[REL] v1.4.10

#v1.4.10

- fix: make arrow function capture backwards-compatible

.github/workflows/deploy.yml

@@ -0,0 +1,27 @@
+# This workflow will do a clean install of node dependencies, build the source code and run tests across different versions of node
+# For more information see: https://help.github.com/actions/language-and-framework-guides/using-nodejs-with-github-actions
+
+name: Node.js CI
+
+on:
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        node-version: [12.x, 14.x, 16.x]
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Use Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v1
+      with:
+        node-version: ${{ matrix.node-version }}
+    - run: npm install
+    - run: npm run test
+    - run: npm run check-formatting

.gitignore

@@ -1,5 +1,6 @@
 /node_modules
 /dist
+
 npm-debug.log
 
 # misc
@@ -14,4 +15,20 @@ yarn-debug.log*
 yarn-error.log*
 
 package-lock.json
-.vscode
+yarn.lock
+
+#ide's
+.vscode
+.idea
+
+node_modules
+
+# Extras temp file
+/tools/owl.js
+
+release-notes.md
+
+.rpt2_cache
+
+# useful in some cases
+/temp

.jshintrc

@@ -0,0 +1,3 @@
+{
+  "esversion": 9
+}

COPYRIGHT

@@ -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.

LICENSE

@@ -0,0 +1,856 @@
+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 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.
+
+**************************************************************************
+
+                   GNU LESSER GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
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+
+
+**************************************************************************

README.md

@@ -0,0 +1,131 @@
+<h1 align="center">🦉 <a href="https://odoo.github.io/owl/">OWL Framework</a> 🦉</h1>
+
+ [![License: LGPL v3](https://img.shields.io/badge/License-LGPL%20v3-blue.svg)](https://www.gnu.org/licenses/lgpl-3.0)
+[![npm version](https://badge.fury.io/js/@odoo%2Fowl.svg)](https://badge.fury.io/js/@odoo%2Fowl)
+[![Downloads](https://img.shields.io/npm/dm/@odoo%2Fowl.svg)](https://www.npmjs.com/package/@odoo/owl)
+
+_Class based components with hooks, reactive state and concurrent mode_
+
+## Project Overview
+
+The Odoo Web Library (OWL) is a smallish (~<20kb gzipped) UI framework intended to
+be the basis for the [Odoo](https://www.odoo.com/) Web Client. Owl is a modern
+framework, written in Typescript, taking the best ideas from React and Vue in a
+simple and consistent way. Owl's main features are:
+
+- a declarative component system,
+- a reactivity system based on hooks,
+- concurrent mode by default,
+- a store and a frontend router
+
+Owl components are defined with ES6 classes, they use QWeb templates, an
+underlying virtual DOM, integrates beautifully with hooks, and the rendering is
+asynchronous.
+
+**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 stable.  Possible future changes are explained in the
+[roadmap](roadmap.md).
+
+## Why Owl?
+
+Why did Odoo decide to make Yet Another Framework?  This is really a question
+that deserves [a long answer](doc/miscellaneous/why_owl.md). But in short, we believe that
+while the current state of the art frameworks are excellent, they are not
+optimized for our use case, and there is still room for something else.
+
+If you are interested in a comparison with React or Vue, you will
+find some more additional information [here](doc/miscellaneous/comparison.md).
+
+## Example
+
+Here is a short example to illustrate interactive components:
+
+```javascript
+const { Component, useState, mount } = 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 };
+}
+
+mount(App, { target: 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 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
+  dynamically with `xpaths`.
+- **templates compilation in the browser**: this may not be a good fit for all
+  applications, but if you need to generate dynamically user interfaces in the
+  browser, this is very powerful. For example, a generic form view component
+  could generate a specific form user interface for each various models, from a XML view.
+- **no toolchain required**: this is extremely useful for some applications, if,
+  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 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). There is no black magic. It just
+works.
+
+
+## Documentation
+
+A complete documentation for Owl can be found here:
+
+- [Main documentation page](doc/readme.md).
+
+Some of the most important pages are:
+
+- [Tutorial: TodoList application](doc/learning/tutorial_todoapp.md)
+- [How to start an Owl project](doc/learning/quick_start.md)
+- [QWeb templating language](doc/reference/qweb_templating_language.md)
+- [Component](doc/reference/component.md)
+- [Hooks](doc/reference/hooks.md)
+
+
+## Installing Owl
+
+Owl is available on `npm` and can be installed with the following command:
+
+```
+npm install @odoo/owl
+```
+
+If you want to use a simple `<script>` tag, the last release can be downloaded here:
+
+- [owl-1.4.10](https://github.com/odoo/owl/releases/tag/v1.4.10)
+
+## License
+
+OWL is [LGPL licensed](./LICENSE).

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-input[type='submit'].button-outline:focus,
-input[type='submit'].button-outline:hover {
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-}
-
-.button.button-outline[disabled]:focus, .button.button-outline[disabled]:hover,
-button.button-outline[disabled]:focus,
-button.button-outline[disabled]:hover,
-input[type='button'].button-outline[disabled]:focus,
-input[type='button'].button-outline[disabled]:hover,
-input[type='reset'].button-outline[disabled]:focus,
-input[type='reset'].button-outline[disabled]:hover,
-input[type='submit'].button-outline[disabled]:focus,
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-
-.button.button-clear,
-button.button-clear,
-input[type='button'].button-clear,
-input[type='reset'].button-clear,
-input[type='submit'].button-clear {
-  background-color: transparent;
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-  color: #9b4dca;
-}
-
-.button.button-clear:focus, .button.button-clear:hover,
-button.button-clear:focus,
-button.button-clear:hover,
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-input[type='reset'].button-clear:hover,
-input[type='submit'].button-clear:focus,
-input[type='submit'].button-clear:hover {
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-}
-
-.button.button-clear[disabled]:focus, .button.button-clear[disabled]:hover,
-button.button-clear[disabled]:focus,
-button.button-clear[disabled]:hover,
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-input[type='reset'].button-clear[disabled]:focus,
-input[type='reset'].button-clear[disabled]:hover,
-input[type='submit'].button-clear[disabled]:focus,
-input[type='submit'].button-clear[disabled]:hover {
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-code {
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-input[type='number']:focus,
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-select:focus {
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-select {
-  background: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" height="14" viewBox="0 0 29 14" width="29"><path fill="#d1d1d1" d="M9.37727 3.625l5.08154 6.93523L19.54036 3.625"/></svg>') center right no-repeat;
-  padding-right: 3.0rem;
-}
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-input[type='checkbox'],
-input[type='radio'] {
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-}
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-.label-inline {
-  display: inline-block;
-  font-weight: normal;
-  margin-left: .5rem;
-}
-
-.container {
-  margin: 0 auto;
-  max-width: 112.0rem;
-  padding: 0 2.0rem;
-  position: relative;
-  width: 100%;
-}
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-.row {
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-.row.row-no-padding {
-  padding: 0;
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-.row.row-no-padding > .column {
-  padding: 0;
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-.row.row-wrap {
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-}
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-.row.row-top {
-  align-items: flex-start;
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-.row.row-bottom {
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-.row.row-center {
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-.row .column {
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-.row .column.column-offset-10 {
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-  margin-left: 20%;
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-.row .column.column-offset-25 {
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-.row .column.column-offset-33, .row .column.column-offset-34 {
-  margin-left: 33.3333%;
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-.row .column.column-offset-50 {
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-.row .column.column-offset-66, .row .column.column-offset-67 {
-  margin-left: 66.6666%;
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-  margin-left: 75%;
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-.row .column.column-offset-80 {
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-.row .column.column-offset-90 {
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-.row .column .column-center {
-  -ms-grid-row-align: center;
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-}
-
-@media (min-width: 40rem) {
-  .row {
-    flex-direction: row;
-    margin-left: -1.0rem;
-    width: calc(100% + 2.0rem);
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-  }
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-a {
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-  list-style: none;
-  margin-top: 0;
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-}
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-dl dl,
-dl ol,
-dl ul,
-ol dl,
-ol ol,
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-ul dl,
-ul ol,
-ul ul {
-  font-size: 90%;
-  margin: 1.5rem 0 1.5rem 3.0rem;
-}
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-.button,
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-  margin-bottom: 1.0rem;
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-  margin-bottom: 1.5rem;
-}
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-ul {
-  margin-bottom: 2.5rem;
-}
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-  border-spacing: 0;
-  width: 100%;
-}
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-td,
-th {
-  border-bottom: 0.1rem solid #e1e1e1;
-  padding: 1.2rem 1.5rem;
-  text-align: left;
-}
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-th:first-child {
-  padding-left: 0;
-}
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-td:last-child,
-th:last-child {
-  padding-right: 0;
-}
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-strong {
-  font-weight: bold;
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-
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-  margin-top: 0;
-}
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-h2,
-h3,
-h4,
-h5,
-h6 {
-  font-weight: 300;
-  letter-spacing: -.1rem;
-  margin-bottom: 2.0rem;
-  margin-top: 0;
-}
-
-h1 {
-  font-size: 4.6rem;
-  line-height: 1.2;
-}
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-h2 {
-  font-size: 3.6rem;
-  line-height: 1.25;
-}
-
-h3 {
-  font-size: 2.8rem;
-  line-height: 1.3;
-}
-
-h4 {
-  font-size: 2.2rem;
-  letter-spacing: -.08rem;
-  line-height: 1.35;
-}
-
-h5 {
-  font-size: 1.8rem;
-  letter-spacing: -.05rem;
-  line-height: 1.5;
-}
-
-h6 {
-  font-size: 1.6rem;
-  letter-spacing: 0;
-  line-height: 1.4;
-}
-
-img {
-  max-width: 100%;
-}
-
-.clearfix:after {
-  clear: both;
-  content: ' ';
-  display: table;
-}
-
-.float-left {
-  float: left;
-}
-
-.float-right {
-  float: right;
-}
-
-/*# sourceMappingURL=milligram.css.map */

