key];`);
+      ctx.dedent();
+      ctx.addLine(`}`);
+      ctx.closeIf();
+    }
+    ctx.addLine(`var vn${nodeID} = h('${node.nodeName}', p${nodeID}, c${nodeID});`);
+    if (ctx.parentNode) {
+      ctx.addLine(`c${ctx.parentNode}.push(vn${nodeID});`);
+    }
+
+    return nodeID;
+  }
+
+  _compileChildren(node: ChildNode, ctx: CompilationContext) {
+    if (node.childNodes.length > 0) {
+      for (let child of Array.from(node.childNodes)) {
+        this._compileNode(child, ctx);
+      }
+    }
+  }
+}
@@ -0,0 +1,48 @@
+import { Component } from "../component/component";
+import { xml } from "../tags";
+import { Destination, RouterEnv } from "./router";
+
+type Props = Destination;
+
+export class Link<Env extends RouterEnv> extends Component<Env, Props> {
+  static template = xml`
+    <a  t-att-class="{'router-link-active': isActive }"
+        t-att-href="href"
+        t-on-click="navigate">
+        <t t-slot="default"/>
+    </a>
+  `;
+
+  href: string = this.env.router.destToPath(this.props);
+
+  async willUpdateProps(nextProps) {
+    this.href = this.env.router.destToPath(nextProps);
+  }
+
+  get isActive() {
+    if (this.env.router.mode === "hash") {
+      return (<any>document.location).hash === this.href;
+    }
+    return (<any>document.location).pathname === this.href;
+  }
+
+  navigate(ev) {
+    // don't redirect with control keys
+    if (ev.metaKey || ev.altKey || ev.ctrlKey || ev.shiftKey) {
+      return;
+    }
+    // don't redirect on right click
+    if (ev.button !== undefined && ev.button !== 0) {
+      return;
+    }
+    // don't redirect if `target="_blank"`
+    if (ev.currentTarget && ev.currentTarget.getAttribute) {
+      const target = ev.currentTarget.getAttribute("target");
+      if (/\b_blank\b/i.test(target)) {
+        return;
+      }
+    }
+    ev.preventDefault();
+    this.env.router.navigate(this.props);
+  }
+}
@@ -0,0 +1,18 @@
+import { Component } from "../component/component";
+import { xml } from "../tags";
+
+export class RouteComponent extends Component<any, {}> {
+  static template = xml`
+    <t>
+        <t
+            t-if="routeComponent"
+            t-component="routeComponent"
+            t-key="env.router.currentRouteName"
+            t-props="env.router.currentParams" />
+    </t>
+  `;
+
+  get routeComponent(): any {
+    return this.env.router.currentRoute && this.env.router.currentRoute.component;
+  }
+}
@@ -0,0 +1,275 @@
+import { Env } from "../component/component";
+import { QWeb } from "../qweb/index";
+import { shallowEqual } from "../utils";
+
+type NavigationGuard = (info: {
+  env: Env;
+  to: Route | null;
+  from: Route | null;
+}) => boolean | Destination;
+
+export interface Route {
+  name: string;
+  path: string;
+  component?: any;
+  redirect?: Destination;
+  params: string[];
+  beforeRouteEnter?: NavigationGuard;
+}
+
+export type RouteParams = { [key: string]: string | number };
+
+export interface RouterEnv extends Env {
+  router: Router;
+}
+
+export interface Destination {
+  path?: string;
+  to?: string;
+  params?: RouteParams;
+}
+
+interface PositiveMatchResult {
+  type: "match";
+  route: Route;
+  params: RouteParams;
+}
+
+interface NegativeMatchResult {
+  type: "nomatch";
+}
+
+interface CancelledMatch {
+  type: "cancelled";
+}
+
+type MatchResult = PositiveMatchResult | NegativeMatchResult | CancelledMatch;
+
+interface Options {
+  mode: Router["mode"];
+}
+
+const paramRegexp = /\{\{(.*?)\}\}/;
+
+export class Router {
+  currentRoute: Route | null = null;
+  currentParams: RouteParams | null = null;
+  mode: "history" | "hash";
+
+  routes: { [id: string]: Route };
+  routeIds: string[];
+  env: RouterEnv;
+
+  constructor(env: Env, routes: Partial<Route>[], options: Options = { mode: "history" }) {
+    env.router = this;
+    this.mode = options.mode;
+    this.env = env as RouterEnv;
+
+    this.routes = {};
+    this.routeIds = [];
+    let nextId = 1;
+    for (let partialRoute of routes) {
+      if (!partialRoute.name) {
+        partialRoute.name = "__route__" + nextId++;
+      }
+      if (partialRoute.component) {
+        QWeb.registerComponent("__component__" + partialRoute.name, partialRoute.component);
+      }
+      if (partialRoute.redirect) {
+        this.validateDestination(partialRoute.redirect);
+      }
+      partialRoute.params = partialRoute.path ? findParams(partialRoute.path) : [];
+      this.routes[partialRoute.name] = partialRoute as Route;
+      this.routeIds.push(partialRoute.name);
+    }
+  }
+
+  //--------------------------------------------------------------------------
+  // Public API
+  //--------------------------------------------------------------------------
+
+  async start() {
+    (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);
+    }
+    const result = await this.matchAndApplyRules(this.currentPath());
+    if (result.type === "match") {
+      this.currentRoute = result.route;
+      this.currentParams = result.params;
+      const currentPath = this.routeToPath(result.route, result.params);
+      if (currentPath !== this.currentPath()) {
+        this.setUrlFromPath(currentPath);
+      }
+    }
+  }
+
+  async navigate(to: Destination): Promise<boolean> {
+    const path = this.destToPath(to);
+    return this._navigate(path);
+  }
+  async _navigate(path: string, ev?: any): Promise<boolean> {
+    const initialName = this.currentRouteName;
+    const initialParams = this.currentParams;
+    const result = await this.matchAndApplyRules(path);
+    if (result.type === "match") {
+      const finalPath = this.routeToPath(result.route, result.params);
+      const isPopStateEvent = ev && ev instanceof PopStateEvent;
+      if (!isPopStateEvent) {
+        this.setUrlFromPath(finalPath);
+      }
+      this.currentRoute = result.route;
+      this.currentParams = result.params;
+    } else if (result.type === "nomatch") {
+      this.currentRoute = null;
+      this.currentParams = null;
+    }
+    const didChange =
+      this.currentRouteName !== initialName || !shallowEqual(this.currentParams, initialParams);
+    if (didChange) {
+      this.env.qweb.forceUpdate();
+      return true;
+    }
+    return false;
+  }
+
+  destToPath(dest: Destination): string {
+    this.validateDestination(dest);
+    return dest.path || this.routeToPath(this.routes[dest.to!], dest.params!);
+  }
+
+  get currentRouteName(): string | null {
+    return this.currentRoute && this.currentRoute.name;
+  }
+
+  //--------------------------------------------------------------------------
+  // Private helpers
+  //--------------------------------------------------------------------------
+
+  private setUrlFromPath(path: string) {
+    const separator = this.mode === "hash" ? location.pathname : "";
+    const url = location.origin + separator + path;
+    if (url !== window.location.href) {
+      window.history.pushState({}, path, url);
+    }
+  }
+
+  private validateDestination(dest: Destination) {
+    if ((!dest.path && !dest.to) || (dest.path && dest.to)) {
+      throw new Error(`Invalid destination: ${JSON.stringify(dest)}`);
+    }
+  }
+
+  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("/");
+  }
+
+  private currentPath(): string {
+    let result = this.mode === "history" ? window.location.pathname : window.location.hash.slice(1);
+    return result || "/";
+  }
+
+  private match(path: string): MatchResult {
+    for (let routeId of this.routeIds) {
+      let route = this.routes[routeId];
+      let params = this.getRouteParams(route, path);
+      if (params) {
+        return {
+          type: "match",
+          route: route,
+          params: params
+        };
+      }
+    }
+    return { type: "nomatch" };
+  }
+
+  private async matchAndApplyRules(path: string): Promise<MatchResult> {
+    const result = this.match(path);
+    if (result.type === "match") {
+      return this.applyRules(result);
+    }
+    return result;
+  }
+
+  private async applyRules(matchResult: PositiveMatchResult): Promise<MatchResult> {
+    const route = matchResult.route;
+    if (route.redirect) {
+      const path = this.destToPath(route.redirect);
+      return this.matchAndApplyRules(path);
+    }
+    if (route.beforeRouteEnter) {
+      const result = await route.beforeRouteEnter({
+        env: this.env,
+        from: this.currentRoute,
+        to: route
+      });
+      if (result === false) {
+        return { type: "cancelled" };
+      } else if (result !== true) {
+        // we want to navigate to another destination
+        const path = this.destToPath(result);
+        return this.matchAndApplyRules(path);
+      }
+    }
+
+    return matchResult;
+  }
+
+  private getRouteParams(route: Route, path: string): RouteParams | false {
+    if (route.path === "*") {
+      return {};
+    }
+    if (path.startsWith("#")) {
+      path = path.slice(1);
+    }
+    const descrParts = route.path.split("/");
+    const targetParts = path.split("/");
+    const l = descrParts.length;
+    if (l !== targetParts.length) {
+      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;
+      }
+    }
+    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]);
+    }
+  } while (m);
+  return result;
+}
@@ -1,218 +1,142 @@
-import { Component } from "./component";
-import { EventBus } from "./event_bus";
-import { Observer } from "./observer";
+import { Component } from "./component/component";
+import { Env } from "./component/component";
+import { Context, useContextWithCB } from "./context";
+import { onWillUpdateProps } from "./hooks";
+
+/**
+ * Owl Store
+ *
+ * We have here:
+ * - a Store class
+ * - useStore hook
+ * - useDispatch hook
+ * - useGetters hook
+ *
+ * The Owl store is our answer to the problem of managing complex state across
+ * components. The main idea is that the store owns some state, allow external
+ * code to modify it through actions, and for each state changes,
+ * connected component will be notified, and updated if necessary.
+ *
+ * Note that this code is partly inspired by VueX and React/Redux
+ */

 //------------------------------------------------------------------------------
 // Store Definition
 //------------------------------------------------------------------------------

+export type Action = ({ state, dispatch, env, getters }, ...payload: any) => any;
+export type Getter = ({ state: any, getters }, payload?) => any;
+
 interface StoreConfig {
-  env?: any;
+  env?: Env;
  state?: any;
-  actions?: any;
-  mutations?: { [name: string]: any };
+  actions?: { [name: string]: Action };
+  getters?: { [name: string]: Getter };
 }

-interface StoreOption {
-  debug?: boolean;
-}
-
-export class Store extends EventBus {
-  state: any;
+export class Store extends Context {
  actions: any;
-  mutations: any;
-  _commitLevel: number = 0;
-  history: any[] = [];
-  debug: boolean;
  env: any;
-  observer: Observer;
-  set: any;
+  getters: { [name: string]: (payload?) => any };
+  updateFunctions: { [key: number]: (() => boolean)[] };

-  constructor(config: StoreConfig, options: StoreOption = {}) {
-    super();
-    this.debug = options.debug || false;
-    this.state = config.state || {};
+  constructor(config: StoreConfig) {
+    super(config.state);
    this.actions = config.actions;
-    this.mutations = config.mutations;
    this.env = config.env;
-    this.observer = new Observer();
-    this.observer.notifyCB = this.trigger.bind(this, "update");
-    this.observer.allowMutations = false;
-    this.observer.observe(this.state);
-
-    if (this.debug) {
-      this.history.push({ state: this.state });
+    this.getters = {};
+    this.updateFunctions = [];
+    if (config.getters) {
+      const firstArg = {
+        state: this.state,
+        getters: this.getters
+      };
+      for (let g in config.getters) {
+        this.getters[g] = config.getters[g].bind(this, firstArg);
+      }
    }
-    this.set = this.observer.set.bind(this.observer);
  }

-  dispatch(action, payload?: any): Promise<void> | void {
+  dispatch(action: string, ...payload: any): Promise<void> | void {
    if (!this.actions[action]) {
      throw new Error(`[Error] action ${action} is undefined`);
    }
    const result = this.actions[action](
      {
-        commit: this.commit.bind(this),
        dispatch: this.dispatch.bind(this),
        env: this.env,
-        state: this.state
-      },
-      payload
-    );
-    if (result instanceof Promise) {
-      return new Promise((resolve, reject) => {
-        result.then(() => resolve());
-        result.catch(reject);
-      });
-    }
-  }
-
-  commit(type, payload?: any) {
-    if (!this.mutations[type]) {
-      throw new Error(`[Error] mutation ${type} is undefined`);
-    }
-    this._commitLevel++;
-    this.observer.allowMutations = true;
-
-    const res = this.mutations[type].call(
-      null,
-      {
-        commit: this.commit.bind(this),
        state: this.state,
-        set: this.set
+        getters: this.getters
      },
-      payload
+      ...payload
    );
+    return result;
+  }
+}

-    if (this._commitLevel === 1) {
-      this.observer.allowMutations = false;
-      if (this.debug) {
-        this.history.push({
-          state: this.state,
-          mutation: type,
-          payload: payload
-        });
-      }
+interface SelectorOptions {
+  store?: Store;
+  isEqual?: (a: any, b: any) => boolean;
+}
+
+const isStrictEqual = (a, b) => a === b;
+
+export function useStore(selector, options: SelectorOptions = {}): any {
+  const component: Component<any, any> = Component.current!;
+  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] = [];
+  }
+  const updateFunctions = store.updateFunctions[component.__owl__.id];
+  updateFunctions.push(function(): boolean {
+    const oldResult = result;
+    result = selector(store!.state, component.props);
+    const newRevNumber = hashFn(result);
+    if (
+      (newRevNumber > 0 && revNumber !== newRevNumber) ||
+      (newRevNumber === 0 && !isEqual(oldResult, result))
+    ) {
+      revNumber = newRevNumber;
+      return true;
    }
-    this._commitLevel--;
-    return res;
-  }
+    return false;
+  });
+
+  useContextWithCB(store, component, function(): Promise<void> | void {
+    let shouldRender = false;
+    updateFunctions.forEach(function(updateFn) {
+      shouldRender = updateFn() || 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);
+  });
+  return new Proxy(result, {
+    get(target, k) {
+      return result[k];
+    },
+    set(target, k, v) {
+      result[k] = v;
+      return true;
+    }
+  });
 }

-//------------------------------------------------------------------------------
-// Connect function
-//------------------------------------------------------------------------------
-
-function revNumber<T extends Object>(o: T): number {
-  if (o !== null && typeof o === "object" && (<any>o).__owl__) {
-    return (<any>o).__owl__.rev;
-  }
-  return 0;
+export function useDispatch(store?: Store): Store["dispatch"] {
+  store = store || (Component.current!.env.store as Store);
+  return store.dispatch.bind(store);
 }