assets/normalize.css

@@ -1,349 +0,0 @@
-/*! normalize.css v8.0.1 | MIT License | github.com/necolas/normalize.css */
-
-/* Document
-   ========================================================================== */
-
-/**
- * 1. Correct the line height in all browsers.
- * 2. Prevent adjustments of font size after orientation changes in iOS.
- */
-
-html {
-  line-height: 1.15; /* 1 */
-  -webkit-text-size-adjust: 100%; /* 2 */
-}
-
-/* Sections
-   ========================================================================== */
-
-/**
- * Remove the margin in all browsers.
- */
-
-body {
-  margin: 0;
-}
-
-/**
- * Render the `main` element consistently in IE.
- */
-
-main {
-  display: block;
-}
-
-/**
- * Correct the font size and margin on `h1` elements within `section` and
- * `article` contexts in Chrome, Firefox, and Safari.
- */
-
-h1 {
-  font-size: 2em;
-  margin: 0.67em 0;
-}
-
-/* Grouping content
-   ========================================================================== */
-
-/**
- * 1. Add the correct box sizing in Firefox.
- * 2. Show the overflow in Edge and IE.
- */
-
-hr {
-  box-sizing: content-box; /* 1 */
-  height: 0; /* 1 */
-  overflow: visible; /* 2 */
-}
-
-/**
- * 1. Correct the inheritance and scaling of font size in all browsers.
- * 2. Correct the odd `em` font sizing in all browsers.
- */
-
-pre {
-  font-family: monospace, monospace; /* 1 */
-  font-size: 1em; /* 2 */
-}
-
-/* Text-level semantics
-   ========================================================================== */
-
-/**
- * Remove the gray background on active links in IE 10.
- */
-
-a {
-  background-color: transparent;
-}
-
-/**
- * 1. Remove the bottom border in Chrome 57-
- * 2. Add the correct text decoration in Chrome, Edge, IE, Opera, and Safari.
- */
-
-abbr[title] {
-  border-bottom: none; /* 1 */
-  text-decoration: underline; /* 2 */
-  text-decoration: underline dotted; /* 2 */
-}
-
-/**
- * Add the correct font weight in Chrome, Edge, and Safari.
- */
-
-b,
-strong {
-  font-weight: bolder;
-}
-
-/**
- * 1. Correct the inheritance and scaling of font size in all browsers.
- * 2. Correct the odd `em` font sizing in all browsers.
- */
-
-code,
-kbd,
-samp {
-  font-family: monospace, monospace; /* 1 */
-  font-size: 1em; /* 2 */
-}
-
-/**
- * Add the correct font size in all browsers.
- */
-
-small {
-  font-size: 80%;
-}
-
-/**
- * Prevent `sub` and `sup` elements from affecting the line height in
- * all browsers.
- */
-
-sub,
-sup {
-  font-size: 75%;
-  line-height: 0;
-  position: relative;
-  vertical-align: baseline;
-}
-
-sub {
-  bottom: -0.25em;
-}
-
-sup {
-  top: -0.5em;
-}
-
-/* Embedded content
-   ========================================================================== */
-
-/**
- * Remove the border on images inside links in IE 10.
- */
-
-img {
-  border-style: none;
-}
-
-/* Forms
-   ========================================================================== */
-
-/**
- * 1. Change the font styles in all browsers.
- * 2. Remove the margin in Firefox and Safari.
- */
-
-button,
-input,
-optgroup,
-select,
-textarea {
-  font-family: inherit; /* 1 */
-  font-size: 100%; /* 1 */
-  line-height: 1.15; /* 1 */
-  margin: 0; /* 2 */
-}
-
-/**
- * Show the overflow in IE.
- * 1. Show the overflow in Edge.
- */
-
-button,
-input { /* 1 */
-  overflow: visible;
-}
-
-/**
- * Remove the inheritance of text transform in Edge, Firefox, and IE.
- * 1. Remove the inheritance of text transform in Firefox.
- */
-
-button,
-select { /* 1 */
-  text-transform: none;
-}
-
-/**
- * Correct the inability to style clickable types in iOS and Safari.
- */
-
-button,
-[type="button"],
-[type="reset"],
-[type="submit"] {
-  -webkit-appearance: button;
-}
-
-/**
- * Remove the inner border and padding in Firefox.
- */
-
-button::-moz-focus-inner,
-[type="button"]::-moz-focus-inner,
-[type="reset"]::-moz-focus-inner,
-[type="submit"]::-moz-focus-inner {
-  border-style: none;
-  padding: 0;
-}
-
-/**
- * Restore the focus styles unset by the previous rule.
- */
-
-button:-moz-focusring,
-[type="button"]:-moz-focusring,
-[type="reset"]:-moz-focusring,
-[type="submit"]:-moz-focusring {
-  outline: 1px dotted ButtonText;
-}
-
-/**
- * Correct the padding in Firefox.
- */
-
-fieldset {
-  padding: 0.35em 0.75em 0.625em;
-}
-
-/**
- * 1. Correct the text wrapping in Edge and IE.
- * 2. Correct the color inheritance from `fieldset` elements in IE.
- * 3. Remove the padding so developers are not caught out when they zero out
- *    `fieldset` elements in all browsers.
- */
-
-legend {
-  box-sizing: border-box; /* 1 */
-  color: inherit; /* 2 */
-  display: table; /* 1 */
-  max-width: 100%; /* 1 */
-  padding: 0; /* 3 */
-  white-space: normal; /* 1 */
-}
-
-/**
- * Add the correct vertical alignment in Chrome, Firefox, and Opera.
- */
-
-progress {
-  vertical-align: baseline;
-}
-
-/**
- * Remove the default vertical scrollbar in IE 10+.
- */
-
-textarea {
-  overflow: auto;
-}
-
-/**
- * 1. Add the correct box sizing in IE 10.
- * 2. Remove the padding in IE 10.
- */
-
-[type="checkbox"],
-[type="radio"] {
-  box-sizing: border-box; /* 1 */
-  padding: 0; /* 2 */
-}
-
-/**
- * Correct the cursor style of increment and decrement buttons in Chrome.
- */
-
-[type="number"]::-webkit-inner-spin-button,
-[type="number"]::-webkit-outer-spin-button {
-  height: auto;
-}
-
-/**
- * 1. Correct the odd appearance in Chrome and Safari.
- * 2. Correct the outline style in Safari.
- */
-
-[type="search"] {
-  -webkit-appearance: textfield; /* 1 */
-  outline-offset: -2px; /* 2 */
-}
-
-/**
- * Remove the inner padding in Chrome and Safari on macOS.
- */
-
-[type="search"]::-webkit-search-decoration {
-  -webkit-appearance: none;
-}
-
-/**
- * 1. Correct the inability to style clickable types in iOS and Safari.
- * 2. Change font properties to `inherit` in Safari.
- */
-
-::-webkit-file-upload-button {
-  -webkit-appearance: button; /* 1 */
-  font: inherit; /* 2 */
-}
-
-/* Interactive
-   ========================================================================== */
-
-/*
- * Add the correct display in Edge, IE 10+, and Firefox.
- */
-
-details {
-  display: block;
-}
-
-/*
- * Add the correct display in all browsers.
- */
-
-summary {
-  display: list-item;
-}
-
-/* Misc
-   ========================================================================== */
-
-/**
- * Add the correct display in IE 10+.
- */
-
-template {
-  display: none;
-}
-
-/**
- * Add the correct display in IE 10.
- */
-
-[hidden] {
-  display: none;
-}

doc/learning/how_to_debug.md

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

doc/learning/how_to_test.md

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

doc/learning/how_to_write_sfc.md

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

doc/learning/overview.md

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

doc/learning/quick_start.md

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

doc/miscellaneous/comparison.md

@@ -0,0 +1,345 @@
+# Comparison with Vue/React
+
+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, a lot of
+effort was put 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
+
+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, gzipped) |
+| ------------------------ | ------------------------ |
+| OWL                      | 18kb                     |
+| Vue + VueX               | 30kb                     |
+| Vue + VueX + Vue Router  | 39kb                     |
+| React + ReactDOM + Redux | 40kb                     |
+| jQuery                   | 30kb                     |
+
+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
+come 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
+be used by simply adding a script tag to a page.
+
+```html
+<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.
+
+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.
+
+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
+particular because templates are described in XML files, and can be modified by
+XPaths. Since Odoo is at its heart a modular application, this is an important
+feature for us.
+
+```xml
+<div>
+  <button t-on-click="increment">Click Me! [<t t-esc="state.value"/>]</button>
+</div>
+```
+
+Vue is actually kind of similar. Its template language is kind of close to QWeb,
+with the `v` replaced by the `t`. However, it is also more fully featured. For
+example, Vue templates have slots, or event modifiers. A large difference is that
+most Vue applications will need to be built ahead of time, to compile the templates
+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. This
+example is done with the (kind of outdated) React class system:
+
+```jsx
+class Clock extends React.Component {
+  render() {
+    return (
+      <div>
+        <h1>Hello, world!</h1>
+        <h2>It is {this.props.date.toLocaleTimeString()}.</h2>
+      </div>
+    );
+  }
+}
+```
+
+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!
+
+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 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 component may want to fetch an external
+library (a calendar component may need a specialized calendar rendering library),
+in its willStart hook.
+
+```javascript
+class MyCalendarComponent extends owl.Component {
+    ...
+
+    willStart() {
+        return utils.lazyLoad('static/libs/fullcalendar/fullcalendar.js');
+    }
+    ...
+}
+```
+
+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. 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
+
+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.
+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
+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 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
+
+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
+are talking about. A small application may not need much more than a simple
+object to contain its state.
+
+However, there are some common solutions for React and Vue: redux and vuex.
+Both of them are a centralized store that own the state, and they dictate how
+the state can be mutated.
+
+**Redux**
+
+In Redux, the state is mutated by reducers. Reducers are functions
+that modify the state by returning a different object:
+
+```javascript
+  ...
+  switch (action.type) {
+    case ADD_TODO: {
+      const { id, content } = action.payload;
+      return {
+        ...state,
+        allIds: [...state.allIds, id],
+        byIds: {
+          ...state.byIds,
+          [id]: {
+            content,
+            completed: false
+          }
+        }
+      };
+    }
+```
+
+This is a little bit awkward to write, but this allows the component system to
+check if a part of the state was changed. This is exactly what is done by the
+`connect` function: it create a _connected_ component, which is subscribed to
+the state and triggers a rerender if some part of the state was modified.
+
+**VueX**
+
+VueX is based on a different principle: the state is mutated through
+some special functions (the mutations), which modify the state in place:
+
+```javascript
+    function ({state}, payload) {
+        const { id, content } = payload;
+        const message = {id, content, completed: false};
+        state.messages.push(message)
+    }
+```
+
+This is simpler, but there is a little bit more happening behind the scene:
+each key from the state is silently replaced by getters and setters, and VueX
+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 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();
+}
+
+Counter.env.store = store;
+const counter = new Counter();
+```
+
+## 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.

doc/miscellaneous/rendering.md

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

doc/miscellaneous/vdom.md

@@ -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).

doc/miscellaneous/why_owl.md

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

doc/readme.md

@@ -0,0 +1,57 @@
+# 🦉 OWL Documentation 🦉
+
+## Learning Owl
+
+Are you new to Owl? This is the place to start!
+
+- [Tutorial: create a TodoList application](learning/tutorial_todoapp.md)
+- [Quick Overview](learning/overview.md)
+- [How to start an Owl project](learning/quick_start.md)
+- [How to test Components](learning/how_to_test.md)
+- [How to write Single File Components](learning/how_to_write_sfc.md)
+- [How to write debug Owl applications](learning/how_to_debug.md)
+
+## Reference
+
+You will find here a complete reference of every feature, class or object
+provided by Owl.
+
+- [Animations](reference/animations.md)
+- [Browser](reference/browser.md)
+- [Component](reference/component.md)
+- [Content](reference/content.md)
+- [Concurrency Model](reference/concurrency_model.md)
+- [Configuration](reference/config.md)
+- [Context](reference/context.md)
+- [Environment](reference/environment.md)
+- [Event Bus](reference/event_bus.md)
+- [Event Handling](reference/event_handling.md)
+- [Error Handling](reference/error_handling.md)
+- [Hooks](reference/hooks.md)
+- [Mounting a component](reference/mounting.md)
+- [Miscellaneous Components](reference/misc.md)
+- [Observer](reference/observer.md)
+- [Props](reference/props.md)
+- [Props Validation](reference/props_validation.md)
+- [QWeb Templating Language](reference/qweb_templating_language.md)
+- [QWeb Engine](reference/qweb_engine.md)
+- [Router](reference/router.md)
+- [Store](reference/store.md)
+- [Slots](reference/slots.md)
+- [Tags](reference/tags.md)
+- [Utils](reference/utils.md)
+
+## Other Topics
+
+This section provides miscellaneous document that explains some topics
+which cannot be considered either a tutorial, or reference documentation.
+
+- [Owl architecture: the Virtual DOM](miscellaneous/vdom.md)
+- [Owl architecture: the rendering pipeline](miscellaneous/rendering.md)
+- [Comparison with React/Vue](miscellaneous/comparison.md)
+- [Why did Odoo built Owl?](miscellaneous/why_owl.md)
+
+---
+
+Found an issue in the documentation? A broken link? Some outdated information?
+Please open an issue or submit a PR!