-function deepRevNumber<T extends Object>(o: T): number {
-  if (o !== null && typeof o === "object" && (<any>o).__owl__) {
-    return (<any>o).__owl__.deepRev;
-  }
-  return 0;
-}
-
-export function connect(mapStateToProps, options: any = {}) {
-  let hashFunction = options.hashFunction || null;
-
-  if (!hashFunction) {
-    let deep = "deep" in options ? options.deep : true;
-    let defaultRevFunction = deep ? deepRevNumber : revNumber;
-    hashFunction = function({ storeProps }, options) {
-      const { currentStoreProps } = options;
-      if ("__owl__" in storeProps) {
-        return defaultRevFunction(storeProps);
-      }
-      let hash = 0;
-      for (let key in storeProps) {
-        const val = storeProps[key];
-        const hashVal = defaultRevFunction(val);
-        if (hashVal === 0) {
-          if (val !== currentStoreProps[key]) {
-            options.didChange = true;
-          }
-        } else {
-          hash += hashVal;
-        }
-      }
-      return hash;
-    };
-  }
-
-  return function(Comp) {
-    return class extends Comp {
-      constructor(parent, props?: any) {
-        const env = parent instanceof Component ? parent.env : parent;
-        const ownProps = Object.assign({}, props || {});
-        const storeProps = mapStateToProps(env.store.state, ownProps);
-        const mergedProps = Object.assign({}, props || {}, storeProps);
-        super(parent, mergedProps);
-        this.__owl__.ownProps = ownProps;
-        this.__owl__.currentStoreProps = storeProps;
-        this.__owl__.storeHash = hashFunction(
-          {
-            state: env.store.state,
-            storeProps: storeProps,
-            revNumber,
-            deepRevNumber
-          },
-          {
-            currentStoreProps: storeProps
-          }
-        );
-      }
-      mounted() {
-        this.env.store.on("update", this, () => {
-          const ownProps = this.__owl__.ownProps;
-          const storeProps = mapStateToProps(this.env.store.state, ownProps);
-          const options: any = {
-            currentStoreProps: this.__owl__.currentStoreProps
-          };
-          const storeHash = hashFunction(
-            {
-              state: this.env.store.state,
-              storeProps: storeProps,
-              revNumber,
-              deepRevNumber
-            },
-            options
-          );
-          let didChange = options.didChange;
-          if (storeHash !== this.__owl__.storeHash) {
-            didChange = true;
-            this.__owl__.storeHash = storeHash;
-          }
-          if (didChange) {
-            this.__owl__.currentStoreProps = storeProps;
-            this._updateProps(ownProps, false);
-          }
-        });
-        super.mounted();
-      }
-      willUnmount() {
-        this.env.store.off("update", this);
-        super.willUnmount();
-      }
-      _updateProps(nextProps, forceUpdate) {
-        if (this.__owl__.ownProps !== nextProps) {
-          this.__owl__.currentStoreProps = mapStateToProps(
-            this.env.store.state,
-            nextProps
-          );
-        }
-        this.__owl__.ownProps = nextProps;
-        const mergedProps = Object.assign(
-          {},
-          nextProps,
-          this.__owl__.currentStoreProps
-        );
-        return super._updateProps(mergedProps, forceUpdate);
-      }
-    };
-  };
+export function useGetters(store?: Store): Store["getters"] {
+  store = store || (Component.current!.env.store as Store);
+  return store.getters;
 }
@@ -0,0 +1,27 @@
+import { QWeb } from "./qweb/index";
+
+/**
+ * Owl Tags
+ *
+ * We have here a (very) small collection of tag functions:
+ *
+ * - xml
+ *
+ * The plan is to add a few other tags such as css, globalcss.
+ */
+
+/**
+ * XML tag helper for defining templates.  With this, one can simply define
+ * an inline template with just the template xml:
+ * ```js
+ *   class A extends Component {
+ *     static template = xml`<div>some template</div>`;
+ *   }
+ * ```
+ */
+export function xml(strings, ...args) {
+  const name = `__template__${QWeb.nextId++}`;
+  const value = String.raw(strings, ...args);
+  QWeb.registerTemplate(name, value);
+  return name;
+}
@@ -1,129 +1,23 @@
-export function escape(str: string | number | undefined): string {
-  if (str === undefined) {
-    return "";
-  }
-  if (typeof str === "number") {
-    return String(str);
-  }
-  return str
-    .replace(/&/g, "&amp;")
-    .replace(/</g, "&lt;")
-    .replace(/>/g, "&gt;")
-    .replace(/"/g, "&#x27;")
-    .replace(/`/g, "&#x60;");
-}
-
-export type HashFn = (args: any[]) => string;
-
-export function memoize<R, T extends (...args: any[]) => R>(
-  f: T,
-  hash?: HashFn
-): T {
-  if (!hash) {
-    hash = args => args.map(a => String(a)).join(",");
-  }
-  let cache: { [key: string]: R } = {};
-  function memoizedFunction(...args: any[]) {
-    let hashValue = hash!(args);
-    if (!(hashValue in cache)) {
-      cache[hashValue] = f(...args);
-    }
-    return cache[hashValue];
-  }
-  return memoizedFunction as T;
-}
-
 /**
- * Returns a function, that, as long as it continues to be invoked, will not
- * be triggered. The function will be called after it stops being called for
- * N milliseconds. If `immediate` is passed, trigger the function on the
- * leading edge, instead of the trailing.
+ * Owl Utils
 *
- * Inspired by https://davidwalsh.name/javascript-debounce-function
+ * We have here a small collection of utility functions:
+ *
+ * - whenReady
+ * - loadJS
+ * - loadFile
+ * - escape
+ * - debounce
 */
-export function debounce(
-  func: Function,
-  wait: number,
-  immediate?: boolean
-): Function {
-  let timeout;
-  return function(this: any) {
-    const context = this;
-    const args = arguments;
-    function later() {
-      timeout = null;
-      if (!immediate) {
-        func.apply(context, args);
-      }
+
+export function whenReady(fn?: any) {
+  return new Promise(function(resolve) {
+    if (document.readyState !== "loading") {
+      resolve();
+    } else {
+      document.addEventListener("DOMContentLoaded", resolve, false);
    }
-    const callNow = immediate && !timeout;
-    clearTimeout(timeout);
-    timeout = setTimeout(later, wait);
-    if (callNow) {
-      func.apply(context, args);
-    }
-  };
-}
-
-export function patch(C: any, patchName: string, patch: any) {
-  const proto = C.prototype;
-  if (!proto.__patches) {
-    proto.__patches = {
-      origMethods: {},
-      patches: {},
-      current: []
-    };
-  }
-  if (proto.__patches.patches[patchName]) {
-    throw new Error(`Patch [${patchName}] already exists`);
-  }
-  proto.__patches.patches[patchName] = patch;
-  applyPatch(proto, patch);
-  proto.__patches.current.push(patchName);
-
-  function applyPatch(proto, patch) {
-    Object.keys(patch).forEach(function(methodName) {
-      const method = patch[methodName];
-      if (typeof method === "function") {
-        const original = proto[methodName];
-        if (!(methodName in proto.__patches.origMethods)) {
-          proto.__patches.origMethods[methodName] = original;
-        }
-        proto[methodName] = function(...args) {
-          this._super = original;
-          return method.call(this, ...args);
-        };
-      }
-    });
-  }
-}
-
-export function unpatch(C: any, patchName: string) {
-  const proto = C.prototype;
-  const patchInfo = proto.__patches;
-  delete proto.__patches;
-
-  // reset to original
-  for (let k in patchInfo.origMethods) {
-    proto[k] = patchInfo.origMethods[k];
-  }
-
-  // apply other patches
-  for (let name of patchInfo.current) {
-    if (name !== patchName) {
-      patch(C, name, patchInfo.patches[name]);
-    }
-  }
-}
-
-export async function loadTemplates(url: string): Promise<string> {
-  const result = await fetch(url);
-  if (!result.ok) {
-    throw new Error("Error while fetching xml templates");
-  }
-  let templates = await result.text();
-  templates = templates.replace(/<!--[\s\S]*?-->/g, "");
-  return templates;
+  }).then(fn || function() {});
 }

 const loadedScripts: { [key: string]: Promise<void> } = {};
@@ -149,10 +43,62 @@ export function loadJS(url: string): Promise<void> {
  return promise;
 }

-export function whenReady(fn) {
-  if (document.readyState === "complete") {
-    fn();
-  } else {
-    document.addEventListener("DOMContentLoaded", fn, false);
+export async function loadFile(url: string): Promise<string> {
+  const result = await fetch(url);
+  if (!result.ok) {
+    throw new Error("Error while fetching xml templates");
  }
+  return await result.text();
+}
+
+export function escape(str: string | number | undefined): string {
+  if (str === undefined) {
+    return "";
+  }
+  if (typeof str === "number") {
+    return String(str);
+  }
+  return str
+    .replace(/&/g, "&amp;")
+    .replace(/</g, "&lt;")
+    .replace(/>/g, "&gt;")
+    .replace(/"/g, "&#x27;")
+    .replace(/`/g, "&#x60;");
+}
+
+/**
+ * Returns a function, that, as long as it continues to be invoked, will not
+ * be triggered. The function will be called after it stops being called for
+ * N milliseconds. If `immediate` is passed, trigger the function on the
+ * leading edge, instead of the trailing.
+ *
+ * Inspired by https://davidwalsh.name/javascript-debounce-function
+ */
+export function debounce(func: Function, wait: number, immediate?: boolean): Function {
+  let timeout;
+  return function(this: any) {
+    const context = this;
+    const args = arguments;
+    function later() {
+      timeout = null;
+      if (!immediate) {
+        func.apply(context, args);
+      }
+    }
+    const callNow = immediate && !timeout;
+    clearTimeout(timeout);
+    timeout = setTimeout(later, wait);
+    if (callNow) {
+      func.apply(context, args);
+    }
+  };
+}
+
+export function shallowEqual(p1, p2): boolean {
+  for (let k in p1) {
+    if (p1[k] !== p2[k]) {
+      return false;
+    }
+  }
+  return true;
 }
@@ -0,0 +1,29 @@
+import { VNode, h } from "./vdom";
+
+const parser = new DOMParser();
+
+export function htmlToVDOM(html: string): VNode[] {
+  const doc = parser.parseFromString(html, "text/html");
+  const result: VNode[] = [];
+  for (let child of doc.body.childNodes) {
+    result.push(htmlToVNode(child));
+  }
+  return result;
+}
+
+function htmlToVNode(node: ChildNode): VNode {
+  if (!(node instanceof Element)) {
+    return { text: node.textContent! } as VNode;
+  }
+  const attrs = {};
+  for (let attr of node.attributes) {
+    attrs[attr.name] = attr.textContent;
+  }
+  const children: VNode[] = [];
+  if (node.hasChildNodes) {
+    for (let c of node.childNodes) {
+      children.push(htmlToVNode(c));
+    }
+  }
+  return h((node as Element).tagName, { attrs }, children);
+}
@@ -0,0 +1,9 @@
+import { attrsModule, classModule, eventListenersModule, propsModule } from "./modules";
+import { init } from "./vdom";
+//------------------------------------------------------------------------------
+// patch
+//------------------------------------------------------------------------------
+
+export { h, VNode } from "./vdom";
+
+export const patch = init([eventListenersModule, attrsModule, propsModule, classModule]);
@@ -0,0 +1,234 @@
+import { Module, VNode, VNodeData } from "./vdom";
+
+//------------------------------------------------------------------------------
+// module/props.ts
+//------------------------------------------------------------------------------
+
+function updateProps(oldVnode: VNode, vnode: VNode): void {
+  var key: string,
+    cur: any,
+    old: any,
+    elm = vnode.elm,
+    oldProps = (oldVnode.data as VNodeData).props,
+    props = (vnode.data as VNodeData).props;
+
+  if (!oldProps && !props) return;
+  if (oldProps === props) return;
+  oldProps = oldProps || {};
+  props = props || {};
+
+  for (key in oldProps) {
+    if (!props[key]) {
+      delete (elm as any)[key];
+    }
+  }
+  for (key in props) {
+    cur = props[key];
+    old = oldProps[key];
+    if (old !== cur && (key !== "value" || (elm as any)[key] !== cur)) {
+      (elm as any)[key] = cur;
+    }
+  }
+}
+
+export const propsModule = {
+  create: updateProps,
+  update: updateProps
+} as Module;
+
+//------------------------------------------------------------------------------
+// module/eventlisteners.ts
+//------------------------------------------------------------------------------
+
+function invokeHandler(handler: any, vnode?: VNode, event?: Event): void {
+  if (typeof handler === "function") {
+    // call function handler
+    handler.call(vnode, event, vnode);
+  } else if (typeof handler === "object") {
+    // call handler with arguments
+    if (typeof handler[0] === "function") {
+      // special case for single argument for performance
+      if (handler.length === 2) {
+        handler[0].call(vnode, handler[1], event, vnode);
+      } else {
+        var args = handler.slice(1);
+        args.push(event);
+        args.push(vnode);
+        handler[0].apply(vnode, args);
+      }
+    } else {
+      // call multiple handlers
+      for (let i = 0, iLen = handler.length; i < iLen; i++) {
+        invokeHandler(handler[i], vnode, event);
+      }
+    }
+  }
+}
+
+function handleEvent(event: Event, vnode: VNode) {
+  var name = event.type,
+    on = (vnode.data as VNodeData).on;
+
+  // call event handler(s) if exists
+  if (on && on[name]) {
+    invokeHandler(on[name], vnode, event);
+  }
+}
+
+function createListener() {
+  return function handler(event: Event) {
+    handleEvent(event, (handler as any).vnode);
+  };
+}
+
+function updateEventListeners(oldVnode: VNode, vnode?: VNode): void {
+  var oldOn = (oldVnode.data as VNodeData).on,
+    oldListener = (oldVnode as any).listener,
+    oldElm: Element = oldVnode.elm as Element,
+    on = vnode && (vnode.data as VNodeData).on,
+    elm: Element = (vnode && vnode.elm) as Element,
+    name: string;
+
+  // optimization for reused immutable handlers
+  if (oldOn === on) {
+    return;
+  }
+
+  // remove existing listeners which no longer used
+  if (oldOn && oldListener) {
+    // if element changed or deleted we remove all existing listeners unconditionally
+    if (!on) {
+      for (name in oldOn) {
+        // remove listener if element was changed or existing listeners removed
+        oldElm.removeEventListener(name, oldListener, false);
+      }
+    } else {
+      for (name in oldOn) {
+        // remove listener if existing listener removed
+        if (!on[name]) {
+          oldElm.removeEventListener(name, oldListener, false);
+        }
+      }
+    }
+  }
+
+  // add new listeners which has not already attached
+  if (on) {
+    // reuse existing listener or create new
+    var listener = ((vnode as any).listener = (oldVnode as any).listener || createListener());
+    // update vnode for listener
+    listener.vnode = vnode;
+
+    // if element changed or added we add all needed listeners unconditionally
+    if (!oldOn) {
+      for (name in on) {
+        // add listener if element was changed or new listeners added
+        elm.addEventListener(name, listener, false);
+      }
+    } else {
+      for (name in on) {
+        // add listener if new listener added
+        if (!oldOn[name]) {
+          elm.addEventListener(name, listener, false);
+        }
+      }
+    }
+  }
+}
+
+export const eventListenersModule = {
+  create: updateEventListeners,
+  update: updateEventListeners,
+  destroy: updateEventListeners
+} as Module;
+
+//------------------------------------------------------------------------------
+// attributes.ts
+//------------------------------------------------------------------------------
+
+const xlinkNS = "http://www.w3.org/1999/xlink";
+const xmlNS = "http://www.w3.org/XML/1998/namespace";
+const colonChar = 58;
+const xChar = 120;
+
+function updateAttrs(oldVnode: VNode, vnode: VNode): void {
+  var key: string,
+    elm: Element = vnode.elm as Element,
+    oldAttrs = (oldVnode.data as VNodeData).attrs,
+    attrs = (vnode.data as VNodeData).attrs;
+
+  if (!oldAttrs && !attrs) return;
+  if (oldAttrs === attrs) return;
+  oldAttrs = oldAttrs || {};
+  attrs = attrs || {};
+
+  // update modified attributes, add new attributes
+  for (key in attrs) {
+    const cur = attrs[key];
+    const old = oldAttrs[key];
+    if (old !== cur) {
+      if (cur === true) {
+        elm.setAttribute(key, "");
+      } else if (cur === false) {
+        elm.removeAttribute(key);
+      } else {
+        if (key.charCodeAt(0) !== xChar) {
+          elm.setAttribute(key, cur);
+        } else if (key.charCodeAt(3) === colonChar) {
+          // Assume xml namespace
+          elm.setAttributeNS(xmlNS, key, cur);
+        } else if (key.charCodeAt(5) === colonChar) {
+          // Assume xlink namespace
+          elm.setAttributeNS(xlinkNS, key, cur);
+        } else {
+          elm.setAttribute(key, cur);
+        }
+      }
+    }
+  }
+  // remove removed attributes
+  // use `in` operator since the previous `for` iteration uses it (.i.e. add even attributes with undefined value)
+  // the other option is to remove all attributes with value == undefined
+  for (key in oldAttrs) {
+    if (!(key in attrs)) {
+      elm.removeAttribute(key);
+    }
+  }
+}
+
+export const attrsModule = {
+  create: updateAttrs,
+  update: updateAttrs
+} as Module;
+
+//------------------------------------------------------------------------------
+// class.ts
+//------------------------------------------------------------------------------
+function updateClass(oldVnode: VNode, vnode: VNode): void {
+  var cur: any,
+    name: string,
+    elm: Element,
+    oldClass = (oldVnode.data as VNodeData).class,
+    klass = (vnode.data as VNodeData).class;
+
+  if (!oldClass && !klass) return;
+  if (oldClass === klass) return;
+  oldClass = oldClass || {};
+  klass = klass || {};
+
+  elm = vnode.elm as Element;
+
+  for (name in oldClass) {
+    if (!klass[name]) {
+      elm.classList.remove(name);
+    }
+  }
+  for (name in klass) {
+    cur = klass[name];
+    if (cur !== oldClass[name]) {
+      (elm.classList as any)[cur ? "add" : "remove"](name);
+    }
+  }
+}
+
+export const classModule = { create: updateClass, update: updateClass } as Module;
@@ -1,12 +1,47 @@
+/**
+ * Owl VDOM
+ *
+ * This file contains an implementation of a virtual DOM, which is a system that
+ * can generate in-memory representations of a DOM tree, compare them, and
+ * eventually change a concrete DOM tree to match its representation, in an
+ * hopefully efficient way.
+ *
+ * Note that this code is a fork of Snabbdom, slightly tweaked/optimized for our
+ * needs (see https://github.com/snabbdom/snabbdom).
+ *
+ * The main exported values are:
+ * - interface VNode
+ * - h function (a helper function to generate a vnode)
+ * - patch function (to apply a vnode to an actual DOM node)
+ */

 // because those in TypeScript are too restrictive: https://github.com/Microsoft/TSJS-lib-generator/pull/237
 declare global {
  interface Element {
    setAttribute(name: string, value: string | number | boolean): void;
-    setAttributeNS(namespaceURI: string, qualifiedName: string, value: string | number | boolean): void;
+    setAttributeNS(
+      namespaceURI: string,
+      qualifiedName: string,
+      value: string | number | boolean
+    ): void;
  }
 }

+type Props = Record<string, any>;
+type Attrs = Record<string, string | number | boolean>;
+type On = { [N in keyof HTMLElementEventMap]?: (ev: HTMLElementEventMap[N]) => void } & {
+  [event: string]: EventListener;
+};
+
+export interface Module {
+  pre: PreHook;
+  create: CreateHook;
+  update: UpdateHook;
+  destroy: DestroyHook;
+  remove: RemoveHook;
+  post: PostHook;
+}
+
 //------------------------------------------------------------------------------
 // vnode.ts
 //------------------------------------------------------------------------------
@@ -21,7 +56,7 @@ export interface VNode {
  key: Key | undefined;
 }

-interface VNodeData {
+export interface VNodeData {
  props?: Props;
  attrs?: Attrs;
  on?: On;
@@ -39,14 +74,7 @@ function vnode(
  elm: Element | Text | undefined
 ): VNode {
  let key = data === undefined ? undefined : data.key;
-  return {
-    sel: sel,
-    data: data,
-    children: children,
-    text: text,
-    elm: elm,
-    key: key
-  };
+  return { sel, data, children, text, elm, key };
 }

 //------------------------------------------------------------------------------
@@ -96,14 +124,7 @@ function createKeyToOldIdx(
  return map;
 }

-const hooks: (keyof Module)[] = [
-  "create",
-  "update",
-  "remove",
-  "destroy",
-  "pre",
-  "post"
-];
+const hooks: (keyof Module)[] = ["create", "update", "remove", "destroy", "pre", "post"];

 export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {
  let i: number,
@@ -125,13 +146,7 @@ export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {
  function emptyNodeAt(elm: Element) {
    const id = elm.id ? "#" + elm.id : "";
    const c = elm.className ? "." + elm.className.split(" ").join(".") : "";
-    return vnode(
-      api.tagName(elm).toLowerCase() + id + c,
-      {},
-      [],
-      undefined,
-      elm
-    );
+    return vnode(api.tagName(elm).toLowerCase() + id + c, {}, [], undefined, elm);
  }

  function createRmCb(childElm: Node, listeners: number) {
@@ -145,6 +160,7 @@ export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {

  function createElm(vnode: VNode, insertedVnodeQueue: VNodeQueue): Node {
    let i: any,
+      iLen: number,
      data = vnode.data;
    if (data !== undefined) {
      if (isDef((i = data.hook)) && isDef((i = i.init))) {
@@ -160,25 +176,13 @@ export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {
      }
      vnode.elm = api.createComment(vnode.text as string);
    } else if (sel !== undefined) {
-      // Parse selector
-      const hashIdx = sel.indexOf("#");
-      const dotIdx = sel.indexOf(".", hashIdx);
-      const hash = hashIdx > 0 ? hashIdx : sel.length;
-      const dot = dotIdx > 0 ? dotIdx : sel.length;
-      const tag =
-        hashIdx !== -1 || dotIdx !== -1
-          ? sel.slice(0, Math.min(hash, dot))
-          : sel;
      const elm = (vnode.elm =
        isDef(data) && isDef((i = (data as VNodeData).ns))
-          ? api.createElementNS(i, tag)
-          : api.createElement(tag));
-      if (hash < dot) elm.setAttribute("id", sel.slice(hash + 1, dot));
-      if (dotIdx > 0)
-        elm.setAttribute("class", sel.slice(dot + 1).replace(/\./g, " "));
-      for (i = 0; i < cbs.create.length; ++i) cbs.create[i](emptyNode, vnode);
+          ? 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; i < children.length; ++i) {
+        for (i = 0, iLen = children.length; i < iLen; ++i) {
          const ch = children[i];
          if (ch != null) {
            api.appendChild(elm, createElm(ch as VNode, insertedVnodeQueue));
@@ -216,13 +220,15 @@ export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {

  function invokeDestroyHook(vnode: VNode) {
    let i: any,
+      iLen: number,
      j: number,
+      jLen: number,
      data = vnode.data;
    if (data !== undefined) {
      if (isDef((i = data.hook)) && isDef((i = i.destroy))) i(vnode);
-      for (i = 0; i < cbs.destroy.length; ++i) cbs.destroy[i](vnode);
+      for (i = 0, iLen = cbs.destroy.length; i < iLen; ++i) cbs.destroy[i](vnode);
      if (vnode.children !== undefined) {
-        for (j = 0; j < vnode.children.length; ++j) {
+        for (j = 0, jLen = vnode.children.length; j < jLen; ++j) {
          i = vnode.children[j];
          if (i != null && typeof i !== "string") {
            invokeDestroyHook(i);
@@ -240,6 +246,7 @@ export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {
  ): void {
    for (; startIdx <= endIdx; ++startIdx) {
      let i: any,
+        iLen: number,
        listeners: number,
        rm: () => void,
        ch = vnodes[startIdx];
@@ -248,12 +255,8 @@ export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {
          invokeDestroyHook(ch);
          listeners = cbs.remove.length + 1;
          rm = createRmCb(ch.elm as Node, listeners);
-          for (i = 0; i < cbs.remove.length; ++i) cbs.remove[i](ch, rm);
-          if (
-            isDef((i = ch.data)) &&
-            isDef((i = i.hook)) &&
-            isDef((i = i.remove))
-          ) {
+          for (i = 0, iLen = cbs.remove.length; i < iLen; ++i) cbs.remove[i](ch, rm);
+          if (isDef((i = ch.data)) && isDef((i = i.hook)) && isDef((i = i.remove))) {
            i(ch, rm);
          } else {
            rm();
@@ -315,11 +318,7 @@ export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {
      } else if (sameVnode(oldEndVnode, newStartVnode)) {
        // Vnode moved left
        patchVnode(oldEndVnode, newStartVnode, insertedVnodeQueue);
-        api.insertBefore(
-          parentElm,
-          oldEndVnode.elm as Node,
-          oldStartVnode.elm as Node
-        );
+        api.insertBefore(parentElm, oldEndVnode.elm as Node, oldStartVnode.elm as Node);
        oldEndVnode = oldCh[--oldEndIdx];
        newStartVnode = newCh[++newStartIdx];
      } else {
@@ -346,11 +345,7 @@ export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {
          } else {
            patchVnode(elmToMove, newStartVnode, insertedVnodeQueue);
            oldCh[idxInOld] = undefined as any;
-            api.insertBefore(
-              parentElm,
-              elmToMove.elm as Node,
-              oldStartVnode.elm as Node
-            );
+            api.insertBefore(parentElm, elmToMove.elm as Node, oldStartVnode.elm as Node);
          }
          newStartVnode = newCh[++newStartIdx];
        }
@@ -359,31 +354,16 @@ export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {
    if (oldStartIdx <= oldEndIdx || newStartIdx <= newEndIdx) {
      if (oldStartIdx > oldEndIdx) {
        before = newCh[newEndIdx + 1] == null ? null : newCh[newEndIdx + 1].elm;
-        addVnodes(
-          parentElm,
-          before,
-          newCh,
-          newStartIdx,
-          newEndIdx,
-          insertedVnodeQueue
-        );
+        addVnodes(parentElm, before, newCh, newStartIdx, newEndIdx, insertedVnodeQueue);
      } else {
        removeVnodes(parentElm, oldCh, oldStartIdx, oldEndIdx);
      }
    }
  }

-  function patchVnode(
-    oldVnode: VNode,
-    vnode: VNode,
-    insertedVnodeQueue: VNodeQueue
-  ) {
-    let i: any, hook: any;
-    if (
-      isDef((i = vnode.data)) &&
-      isDef((hook = i.hook)) &&
-      isDef((i = hook.prepatch))
-    ) {
+  function patchVnode(oldVnode: VNode, vnode: VNode, insertedVnodeQueue: VNodeQueue) {
+    let i: any, iLen: number, hook: any;
+    if (isDef((i = vnode.data)) && isDef((hook = i.hook)) && isDef((i = hook.prepatch))) {
      i(oldVnode, vnode);
    }
    const elm = (vnode.elm = oldVnode.elm as Node);
@@ -391,19 +371,14 @@ export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {
    let ch = vnode.children;
    if (oldVnode === vnode) return;
    if (vnode.data !== undefined) {
-      for (i = 0; i < cbs.update.length; ++i) cbs.update[i](oldVnode, vnode);
+      for (i = 0, iLen = cbs.update.length; i < iLen; ++i) cbs.update[i](oldVnode, vnode);
      i = vnode.data.hook;
      if (isDef(i) && isDef((i = i.update))) i(oldVnode, vnode);
    }
    if (isUndef(vnode.text)) {
      if (isDef(oldCh) && isDef(ch)) {
        if (oldCh !== ch)
-          updateChildren(
-            elm,
-            oldCh as Array<VNode>,
-            ch as Array<VNode>,
-            insertedVnodeQueue
-          );
+          updateChildren(elm, oldCh as Array<VNode>, ch as Array<VNode>, insertedVnodeQueue);
      } else if (isDef(ch)) {
        if (isDef(oldVnode.text)) api.setTextContent(elm, "");
        addVnodes(
@@ -415,23 +390,13 @@ export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {
          insertedVnodeQueue
        );
      } else if (isDef(oldCh)) {
-        removeVnodes(
-          elm,
-          oldCh as Array<VNode>,
-          0,
-          (oldCh as Array<VNode>).length - 1
-        );
+        removeVnodes(elm, oldCh as Array<VNode>, 0, (oldCh as Array<VNode>).length - 1);
      } else if (isDef(oldVnode.text)) {
        api.setTextContent(elm, "");
      }
    } else if (oldVnode.text !== vnode.text) {
      if (isDef(oldCh)) {
-        removeVnodes(
-          elm,
-          oldCh as Array<VNode>,
-          0,
-          (oldCh as Array<VNode>).length - 1
-        );
+        removeVnodes(elm, oldCh as Array<VNode>, 0, (oldCh as Array<VNode>).length - 1);
      }
      api.setTextContent(elm, vnode.text as string);
    }
@@ -441,9 +406,9 @@ export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {
  }

  return function patch(oldVnode: VNode | Element, vnode: VNode): VNode {
-    let i: number, elm: Node, parent: Node;
+    let i: number, iLen: number, elm: Node, parent: Node;
    const insertedVnodeQueue: VNodeQueue = [];
-    for (i = 0; i < cbs.pre.length; ++i) cbs.pre[i]();
+    for (i = 0, iLen = cbs.pre.length; i < iLen; ++i) cbs.pre[i]();

    if (!isVnode(oldVnode)) {
      oldVnode = emptyNodeAt(oldVnode);
@@ -463,12 +428,12 @@ export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {
      }
    }

-    for (i = 0; i < insertedVnodeQueue.length; ++i) {
+    for (i = 0, iLen = insertedVnodeQueue.length; i < iLen; ++i) {
      (((insertedVnodeQueue[i].data as VNodeData).hook as Hooks).insert as any)(
        insertedVnodeQueue[i]
      );
    }
-    for (i = 0; i < cbs.post.length; ++i) cbs.post[i]();
+    for (i = 0, iLen = cbs.post.length; i < iLen; ++i) cbs.post[i]();
    return vnode;
  };
 }
@@ -489,21 +454,13 @@ interface DOMAPI {
  createElementNS: (namespaceURI: string, qualifiedName: string) => Element;
  createTextNode: (text: string) => Text;
  createComment: (text: string) => Comment;
-  insertBefore: (
-    parentNode: Node,
-    newNode: Node,
-    referenceNode: Node | null
-  ) => void;
+  insertBefore: (parentNode: Node, newNode: Node, referenceNode: Node | null) => void;
  removeChild: (node: Node, child: Node) => void;
  appendChild: (node: Node, child: Node) => void;
  parentNode: (node: Node) => Node;
  nextSibling: (node: Node) => Node;
  tagName: (elm: Element) => string;
  setTextContent: (node: Node, text: string | null) => void;
-  getTextContent: (node: Node) => string | null;
-  isElement: (node: Node) => node is Element;
-  isText: (node: Node) => node is Text;
-  isComment: (node: Node) => node is Comment;
 }

 function createElement(tagName: any): HTMLElement {
@@ -522,11 +479,7 @@ function createComment(text: string): Comment {
  return document.createComment(text);
 }

-function insertBefore(
-  parentNode: Node,
-  newNode: Node,
-  referenceNode: Node | null
-): void {
+function insertBefore(parentNode: Node, newNode: Node, referenceNode: Node | null): void {
  parentNode.insertBefore(newNode, referenceNode);
 }

@@ -554,22 +507,6 @@ function setTextContent(node: Node, text: string | null): void {
  node.textContent = text;
 }

-function getTextContent(node: Node): string | null {
-  return node.textContent;
-}
-
-function isElement(node: Node): node is Element {
-  return node.nodeType === 1;
-}
-
-function isText(node: Node): node is Text {
-  return node.nodeType === 3;
-}
-
-function isComment(node: Node): node is Comment {
-  return node.nodeType === 8;
-}
-
 const htmlDomApi = {
  createElement,
  createElementNS,
@@ -581,11 +518,7 @@ const htmlDomApi = {
  parentNode,
  nextSibling,
  tagName,
-  setTextContent,
-  getTextContent,
-  isElement,
-  isText,
-  isComment
+  setTextContent
 } as DOMAPI;

 //------------------------------------------------------------------------------
@@ -623,21 +556,19 @@ type VNodeChildElement = VNode | string | number | undefined | null;
 type ArrayOrElement<T> = T | T[];
 type VNodeChildren = ArrayOrElement<VNodeChildElement>;