doc/reference/animations.md

@@ -0,0 +1,127 @@
+# 🦉 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).
+- at the end of the transition, `name-enter-to` and `name-enter-active` will be removed.
+
+At node destruction:
+
+- the css classes `name-leave` and `name-leave-active` will be added before the
+  node is removed to the DOM.
+- on the next animation frame: the css class `name-leave` will be removed and the
+  class `name-leave-to` will be added (so they can be used to trigger css
+  transition effects).
+- at the end of the transition, `name-leave-to` and `name-leave-active` will be removed.
+
+For example, a simple fade in/out effect can be done with this:
+
+```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).
+
+## SCSS Mixins
+
+If you use SCSS, you can use mixins to make generic animations. Here is an exemple with a fade in / fade out animation:
+
+```scss
+@mixin animation-fade($time, $name) {
+  .#{$name}_fade-enter-active,
+  .#{$name}_fade-active {
+    transition: all $time;
+  }
+
+  .#{$name}_fade-enter {
+    opacity: 0;
+  }
+
+  .#{$name}_fade-leave-to {
+    opacity: 0;
+  }
+}
+```
+
+Usage:
+
+```scss
+@include animation-fade(0.5s, "o_notification");
+```
+
+You can now have in your template:
+
+```xml
+<SomeTag  t-transition="o_notification_fade"/>
+```