-function addNS(
-  data: any,
-  children: VNodes | undefined,
-  sel: string | undefined
-): void {
+export function addNS(data: any, children: VNodes | undefined, sel: string | undefined): void {
+  if (sel === "dummy") {
+    // we do not need to add the namespace on dummy elements, they come from a
+    // subcomponent, which will handle the namespace itself
+    return;
+  }
  data.ns = "http://www.w3.org/2000/svg";
  if (sel !== "foreignObject" && children !== undefined) {
-    for (let i = 0; i < children.length; ++i) {
-      let childData = children[i].data;
+    for (let i = 0, iLen = children.length; i < iLen; ++i) {
+      const child = children[i];
+      let childData = child.data;
      if (childData !== undefined) {
-        addNS(
-          childData,
-          (children[i] as VNode).children as VNodes,
-          children[i].sel
-        );
+        addNS(childData, (child as VNode).children as VNodes, child.sel);
      }
    }
  }
@@ -651,7 +582,8 @@ export function h(sel: any, b?: any, c?: any): VNode {
  var data: VNodeData = {},
    children: any,
    text: any,
-    i: number;
+    i: number,
+    iLen: number;
  if (c !== undefined) {
    data = b;
    if (array(c)) {
@@ -673,247 +605,10 @@ export function h(sel: any, b?: any, c?: any): VNode {
    }
  }
  if (children !== undefined) {
-    for (i = 0; i < children.length; ++i) {
+    for (i = 0, iLen = children.length; i < iLen; ++i) {
      if (primitive(children[i]))
-        children[i] = vnode(
-          undefined,
-          undefined,
-          undefined,
-          children[i],
-          undefined
-        );
+        children[i] = vnode(undefined, undefined, undefined, children[i], undefined);
    }
  }
-  if (
-    sel[0] === "s" &&
-    sel[1] === "v" &&
-    sel[2] === "g" &&
-    (sel.length === 3 || sel[3] === "." || sel[3] === "#")
-  ) {
-    addNS(data, children, sel);
-  }
  return vnode(sel, data, children, text, undefined);
 }
-
-//------------------------------------------------------------------------------
-// module/props.ts
-//------------------------------------------------------------------------------
-type Props = Record<string, any>;
-
-function updateProps(oldVnode: VNode, vnode: VNode): void {
-  var key: string,
-    cur: any,
-    old: any,
-    elm = vnode.elm,
-    oldProps = (oldVnode.data as VNodeData).props,
-    props = (vnode.data as VNodeData).props;
-
-  if (!oldProps && !props) return;
-  if (oldProps === props) return;
-  oldProps = oldProps || {};
-  props = props || {};
-
-  for (key in oldProps) {
-    if (!props[key]) {
-      delete (elm as any)[key];
-    }
-  }
-  for (key in props) {
-    cur = props[key];
-    old = oldProps[key];
-    if (old !== cur && (key !== "value" || (elm as any)[key] !== cur)) {
-      (elm as any)[key] = cur;
-    }
-  }
-}
-
-export const propsModule = {
-  create: updateProps,
-  update: updateProps
-} as Module;
-
-//------------------------------------------------------------------------------
-// module/module.ts
-//------------------------------------------------------------------------------
-interface Module {
-  pre: PreHook;
-  create: CreateHook;
-  update: UpdateHook;
-  destroy: DestroyHook;
-  remove: RemoveHook;
-  post: PostHook;
-}
-
-//------------------------------------------------------------------------------
-// module/eventlisteners.ts
-//------------------------------------------------------------------------------
-type On = {
-  [N in keyof HTMLElementEventMap]?: (ev: HTMLElementEventMap[N]) => void
-} & {
-  [event: string]: EventListener;
-};
-
-function invokeHandler(handler: any, vnode?: VNode, event?: Event): void {
-  if (typeof handler === "function") {
-    // call function handler
-    handler.call(vnode, event, vnode);
-  } else if (typeof handler === "object") {
-    // call handler with arguments
-    if (typeof handler[0] === "function") {
-      // special case for single argument for performance
-      if (handler.length === 2) {
-        handler[0].call(vnode, handler[1], event, vnode);
-      } else {
-        var args = handler.slice(1);
-        args.push(event);
-        args.push(vnode);
-        handler[0].apply(vnode, args);
-      }
-    } else {
-      // call multiple handlers
-      for (var i = 0; i < handler.length; i++) {
-        invokeHandler(handler[i], vnode, event);
-      }
-    }
-  }
-}
-
-function handleEvent(event: Event, vnode: VNode) {
-  var name = event.type,
-    on = (vnode.data as VNodeData).on;
-
-  // call event handler(s) if exists
-  if (on && on[name]) {
-    invokeHandler(on[name], vnode, event);
-  }
-}
-
-function createListener() {
-  return function handler(event: Event) {
-    handleEvent(event, (handler as any).vnode);
-  };
-}
-
-function updateEventListeners(oldVnode: VNode, vnode?: VNode): void {
-  var oldOn = (oldVnode.data as VNodeData).on,
-    oldListener = (oldVnode as any).listener,
-    oldElm: Element = oldVnode.elm as Element,
-    on = vnode && (vnode.data as VNodeData).on,
-    elm: Element = (vnode && vnode.elm) as Element,
-    name: string;
-
-  // optimization for reused immutable handlers
-  if (oldOn === on) {
-    return;
-  }
-
-  // remove existing listeners which no longer used
-  if (oldOn && oldListener) {
-    // if element changed or deleted we remove all existing listeners unconditionally
-    if (!on) {
-      for (name in oldOn) {
-        // remove listener if element was changed or existing listeners removed
-        oldElm.removeEventListener(name, oldListener, false);
-      }
-    } else {
-      for (name in oldOn) {
-        // remove listener if existing listener removed
-        if (!on[name]) {
-          oldElm.removeEventListener(name, oldListener, false);
-        }
-      }
-    }
-  }
-
-  // add new listeners which has not already attached
-  if (on) {
-    // reuse existing listener or create new
-    var listener = ((vnode as any).listener =
-      (oldVnode as any).listener || createListener());
-    // update vnode for listener
-    listener.vnode = vnode;
-
-    // if element changed or added we add all needed listeners unconditionally
-    if (!oldOn) {
-      for (name in on) {
-        // add listener if element was changed or new listeners added
-        elm.addEventListener(name, listener, false);
-      }
-    } else {
-      for (name in on) {
-        // add listener if new listener added
-        if (!oldOn[name]) {
-          elm.addEventListener(name, listener, false);
-        }
-      }
-    }
-  }
-}
-
-export const eventListenersModule = {
-  create: updateEventListeners,
-  update: updateEventListeners,
-  destroy: updateEventListeners
-} as Module;
-
-//------------------------------------------------------------------------------
-// attributes.ts
-//------------------------------------------------------------------------------
-type Attrs = Record<string, string | number | boolean>;
-
-const xlinkNS = "http://www.w3.org/1999/xlink";
-const xmlNS = "http://www.w3.org/XML/1998/namespace";
-const colonChar = 58;
-const xChar = 120;
-
-function updateAttrs(oldVnode: VNode, vnode: VNode): void {
-  var key: string,
-    elm: Element = vnode.elm as Element,
-    oldAttrs = (oldVnode.data as VNodeData).attrs,
-    attrs = (vnode.data as VNodeData).attrs;
-
-  if (!oldAttrs && !attrs) return;
-  if (oldAttrs === attrs) return;
-  oldAttrs = oldAttrs || {};
-  attrs = attrs || {};
-
-  // update modified attributes, add new attributes
-  for (key in attrs) {
-    const cur = attrs[key];
-    const old = oldAttrs[key];
-    if (old !== cur) {
-      if (cur === true) {
-        elm.setAttribute(key, "");
-      } else if (cur === false) {
-        elm.removeAttribute(key);
-      } else {
-        if (key.charCodeAt(0) !== xChar) {
-          elm.setAttribute(key, cur);
-        } else if (key.charCodeAt(3) === colonChar) {
-          // Assume xml namespace
-          elm.setAttributeNS(xmlNS, key, cur);
-        } else if (key.charCodeAt(5) === colonChar) {
-          // Assume xlink namespace
-          elm.setAttributeNS(xlinkNS, key, cur);
-        } else {
-          elm.setAttribute(key, cur);
-        }
-      }
-    }
-  }
-  // remove removed attributes
-  // use `in` operator since the previous `for` iteration uses it (.i.e. add even attributes with undefined value)
-  // the other option is to remove all attributes with value == undefined
-  for (key in oldAttrs) {
-    if (!(key in attrs)) {
-      elm.removeAttribute(key);
-    }
-  }
-}
-
-export const attrsModule = {
-  create: updateAttrs,
-  update: updateAttrs
-} as Module;
-
-export const patch = init([eventListenersModule, attrsModule, propsModule]);
@@ -0,0 +1,133 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`animations t-transition combined with component 1`] = `
+"function anonymous(context,extra
+) {
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let owner = context;
+    let sibling = null;
+    var 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;
+    }
+    if (w3) {
+        w3.__updateProps(props3, extra.fiber, undefined, undefined, sibling);
+        let pvnode = w3.__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();
+        };
+        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;
+    }
+    sibling = w3.__owl__.currentFiber || sibling;
+    return vn1;
+}"
+`;
+
+exports[`animations t-transition combined with t-component and t-if 1`] = `
+"function anonymous(context,extra
+) {
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let owner = context;
+    let sibling = null;
+    var 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;
+        }
+        if (w3) {
+            w3.__updateProps(props3, extra.fiber, undefined, undefined, sibling);
+            let pvnode = w3.__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();
+        };
+        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;
+        }
+        sibling = w3.__owl__.currentFiber || sibling;
+    }
+    return vn1;
+}"
+`;
+
+exports[`animations t-transition with no delay/duration 1`] = `
+"function anonymous(context,extra
+) {
+    let utils = this.constructor.utils;
+    let sibling = null;
+    var h = this.h;
+    let c1 = [], p1 = {key:1};
+    var vn1 = h('span', p1, c1);
+    p1.hook = {
+      insert: vn => {
+        utils.transitionInsert(vn, 'jupiler');
+      },
+      remove: (vn, rm) => {
+        utils.transitionRemove(vn, 'jupiler', rm);
+      },
+    };
+    c1.push({text: \`blue\`});
+    return vn1;
+}"
+`;
+
+exports[`animations t-transition, on a simple node (insert) 1`] = `
+"function anonymous(context,extra
+) {
+    let utils = this.constructor.utils;
+    let sibling = null;
+    var h = this.h;
+    let c1 = [], p1 = {key:1};
+    var 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;
+}"
+`;
@@ -1,155 +0,0 @@
-// Jest Snapshot v1, https://goo.gl/fbAQLP
-
-exports[`composition sub widgets with some state rendered in a loop 1`] = `
-"function anonymous(context,extra
-) {
-    let owner = context;
-    context = Object.create(context);
-    var h = this.utils.h;
-    var c1 = [], p1 = {key:1};
-    var vn1 = h('div', p1, c1);
-    var _2 = context['state'].numbers;
-    if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    if (typeof _2 === 'number') { _2 = Array.from(Array(_2).keys())}
-    var _3 = _2 instanceof Array ? _2 : Object.keys(_2);
-    var _4 = _2 instanceof Array ? _2 : Object.values(_2);
-    for (let i = 0; i < _3.length; i++) {
-        context.number_first = i === 0;
-        context.number_last = i === _3.length - 1;
-        context.number_parity = i % 2 === 0 ? 'even' : 'odd';
-        context.number_index = i;
-        context.number = _3[i];
-        context.number_value = _4[i];
-        //WIDGET
-        let key8 = context['number'];
-        let _5_index = c1.length;
-        c1.push(null);
-        let def6;
-        let w7 = key8 in context.__owl__.cmap ? context.__owl__.children[context.__owl__.cmap[key8]] : false;
-        let props7 = {};
-        let isNew7 = !w7;
-        if (w7 && w7.__owl__.renderPromise) {
-            if (w7.__owl__.isStarted) {
-                def6 = w7._updateProps(props7, extra.forceUpdate, extra.patchQueue);
-            } else {
-                isNew7 = true
-                if (props7 === w7.__owl__.renderProps) {
-                    def6 = w7.__owl__.renderPromise;
-                } else {
-                    w7.destroy();
-                    w7 = false
-                }
-            }
-        }
-        if (!def6) {
-            if (w7) {
-                def6 = w7._updateProps(props7, extra.forceUpdate, extra.patchQueue);
-            } else {
-                w7 = new context.widgets['ChildWidget'](owner, props7);
-                context.__owl__.cmap[key8] = w7.__owl__.id;
-                def6 = w7._prepare();
-            }
-        }
-        if (isNew7) {
-            def6 = def6.then(vnode=>{let pvnode=h(vnode.sel, {key: key8});c1[_5_index]=pvnode;pvnode.data.hook = {insert(vn){let nvn=w7._mount(vnode, vn.elm);pvnode.elm=nvn.elm;},remove(){w7.destroy()},destroy(){w7.destroy()}}; w7.__owl__.pvnode = pvnode;});
-        } else {
-            def6 = def6.then(()=>{if (w7.__owl__.isDestroyed) {return};let vnode;if (!w7.__owl__.vnode){vnode=w7.__owl__.pvnode} else { vnode=h(w7.__owl__.vnode.sel, {key: key8});vnode.elm=w7.el;vnode.data.hook = {insert(a){a.elm.parentNode.replaceChild(w7.el,a.elm);a.elm=w7.el;w7.__mount();},remove(){w7.destroy()}, destroy() {w7.destroy()}}}c1[_5_index]=vnode;});
-        }
-        extra.promises.push(def6);
-    }
-    return vn1;
-}"
-`;
-
-exports[`random stuff/miscellaneous snapshotting compiled code 1`] = `
-"function anonymous(context,extra
-) {
-    let owner = context;
-    var h = this.utils.h;
-    var c1 = [], p1 = {key:1};
-    var vn1 = h('div', p1, c1);
-    //WIDGET
-    let key5 = 'somestring';
-    let _2_index = c1.length;
-    c1.push(null);
-    let def3;
-    let w4 = key5 in context.__owl__.cmap ? context.__owl__.children[context.__owl__.cmap[key5]] : false;
-    let props4 = {flag: context['state'].flag};
-    let isNew4 = !w4;
-    if (w4 && w4.__owl__.renderPromise) {
-        if (w4.__owl__.isStarted) {
-            def3 = w4._updateProps(props4, extra.forceUpdate, extra.patchQueue);
-        } else {
-            isNew4 = true
-            if (props4 === w4.__owl__.renderProps) {
-                def3 = w4.__owl__.renderPromise;
-            } else {
-                w4.destroy();
-                w4 = false
-            }
-        }
-    }
-    if (!def3) {
-        if (w4) {
-            def3 = w4._updateProps(props4, extra.forceUpdate, extra.patchQueue);
-        } else {
-            w4 = new context.widgets['child'](owner, props4);
-            context.__owl__.cmap[key5] = w4.__owl__.id;
-            def3 = w4._prepare();
-        }
-    }
-    if (isNew4) {
-        def3 = def3.then(vnode=>{let pvnode=h(vnode.sel, {key: key5});c1[_2_index]=pvnode;pvnode.data.hook = {insert(vn){let nvn=w4._mount(vnode, vn.elm);pvnode.elm=nvn.elm;},remove(){w4.destroy()},destroy(){w4.destroy()}}; w4.__owl__.pvnode = pvnode;});
-    } else {
-        def3 = def3.then(()=>{if (w4.__owl__.isDestroyed) {return};let vnode;if (!w4.__owl__.vnode){vnode=w4.__owl__.pvnode} else { vnode=h(w4.__owl__.vnode.sel, {key: key5});vnode.elm=w4.el;vnode.data.hook = {insert(a){a.elm.parentNode.replaceChild(w4.el,a.elm);a.elm=w4.el;w4.__mount();},remove(){w4.destroy()}, destroy() {w4.destroy()}}}c1[_2_index]=vnode;});
-    }
-    extra.promises.push(def3);
-    return vn1;
-}"
-`;
-
-exports[`random stuff/miscellaneous t-props should not be undefined (snapshotting) 1`] = `
-"function anonymous(context,extra
-) {
-    let owner = context;
-    var h = this.utils.h;
-    var c1 = [], p1 = {key:1};
-    var vn1 = h('div', p1, c1);
-    //WIDGET
-    let _2_index = c1.length;
-    c1.push(null);
-    let def3;
-    let w4 = 4 in context.__owl__.cmap ? context.__owl__.children[context.__owl__.cmap[4]] : false;
-    let props4 = {};
-    let isNew4 = !w4;
-    if (w4 && w4.__owl__.renderPromise) {
-        if (w4.__owl__.isStarted) {
-            def3 = w4._updateProps(props4, extra.forceUpdate, extra.patchQueue);
-        } else {
-            isNew4 = true
-            if (props4 === w4.__owl__.renderProps) {
-                def3 = w4.__owl__.renderPromise;
-            } else {
-                w4.destroy();
-                w4 = false
-            }
-        }
-    }
-    if (!def3) {
-        if (w4) {
-            def3 = w4._updateProps(props4, extra.forceUpdate, extra.patchQueue);
-        } else {
-            w4 = new context.widgets['child'](owner, props4);
-            context.__owl__.cmap[4] = w4.__owl__.id;
-            def3 = w4._prepare();
-        }
-    }
-    if (isNew4) {
-        def3 = def3.then(vnode=>{let pvnode=h(vnode.sel, {key: 4});c1[_2_index]=pvnode;pvnode.data.hook = {insert(vn){let nvn=w4._mount(vnode, vn.elm);pvnode.elm=nvn.elm;},remove(){w4.destroy()},destroy(){w4.destroy()}}; w4.__owl__.pvnode = pvnode;});
-    } else {
-        def3 = def3.then(()=>{if (w4.__owl__.isDestroyed) {return};let vnode;if (!w4.__owl__.vnode){vnode=w4.__owl__.pvnode} else { vnode=h(w4.__owl__.vnode.sel, {key: 4});vnode.elm=w4.el;vnode.data.hook = {insert(a){a.elm.parentNode.replaceChild(w4.el,a.elm);a.elm=w4.el;w4.__mount();},remove(){w4.destroy()}, destroy() {w4.destroy()}}}c1[_2_index]=vnode;});
-    }
-    extra.promises.push(def3);
-    return vn1;
-}"
-`;
@@ -1,13 +0,0 @@
-// Jest Snapshot v1, https://goo.gl/fbAQLP
-
-exports[`connecting a component to store connecting a component works 1`] = `"<div></div>"`;
-
-exports[`connecting a component to store connecting a component works 2`] = `"<div><span>hello</span></div>"`;
-
-exports[`connecting a component to store deep and shallow connecting a component 1`] = `"<div><span>Kasteel</span></div>"`;
-
-exports[`connecting a component to store deep and shallow connecting a component 2`] = `"<div><span>Kasteel</span></div>"`;
-
-exports[`connecting a component to store deep and shallow connecting a component 3`] = `"<div><span>Bertinchamps</span></div>"`;
-
-exports[`connecting a component to store deep and shallow connecting a component 4`] = `"<div><span>Kasteel</span></div>"`;
@@ -0,0 +1,5 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`various scenarios scenarios with async store updates and some components events 1`] = `"<div><button>Do stuff</button><div><span>Attachment 100</span><span>Name: text.txt</span></div></div>"`;
+
+exports[`various scenarios scenarios with async store updates and some components events 2`] = `"<div><button>Do stuff</button></div>"`;
@@ -0,0 +1,379 @@
+import { Component, Env } from "../src/component/component";
+import { QWeb } from "../src/qweb/index";
+import { useState, useRef } from "../src/hooks";
+import {
+  makeDeferred,
+  makeTestFixture,
+  makeTestEnv,
+  patchNextFrame,
+  renderToDOM,
+  unpatchNextFrame
+} 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.
+// - qweb: a new QWeb instance
+// - env: a WEnv, necessary to create new components
+// - cssEl: a stylesheet injected into the dom
+
+let fixture: HTMLElement;
+let qweb: QWeb;
+let env: Env;
+let cssEl: HTMLElement;
+
+beforeEach(() => {
+  fixture = makeTestFixture();
+  env = makeTestEnv();
+  qweb = new QWeb();
+});
+
+afterEach(() => {
+  fixture.remove();
+});
+
+class Widget extends Component<any, any> {}
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+describe("animations", () => {
+  beforeEach(() => {
+    cssEl = document.createElement("style");
+    let css = `
+      .chimay-enter-active, .chimay-leave-active {
+        transition-property: opacity;
+        transition-duration: 0.1s;
+      }
+      .chimay-enter, .chimay-leave-to {
+        opacity: 0;
+      }
+    `;
+    cssEl.textContent = css.trim();
+    document.head.appendChild(cssEl);
+  });
+
+  afterEach(() => {
+    document.head.removeChild(cssEl);
+    unpatchNextFrame();
+  });
+
+  test("t-transition, on a simple node (insert)", 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");
+      def.resolve();
+    });
+    let node: HTMLElement = <HTMLElement>renderToDOM(qweb, "test");
+
+    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 with no delay/duration", async () => {
+    expect.assertions(4);
+    qweb.addTemplate("test", `<span t-transition="jupiler">blue</span>`);
+
+    let def = makeDeferred();
+    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");
+    expect(node.className).toBe("jupiler-enter jupiler-enter-active");
+    await def;
+  });
+
+  test("t-transition on a conditional node", async () => {
+    expect.assertions(7);
+
+    env.qweb.addTemplate(
+      "TestWidget",
+      `<div><span t-if="!state.hide" t-transition="chimay">blue</span></div>`
+    );
+    class TestWidget extends Widget {
+      state = useState({ hide: false });
+    }
+    const widget = new TestWidget(env);
+
+    // insert widget into the DOM
+    let def = makeDeferred();
+    var spanNode;
+    patchNextFrame(cb => {
+      expect(spanNode.className).toBe("chimay-enter chimay-enter-active");
+      cb();
+      expect(spanNode.className).toBe("chimay-enter-active chimay-enter-to");
+      def.resolve();
+    });
+    await widget.mount(fixture);
+    spanNode = widget.el!.children[0];
+    expect(spanNode.className).toBe("chimay-enter chimay-enter-active");
+    await def; // wait for the mocked repaint to be done
+    spanNode.dispatchEvent(new Event("transitionend")); // mock end of css transition
+    expect(spanNode.className).toBe("");
+
+    // remove span from the DOM
+    def = makeDeferred();
+    widget.state.hide = true;
+    patchNextFrame(cb => {
+      expect(spanNode.className).toBe("chimay-leave chimay-leave-active");
+      cb();
+      expect(spanNode.className).toBe("chimay-leave-active chimay-leave-to");
+      def.resolve();
+    });
+    await def; // wait for the mocked repaint to be done
+    spanNode.dispatchEvent(new Event("transitionend")); // mock end of css transition
+    expect(spanNode.className).toBe("");
+  });
+
+  test("t-transition combined with t-ref", async () => {
+    expect.assertions(5);
+
+    env.qweb.addTemplate(
+      "TestWidget",
+      `<div><span t-ref="span" t-transition="chimay">blue</span></div>`
+    );
+    class TestWidget extends Widget {
+      state = useState({ hide: false });
+      span = useRef("span");
+    }
+    const widget = new TestWidget(env);
+
+    // insert widget into the DOM
+    let def = makeDeferred();
+    var spanNode;
+    patchNextFrame(cb => {
+      expect(spanNode.className).toBe("chimay-enter chimay-enter-active");
+      cb();
+      expect(spanNode.className).toBe("chimay-enter-active chimay-enter-to");
+      def.resolve();
+    });
+    await widget.mount(fixture);
+    spanNode = widget.el!.children[0];
+    expect(widget.span.el).toBe(spanNode);
+    expect(spanNode.className).toBe("chimay-enter chimay-enter-active");
+    await def; // wait for the mocked repaint to be done
+    spanNode.dispatchEvent(new Event("transitionend")); // mock end of css transition
+    expect(spanNode.className).toBe("");
+  });
+
+  test("t-transition combined with component", async () => {
+    expect.assertions(5);
+
+    env.qweb.addTemplate("Parent", `<div><Child t-transition="chimay"/></div>`);
+    env.qweb.addTemplate("Child", `<span>blue</span>`);
+    class Child extends Widget {}
+    class Parent extends Widget {
+      static components = { Child: Child };
+    }
+    const widget = new Parent(env);
+
+    let def = makeDeferred();
+    var spanNode;
+    patchNextFrame(cb => {
+      expect(fixture.innerHTML).toBe(
+        '<div><span class="chimay-enter chimay-enter-active">blue</span></div>'
+      );
+      cb();
+      expect(fixture.innerHTML).toBe(
+        '<div><span class="chimay-enter-active chimay-enter-to">blue</span></div>'
+      );
+      def.resolve();
+    });
+    await widget.mount(fixture);
+    spanNode = widget.el!.children[0];
+
+    expect(env.qweb.templates.Parent.fn.toString()).toMatchSnapshot();
+    expect(fixture.innerHTML).toBe(
+      '<div><span class="chimay-enter chimay-enter-active">blue</span></div>'
+    );
+
+    await def; // wait for the mocked repaint to be done
+    spanNode.dispatchEvent(new Event("transitionend")); // mock end of css transition
+    expect(fixture.innerHTML).toBe('<div><span class="">blue</span></div>');
+  });
+
+  test("t-transition combined with t-component and t-if", async () => {
+    expect.assertions(8);
+
+    env.qweb.addTemplate(
+      "Parent",
+      `<div><t t-if="state.display" t-component="Child" t-transition="chimay"/></div>`
+    );
+    env.qweb.addTemplate("Child", `<span>blue</span>`);
+    class Child extends Widget {}
+    class Parent extends Widget {
+      static components = { Child: Child };
+      state = useState({ display: true });
+    }
+    const widget = new Parent(env);
+
+    let def = makeDeferred();
+    var spanNode;
+    patchNextFrame(cb => {
+      expect(fixture.innerHTML).toBe(
+        '<div><span class="chimay-enter chimay-enter-active">blue</span></div>'
+      );
+      cb();
+      expect(fixture.innerHTML).toBe(
+        '<div><span class="chimay-enter-active chimay-enter-to">blue</span></div>'
+      );
+      def.resolve();
+    });
+    await widget.mount(fixture);
+    spanNode = widget.el!.children[0];
+
+    expect(env.qweb.templates.Parent.fn.toString()).toMatchSnapshot();
+    expect(fixture.innerHTML).toBe(
+      '<div><span class="chimay-enter chimay-enter-active">blue</span></div>'
+    );
+
+    await def; // wait for the mocked repaint to be done
+    spanNode.dispatchEvent(new Event("transitionend")); // mock end of css transition
+    expect(fixture.innerHTML).toBe('<div><span class="">blue</span></div>');
+
+    // remove span from the DOM
+    def = makeDeferred();
+    widget.state.display = false;
+    patchNextFrame(cb => {
+      expect(fixture.innerHTML).toBe(
+        '<div><span class="chimay-leave chimay-leave-active" data-owl-key="__4__">blue</span></div>'
+      );
+      cb();
+      expect(fixture.innerHTML).toBe(
+        '<div><span class="chimay-leave-active chimay-leave-to" data-owl-key="__4__">blue</span></div>'
+      );
+      def.resolve();
+    });
+    await def; // wait for the mocked repaint to be done
+    spanNode.dispatchEvent(new Event("transitionend")); // mock end of css transition
+    expect(fixture.innerHTML).toBe("<div></div>");
+  });
+
+  test("t-transition, remove and re-add before transitionend", async () => {
+    expect.assertions(11);
+
+    env.qweb.addTemplates(
+      `<templates>
+        <div t-name="Parent">
+          <button t-on-click="toggle">Toggle</button>
+          <span t-if="state.flag" t-transition="chimay">blue</span>
+        </div>
+      </templates>`
+    );
+    class Parent extends Widget {
+      state = useState({ flag: false });
+
+      toggle() {
+        this.state.flag = !this.state.flag;
+      }
+    }
+
+    const widget = new Parent(env);
+    await widget.mount(fixture);
+    let button = widget.el!.querySelector("button");
+
+    let def = makeDeferred();
+    let phase = "enter";
+    patchNextFrame(cb => {
+      let spans = fixture.querySelectorAll("span");
+      expect(spans.length).toBe(1);
+      expect(spans[0].className).toBe(`chimay-${phase} chimay-${phase}-active`);
+      cb();
+      expect(spans[0].className).toBe(`chimay-${phase}-active chimay-${phase}-to`);
+      def.resolve();
+    });
+
+    // click display the span
+    button!.click();
+    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>');
+
+    // click to remove the span, and click again to re-add it before transitionend
+    def = makeDeferred();
+    phase = "leave";
+    button!.click();
+
+    await def; // wait for the mocked repaint to be done
+    def = makeDeferred();
+    phase = "enter";
+    button!.click();
+
+    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>');
+  });
+
+  test("t-transition combined with t-component, remove and re-add before transitionend", async () => {
+    expect.assertions(11);
+
+    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 Parent extends Widget {
+      static components = { Child };
+      state = useState({ flag: false });
+
+      toggle() {
+        this.state.flag = !this.state.flag;
+      }
+    }
+
+    const widget = new Parent(env);
+    await widget.mount(fixture);
+    let button = widget.el!.querySelector("button");
+
+    let def = makeDeferred();
+    let phase = "enter";
+    patchNextFrame(cb => {
+      let spans = fixture.querySelectorAll("span");
+      expect(spans.length).toBe(1);
+      expect(spans[0].className).toBe(`chimay-${phase} chimay-${phase}-active`);
+      cb();
+      expect(spans[0].className).toBe(`chimay-${phase}-active chimay-${phase}-to`);
+      def.resolve();
+    });
+
+    // click display the span
+    button!.click();
+    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>');
+
+    // click to remove the span, and click again to re-add it before transitionend
+    def = makeDeferred();
+    phase = "leave";
+    button!.click();
+
+    await def; // wait for the mocked repaint to be done
+    def = makeDeferred();
+    phase = "enter";
+    button!.click();
+
+    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>');
+  });
+});
@@ -0,0 +1,42 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`props validation props are validated in dev mode (code snapshot) 1`] = `
+"function anonymous(context,extra
+) {
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let owner = context;
+    let sibling = null;
+    var 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;
+    }
+    if (w3) {
+        w3.__updateProps(props3, extra.fiber, undefined, undefined, sibling);
+        let pvnode = w3.__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; });
+        c1.push(pvnode);
+        w3.__owl__.pvnode = pvnode;
+    }
+    sibling = w3.__owl__.currentFiber || sibling;
+    return vn1;
+}"
+`;
@@ -0,0 +1,447 @@
+import { Component, Env } from "../../src/component/component";
+import { makeTestFixture, makeTestEnv, nextTick } from "../helpers";
+import { useState } from "../../src/hooks";
+import { QWeb } from "../../src/qweb";
+import { xml } from "../../src/tags";
+
+//------------------------------------------------------------------------------
+// Setup and helpers
+//------------------------------------------------------------------------------
+
+let fixture: HTMLElement;
+let env: Env;
+let dev: boolean = false;
+
+beforeEach(() => {
+  fixture = makeTestFixture();
+  env = makeTestEnv();
+  dev = QWeb.dev;
+  QWeb.dev = true;
+});
+
+afterEach(() => {
+  fixture.remove();
+  QWeb.dev = dev;
+});
+
+class Widget extends Component<any, any> {}
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+describe("props validation", () => {
+  test("validation is only done in dev mode", async () => {
+    class TestWidget extends Widget {
+      static props = ["message"];
+      static template = xml`<div>hey</div>`;
+    }
+
+    QWeb.dev = true;
+    expect(() => {
+      new TestWidget(env);
+    }).toThrow();
+
+    QWeb.dev = false;
+
+    expect(() => {
+      new TestWidget(env);
+    }).not.toThrow();
+  });
+
+  test("props: list of strings", async () => {
+    class TestWidget extends Widget {
+      static props = ["message"];
+      static template = xml`<div>hey</div>`;
+    }
+
+    expect(() => {
+      new TestWidget(env);
+    }).toThrow("Missing props 'message' (component 'TestWidget')");
+  });
+
+  test("validate simple types", async () => {
+    const Tests = [
+      { type: Number, ok: 1, ko: "1" },
+      { type: Boolean, ok: true, ko: "1" },
+      { type: String, ok: "1", ko: 1 },
+      { type: Object, ok: {}, ko: "1" },
+      { type: Date, ok: new Date(), ko: "1" },
+      { type: Function, ok: () => {}, ko: "1" }
+    ];
+
+    for (let test of Tests) {
+      let TestWidget = class extends Widget {
+        static template = xml`<div>hey</div>`;
+        static props = { p: test.type };
+      };
+
+      expect(() => {
+        new TestWidget(env);
+      }).toThrow("Missing props 'p'");
+
+      expect(() => {
+        new TestWidget(env, { p: test.ok });
+      }).not.toThrow();
+
+      expect(() => {
+        new TestWidget(env, { p: test.ko });
+      }).toThrow("Props 'p' of invalid type in component");
+    }
+  });
+
+  test("validate simple types, alternate form", async () => {
+    const Tests = [
+      { type: Number, ok: 1, ko: "1" },
+      { type: Boolean, ok: true, ko: "1" },
+      { type: String, ok: "1", ko: 1 },
+      { type: Object, ok: {}, ko: "1" },
+      { type: Date, ok: new Date(), ko: "1" },
+      { type: Function, ok: () => {}, ko: "1" }
+    ];
+
+    for (let test of Tests) {
+      let TestWidget = class extends Widget {
+        static template = xml`<div>hey</div>`;
+        static props = { p: { type: test.type } };
+      };
+
+      expect(() => {
+        new TestWidget(env);
+      }).toThrow("Missing props 'p'");
+
+      expect(() => {
+        new TestWidget(env, { p: test.ok });
+      }).not.toThrow();
+
+      expect(() => {
+        new TestWidget(env, { p: test.ko });
+      }).toThrow("Props 'p' of invalid type in component");
+    }
+  });
+
+  test("can validate a prop with multiple types", async () => {
+    let TestWidget = class extends Widget {
+      static template = xml`<div>hey</div>`;
+      static props = { p: [String, Boolean] };
+    };
+
+    expect(() => {
+      new TestWidget(env, { p: "string" });
+      new TestWidget(env, { p: true });
+    }).not.toThrow();
+
+    expect(() => {
+      new TestWidget(env, { p: 1 });
+    }).toThrow("Props 'p' of invalid type in component");
+  });
+
+  test("can validate an optional props", async () => {
+    let TestWidget = class extends Widget {
+      static template = xml`<div>hey</div>`;
+      static props = { p: { type: String, optional: true } };
+    };
+
+    expect(() => {
+      new TestWidget(env, { p: "hey" });
+      new TestWidget(env, {});
+    }).not.toThrow();
+
+    expect(() => {
+      new TestWidget(env, { p: 1 });
+    }).toThrow();
+  });
+
+  test("can validate an array with given primitive type", async () => {
+    let TestWidget = class extends Widget {
+      static template = xml`<div>hey</div>`;
+      static props = { p: { type: Array, element: String } };
+    };
+
+    expect(() => {
+      new TestWidget(env, { p: [] });
+      new TestWidget(env, { p: ["string"] });
+    }).not.toThrow();
+
+    expect(() => {
+      new TestWidget(env, { p: [1] });
+    }).toThrow();
+
+    expect(() => {
+      new TestWidget(env, { p: ["string", 1] });
+    }).toThrow();
+  });
+
+  test("can validate an array with multiple sub element types", async () => {
+    let TestWidget = class extends Widget {
+      static template = xml`<div>hey</div>`;
+      static props = { p: { type: Array, element: [String, Boolean] } };
+    };
+
+    expect(() => {
+      new TestWidget(env, { p: [] });
+      new TestWidget(env, { p: ["string"] });
+      new TestWidget(env, { p: [false, true, "string"] });
+    }).not.toThrow();
+
+    expect(() => {
+      new TestWidget(env, { p: [true, 1] });
+    }).toThrow();
+  });
+
+  test("can validate an object with simple shape", async () => {
+    let TestWidget = class extends Widget {
+      static template = xml`<div>hey</div>`;
+      static props = {
+        p: { type: Object, shape: { id: Number, url: String } }
+      };
+    };
+
+    expect(() => {
+      new TestWidget(env, { p: { id: 1, url: "url" } });
+      new TestWidget(env, { p: { id: 1, url: "url", extra: true } });
+    }).not.toThrow();
+
+    expect(() => {
+      new TestWidget(env, { p: { id: "1", url: "url" } });
+    }).toThrow();
+
+    expect(() => {
+      new TestWidget(env, { p: { id: 1 } });
+    }).toThrow();
+  });
+
+  test("can validate recursively complicated prop def", async () => {
+    let TestWidget = class extends Widget {
+      static template = xml`<div>hey</div>`;
+      static props = {
+        p: {
+          type: Object,
+          shape: {
+            id: Number,
+            url: [Boolean, { type: Array, element: Number }]
+          }
+        }
+      };
+    };
+
+    expect(() => {
+      new TestWidget(env, { p: { id: 1, url: true } });
+      new TestWidget(env, { p: { id: 1, url: [12] } });
+    }).not.toThrow();
+
+    expect(() => {
+      new TestWidget(env, { p: { id: 1, url: [12, true] } });
+    }).toThrow();
+  });
+
+  test("props are validated in dev mode (code snapshot)", async () => {
+    env.qweb.addTemplates(`
+      <templates>
+        <div t-name="App">
+          <Child message="1"/>
+        </div>
+        <div t-name="Child"><t t-esc="props.message"/></div>
+      </templates>`);
+
+    class Child extends Widget {
+      static props = ["message"];
+    }
+    class App extends Widget {
+      static components = { Child };
+    }
+    const app = new App(env);
+    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
+    // creation, and one at update time.
+    expect(env.qweb.templates.App.fn.toString()).toMatchSnapshot();
+  });
+
+  test("props: list of strings with optional props", async () => {
+    class TestWidget extends Widget {
+      static props = ["message", "someProp?"];
+    }
+
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, { someProp: 1 });
+    }).toThrow();
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, { message: 1 });
+    }).not.toThrow();
+  });
+
+  test("props: can be defined with a boolean", async () => {
+    class TestWidget extends Widget {
+      static props = { message: true };
+    }
+
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, {});
+    }).toThrow();
+  });
+
+  test("props: extra props cause an error", async () => {
+    class TestWidget extends Widget {
+      static props = ["message"];
+    }
+
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, { message: 1, flag: true });
+    }).toThrow();
+  });
+
+  test("props: extra props cause an error, part 2", async () => {
+    class TestWidget extends Widget {
+      static props = { message: true };
+    }
+
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, { message: 1, flag: true });
+    }).toThrow();
+  });
+
+  test("props: optional prop do not cause an error", async () => {
+    class TestWidget extends Widget {
+      static props = ["message?"];
+    }
+
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, { message: 1 });
+    }).not.toThrow();
+  });
+
+  test("optional prop do not cause an error if value is undefined", async () => {
+    class TestWidget extends Widget {
+      static props = { message: { type: String, optional: true } };
+    }
+
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, { message: undefined });
+    }).not.toThrow();
+    expect(() => {
+      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(env, {});
+    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<any, any> {
+      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<any, any> {
+      static template = xml`<div><TestWidget p="state.p"/></div>`;
+      static components = { TestWidget };
+      state: any = useState({ p: 1 });
+    }
+
+    const w = new Parent(env);
+    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<any, any> {
+      static props = { p: { type: Number } };
+      static template = xml`<div><t t-esc="props.p"/></div>`;
+      static defaultProps = { p: 4 };
+    }
+    class Parent extends Component<any, any> {
+      static template = xml`<div><TestWidget p="state.p"/></div>`;
+      static components = { TestWidget };
+      state: any = useState({ p: 1 });
+    }
+
+    const w = new Parent(env);
+    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>");
+  });
+});
+
+describe("default props", () => {
+  test("can set default values", async () => {
+    class TestWidget extends Widget {
+      static defaultProps = { p: 4 };
+      static template = xml`<div>hey</div>`;
+    }
+
+    const w = new TestWidget(env, {});
+    expect(w.props.p).toBe(4);
+  });
+
+  test("default values are also set whenever component is updated", async () => {
+    class TestWidget extends Widget {
+      static template = xml`<div><t t-esc="props.p"/></div>`;
+      static defaultProps = { p: 4 };
+    }
+    class Parent extends Widget {
+      static template = xml`<div><TestWidget p="state.p"/></div>`;
+      static components = { TestWidget };
+      state: any = useState({ p: 1 });
+    }
+
+    const w = new Parent(env);
+    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("can set default required boolean values", async () => {
+    class TestWidget extends Widget {
+      static props = ["p", "q"];
+      static defaultProps = { p: true, q: false };
+      static template = xml`<span><t t-if="props.p">hey</t><t t-if="!props.q">hey</t></span>`;
+    }
+
+    class App extends Widget {
+      static template = xml`<div><TestWidget/></div>`;
+      static components = { TestWidget };
+    }
+
+    const w = new App(env, {});
+    await w.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><span>heyhey</span></div>");
+  });
+});
@@ -0,0 +1,224 @@
+import { makeDeferred, makeTestEnv, makeTestFixture, nextTick } from "./helpers";
+import { Component, Env } from "../src/component/component";
+import { Context, useContext } from "../src/context";
+import { xml } from "../src/tags";
+import { useState } from "../src/hooks";
+
+//------------------------------------------------------------------------------
+// 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();
+});
+
+afterEach(() => {
+  fixture.remove();
+});
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+describe("Context", () => {
+  test("very simple use, with initial value", async () => {
+    const testContext = new Context({ value: 123 });
+
+    class Test extends Component<any, any> {
+      static template = xml`<div><t t-esc="contextObj.value"/></div>`;
+      contextObj = useContext(testContext);
+    }
+    const test = new Test(env);
+    await test.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>123</div>");
+  });
+
+  test("useContext hook is reactive, for one component", async () => {
+    const testContext = new Context({ value: 123 });
+
+    class Test extends Component<any, any> {
+      static template = xml`<div><t t-esc="contextObj.value"/></div>`;
+      contextObj = useContext(testContext);
+    }
+    const test = new Test(env);
+    await test.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>123</div>");
+    test.contextObj.value = 321;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div>321</div>");
+  });
+
+  test("two components can subscribe to same context", async () => {
+    const testContext = new Context({ value: 123 });
+
+    class Child extends Component<any, any> {
+      static template = xml`<span><t t-esc="contextObj.value"/></span>`;
+      contextObj = useContext(testContext);
+    }
+    class Parent extends Component<any, any> {
+      static template = xml`<div><Child /><Child /></div>`;
+      static components = { Child };
+    }
+    const parent = new Parent(env);
+    await parent.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><span>123</span><span>123</span></div>");
+    testContext.state.value = 321;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><span>321</span><span>321</span></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> {
+      static template = xml`<span><t t-esc="contextObj1.a"/><t t-esc="contextObj2.b"/></span>`;
+      contextObj1 = useContext(testContext);
+      contextObj2 = useContext(testContext);
+      __render(fiber) {
+        steps.push("child");
+        return super.__render(fiber);
+      }
+    }
+    class Parent extends Component<any, any> {
+      static template = xml`<div><Child /></div>`;
+      static components = { Child };
+    }
+    const parent = new Parent(env);
+    await parent.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><span>12</span></div>");
+    expect(steps).toEqual(["child"]);
+    testContext.state.a = 3;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><span>32</span></div>");
+    expect(steps).toEqual(["child", "child"]);
+  });
+
+  test("parent and children subscribed to same context", async () => {
+    const testContext = new Context({ a: 123, b: 321 });
+    const steps: string[] = [];
+
+    class Child extends Component<any, any> {
+      static template = xml`<span><t t-esc="contextObj.a"/></span>`;
+      contextObj = useContext(testContext);
+      __render(fiber) {
+        steps.push("child");
+        return super.__render(fiber);
+      }
+    }
+    class Parent extends Component<any, any> {
+      static template = xml`<div><Child /><t t-esc="contextObj.b"/></div>`;
+      static components = { Child };
+      contextObj = useContext(testContext);
+      __render(fiber) {
+        steps.push("parent");
+        return super.__render(fiber);
+      }
+    }
+    const parent = new Parent(env);
+    await parent.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><span>123</span>321</div>");
+    expect(steps).toEqual(["parent", "child"]);
+
+    parent.contextObj.a = 124;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><span>124</span>321</div>");
+
+    // we only  want one render from the child here, not two
+    expect(steps).toEqual(["parent", "child", "parent", "child"]);
+  });
+
+  test("destroyed component is inactive", async () => {
+    const testContext = new Context({ a: 123 });
+    const steps: string[] = [];
+
+    class Child extends Component<any, any> {
+      static template = xml`<span><t t-esc="contextObj.a"/></span>`;
+      contextObj = useContext(testContext);
+      __render(fiber) {
+        steps.push("child");
+        return super.__render(fiber);
+      }
+    }
+    class Parent extends Component<any, any> {
+      static template = xml`<div><Child t-if="state.flag"/></div>`;
+      static components = { Child };
+      state = useState({ flag: true });
+      __render(fiber) {
+        steps.push("parent");
+        return super.__render(fiber);
+      }
+    }
+    const parent = new Parent(env);
+    await parent.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><span>123</span></div>");
+    expect(steps).toEqual(["parent", "child"]);
+    expect(testContext.subscriptions.update.length).toBe(1);
+
+    parent.state.flag = false;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div></div>");
+    expect(steps).toEqual(["parent", "child", "parent"]);
+    // 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("concurrent renderings", async () => {
+    const testContext = new Context({ x: { n: 1 }, key: "x" });
+    const def = makeDeferred();
+    let stateC;
+    class ComponentC extends Component<any, any> {
+      static template = xml`<span><t t-esc="context[props.key].n"/><t t-esc="state.x"/></span>`;
+      context = useContext(testContext);
+      state = useState({ x: "a" });
+
+      constructor(parent, props) {
+        super(parent, props);
+        stateC = this.state;
+      }
+    }
+    class ComponentB extends Component<any, any> {
+      static components = { ComponentC };
+      static template = xml`<p><ComponentC key="props.key"/></p>`;
+
+      willUpdateProps() {
+        return def;
+      }
+    }
+    class ComponentA extends Component<any, any> {
+      static components = { ComponentB };
+      static template = xml`<div><ComponentB key="context.key"/></div>`;
+      context = useContext(testContext);
+    }
+
+    const component = new ComponentA(env);
+    await component.mount(fixture);
+
+    expect(fixture.innerHTML).toBe("<div><p><span>1a</span></p></div>");
+    testContext.state.key = "y";
+    testContext.state.y = { n: 2 };
+    delete testContext.state.x;
+    await nextTick();
+
+    expect(fixture.innerHTML).toBe("<div><p><span>1a</span></p></div>");
+    stateC.x = "b";
+    await nextTick();
+
+    expect(fixture.innerHTML).toBe("<div><p><span>1a</span></p></div>");
+    def.resolve();
+    await nextTick();
+
+    expect(fixture.innerHTML).toBe("<div><p><span>2b</span></p></div>");
+  });
+});
@@ -1,4 +1,4 @@
-import { EventBus } from "../src/event_bus";
+import { EventBus } from "../../src/core/event_bus";