doc/reference/browser.md

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

doc/reference/component.md

@@ -0,0 +1,855 @@
+# 🦉 OWL Component 🦉
+
+## Content
+
+- [Overview](#overview)
+- [Example](#example)
+- [Reference](#reference)
+  - [Reactive System](#reactive-system)
+  - [Properties](#properties)
+  - [Static Properties](#static-properties)
+  - [Methods](#methods)
+  - [Lifecycle](#lifecycle)
+    - [`constructor(parent, props)`](#constructorparent-props)
+    - [`setup()`](#setup)
+    - [`willStart()`](#willstart)
+    - [`mounted()`](#mounted)
+    - [`willUpdateProps(nextProps)`](#willupdatepropsnextprops)
+    - [`willPatch()`](#willpatch)
+    - [`patched(snapshot)`](#patchedsnapshot)
+    - [`willUnmount()`](#willunmount)
+    - [`catchError(error)`](#catcherrorerror)
+  - [Root Component](#root-component)
+  - [Composition](#composition)
+  - [Form Input Bindings](#form-input-bindings)
+  - [References](#references)
+  - [Dynamic sub components](#dynamic-sub-components)
+  - [Functional Components](#functional-components)
+  - [SVG Components](#svg-components)
+
+## Overview
+
+OWL components are the building blocks for user interface. They are designed to be:
+
+1. **declarative:** the user interface should be described in terms of the state
+   of the application, not as a sequence of imperative steps.
+
+2. **composable:** each component can seamlessly be created in a parent component by
+   a simple tag or directive in its template.
+
+3. **asynchronous rendering:** the framework will transparently wait for each
+   sub components 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_templating_language.md) template (which needs to be preloaded in QWeb).
+Rendering a component generates a virtual dom representation
+of the component, which is then patched to the DOM, in order to apply the changes in an efficient way.
+
+## Example
+
+Let us have a look at a simple component:
+
+```javascript
+const { useState } = owl.hooks;
+
+class ClickCounter extends owl.Component {
+  state = useState({ value: 0 });
+
+  increment() {
+    this.state.value++;
+  }
+}
+```
+
+```xml
+<button t-name="ClickCounter" 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 shows how a component should be defined: it simply subclasses the
+Component class. If no static `template` key is defined, then
+Owl will use the component's name as template name. Here,
+a state object is defined, by using the `useState` hook. It is not mandatory to use the state object, but it is certainly encouraged. The result of the `useState` call is
+[observed](observer.md), and any change to it will cause a rerendering.
+
+## Reference
+
+An Owl component is a small class which represents a component or some UI element.
+It exists in the context of an [environment](environment.md) (`env`), which is propagated from a
+parent to its children. The environment needs to have a [QWeb](qweb_templating_language.md) instance, which
+will be used to render the component template.
+
+Be aware that the name of the component may be significant: if a component does
+not define a `template` key, then Owl will lookup in QWeb to
+find a template with the component name (or one of its ancestors).
+
+### Reactive system
+
+OWL components are normal javascript classes. So, changing a component internal
+state does nothing more:
+
+```js
+class Counter extends Component {
+  static template = xml`<div t-on-click="increment"><t t-esc="state.value"/></div>`;
+  state = { value: 0 };
+
+  increment() {
+    this.state.value++;
+  }
+}
+```
+
+Clicking on the `Counter` component defined above will call the `increment`
+method, but it will not rerender the component. To fix that, one could add an
+explicit call to `render` in `increment`:
+
+```js
+    increment() {
+        this.state.value++;
+        this.render();
+    }
+```
+
+However, it may be simple in this case, but it quickly become cumbersome, as a
+component get more complex, and its internal state is modified by more than one
+method.
+
+A better way is to use the reactive system: by using the `useState` hook (see the
+[hooks](hooks.md) section for more details), one can make Owl react to state
+changes. The `useState` hook generates a proxy version of an object
+(this is done by an [observer](observer.md)), which allows the component to
+react to any change. So, the `Counter` example above can be improved like this:
+
+```js
+const { useState } = owl.hooks;
+
+class Counter extends Component {
+  static template = xml`<div t-on-click="increment"><t t-esc="state.value"/></div>`;
+  state = useState({ value: 0 });
+
+  increment() {
+    this.state.value++;
+  }
+}
+```
+
+Obviously, we can call the `useState` hook more than once:
+
+```js
+const { useState } = owl.hooks;
+
+class Counter extends Component {
+  static template = xml`
+      <div>
+        <span t-on-click="increment(counter1)"><t t-esc="counter1.value"/></span>
+        <span t-on-click="increment(counter2)"><t t-esc="counter2.value"/></span>
+      </div>`;
+  counter1 = useState({ value: 0 });
+  counter2 = useState({ value: 0 });
+
+  increment(counter) {
+    counter.value++;
+  }
+}
+```
+
+Note that hooks are subject to one important [rule](hooks.md#one-rule): they need
+to be called in the constructor.
+
+### 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](environment.md), which contains a QWeb instance.
+
+- **`props`** (Object): this is an object containing all the properties given by
+  the parent to a child component. For example, in the following situation,
+  the parent component gives a `user` and a `color` value to the `ChildComponent`.
+
+  ```xml
+    <div>
+      <ChildComponent user="state.user" color="color">
+    </div>
+  ```
+
+  Note that `props` are owned by the parent, not by the component.
+  As such, it should not ever be modified by the component (otherwise you risk
+  unintended effects, since the parent may not be aware of the change)!!
+
+  The `props` can be modified dynamically by the parent. In that case, the
+  component will go through the following lifecycle methods: `willUpdateProps`,
+  `willPatch` and `patched`.
+
+### Static Properties
+
+- **`template`** (string, optional): if given, this is the name of the QWeb template that will render the component. Note that there is a helper `xml` to
+  make it easy to define an inline template.
+
+* **`components`** (Object, optional): if given, this is an object that contains
+  the classes of any sub components needed by the template. This is the main way
+  used by Owl to be able to create sub components.
+
+  ```js
+  class ParentComponent extends owl.Component {
+    static components = { SubComponent };
+  }
+  ```
+
+* **`props`** (Object, optional): if given, this is an object that describes the
+  type and shape of the (actual) props given to the component. If Owl mode is
+  `dev`, this will be used to validate the props each time the component is
+  created/updated. See [Props Validation](props_validation.md) for more information.
+
+  ```js
+  class Counter extends owl.Component {
+    static props = {
+      initialValue: Number,
+      optional: true,
+    };
+  }
+  ```
+
+- **`defaultProps`** (Object, optional): if given, this object define default
+  values for (top-level) props. Whenever `props` are given to the object, they
+  will be altered to add default value (if missing). Note that it does not
+  change the initial object, a new object will be created instead.
+
+  ```js
+  class Counter extends owl.Component {
+    static defaultProps = {
+      initialValue: 0,
+    };
+  }
+  ```
+
+- **`style`** (string, optional): it should be the return value of the [`css` tag](tags.md#css-tag),
+  which is used to inject stylesheet whenever the component is visible on the
+  screen.
+
+There is another static property defined on the `Component` class: `current`.
+This property is set to the currently being defined component (in the constructor).
+This is the way [hooks](hooks.md) are able to get a reference to the target
+component.
+
+### Methods
+
+We explain here all the public methods of the `Component` class.
+
+- **`mount(target, options)`** (async): this is the main way a
+  component is added to the DOM: the root component is mounted to a target
+  HTMLElement (or document fragment). Obviously, this is asynchronous, since each children need to be
+  created as well. Most applications will need to call `mount` exactly once, on
+  the root component.
+
+  The `options` argument is an optional object with a `position` key. The
+  `position` key can have three possible values: `first-child`, `last-child`, `self`.
+
+  - `first-child`: with this option, the component will be prepended inside the target,
+  - `last-child` (default value): with this option, the component will be
+    appended in the target element,
+  - `self`: the target will be used as the root element for the component. This
+    means that the target has to be an HTMLElement (and not a document fragment).
+    In this situation, it is possible that the component cannot be unmounted. For
+    example, if its target is `document.body`.
+
+  Note that if a component is mounted, unmounted and remounted, it will be
+  automatically re-rendered to ensure that changes in its state (or something
+  in the environment, or in the store, or ...) will be taken into account.
+
+  If a component is mounted inside an element or a fragment which is not in the
+  DOM, then it will be rendered fully, but not active: the `mounted` hooks will
+  not be called. This is sometimes useful if we want to load an application in
+  memory. In that case, we need to mount the root component again in an element
+  which is in the DOM:
+
+  ```js
+  const app = new App();
+  await app.mount(document.createDocumentFragment());
+  // app is rendered in memory, but not active
+  await app.mount(document.body);
+  // app is now visible
+  ```
+
+  Note that the normal way of mounting an application is by using the `mount`
+  method on a component class, not by creating the instance by hand. See the
+  documentation on [mounting applications](mounting.md).
+
+* **`unmount()`**: in case a component needs to be detached/removed from the DOM, this
+  method can be used. Most applications should not call `unmount`, this is more
+  useful to the underlying component system.
+
+* **`render()`** (async): calling this method directly will cause a rerender. Note
+  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 component should
+  ignore a props update. If it returns false, then `willUpdateProps` will not
+  be called, and no rendering will occur. Its default implementation is to
+  always return true. Note that this is an optimization, similar to React's `shouldComponentUpdate`. Most of the time, this should not be used, but it
+  can be useful if we are handling large number of components. Since this is an
+  optimization, Owl has the freedom to ignore the result of `shouldUpdate` in
+  some cases (for example, if a component is remounted, or if we want to force
+  a full rerender of the UI). However, if `shouldUpdate` returns true, then Owl
+  provides the guarantee that the component will be rendered at some point in
+  the future (except if the component is destroyed or if some part of the UI crashes).
+
+* **`destroy()`**. As its name suggests, this method will remove the component,
+  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.
+
+Obviously, these methods are reserved for Owl, and should not be used by Owl
+users, unless they want to override them. Also, Owl reserves all method names
+starting with `__`, in order to prevent possible future conflicts with user code
+whenever Owl needs to change.
+
+### 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                                                 |
+| ------------------------------------------------ | ----------------------------------------------------------- |
+| **[setup](#setup)**                              | setup                                                       |
+| **[willStart](#willstart)**                      | async, before first rendering                               |
+| **[mounted](#mounted)**                          | just after component is rendered and added to the DOM       |
+| **[willUpdateProps](#willupdatepropsnextprops)** | async, before props update                                  |
+| **[willPatch](#willpatch)**                      | just before the DOM is patched                              |
+| **[patched](#patchedsnapshot)**                  | just after the DOM is patched                               |
+| **[willUnmount](#willunmount)**                  | just before removing component from DOM                     |
+| **[catchError](#catcherrorerror)**               | catch errors (see [error handling page](error_handling.md)) |
+
+Notes:
+
+- 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 = useState({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 {
+  state = useState({ value: 0 });
+
+  ...
+}
+```
+
+Hook functions can be called in the constructor.
+
+#### `setup()`
+
+_setup_ is run just after the component is constructed. It is a lifecycle method,
+very similar to the _constructor_, except that it does not receive any argument.
+
+It is a valid method to call hook functions. Note that one of the main reason to