 describe("event bus behaviour", () => {
  test("can subscribe and be notified", () => {
@@ -23,9 +23,7 @@ describe("event bus behaviour", () => {
  test("throw error if callback is undefined", () => {
    expect.assertions(1);
    const bus = new EventBus();
-    expect(() => bus.on("event", {}, <any>undefined)).toThrow(
-      `Missing callback`
-    );
+    expect(() => bus.on("event", {}, <any>undefined)).toThrow(`Missing callback`);
  });

  test("can unsubscribe", () => {
@@ -0,0 +1,466 @@
+import { Observer } from "../../src/core/observer";
+import { nextMicroTick } from "../helpers";
+
+describe("observer", () => {
+  test("properly observe objects", () => {
+    const observer = new Observer();
+    const obj: any = observer.observe({});
+
+    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;
+
+    expect(observer.revNumber(obj)).toBe(1);
+    expect(observer.revNumber(obj2)).toBe(2);
+    expect(observer.rev).toBe(2);
+
+    expect(obj2).toEqual({
+      a: 2
+    });
+  });
+
+  test("properly handle null or undefined", () => {
+    const observer = new 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
+    });
+  });
+
+  test("properly handle dates", () => {
+    const observer = new Observer();
+    const date = new Date();
+    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);
+
+    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("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.rev).toBe(2);
+  });
+
+  test("various object property changes", () => {
+    const observer = new 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);
+  });
+
+  test("properly observe arrays", () => {
+    const observer = new Observer();
+    const arr: any = observer.observe([]);
+
+    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);
+
+    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);
+
+    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);
+  });
+
+  test("object pushed into arrays are observed", () => {
+    const observer = new Observer();
+    const arr: any = observer.observe([]);
+    expect(observer.rev).toBe(1);
+
+    arr.push({ kriek: 5 });
+    expect(observer.rev).toBe(2);
+    expect(observer.revNumber(arr)).toBe(2);
+    expect(observer.revNumber(arr[0])).toBe(2);
+
+    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[0])).toBe(3);
+  });
+
+  test("set new property on observed object", async () => {
+    const observer = new Observer();
+    observer.notifyCB = jest.fn();
+    const state: any = observer.observe({ a: 1 });
+    expect(observer.notifyCB).toBeCalledTimes(0);
+    expect(observer.rev).toBe(1);
+    expect(observer.revNumber(state)).toBe(1);
+
+    state.b = 8;
+
+    await nextMicroTick();
+
+    expect(observer.notifyCB).toBeCalledTimes(1);
+    expect(observer.rev).toBe(2);
+    expect(observer.revNumber(state)).toBe(2);
+
+    expect(state.b).toBe(8);
+  });
+
+  test("delete property from observed object", async () => {
+    const observer = new Observer();
+    observer.notifyCB = jest.fn();
+    const state: any = observer.observe({ a: 1, b: 8 });
+    observer.observe(state);
+
+    expect(observer.notifyCB).toBeCalledTimes(0);
+    expect(observer.rev).toBe(1);
+    expect(observer.revNumber(state)).toBe(1);
+
+    delete state.b;
+    await nextMicroTick();
+
+    expect(observer.notifyCB).toBeCalledTimes(1);
+    expect(observer.rev).toBe(2);
+    expect(observer.revNumber(state)).toBe(2);
+
+    expect(state).toEqual({ a: 1 });
+  });
+
+  test("set element in observed array", async () => {
+    const observer = new Observer();
+    observer.notifyCB = jest.fn();
+    const state: any = observer.observe(["a"]);
+
+    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";
+
+    await nextMicroTick();
+
+    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"]);
+  });
+
+  test("properly observe arrays in object", () => {
+    const observer = new Observer();
+    const state: any = observer.observe({ arr: [] });
+
+    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);
+  });
+
+  test("properly observe objects in array", () => {
+    const observer = new Observer();
+    const state: any = observer.observe({ arr: [{ something: 1 }] });
+    observer.observe(state);
+
+    expect(observer.rev).toBe(1);
+    expect(observer.revNumber(state.arr)).toBe(1);
+    expect(observer.revNumber(state.arr[0])).toBe(1);
+
+    state.arr[0].something = 2;
+    expect(observer.rev).toBe(2);
+    expect(observer.revNumber(state.arr)).toBe(1);
+    expect(observer.revNumber(state.arr[0])).toBe(2);
+  });
+
+  test("properly observe objects in object", () => {
+    const observer = new Observer();
+    const state: any = observer.observe({ a: { b: 1 } });
+
+    expect(observer.rev).toBe(1);
+    expect(observer.revNumber(state)).toBe(1);
+    expect(observer.revNumber(state.a)).toBe(1);
+
+    state.a.b = 2;
+    expect(observer.rev).toBe(2);
+    expect(observer.revNumber(state)).toBe(1);
+    expect(observer.revNumber(state.a)).toBe(2);
+  });
+
+  test("reobserve new object values", () => {
+    const observer = new Observer();
+    const obj: any = observer.observe({ a: 1 });
+
+    expect(observer.rev).toBe(1);
+    expect(observer.revNumber(obj)).toBe(1);
+
+    obj.a = { b: 2 };
+
+    expect(observer.rev).toBe(2);
+    expect(observer.revNumber(obj)).toBe(2);
+    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.a)).toBe(3);
+  });
+
+  test("deep observe misc changes", () => {
+    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);
+
+    state.arr.push(2);
+    expect(observer.rev).toBe(3);
+    expect(observer.revNumber(state)).toBe(1);
+    expect(observer.deepRevNumber(state)).toBe(3);
+
+    state.n = 155;
+    expect(observer.rev).toBe(4);
+    expect(observer.revNumber(state)).toBe(2);
+    expect(observer.deepRevNumber(state)).toBe(4);
+  });
+
+  test("properly handle already observed state", () => {
+    const observer = new Observer();
+    const obj1: any = observer.observe({ a: 1 });
+    const obj2: any = observer.observe({ b: 1 });
+
+    expect(observer.revNumber(obj1)).toBe(1);
+    expect(observer.revNumber(obj2)).toBe(1);
+
+    obj1.a = 2;
+    obj2.b = 3;
+    expect(observer.revNumber(obj1)).toBe(2);
+    expect(observer.revNumber(obj2)).toBe(2);
+
+    obj2.b = obj1;
+    expect(observer.revNumber(obj1)).toBe(2);
+    expect(observer.revNumber(obj2)).toBe(3);
+  });
+
+  test("can set a property more than once", () => {
+    const observer = new 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);
+  });
+
+  test("properly handle swapping elements", () => {
+    const observer = new Observer();
+    const obj: any = observer.observe({ a: { arr: [] }, b: 1 });
+
+    // swap a and b
+    const b = obj.b;
+    obj.b = obj.a;
+    obj.a = b;
+    expect(observer.rev).toBe(3);
+
+    // push something into array to make sure it works
+    obj.b.arr.push("blanche");
+    expect(observer.rev).toBe(4);
+  });
+
+  test("properly handle assigning observed obj containing array", () => {
+    const observer = new Observer();
+    const obj: any = observer.observe({ a: { arr: [], val: "test" } });
+
+    expect(observer.rev).toBe(1);
+    obj.a = { ...obj.a, val: "test2" };
+    expect(observer.rev).toBe(2);
+
+    // push something into array to make sure it works
+    obj.a.arr.push("blanche");
+    expect(observer.rev).toBe(3);
+  });
+
+  test("accept cycles in observed state", () => {
+    const observer = new Observer();
+    let obj1: any = {};
+    let obj2: any = { b: obj1, key: 1 };
+    obj1.a = obj2;
+    obj1 = observer.observe(obj1);
+    obj2 = obj1.a;
+
+    expect(observer.revNumber(obj1)).toBe(1);
+    expect(observer.revNumber(obj2)).toBe(1);
+
+    obj2.key = 3;
+    expect(observer.revNumber(obj1)).toBe(1);
+    expect(observer.revNumber(obj2)).toBe(2);
+  });
+
+  test("call callback when state is changed", async () => {
+    const observer = new Observer();
+    observer.notifyCB = jest.fn();
+    const obj: any = observer.observe({ a: 1, b: { c: 2 }, d: [{ e: 3 }], f: 4 });
+
+    expect(observer.notifyCB).toBeCalledTimes(0);
+
+    obj.a = 2;
+    await nextMicroTick();
+    expect(observer.notifyCB).toBeCalledTimes(1);
+
+    obj.b.c = 3;
+    await nextMicroTick();
+    expect(observer.notifyCB).toBeCalledTimes(2);
+
+    obj.d[0].e = 5;
+    await nextMicroTick();
+    expect(observer.notifyCB).toBeCalledTimes(3);
+
+    obj.a = 111;
+    obj.f = 222;
+    await nextMicroTick();
+    expect(observer.notifyCB).toBeCalledTimes(4);
+  });
+
+  test("throw error when state is mutated in object if allowMutation=false", async () => {
+    const observer = new Observer();
+    observer.allowMutations = false;
+    const obj: any = observer.observe({ a: 1 });
+    expect(() => {
+      obj.a = 2;
+    }).toThrow('Observed state cannot be changed here! (key: "a", val: "2")');
+  });
+
+  test("throw error when state is mutated in array if allowMutation=false", async () => {
+    const observer = new Observer();
+    observer.allowMutations = false;
+    const obj: any = observer.observe({ a: [1] });
+
+    expect(() => {
+      obj.a.push(2);
+    }).toThrow('Observed state cannot be changed here! (key: "1", val: "2")');
+  });
+});
@@ -0,0 +1,188 @@
+/**
+ * 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";
+
+//--------------------------------------------------------------------------
+// Helpers
+//--------------------------------------------------------------------------
+
+interface MarkDownLink {
+  name: string;
+  link: string;
+}
+
+interface MarkDownSection {
+  name: string;
+  slug: string;
+}
+
+interface FileData {
+  name: string;
+  path: string[];
+  fullName: string
+  links: MarkDownLink[];
+  sections: MarkDownSection[];
+}
+
+const LINK_REGEXP = /\[([^\[]+)\]\(([^\)]+)\)/g;
+const HEADING_REGEXP = /\n(#+\s*)(.*)/g;
+
+
+
+export function addMardownData(fileData): void {
+    const sep = fileData.path.length > 0 ? '/' : '';
+    const fullName = fileData.path.join('/') + sep + fileData.name;
+    const content = fs.readFileSync(fullName, { 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);
+}
+
+
+/**
+ * Returns a list of FileData corresponding to all files that need to be
+ * validated.
+ */
+function getFiles(path: string[] = []): FileData[] {
+  if (path.length === 0) {
+    const baseFiles: FileData[] = [
+      { name: "README.md", path: [], links: [], sections: [], fullName: "README.md" },
+      { name: "roadmap.md", path: [], links: [], sections: [], fullName: "roadmap.md" }
+    ];
+    const rest = getFiles(["doc"]);
+    const result = baseFiles.concat(rest);
+    result.forEach(addMardownData);
+    return result;
+  }
+  const files = fs.readdirSync(path.join("/"), { withFileTypes: true }).map(f => {
+    if (f.isDirectory()) {
+      return getFiles(path.concat(f.name));
+    }
+    const fullName = path.join('/') + (path.length > 0 ? '/' : '') + f.name;
+    return [
+      {
+        name: f.name,
+        path,
+        links: [],
+        sections: [],
+        fullName
+      }
+    ];
+  });
+  return Array.prototype.concat(...files);
+}
+
+const LOCAL_FILES = ['LICENSE'];
+export function isLinkValid(link: MarkDownLink, current: FileData, files: FileData[]): boolean {
+  if (link.link.startsWith("http")) {
+    // no check on external links
+    return true;
+  }
+    // Step 1: extract path, name, hash
+    //      path = ['doc', 'architecture]
+    //      name = 'rendering.md'
+    //      hash = 'blabla' (or '' if no hash)
+
+    const parts = link.link.split('#');
+    const hash = parts[1] || '';
+    let name;
+    let path;
+    if (parts[0]) {
+        let temp = parts[0].split('/');
+        name = temp[temp.length - 1];
+        temp.splice(-1);
+        path = current.path.slice();
+        for (let elem of temp) {
+            if (elem === '..') {
+                path.splice(-1);
+             } else if (elem !== '.') {
+                 path.push(elem);
+             }
+        }
+    } else {
+        // there are no file name, so this is a relative link to the current file
+        name = current.name;
+        path = current.path;
+    }
+
+    // Step 2: build normalized link file name
+    const linkFullName = path.join('/') + (path.length > 0 ? '/' : '') + name;
+
+    // Step 3: check link name against white list of local files
+    if (LOCAL_FILES.includes(linkFullName)) {
+        return true;
+    }
+
+    // Step 4: check if there is a matching file
+    let target: FileData | undefined = files.find(f => f.fullName === linkFullName);
+    if (!target) {
+        return false;
+    }
+
+    // Step 5: if necessary, check if there is a corresponding link inside the target
+    // link name
+    if (hash) {
+        if (!target.sections.find(s => s.slug === hash)) {
+            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(/-+$/, ""); // Trim - from end of text
+}
+
+
+
+//--------------------------------------------------------------------------
+// Test
+//--------------------------------------------------------------------------
+
+test("All markdown links work", () => {
+    let linkNumber = 0;
+    let invalidLinkNumber = 0;
+    const data = getFiles();
+    for (let file of data) {
+      for (let link of file.links) {
+        linkNumber++;
+        if (!isLinkValid(link, file, data)) {
+          console.warn(`Invalid Link: "${link.name}" in "${file.name}"`);
+          invalidLinkNumber++;
+        }
+    }
+    }
+    expect(invalidLinkNumber).toBe(0);
+    expect(linkNumber).toBeGreaterThan(10);
+});
@@ -1,12 +1,45 @@
-import { Env } from "../src/component";
-import { QWeb } from "../src/qweb";
+import { Env, scheduler } from "../src/component/component";
+import { EvalContext, QWeb } from "../src/qweb/qweb";
+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;
+};
+
+// Some static cleanup
+let nextSlotId;
+let slots;
+let nextId;
+let TEMPLATES;
+
+beforeEach(() => {
+  nextSlotId = QWeb.nextSlotId;
+  slots = Object.assign({}, QWeb.slots);
+  nextId = QWeb.nextId;
+  TEMPLATES = Object.assign({}, QWeb.TEMPLATES);
+});
+
+afterEach(() => {
+  QWeb.nextSlotId = nextSlotId;
+  QWeb.slots = slots;
+  QWeb.nextId = nextId;
+  QWeb.TEMPLATES = TEMPLATES;
+});
+
+// helpers
 export function nextMicroTick(): Promise<void> {
  return Promise.resolve();
 }

-export function nextTick(): Promise<void> {
-  return new Promise(resolve => setTimeout(resolve));
+export async function nextTick(): Promise<void> {
+  return new Promise(function(resolve) {
+    setTimeout(() => scheduler.requestAnimationFrame(() => resolve()));
+  });
 }

 export function makeTestFixture() {
@@ -35,8 +68,77 @@ export function makeDeferred(): Deferred {
  return <Deferred>def;
 }