+have the `setup` hook in the component lifecycle is to make it possible to
+monkey patch it. It is a common need in the Odoo ecosystem.
+
+```javascript
+setup() {
+  useSetupAutofocus();
+}
+```
+
+#### `willStart()`
+
+willStart is an asynchronous hook that can be implemented to
+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. 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.
+
+#### `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.
+
+It is 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 to perform an asynchronous task,
+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
+information from the DOM. For example, the current position of the
+scrollbar.
+
+Note that modifying the state is not allowed here. This method is called just
+before an actual DOM patch, and is only intended to be used to save some local
+DOM state. Also, it will not be called if the component is not in the DOM.
+
+#### `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 component is
+not in the DOM.
+
+Updating the component state in this hook is possible, but not encouraged.
+One needs to be careful, because updates here will create an additional rendering, which in
+turn will cause other calls to the `patched` method. 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 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`.
+
+#### `catchError(error)`
+
+The `catchError` method is useful when we need to intercept and properly react
+to (rendering) errors that occur in some sub components. See the page on
+[error handling](error_handling.md).
+
+### Root Component
+
+Most of the time, an Owl component will be created automatically by a tag (or the `t-component`
+directive) in a template. There is however an obvious exception: the root component
+of an Owl application has to be created manually:
+
+```js
+class App extends owl.Component { ... }
+
+const app = new App();
+app.mount(document.body);
+```
+
+The root component does not have a parent nor `props` (see note below). It will be setup with an
+[environment](environment.md) (either the `env` defined on its class, or a
+default empty environment).
+
+Note: a root component can however be given a `props` object in its constructor,
+like this: `new App(null, {some: 'object'});`. It will not be a true `props`
+object, managed by Owl (so, for example, it will never be updated).
+
+### Composition
+
+The example above shows a QWeb template with a sub component. In a template,
+components are declared with a tagname corresponding to the class name. It has
+to be capitalized.
+
+```xml
+<div t-name="ParentComponent">
+  <span>some text</span>
+  <MyComponent info="13" />
+</div>
+```
+
+```js
+class ParentComponent extends owl.Component {
+    static components = { MyComponent: MyComponent};
+    ...
+}
+```
+
+In this example, the `ParentComponent`'s template creates a component `MyComponent` just
+after the span. The `info` key will be added to the subcomponent's `props`. Each
+`props` is a string which represents a javascript (QWeb) expression, so it is
+dynamic. If it is necessary to give a string, this can be done by quoting it:
+`someString="'somevalue'"`.
+
+Note that the rendering context for the template is the component itself. This means
+that the template can access `state` (if it exists), `props`, `env`, or any
+methods defined in the component.
+
+```xml
+<div t-name="ParentComponent">
+    <ChildComponent count="state.val" />
+</div>
+```
+
+```js
+class ParentComponent {
+  static components = { ChildComponent };
+  state = useState({ val: 4 });
+}
+```
+
+Whenever the template is rendered, it will automatically create the subcomponent
+`ChildComponent` at the correct place. It needs to find the reference to the
+actual component class in the special static `components` key, or the class registered in
+QWeb's global registry (see `register` function of QWeb). It first looks inside
+the static `components` key, then fallbacks on the global registry.
+
+_Props_: In this example, the child component will receive the object `{count: 4}` in its
+constructor. This will be assigned to the `props` variable, which can be accessed
+on the component (and also, in the template). Whenever the state is updated, then
+the sub component will also be updated automatically. See the [props section](props.md)
+for more information.
+
+**CSS and style:** Owl allows the parent to declare
+additional css classes or style for the sub component: css declared in `class`, `style`, `t-att-class` or `t-att-style` will be added to the
+root component element.
+
+```xml
+<div t-name="ParentComponent">
+  <MyComponent class="someClass" style="font-weight:bold;" info="13" />
+</div>
+```
+
+Warning: there is a small caveat with dynamic class attributes: since Owl needs
+to be able to add/remove proper classes whenever necessary, it needs to be aware
+of the possible classes. Otherwise, it will not be able to make the difference
+between a valid css class added by the component, or other custom code, and a
+class that need to be removed. This is why we only support the explicit syntax
+with a class object:
+
+```xml
+<MyComponent t-att-class="{a: state.flagA, b: state.flagB}" />
+```
+
+### Form Input Bindings
+
+It is very common to need to be able to read the value out of an html `input` (or
+`textarea`, or `select`) in order to use it (note: it does not need to be in a
+form!). A possible way to do this is to do it by hand:
+
+```js
+class Form extends owl.Component {
+  state = useState({ text: "" });
+
+  _updateInputValue(event) {
+    this.state.text = event.target.value;
+  }
+}
+```
+
+```xml
+<div>
+  <input t-on-input="_updateInputValue" />
+  <span t-esc="state.text" />
+</div>
+```
+
+This works. However, this requires a little bit of _plumbing_ code. Also, the
+plumbing code is slightly different if you need to interact with a checkbox,
+or with radio buttons, or with select tags.
+
+To help with this situation, Owl has a builtin directive `t-model`: its value
+should be an observed value in the component (usually `state.someValue`). With
+the `t-model` directive, we can write a shorter code, equivalent to the previous
+example:
+
+```js
+class Form extends owl.Component {
+  state = { text: "" };
+}
+```
+
+```xml
+<div>
+  <input t-model="state.text" />
+  <span t-esc="state.text" />
+</div>
+```
+
+The `t-model` directive works with `<input>`, `<input type="checkbox">`,
+`<input type="radio">`, `<textarea>` and `<select>`:
+
+```xml
+<div>
+    <div>Text in an input: <input t-model="state.someVal"/></div>
+    <div>Textarea: <textarea t-model="state.otherVal"/></div>
+    <div>Boolean value: <input type="checkbox" t-model="state.someFlag"/></div>
+    <div>Selection:
+        <select t-model="state.color">
+            <option value="">Select a color</option>
+            <option value="red">Red</option>
+            <option value="blue">Blue</option>
+        </select>
+    </div>
+    <div>
+        Selection with radio buttons:
+        <span>
+            <input type="radio" name="color" id="red" value="red" t-model="state.color"/>
+            <label for="red">Red</label>
+        </span>
+        <span>
+            <input type="radio" name="color" id="blue" value="blue" t-model="state.color" />
+            <label for="blue">Blue</label>
+        </span>
+    </div>
+</div>
+```
+
+Like event handling, the `t-model` directive accepts the following modifiers:
+
+| Modifier  | Description                                                          |
+| --------- | -------------------------------------------------------------------- |
+| `.lazy`   | update the value on the `change` event (default is on `input` event) |
+| `.number` | try to parse the value to a number (using `parseFloat`)              |
+| `.trim`   | trim the resulting value                                             |
+
+For example:
+
+```xml
+<input t-model.lazy="state.someVal" />
+```
+
+These modifiers can be combined. For instance, `t-model.lazy.number` will only
+update a number whenever the change is done.
+
+Note: the online playground has an example to show how it works.
+
+### References
+
+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. See the [hooks section](hooks.md#useref) for
+more detail.
+
+As a short example, here is how we could set the focus on a given input:
+
+```xml
+<div>
+    <input t-ref="input"/>
+    <button t-on-click="focusInput">Click</button>
+</div>
+```
+
+```js
+import { useRef } from "owl/hooks";
+
+class SomeComponent extends Component {
+  inputRef = useRef("input");
+
+  focusInput() {
+    this.inputRef.el.focus();
+  }
+}
+```
+
+The `useRef` hook can also be used to get a reference to an instance of a sub
+component rendered by Owl. In that case, we need to access it with the `comp`
+property instead of `el`:
+
+```xml
+<div>
+    <SubComponent t-ref="sub"/>
+    <button t-on-click="doSomething">Click</button>
+</div>
+```
+
+```js
+import { useRef } from "owl/hooks";
+
+class SomeComponent extends Component {
+  static components = { SubComponent };
+  subRef = useRef("sub");
+
+  doSomething() {
+    this.subRef.comp.doSomeThingElse();
+  }
+}
+```
+
+Note that these two examples uses the suffix `ref` to name the reference. This
+is not mandatory, but it is a useful convention, so we do not forget to access
+it with the `el` or `comp` suffix.
+
+### Dynamic sub components
+
+It is not common, but sometimes we need a dynamic component name. In this case,
+the `t-component` directive can also be used to accept dynamic values with string interpolation (like the [`t-attf-`](qweb_templating_language.md#dynamic-attributes) directive):
+
+```xml
+<div t-name="ParentComponent">
+    <t t-component="ChildComponent{{id}}" />
+</div>
+```
+
+```js
+class ParentComponent {
+  static components = { ChildComponent1, ChildComponent2 };
+  state = { id: 1 };
+}
+```
+
+There is an even more dynamic way to use `t-component`: its value can be an
+expression evaluating to an actual component class. In that case, this is the
+class that will be used to create the component:
+
+```js
+class A extends Component<any, any, any> {
+  static template = xml`<span>child a</span>`;
+}
+class B extends Component<any, any, any> {
+  static template = xml`<span>child b</span>`;
+}
+class App extends Component<any, any, any> {
+  static template = xml`<t t-component="myComponent" t-key="state.child"/>`;
+
+  state = { child: "a" };
+
+  get myComponent() {
+    return this.state.child === "a" ? A : B;
+  }
+}
+```
+
+In this example, the component `App` selects dynamically the concrete sub
+component class.
+
+Note that the `t-component` directive can only be used on `<t>` nodes.
+
+### Functional Components
+
+Owl does not exactly have functional components. However, there is an extremely
+close alternative: calling sub templates.
+
+A stateless functional component in react is usually some kind of function that
+maps props to a virtual dom (often with `jsx`). So, basically, almost like a
+template rendered with `props`. In Owl, this can be done by
+simply defining a template, that will access the `props` object:
+
+```js
+const Welcome = xml`<h1>Hello, <t t-esc="props.name"/></h1>`;
+
+class MyComponent extends Component {
+  static template = xml`
+        <div>
+            <t t-call=${Welcome}/>
+            <div>something</div>
+        </div>
+    `;
+}
+```
+
+The way this works is that sub templates are inlined, and have access to the
+ambient context. They can therefore access `props`, and any other part of the
+caller component.
+
+### SVG Components
+
+Owl components can be used to generate dynamic SVG graphs:
+
+```js
+class Node extends Component {
+  static template = xml`
+        <g>
+            <circle t-att-cx="props.x" t-att-cy="props.y" r="4" fill="black"/>
+            <text t-att-x="props.x - 5" t-att-y="props.y + 18"><t t-esc="props.node.label"/></text>
+            <t t-set="childx" t-value="props.x + 100"/>
+            <t t-set="height" t-value="props.height/(props.node.children || []).length"/>
+            <t t-foreach="props.node.children || []" t-as="child">
+                <t t-set="childy" t-value="props.y + child_index*height"/>
+                <line t-att-x1="props.x" t-att-y1="props.y" t-att-x2="childx" t-att-y2="childy" stroke="black" />
+                <Node x="childx" y="childy" node="child" height="height"/>
+            </t>
+        </g>
+    `;
+  static components = { Node };
+}
+
+class RootNode extends Component {
+  static template = xml`
+        <svg height="180">
+            <Node node="graph" x="10" y="20" height="180"/>
+        </svg>
+    `;
+  static components = { Node };
+  graph = {
+    label: "a",
+    children: [
+      { label: "b" },
+      { label: "c", children: [{ label: "d" }, { label: "e" }] },
+      { label: "f", children: [{ label: "g" }] },
+    ],
+  };
+}
+```
+
+This `RootNode` component will then display a live SVG representation of the
+graph described by the `graph` property. Note that there is a recursive structure
+here: the `Node` component uses itself as a subcomponent.
+
+Note that since SVG needs to be handled in a specific way (its namespace needs
+to be properly set), there is a small constraint for Owl components: if an owl
+component is supposed to be a part of an svg graph, then its root node needs to
+be a `g` tag, so Owl can properly set the namespace.

doc/reference/concurrency_model.md

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

doc/reference/config.md

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

doc/reference/content.md

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

doc/reference/context.md

@@ -0,0 +1,105 @@
+# 🦉 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 });
+App.env.deviceContext = 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="">
+          a more advanced user interface
+      </t>
+    </div>`;
+  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.

doc/reference/environment.md

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

doc/reference/error_handling.md

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

doc/reference/event_bus.md

@@ -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`.

doc/reference/event_handling.md

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

doc/reference/hooks.md

@@ -0,0 +1,464 @@
+# 🦉 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)
+  - [`useExternalListener`](#useexternallistener)
+  - [`useStore`](#usestore)
+  - [`useDispatch`](#usedispatch)
+  - [`useGetters`](#usegetters)
+  - [`useComponent`](#usecomponent)
+  - [`useEnv`](#useenv)
+  - [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, in the _setup_ method, 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 });
+  }
+}
+
+// also ok
+class SomeComponent extends Component {
+  setup() {
+    this.state = useState({ value: 0 });
+  }
+}
+
+// not ok: this is executed after the constructor is called
+class SomeComponent extends Component {
+  async willStart() {
+    this.state = useState({ value: 0 });
+  }
+}
+```
+
+As you can see, the `useState` hook does not need to be given a reference to
+the component. This is possible because there is a way to get a reference to the
+current component: the `Component.current` static property is the reference to the
+component instance that is currently being created.
+
+Hooks need to be called in the constructor to ensure that this reference is
+properly set. This is also a good thing for performance reasons (Owl can use
+this to optimize its implementation), and for a clean architecture (this makes
+it easier for developers to understand what is really happening in a component).
+
+### `useState`
+
+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
+    // - this.subRef.el is the root HTML node of the sub component (i.e. this.subRef.comp.el)
+  }
+}
+```
+
+As shown by the example above, html elements are accessed by using the `el`
+key, and components references are accessed with `comp`.
+
+Notes:
+
+- if used on a component, the reference will be set in the `refs`
+  variable between `willPatch` and `patched`,
+- on a component, accessing `ref.el` will get the root node of the component.
+
+The `t-ref` directive also accepts dynamic values with string interpolation
+(like the [`t-attf-`](qweb_templating_language.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.
+
+### `useExternalListener`
+
+The `useExternalListener` hook helps solve a very common problem: adding and removing
+a listener on some target whenever a component is mounted/unmounted. For example,
+a dropdown menu (or its parent) may need to listen to a `click` event on `window`
+to be closed:
+
+```js
+useExternalListener(window, "click", this.closeMenu);
+```
+
+### `useStore`
+
+The `useStore` hook is the entry point for a component to connect to the store.
+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.
+
+### `useComponent`
+
+The `useComponent` hook is useful as a building block for some customized hooks,
+that may need a reference to the component calling them.
+
+### `useEnv`
+
+The `useEnv` hook is useful as a building block for some customized hooks,
+that may need a reference to the env of the component calling them.
+
+### Making customized hooks
+
+Hooks are a wonderful way to organize the code of a complex component by feature
+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() {
+    const env = useEnv();
+    return env.router;
+  }
+  ```
+
+  This means that we give control to the application developer to create the
+  router, which is good, so they can set it up, subclass it, ... And then, to
+  test our components, we can just add a mock router in the environment.

doc/reference/misc.md

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

doc/reference/mounting.md

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

doc/reference/observer.md

@@ -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.core.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.core.Observer();
+const obj = observer.observe({ a: { b: 1 } });
+
+observer.revNumber(obj.a); // 1
+obj.a.b = 2;
+
+observer.revNumber(obj.a); // 2
+```
+
+The `revNumber` can also return 0, which indicates that the value is not
+observed.

doc/reference/props.md

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

doc/reference/props_validation.md

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

doc/reference/qweb_engine.md

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

doc/reference/qweb_templating_language.md

@@ -0,0 +1,613 @@
+# 🦉 QWeb Templating Language🦉
+
+## Content
+
+- [Overview](#overview)
+- [Directives](#directives)
+- [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)
+  - [Dynamic Class Attribute](#dynamic-class-attribute)
+  - [Dynamic Tag Names](#dynamic-tag-names)
+  - [Loops](#loops)
+  - [Rendering Sub Templates](#rendering-sub-templates)
+  - [Dynamic Sub Templates](#dynamic-sub-templates)
+  - [Translations](#translations)
+  - [Debugging](#debugging)
+
+## Overview
+
+[QWeb](https://www.odoo.com/documentation/13.0/reference/qweb.html) is the primary
+templating engine used by Odoo. It is based on the XML format, and used
+mostly to generate HTML. In OWL, QWeb templates are compiled into functions that
+generate a virtual dom representation of the HTML.
+
+```xml
+<div>
+    <span t-if="somecondition">Some string</span>
+    <ul t-else="">
+        <li t-foreach="messages" t-as="message">
+            <t t-esc="message"/>
+        </li>
+    </ul>
+</div>
+```
+
+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.
+
+We present in this section the templating language, including its Owl specific
+extensions.
+
+## Directives
+
+For reference, here is a list of all standard QWeb directives:
+
+| Name                           | Description                                                    |
+| ------------------------------ | -------------------------------------------------------------- |
+| `t-esc`                        | [Outputting safely a value](#outputting-data)                  |
+| `t-raw`                        | [Outputting value, without escaping](#outputting-data)         |
+| `t-set`, `t-value`             | [Setting variables](#setting-variables)                        |
+| `t-if`, `t-elif`, `t-else`,    | [conditionally rendering](#conditionals)                       |
+| `t-foreach`, `t-as`            | [Loops](#loops)                                                |
+| `t-att`, `t-attf-*`, `t-att-*` | [Dynamic attributes](#dynamic-attributes)                      |
+| `t-call`                       | [Rendering sub templates](#rendering-sub-templates)            |
+| `t-debug`, `t-log`             | [Debugging](#debugging)                                        |
+| `t-translation`                | [Disabling the translation of a node](#translations)           |
+| `t-name`                       | [Defining a template (not really a directive)](qweb_engine.md) |
+
+The component system in Owl requires additional directives, to express various
+needs. Here is a list of all Owl specific directives:
+
+| Name                     | Description                                                                     |
+| ------------------------ | ------------------------------------------------------------------------------- |
+| `t-component`, `t-props` | [Defining a sub component](component.md#composition)                            |
+| `t-ref`                  | [Setting a reference to a dom node or a sub component](component.md#references) |
+| `t-key`                  | [Defining a key (to help virtual dom reconciliation)](#loops)                   |
+| `t-on-*`                 | [Event handling](event_handling.md)                                             |
+| `t-transition`           | [Defining an animation](animations.md#css-transitions)                          |
+| `t-slot`                 | [Rendering a slot](slots.md)                                                    |
+| `t-model`                | [Form input bindings](component.md#form-input-bindings)                         |
+| `t-tag`                  | [Rendering nodes with dynamic tag name](#dynamic-tag-names)                     |
+
+## Reference
+
+### 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="">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> -->
+```
+
+### Dynamic class attribute
+
+For convenience, Owl supports a special case for the `t-att-class` case: one can
+use an object with keys describing the classes, and values boolean value denoting
+if the class is or is not present:
+
+```xml
+<div t-att-class="{'a': true, 'b': true}"/> <!-- result: <div class="a b"></div> -->
+
+<div t-att-class="{'a b': true, 'c': true}"/> <!-- result: <div class="a b c"></div> -->
+```
+
+Note that it can be combined with normal class attribute:
+
+```xml
+<div class="a" t-att-class="{'b': true}"/> <!-- result: <div class="a b"></div> -->
+```
+
+### Dynamic tag names
+
+When writing generic components or templates, the specific concrete tag for an
+HTML element is not known yet. In those situations, the `t-tag` directive is
+useful. It simply evaluates dynamically an expression to use as a tag name. The
+template:
+
+```xml
+<t t-tag="tag">
+    <span>content</span>
+</t>
+```
+
+will be rendered as `<div><span>content</span></div>` if the `tag` context key
+is set to `div`.
+
+### Loops
+
+QWeb has an iteration directive `t-foreach` which take an expression returning the
+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 -->
+```
+
+Even though Owl tries to be as declarative as possible, the DOM does not fully