-export function makeTestWEnv(): Env {
+export function makeTestEnv(): Env {
  return {
    qweb: new QWeb()
  };
 }
+
+export function trim(str: string): string {
+  return str.replace(/\s/g, "");
+}
+
+export function renderToDOM(
+  qweb: QWeb,
+  template: string,
+  context: EvalContext = {},
+  extra?: any
+): HTMLElement | Text {
+  const vnode = qweb.render(template, context, extra);
+
+  // we snapshot here the compiled code. This is useful to prevent unwanted code
+  // change.
+  expect(qweb.templates[template].fn.toString()).toMatchSnapshot();
+
+  if (vnode.sel === undefined) {
+    return document.createTextNode(vnode.text!);
+  }
+  const node = document.createElement(vnode.sel!);
+  const result = patch(node, vnode);
+  return result.elm as HTMLElement;
+}
+
+/**
+ * Render a template to an html string. The big difference with the
+ * renderToString method in QWeb is that we use the renderToDom method, which
+ * snapshots the resulting template function.  Doing so gives us a large body
+ * of reference to evaluate changes in the generated QWeb code.
+ *
+ * Note that the result of renderToString is guaranteed to be the same as the
+ * one from QWeb.
+ */
+export function renderToString(
+  qweb: QWeb,
+  t: string,
+  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");
+  }
+  return result;
+}
+
+// hereafter, we define two helpers to patch/unpatch the nextFrame utils. This
+// 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;
+export function patchNextFrame(f: Function) {
+  QWeb.utils.nextFrame = (cb: () => void) => {
+    setTimeout(() => f(cb));
+  };
+}
+
+export function unpatchNextFrame() {
+  QWeb.utils.nextFrame = nextFrame;
+}
+
+export async function editInput(input: HTMLInputElement | HTMLTextAreaElement, value: string) {
+  input.value = value;
+  input.dispatchEvent(new Event("input"));
+  input.dispatchEvent(new Event("change"));
+  return nextTick();
+}
@@ -0,0 +1,493 @@
+import { makeTestEnv, makeTestFixture, nextTick } from "./helpers";
+import { Component, Env } from "../src/component/component";
+import {
+  useState,
+  onMounted,
+  onWillUnmount,
+  useRef,
+  onPatched,
+  onWillPatch,
+  onWillStart,
+  onWillUpdateProps,
+  useSubEnv
+} from "../src/hooks";
+import { xml } from "../src/tags";
+
+//------------------------------------------------------------------------------
+// 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();
+});
+
+afterEach(() => {
+  fixture.remove();
+});
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+describe("hooks", () => {
+  test("can use a state hook", async () => {
+    class Counter extends Component<any, any> {
+      static template = xml`<div><t t-esc="counter.value"/></div>`;
+      counter = useState({ value: 42 });
+    }
+    const counter = new Counter(env);
+    await counter.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>42</div>");
+    counter.counter.value = 3;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div>3</div>");
+  });
+
+  test("can use onMounted, onWillUnmount", async () => {
+    const steps: string[] = [];
+    function useMyHook() {
+      onMounted(() => {
+        steps.push("mounted");
+      });
+      onWillUnmount(() => {
+        steps.push("willunmount");
+      });
+    }
+    class MyComponent extends Component<any, any> {
+      static template = xml`<div>hey</div>`;
+      constructor(env) {
+        super(env);
+        useMyHook();
+      }
+    }
+    const component = new MyComponent(env);
+    await component.mount(fixture);
+    expect(component).not.toHaveProperty("mounted");
+    expect(component).not.toHaveProperty("willUnmount");
+    expect(fixture.innerHTML).toBe("<div>hey</div>");
+    expect(steps).toEqual(["mounted"]);
+    component.unmount();
+    expect(fixture.innerHTML).toBe("");
+    expect(steps).toEqual(["mounted", "willunmount"]);
+  });
+
+  test("can use onMounted, onWillUnmount, part 2", async () => {
+    const steps: string[] = [];
+    function useMyHook() {
+      onMounted(() => {
+        steps.push("mounted");
+      });
+      onWillUnmount(() => {
+        steps.push("willunmount");
+      });
+    }
+    class MyComponent extends Component<any, any> {
+      static template = xml`<div>hey</div>`;
+      constructor(env) {
+        super(env);
+        useMyHook();
+      }
+    }
+
+    class Parent extends Component<any, any> {
+      static template = xml`<div><MyComponent t-if="state.flag"/></div>`;
+      static components = { MyComponent };
+      state = useState({ flag: true });
+    }
+    const parent = new Parent(env);
+    await parent.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>hey</div></div>");
+    expect(steps).toEqual(["mounted"]);
+
+    parent.state.flag = false;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div></div>");
+    expect(steps).toEqual(["mounted", "willunmount"]);
+  });
+
+  test("mounted, willUnmount, onMounted, onWillUnmount order", async () => {
+    const steps: string[] = [];
+    function useMyHook() {
+      onMounted(() => {
+        steps.push("hook:mounted");
+      });
+      onWillUnmount(() => {
+        steps.push("hook:willunmount");
+      });
+    }
+    class MyComponent extends Component<any, any> {
+      static template = xml`<div>hey</div>`;
+      constructor(env) {
+        super(env);
+        useMyHook();
+      }
+      mounted() {
+        steps.push("comp:mounted");
+      }
+      willUnmount() {
+        steps.push("comp:willunmount");
+      }
+    }
+    const component = new MyComponent(env);
+    await component.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>hey</div>");
+    component.unmount();
+    expect(fixture.innerHTML).toBe("");
+    expect(steps).toEqual(["comp:mounted", "hook:mounted", "hook:willunmount", "comp:willunmount"]);
+  });
+
+  test("mounted, willUnmount, onMounted, onWillUnmount order, part 2", async () => {
+    const steps: string[] = [];
+    function useMyHook() {
+      onMounted(() => {
+        steps.push("hook:mounted");
+      });
+      onWillUnmount(() => {
+        steps.push("hook:willunmount");
+      });
+    }
+    class MyComponent extends Component<any, any> {
+      static template = xml`<div>hey</div>`;
+      constructor(env) {
+        super(env);
+        useMyHook();
+      }
+      mounted() {
+        steps.push("comp:mounted");
+      }
+      willUnmount() {
+        steps.push("comp:willunmount");
+      }
+    }
+
+    class Parent extends Component<any, any> {
+      static template = xml`<div><MyComponent t-if="state.flag"/></div>`;
+      static components = { MyComponent };
+      state = useState({ flag: true });
+    }
+
+    const parent = new Parent(env);
+    await parent.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>hey</div></div>");
+    parent.state.flag = false;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div></div>");
+
+    expect(steps).toEqual(["comp:mounted", "hook:mounted", "hook:willunmount", "comp:willunmount"]);
+  });
+
+  test("two different call to mounted/willunmount should work", async () => {
+    const steps: string[] = [];
+    function useMyHook(i) {
+      onMounted(() => {
+        steps.push("hook:mounted" + i);
+      });
+      onWillUnmount(() => {
+        steps.push("hook:willunmount" + i);
+      });
+    }
+    class MyComponent extends Component<any, any> {
+      static template = xml`<div>hey</div>`;
+      constructor(env) {
+        super(env);
+        useMyHook(1);
+        useMyHook(2);
+      }
+    }
+    const component = new MyComponent(env);
+    await component.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>hey</div>");
+    component.unmount();
+    expect(fixture.innerHTML).toBe("");
+    expect(steps).toEqual([
+      "hook:mounted1",
+      "hook:mounted2",
+      "hook:willunmount2",
+      "hook:willunmount1"
+    ]);
+  });
+
+  test("useRef hook", async () => {
+    class Counter extends Component<any, any> {
+      static template = xml`<div><button t-ref="button"><t t-esc="value"/></button></div>`;
+      button = useRef("button");
+      value = 0;
+      increment() {
+        this.value++;
+        (this.button.el as HTMLButtonElement).innerHTML = String(this.value);
+      }
+    }
+    const counter = new Counter(env);
+    await counter.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><button>0</button></div>");
+    counter.increment();
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><button>1</button></div>");
+  });
+
+  test("useRef hook is null if ref is removed ", async () => {
+    expect.assertions(4);
+    class TestRef extends Component<any, any> {
+      static template = xml`<div><span t-if="state.flag" t-ref="span">owl</span></div>`;
+      spanRef = useRef("span");
+      state = useState({ flag: true });
+      willPatch() {
+        expect(this.spanRef.el).not.toBeNull();
+      }
+      patched() {
+        expect(this.spanRef.el).toBeNull();
+      }
+    }
+    const component = new TestRef(env);
+    await component.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><span>owl</span></div>");
+    component.state.flag = false;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div></div>");
+  });
+
+  test("can use onPatched, onWillPatch", async () => {
+    const steps: string[] = [];
+    function useMyHook() {
+      onWillPatch(() => {
+        steps.push("willPatch");
+      });
+      onPatched(() => {
+        steps.push("patched");
+      });
+    }
+
+    class MyComponent extends Component<any, any> {
+      static template = xml`<div><t t-if="state.flag">hey</t></div>`;
+      state = useState({ flag: true });
+
+      constructor(env) {
+        super(env);
+        useMyHook();
+      }
+    }
+
+    const component = new MyComponent(env);
+    await component.mount(fixture);
+    expect(component).not.toHaveProperty("patched");
+    expect(component).not.toHaveProperty("willPatch");
+    expect(steps).toEqual([]);
+
+    expect(fixture.innerHTML).toBe("<div>hey</div>");
+    component.state.flag = false;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div></div>");
+
+    expect(steps).toEqual(["willPatch", "patched"]);
+  });
+
+  test("patched, willPatch, onPatched, onWillPatch order", async () => {
+    const steps: string[] = [];
+    function useMyHook() {
+      onPatched(() => {
+        steps.push("hook:patched");
+      });
+      onWillPatch(() => {
+        steps.push("hook:willPatch");
+      });
+    }
+    class MyComponent extends Component<any, any> {
+      static template = xml`<div><t t-if="state.flag">hey</t></div>`;
+      state = useState({ flag: true });
+
+      constructor(env) {
+        super(env);
+        useMyHook();
+      }
+      willPatch() {
+        steps.push("comp:willPatch");
+      }
+      patched() {
+        steps.push("comp:patched");
+      }
+    }
+    const component = new MyComponent(env);
+    await component.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>hey</div>");
+    component.state.flag = false;
+    await nextTick();
+
+    expect(steps).toEqual(["hook:willPatch", "comp:willPatch", "comp:patched", "hook:patched"]);
+  });
+
+  test("two different call to willPatch/patched should work", async () => {
+    const steps: string[] = [];
+    function useMyHook(i) {
+      onPatched(() => {
+        steps.push("hook:patched" + i);
+      });
+      onWillPatch(() => {
+        steps.push("hook:willPatch" + i);
+      });
+    }
+    class MyComponent extends Component<any, any> {
+      static template = xml`<div>hey<t t-esc="state.value"/></div>`;
+      state = useState({ value: 1 });
+      constructor(env) {
+        super(env);
+        useMyHook(1);
+        useMyHook(2);
+      }
+    }
+    const component = new MyComponent(env);
+    await component.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>hey1</div>");
+    component.state.value++;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div>hey2</div>");
+
+    expect(steps).toEqual(["hook:willPatch2", "hook:willPatch1", "hook:patched1", "hook:patched2"]);
+  });
+
+  describe("autofocus hook", () => {
+    function useAutofocus(name) {
+      let ref = useRef(name);
+      let isInDom = false;
+      function updateFocus() {
+        if (!isInDom && ref.el) {
+          isInDom = true;
+          ref.el.focus();
+        } else if (isInDom && !ref.el) {
+          isInDom = false;
+        }
+      }
+      onPatched(updateFocus);
+      onMounted(updateFocus);
+    }
+
+    test("simple input", async () => {
+      class SomeComponent extends Component<any, any> {
+        static template = xml`
+            <div>
+                <input t-ref="input1"/>
+                <input t-ref="input2"/>
+            </div>`;
+
+        constructor(env) {
+          super(env);
+          useAutofocus("input2");
+        }
+      }
+
+      const component = new SomeComponent(env);
+      await component.mount(fixture);
+      expect(fixture.innerHTML).toBe("<div><input><input></div>");
+      const input2 = fixture.querySelectorAll("input")[1];
+      expect(input2).toBe(document.activeElement);
+    });
+
+    test("input in a t-if", async () => {
+      class SomeComponent extends Component<any, any> {
+        static template = xml`
+            <div>
+                <input t-ref="input1"/>
+                <t t-if="state.flag"><input t-ref="input2"/></t>
+            </div>`;
+
+        state = useState({ flag: false });
+        constructor(env) {
+          super(env);
+          useAutofocus("input2");
+        }
+      }
+
+      const component = new SomeComponent(env);
+      await component.mount(fixture);
+      expect(fixture.innerHTML).toBe("<div><input></div>");
+      expect(document.activeElement).toBe(document.body);
+
+      component.state.flag = true;
+      await nextTick();
+      const input2 = fixture.querySelectorAll("input")[1];
+      expect(input2).toBe(document.activeElement);
+    });
+  });
+
+  test("can use sub env", async () => {
+    class TestComponent extends Component<any, any> {
+      static template = xml`<div><t t-esc="env.val"/></div>`;
+      constructor(env) {
+        super(env);
+        useSubEnv({ val: 3 });
+      }
+    }
+    const component = new TestComponent(env);
+    await component.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>3</div>");
+    expect(env).not.toHaveProperty("val");
+    expect(component.env).toHaveProperty("val");
+  });
+
+  test("parent and child env", async () => {
+    class Child extends Component<any, any> {
+      static template = xml`<div><t t-esc="env.val"/></div>`;
+      constructor(env) {
+        super(env);
+        useSubEnv({ val: 5 });
+      }
+    }
+
+    class Parent extends Component<any, any> {
+      static template = xml`<div><t t-esc="env.val"/><Child/></div>`;
+      static components = { Child };
+      constructor(env) {
+        super(env);
+        useSubEnv({ val: 3 });
+      }
+    }
+    const component = new Parent(env);
+    await component.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>3<div>5</div></div>");
+  });
+
+  test("can use onWillStart, onWillUpdateProps", async () => {
+    const steps: string[] = [];
+    function useMyHook() {
+      onWillStart(() => {
+        steps.push("onWillStart");
+      });
+      onWillUpdateProps(nextProps => {
+        expect(nextProps).toEqual({ value: 2 });
+        steps.push("onWillUpdateProps");
+      });
+    }
+    class MyComponent extends Component<any, any> {
+      static template = xml`<span><t t-esc="props.value"/></span>`;
+      constructor(parent, props) {
+        super(parent, props);
+        useMyHook();
+      }
+    }
+    class App extends Component<any, any> {
+      static template = xml`<div><MyComponent value="state.value"/></div>`;
+      static components = { MyComponent };
+      state = useState({ value: 1 });
+    }
+
+    const app = new App(env);
+    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"]);
+
+    app.state.value = 2;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><span>2</span></div>");
+    expect(steps).toEqual(["onWillStart", "onWillUpdateProps"]);
+  });
+});
@@ -0,0 +1,189 @@
+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";
+
+//------------------------------------------------------------------------------
+// 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();
+});
+
+afterEach(() => {
+  fixture.remove();
+});
+
+describe("Asyncroot", () => {
+  test("delayed component with AsyncRoot component", async () => {
+    let def;
+    class Child extends Component<any, any> {
+      static template = xml`<span><t t-esc="props.val"/></span>`;
+    }
+    class AsyncChild extends Child {
+      willUpdateProps() {
+        return def;
+      }
+    }
+    class Parent extends Component<any, any> {
+      static template = xml`
+          <div>
+            <button t-on-click="updateApp">Update App State</button>
+            <div class="children">
+              <Child val="state.val"/>
+              <AsyncRoot>
+                  <AsyncChild val="state.val"/>
+              </AsyncRoot>
+            </div>
+          </div>`;
+      static components = { Child, AsyncChild, AsyncRoot };
+      state = useState({ val: 0 });
+
+      updateApp() {
+        this.state.val++;
+      }
+    }
+
+    const parent = new Parent(env);
+    await parent.mount(fixture);
+
+    expect(fixture.querySelector(".children")!.innerHTML).toBe("<span>0</span><span>0</span>");
+
+    // click on button to increment Parent counter
+    def = makeDeferred();
+    fixture.querySelector("button")!.click();
+    await nextTick();
+
+    expect(fixture.querySelector(".children")!.innerHTML).toBe("<span>1</span><span>0</span>");
+
+    def.resolve();
+    await nextTick();
+
+    expect(fixture.querySelector(".children")!.innerHTML).toBe("<span>1</span><span>1</span>");
+  });
+
+  test("fast component with AsyncRoot", async () => {
+    let def;
+    class Child extends Component<any, any> {
+      static template = xml`<span><t t-esc="props.val"/></span>`;
+    }
+    class AsyncChild extends Child {
+      willUpdateProps() {
+        return def;
+      }
+    }
+
+    class Parent extends Component<any, any> {
+      static template = xml`
+          <div>
+            <button t-on-click="updateApp">Update App State</button>
+            <div class="children">
+              <AsyncRoot>
+                <Child val="state.val"/>
+              </AsyncRoot>
+              <AsyncChild val="state.val"/>
+            </div>
+          </div>`;
+      static components = { Child, AsyncChild, AsyncRoot };
+      state = useState({ val: 0 });
+
+      updateApp() {
+        this.state.val++;
+      }
+    }
+
+    const parent = new Parent(env);
+    await parent.mount(fixture);
+
+    expect(fixture.querySelector(".children")!.innerHTML).toBe("<span>0</span><span>0</span>");
+
+    // click on button to increment Parent counter
+    def = makeDeferred();
+    fixture.querySelector("button")!.click();
+    await nextTick();
+
+    expect(fixture.querySelector(".children")!.innerHTML).toBe("<span>1</span><span>0</span>");
+
+    def.resolve();
+    await nextTick();
+
+    expect(fixture.querySelector(".children")!.innerHTML).toBe("<span>1</span><span>1</span>");
+  });
+
+  test("asyncroot component: mixed re-renderings", async () => {
+    let def;
+    class Child extends Component<any, any> {
+      static template = xml`
+        <span t-on-click="increment">
+          <t t-esc="state.val"/>/<t t-esc="props.val"/>
+        </span>`;
+      state = useState({ val: 0 });
+
+      increment() {
+        this.state.val++;
+      }
+    }
+    class AsyncChild extends Child {
+      willUpdateProps() {
+        return def;
+      }
+    }
+    class Parent extends Component<any, any> {
+      static template = xml`
+        <div>
+          <button t-on-click="updateApp">Update App State</button>
+          <div class="children">
+            <Child val="state.val"/>
+            <AsyncRoot>
+              <AsyncChild val="state.val"/>
+            </AsyncRoot>
+          </div>
+        </div>`;
+      static components = { Child, AsyncChild, AsyncRoot };
+      state = useState({ val: 0 });
+
+      updateApp() {
+        this.state.val++;
+      }
+    }
+
+    const parent = new Parent(env);
+    await parent.mount(fixture);
+
+    expect(fixture.querySelector(".children")!.innerHTML).toBe("<span>0/0</span><span>0/0</span>");
+
+    // click on button to increment Parent counter
+    def = makeDeferred();
+    fixture.querySelector("button")!.click();
+    await nextTick();
+
+    expect(fixture.querySelector(".children")!.innerHTML).toBe("<span>0/1</span><span>0/0</span>");
+
+    // click on each Child to increment their local counter
+    const children = parent.el!.querySelectorAll("span");
+    children[0]!.click();
+    await nextTick();
+    expect(fixture.querySelector(".children")!.innerHTML).toBe("<span>1/1</span><span>0/0</span>");
+
+    children[1]!.click();
+    await nextTick();
+    expect(fixture.querySelector(".children")!.innerHTML).toBe("<span>1/1</span><span>0/0</span>");
+
+    // finalize first re-rendering (coming from the props update)
+    def.resolve();
+    await nextTick();
+
+    expect(fixture.querySelector(".children")!.innerHTML).toBe("<span>1/1</span><span>1/1</span>");
+  });
+});
@@ -1,321 +0,0 @@
-import { Observer } from "../src/observer";
-import { nextMicroTick } from "./helpers";
-
-describe("observer", () => {
-  test("properly observe objects", () => {
-    const observer = new Observer();
-    const obj: any = {};
-
-    observer.observe(obj);
-    expect(obj.__owl__.rev).toBe(1);
-    expect(observer.rev).toBe(1);
-
-    const ob2: any = { a: 1 };
-    observer.observe(ob2);
-    expect(ob2.__owl__.rev).toBe(1);
-    ob2.a = 2;
-    expect(observer.rev).toBe(2);
-    expect(ob2.__owl__.rev).toBe(2);
-
-    ob2.b = 3;
-    expect(observer.rev).toBe(2);
-    expect(ob2.__owl__.rev).toBe(2);
-
-    observer.set(ob2, "b", 4);
-    expect(observer.rev).toBe(3);
-    expect(ob2.__owl__.rev).toBe(3);
-  });
-
-  test("properly handle null or undefined", () => {
-    const observer = new Observer();
-    const obj: any = { a: null, b: undefined };
-
-    observer.observe(obj);
-    expect(obj.__owl__.rev).toBe(1);
-    expect(observer.rev).toBe(1);
-
-    obj.a = 3;
-    expect(obj.__owl__.rev).toBe(2);
-
-    obj.b = 5;
-    expect(obj.__owl__.rev).toBe(3);
-
-    obj.a = null;
-    obj.b = undefined;
-    expect(obj.__owl__.rev).toBe(5);
-  });
-
-  test("can change values in array", () => {
-    const observer = new Observer();
-    const obj: any = { arr: [1, 2] };
-
-    observer.observe(obj);
-    expect(obj.arr.__owl__.rev).toBe(1);
-    expect(observer.rev).toBe(1);
-
-    obj.arr[0] = "nope";
-    expect(obj.arr.__owl__.rev).toBe(1);
-    expect(observer.rev).toBe(1);
-
-    observer.set(obj.arr, 0, "yep");
-    expect(obj.arr.__owl__.rev).toBe(2);
-    expect(observer.rev).toBe(2);
-  });
-
-  test("various object property changes", () => {
-    const observer = new Observer();
-    const obj: any = { a: 1 };
-    observer.observe(obj);
-    expect(obj.__owl__.rev).toBe(1);
-    obj.a = 2;
-    expect(observer.rev).toBe(2);
-    expect(obj.__owl__.rev).toBe(2);
-
-    // same value again
-    obj.a = 2;
-    expect(observer.rev).toBe(2);
-    expect(obj.__owl__.rev).toBe(2);
-
-    obj.a = 3;
-    expect(observer.rev).toBe(3);
-    expect(obj.__owl__.rev).toBe(3);
-  });
-
-  test("properly observe arrays", () => {
-    const observer = new Observer();
-    const arr: any = [];
-    observer.observe(arr);
-    expect(arr.__owl__.rev).toBe(1);
-    expect(observer.rev).toBe(1);
-    expect(arr.length).toBe(0);
-
-    arr.push(1);
-    expect(arr.__owl__.rev).toBe(2);
-    expect(observer.rev).toBe(2);
-    expect(arr.length).toBe(1);
-
-    arr.splice(1, 0, "hey");
-    expect(arr.__owl__.rev).toBe(3);
-    expect(observer.rev).toBe(3);
-    expect(arr.length).toBe(2);
-
-    arr.unshift("lindemans");
-    expect(arr.__owl__.rev).toBe(4);
-
-    arr.reverse();
-    expect(arr.__owl__.rev).toBe(5);
-
-    arr.pop();
-    expect(arr.__owl__.rev).toBe(6);
-
-    arr.shift();
-    expect(arr.__owl__.rev).toBe(7);
-
-    arr.sort();
-    expect(arr.__owl__.rev).toBe(8);
-
-    expect(arr).toEqual([1]);
-  });
-
-  test("object pushed into arrays are observed", () => {
-    const observer = new Observer();
-    const arr: any = [];
-    observer.observe(arr);
-    expect(observer.rev).toBe(1);
-
-    arr.push({ kriek: 5 });
-    expect(observer.rev).toBe(2);
-    expect(arr.__owl__.rev).toBe(2);
-    expect(arr[0].__owl__.rev).toBe(1);
-
-    arr[0].kriek = 6;
-    expect(observer.rev).toBe(3);
-    expect(arr.__owl__.rev).toBe(2);
-    expect(arr[0].__owl__.rev).toBe(2);
-  });
-
-  test("properly observe arrays in object", () => {
-    const observer = new Observer();
-    const state: any = { arr: [] };
-    observer.observe(state);
-    expect(state.arr.__owl__.rev).toBe(1);
-    expect(observer.rev).toBe(1);
-    expect(state.arr.length).toBe(0);
-
-    state.arr.push(1);
-    expect(state.arr.__owl__.rev).toBe(2);
-    expect(observer.rev).toBe(2);
-    expect(state.arr.length).toBe(1);
-  });
-
-  test("properly observe objects in array", () => {
-    const observer = new Observer();
-    const state: any = { arr: [{ something: 1 }] };
-    observer.observe(state);
-    expect(state.arr.__owl__.rev).toBe(1);
-    expect(state.arr[0].__owl__.rev).toBe(1);
-
-    state.arr[0].something = 2;
-    expect(state.arr.__owl__.rev).toBe(1);
-    expect(state.arr[0].__owl__.rev).toBe(2);
-  });
-
-  test("properly observe objects in object", () => {
-    const observer = new Observer();
-    const state: any = { a: { b: 1 } };
-    observer.observe(state);
-    expect(state.__owl__.rev).toBe(1);
-    expect(state.a.__owl__.rev).toBe(1);
-
-    state.a.b = 2;
-    expect(state.__owl__.rev).toBe(1);
-    expect(state.a.__owl__.rev).toBe(2);
-  });
-
-  test("reobserve new object values", () => {
-    const observer = new Observer();
-    const obj: any = { a: 1 };
-    observer.observe(obj);
-    expect(obj.__owl__.rev).toBe(1);
-    obj.a = { b: 2 };
-    expect(observer.rev).toBe(2);
-    expect(obj.__owl__.rev).toBe(2);
-    expect(obj.a.__owl__.rev).toBe(1);
-
-    obj.a.b = 3;
-    expect(observer.rev).toBe(3);
-    expect(obj.__owl__.rev).toBe(2);
-    expect(obj.a.__owl__.rev).toBe(2);
-  });
-
-  test("deep observe misc changes", () => {
-    const observer = new Observer();
-    const state: any = { o: { a: 1 }, arr: [1], n: 13 };
-    observer.observe(state);
-    expect(state.__owl__.rev).toBe(1);
-    expect(state.__owl__.deepRev).toBe(1);
-
-    state.o.a = 2;
-    expect(observer.rev).toBe(2);
-    expect(state.__owl__.rev).toBe(1);
-    expect(state.__owl__.deepRev).toBe(2);
-
-    state.arr.push(2);
-    expect(state.__owl__.rev).toBe(1);
-    expect(state.__owl__.deepRev).toBe(3);
-
-    state.n = 155;
-    expect(state.__owl__.rev).toBe(2);
-    expect(state.__owl__.deepRev).toBe(4);
-  });
-
-  test("properly handle already observed state", () => {
-    const observer = new Observer();
-    const obj1: any = { a: 1 };
-    const obj2: any = { b: 1 };
-    observer.observe(obj1);
-    observer.observe(obj2);
-    expect(obj1.__owl__.rev).toBe(1);
-    expect(obj2.__owl__.rev).toBe(1);
-
-    obj1.a = 2;
-    obj2.b = 3;
-    expect(obj1.__owl__.rev).toBe(2);
-    expect(obj2.__owl__.rev).toBe(2);
-
-    obj2.b = obj1;
-    expect(obj1.__owl__.rev).toBe(2);
-    expect(obj2.__owl__.rev).toBe(3);
-  });
-
-  test("properly handle swapping elements", () => {
-    const observer = new Observer();
-    const obj: any = { a: { arr: [] }, b: 1 };
-    observer.observe(obj);
-
-    // swap a and b
-    const b = obj.b;
-    obj.b = obj.a;
-    obj.a = b;
-    expect(observer.rev).toBe(3);
-
-    // push something into array to make sure it works
-    obj.b.arr.push("blanche");
-    expect(observer.rev).toBe(4);
-  });
-
-  test("properly handle assigning observed obj containing array", () => {
-    const observer = new Observer();
-    const obj: any = { a: { arr: [], val: "test" } };
-    observer.observe(obj);
-
-    obj.a = { ...obj.a, val: "test2" };
-    expect(observer.rev).toBe(2);
-
-    // push something into array to make sure it works
-    obj.a.arr.push("blanche");
-    expect(observer.rev).toBe(3);
-  });
-
-  test("accept cycles in observed state", () => {
-    const observer = new Observer();
-    const obj1: any = {};
-    const obj2: any = { b: obj1, key: 1 };
-    obj1.a = obj2;
-    observer.observe(obj1);
-    expect(obj1.__owl__.rev).toBe(1);
-    expect(obj2.__owl__.rev).toBe(1);
-
-    obj2.key = 3;
-    expect(obj1.__owl__.rev).toBe(1);
-    expect(obj2.__owl__.rev).toBe(2);
-  });
-
-  test("call callback when state is changed", async () => {
-    const observer = new Observer();
-    observer.notifyCB = jest.fn();
-    const obj: any = { a: 1, b: { c: 2 }, d: [{ e: 3 }], f: 4 };
-
-    observer.observe(obj);
-    expect(observer.notifyCB).toBeCalledTimes(0);
-
-    obj.a = 2;
-    await nextMicroTick();
-    expect(observer.notifyCB).toBeCalledTimes(1);
-
-    obj.b.c = 3;
-    await nextMicroTick();
-    expect(observer.notifyCB).toBeCalledTimes(2);
-
-    obj.d[0].e = 5;
-    await nextMicroTick();
-    expect(observer.notifyCB).toBeCalledTimes(3);
-
-    obj.a = 111;
-    obj.f = 222;
-    await nextMicroTick();
-    expect(observer.notifyCB).toBeCalledTimes(4);
-  });
-
-  test("throw error when state is mutated in object if allowMutation=false", async () => {
-    const observer = new Observer();
-    observer.allowMutations = false;
-    const obj: any = { a: 1 };
-    observer.observe(obj);
-
-    expect(() => {
-      obj.a = 2;
-    }).toThrow('Observed state cannot be changed here! (key: "a", val: "2")');
-  });
-
-  test("throw error when state is mutated in array if allowMutation=false", async () => {
-    const observer = new Observer();
-    observer.allowMutations = false;
-    const obj: any = { a: [1] };
-    observer.observe(obj);
-
-    expect(() => {
-      obj.a.push(2);
-    }).toThrow("Array cannot be changed here");
-  });
-});
@@ -0,0 +1,158 @@
+import { compileExpr, tokenize } from "../../src/qweb/expression_parser";
+
+describe("tokenizer", () => {
+  test("simple tokens", () => {
+    expect(tokenize("1.3")).toEqual([{ type: "VALUE", value: "1.3" }]);
+
+    expect(tokenize("{}")).toEqual([
+      { type: "LEFT_BRACE", value: "{" },
+      { type: "RIGHT_BRACE", value: "}" }
+    ]);
+    expect(tokenize("{ }}")).toEqual([
+      { type: "LEFT_BRACE", value: "{" },
+      { type: "RIGHT_BRACE", value: "}" },
+      { type: "RIGHT_BRACE", value: "}" }
+    ]);
+    expect(tokenize("a")).toEqual([{ type: "SYMBOL", value: "a" }]);
+    expect(tokenize("true")).toEqual([{ type: "SYMBOL", value: "true" }]);
+    expect(tokenize("abcde")).toEqual([{ type: "SYMBOL", value: "abcde" }]);
+    expect(tokenize("_ab2")).toEqual([{ type: "SYMBOL", value: "_ab2" }]);
+    expect(tokenize("$ab2")).toEqual([{ type: "SYMBOL", value: "$ab2" }]);
+    expect(tokenize("ABC")).toEqual([{ type: "SYMBOL", value: "ABC" }]);
+
+    expect(tokenize("{a: 2}")).toEqual([
+      { type: "LEFT_BRACE", value: "{" },
+      { type: "SYMBOL", value: "a" },
+      { type: "COLON", value: ":" },
+      { type: "VALUE", value: "2" },
+      { type: "RIGHT_BRACE", value: "}" }
+    ]);
+    expect(tokenize("a,")).toEqual([{ type: "SYMBOL", value: "a" }, { type: "COMMA", value: "," }]);
+    expect(tokenize("][")).toEqual([
+      { type: "RIGHT_BRACKET", value: "]" },
+      { type: "LEFT_BRACKET", value: "[" }
+    ]);
+  });
+
+  test("various operators", () => {
+    expect(tokenize(">= <= < > !== !=")).toEqual([
+      { type: "OPERATOR", value: ">=" },
+      { type: "OPERATOR", value: "<=" },
+      { type: "OPERATOR", value: "<" },
+      { type: "OPERATOR", value: ">" },
+      { type: "OPERATOR", value: "!==" },
+      { type: "OPERATOR", value: "!=" }
+    ]);
+  });
+
+  test("strings", () => {
+    expect(() => tokenize("'")).toThrow("Invalid expression");
+    expect(() => tokenize("'\\")).toThrow("Invalid expression");
+    expect(() => tokenize("'\\'")).toThrow("Invalid expression");
+    expect(tokenize("'hello ged'")).toEqual([{ type: "VALUE", value: "'hello ged'" }]);
+    expect(tokenize("'hello \\'ged\\''")).toEqual([{ type: "VALUE", value: "'hello \\'ged\\''" }]);
+
+    expect(() => tokenize('"')).toThrow("Invalid expression");
+    expect(() => tokenize('"\\"')).toThrow("Invalid expression");
+    expect(tokenize('"hello ged"')).toEqual([{ type: "VALUE", value: '"hello ged"' }]);
+    expect(tokenize('"hello ged"}')).toEqual([
+      { type: "VALUE", value: '"hello ged"' },
+      { type: "RIGHT_BRACE", value: "}" }
+    ]);
+    expect(tokenize('"hello \\"ged\\""')).toEqual([{ type: "VALUE", value: '"hello \\"ged\\""' }]);
+  });
+});
+
+describe("expression evaluation", () => {
+  test("simple static values", () => {
+    expect(compileExpr("1", {})).toBe("1");
+    expect(compileExpr("1 ", {})).toBe("1");
+    expect(compileExpr("'some string#/, {' ", {})).toBe("'some string#/, {'");
+    expect(compileExpr("{ } ", {})).toBe("{}");
+    expect(compileExpr("{a: 1} ", {})).toBe("{a:1}");
+    expect(compileExpr("{a: 1, b: 2   } ", {})).toBe("{a:1,b:2}");
+    expect(compileExpr("[] ", {})).toBe("[]");
+    expect(compileExpr("[1] ", {})).toBe("[1]");
+    expect(compileExpr("['1', '2'] ", {})).toBe("['1','2']");
+    expect(compileExpr("['1', \"2\"] ", {})).toBe("['1',\"2\"]");
+  });
+
+  test("various types of 'words'", () => {
+    expect(compileExpr("true", {})).toBe("true");
+    expect(compileExpr("false", {})).toBe("false");
+    expect(compileExpr("debugger", {})).toBe("debugger");
+  });
+
+  test("parenthesis", () => {
+    expect(compileExpr("(1)", {})).toBe("(1)");
+    expect(compileExpr("a*(1 +3)", {})).toBe("context['a']*(1+3)");
+  });
+
+  test("objects and sub objects", () => {
+    expect(compileExpr("{a:{b:1}} ", {})).toBe("{a:{b:1}}");
+  });
+
+  test("replacing variables", () => {
+    expect(compileExpr("a", {})).toBe("context['a']");
+    expect(compileExpr("a", { a: { id: "_3", expr: "" } })).toBe("_3");
+  });
+
+  test("arrays and objects", () => {
+    expect(compileExpr("[{b:1}] ", {})).toBe("[{b:1}]");
+    expect(compileExpr("{a: []} ", {})).toBe("{a:[]}");
+    expect(compileExpr("[{b:1, c: [1, {d: {e: 3}} ]}] ", {})).toBe("[{b:1,c:[1,{d:{e:3}}]}]");
+  });
+
+  test("dot operator", () => {
+    expect(compileExpr("a.b", {})).toBe("context['a'].b");
+    expect(compileExpr("a.b.c", {})).toBe("context['a'].b.c");
+  });
+
+  test("various unary operators", () => {
+    expect(compileExpr("!flag", {})).toBe("!context['flag']");
+    expect(compileExpr("-3", {})).toBe("-3");
+    expect(compileExpr("-a", {})).toBe("-context['a']");
+  });
+
+  test("various binary operators", () => {
+    expect(compileExpr("color == 'black'", {})).toBe("context['color']=='black'");
+    expect(compileExpr("a || b", {})).toBe("context['a']||context['b']");
+    expect(compileExpr("color === 'black'", {})).toBe("context['color']==='black'");
+    expect(compileExpr("'li_'+item", {})).toBe("'li_'+context['item']");
+    expect(compileExpr("state.val > 1", {})).toBe("context['state'].val>1");
+  });
+
+  test("boolean operations", () => {
+    expect(compileExpr("a && b", {})).toBe("context['a']&&context['b']");
+  });
+
+  test("ternary operators", () => {
+    expect(compileExpr("a ? b: '2'", {})).toBe("context['a']?context['b']:'2'");
+    expect(compileExpr("a ? b: (c or '2') ", {})).toBe(
+      "context['a']?context['b']:(context['c']||'2')"
+    );
+    expect(compileExpr("a ? {test:c}: [1,u]", {})).toBe(
+      "context['a']?{test:context['c']}:[1,context['u']]"
+    );
+  });
+
+  test("word replacement", () => {
+    expect(compileExpr("a or b", {})).toBe("context['a']||context['b']");
+    expect(compileExpr("a and b", {})).toBe("context['a']&&context['b']");
+  });
+
+  test("function calls", () => {
+    expect(compileExpr("a()", {})).toBe("context['a']()");
+    expect(compileExpr("a(1)", {})).toBe("context['a'](1)");
+    expect(compileExpr("a(1,2)", {})).toBe("context['a'](1,2)");
+    expect(compileExpr("a(1,2,{a:[a]})", {})).toBe("context['a'](1,2,{a:[context['a']]})");
+    expect(compileExpr("'x'.toUpperCase()", {})).toBe("'x'.toUpperCase()");
+    expect(compileExpr("'x'.toUpperCase({a: 3})", {})).toBe("'x'.toUpperCase({a:3})");
+    expect(compileExpr("'x'.toUpperCase(a)", { a: { id: "_v5", expr: "" } })).toBe(
+      "'x'.toUpperCase(_v5)"
+    );
+    expect(compileExpr("'x'.toUpperCase({b: a})", { a: { id: "_v5", expr: "" } })).toBe(
+      "'x'.toUpperCase({b:_v5})"
+    );
+  });
+});
--- a/Show More
+++ b/Show More