+expose its state declaratively in the DOM tree. For example, the scrolling state,
+the current user selection, the focused element or the state of an input are not
+set as attribute in the DOM tree. This is why we use a virtual dom
+algorithm to keep the actual DOM node as much as possible.
+
+However, in some situations, this is not enough, and we need to help Owl decide
+if an element is actually the same, or is a different element with the same
+properties.
+
+Consider the following situation: we have a list of two items `[{text: "a"}, {text: "b"}]`
+and we render them in this template:
+
+```xml
+<p t-foreach="items" t-as="item"><t t-esc="item.text"/></p>
+```
+
+The result will be two `<p>` tags with text `a` and `b`. Now, if we swap them,
+and rerender the template, Owl needs to know what the intent is:
+
+- should Owl actually swap the DOM nodes,
+- or should it keep the DOM nodes, but with an updated text content?
+
+This might look trivial, but it actually matters. These two possibilities lead
+to different results in some cases. For example, if the user selected the text
+of the first `p`, swapping them will keep the selection while updating the
+text content will not.
+
+There are many other cases where this is important: `input` tags with their
+value, css classes and animations, scroll position...
+
+So, the `t-key` directive is used to give an identity to an element. It allows
+Owl to understand if different elements of a list are actually different or not.
+
+The above example could be modified by adding an ID: `[{id: 1, text: "a"}, {id: 2, text: "b"}]`.
+Then, the template could look like this:
+
+```xml
+<p t-foreach="items" t-as="item" t-key="item.id"><t t-esc="item.text"/></p>
+```
+
+The `t-key` directive is useful for lists (`t-foreach`). A key should be
+a unique number or string (objects will not work: they will be cast to the
+`"[object Object]"` string, which is obviously not unique).
+
+Also, the key can be set on a `t` tag or on its children. The following variations
+are all equivalent:
+
+```xml
+<p t-foreach="items" t-as="item" t-key="item.id">
+  <t t-esc="item.text"/>
+</p>
+
+<t t-foreach="items" t-as="item" t-key="item.id">
+  <p t-esc="item.text"/>
+</t>
+
+<t t-foreach="items" t-as="item">
+  <p t-key="item.id" t-esc="item.text"/>
+</t>
+```
+
+If there is no `t-key` directive, Owl will use the index as a default key.
+
+Note: the `t-foreach` directive only accepts arrays (lists) or objects. It does
+not work with other iterables, such as `Set`. However, it is only a matter of
+using the `...` javascript operator. For example:
+
+```xml
+<t t-foreach="...items" t-as="item">...</t>
+```
+
+The `...` operator will convert the `Set` (or any other iterables) into a list,
+which will work with Owl QWeb.
+
+### Rendering Sub Templates
+
+QWeb templates can be used for top level rendering, but they can also be used
+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>
+```
+
+This can be used to define variables scoped to a sub template:
+
+```xml
+<t t-call="other-template">
+    <t t-set="var" t-value="1"/>
+</t>
+<!-- "var" does not exist here -->
+```
+
+### Dynamic sub templates
+
+The `t-call` directive can also be used to dynamically call a sub template,
+using string interpolation. For example:
+
+```xml
+<div t-name="main-template">
+    <t t-call="{{template}}">
+        <em>content</em>
+    </t>
+</div>
+```
+
+Here, the name of the template is obtained from the `template` value in the
+template rendering context.
+
+### Translations
+
+By default, QWeb specify that templates should be translated. If this behaviour
+is not wanted, there is a `t-translation` directive which can turn off
+translations (if it is set to the `off` value), with the following rules:
+
+- each text node will be replaced with its translation,
+- each of the following attribute values will be translated as well: `title`,
+  `placeholder`, `label` and `alt`,
+- translating text nodes can be disabled with the special attribute `t-translation`,
+  if its value is `off`.
+
+See [here](qweb_engine.md#translations) for more information on how to setup a
+translate function in Owl QWeb.
+
+### Debugging
+
+The javascript QWeb implementation provides two useful debugging directives:
+
+`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.

doc/reference/router.md

@@ -0,0 +1,181 @@
+# 🦉 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;
+}
+
+App.env = makeEnvironment();
+// create root component here
+```
+
+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>
+```

doc/reference/slots.md

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

doc/reference/store.md

@@ -0,0 +1,349 @@
+# 🦉 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 to read their relevant
+state, and they will be rerendered if the state is updated.
+
+Note: Owl store is inspired by React Redux and VueX.
+
+## 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
+means that the component needs a reference to the store. By default, it looks
+for it in the `env.store` key. However, this can be configured with the `useStore`
+hook.
+
+Every component-store interactions are done with the help of the three store hooks:
+
+- [`useStore`](#usestore) to subscribe a component to some part of the store state,
+- [`useDispatch`](#usedispatch) to get a reference to a dispatch function,
+- [`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 });
+```
+
+To make it accessible to the complete application, we will put it in the
+environment:
+
+```js
+// in this example, the root component is App
+App.env.store = store;
+```
+
+A counter component can then select this value and dispatch an action like this:
+
+```js
+class Counter extends Component {
+  counter = useStore((state) => state.counter);
+  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 which must return the part of the
+  store state that will be made available and observed for changes,
+- optionally, an object which can have the following optional keys:
+  - a `store` key containing a store object if we want to use another store than
+    the default store,
+  - an `isEqual` key containing an equality function if we want to specialize
+    the comparison (the function must accept two arguments: the previous result
+    and the new result, and must return whether they are equal),
+  - and an `onUpdate` key containing an update function if we want to execute an
+    arbitrary code every time the selected state changes (the function will
+    receive one argument, the new result, and can execute arbitrary code).
+
+If the `useStore` selector returns a sub part of the store state, the component
+will only be rerendered whenever this part of the state changes. Otherwise, it
+will perform a strict equality check (unless the `isEqual` option is defined,
+then it will call it) and will update the component every time this check fails.
+
+Note that if the selector function returns a primitive type, the result of
+`useStore` will be immutable and it will not react to changes. In this case, it
+is important to define the `onUpdate` option to properly update the value
+manually when it changes.
+
+Also, the return value from `useStore` is not supposed to be modified. The store
+state should only be updated with actions.
+
+### `useDispatch`
+
+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.

doc/reference/tags.md

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

doc/reference/utils.md

@@ -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 env = { qweb };
+  await mount(App, { env, target: document.body });
+});
+```
+
+or alternatively:
+
+```js
+owl.utils.whenReady(function () {
+  const qweb = new owl.QWeb();
+  const env = { qweb };
+  await mount(App, { env, target: 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);
+```

index.html

@@ -1,109 +0,0 @@
-<!DOCTYPE html>
-<html lang="en">
-<head>
-  <meta charset="utf-8">
-  <meta name="viewport" content="width=device-width, initial-scale=1.0">
-  <title>OWL Framework</title>
-  <link rel="icon" href="data:,">
-  <link rel="stylesheet" href="//fonts.googleapis.com/css?family=Roboto:300,300italic,700,700italic">
-  <link rel="stylesheet" href="assets/normalize.css">
-  <link rel="stylesheet" href="assets/milligram.css">
-  <link rel="stylesheet" href="assets/highlight.tomorrow.css">
-  <link rel="stylesheet" href="assets/main.css">
-  <script src="./owl.js"></script>
-</head>
-<body>
-  <header class="container">
-    <img class="homepage-logo" src="assets/owl_1f989.png" alt="OWL Logo">
-    <hgroup>
-      <h1>OWL Framework</h1>
-      <p>Mysterious OWL: A web framework for structured, dynamic and maintainable applications</p>
-    </hgroup>
-  </header>
-  <nav class="container">
-    <p>
-      <a href="https://github.com/odoo/owl" title="https://github.com/odoo/owl">Github</a>
-      &bull;
-      <a href="https://github.com/odoo/owl/blob/master/doc/readme.md">Documentation</a>
-      &bull;
-      <a href="playground/">Playground</a>
-    </p>
-  </nav>
-  <main>
-    <article class="design">
-      <div class="container">
-        <h2>Why OWL?</h2>
-        <div class="row">
-          <section class="column">
-            <h3>XML based</h3>
-            <p>Templates are based on the XML format, which allows interesting applications. For example, they could be stored in a database and modified dynamically with <tt>xpaths</tt>.</p>
-          </section>
-          <section class="column">
-            <h3>Templates compiled in the browser</h3>
-            <p>This may not be a good fit for all applications, but if you need to generate dynamically user interfaces in the browser, this is very powerful. For example, a generic form view component could generate a specific form user interface for each various models, from a XML view.</p>
-          </section>
-          <section class="column">
-            <h3>No toolchain required</h3>
-            <p>This is extremely useful for some applications, if, for various reasons (security/deployment/dynamic modules/specific assets tools), it is not ok to use standard web tools based on <tt>npm</tt>.</p>
-          </section>
-        </div>
-      </div>
-    </article>
-    <article class="example">
-      <div class="container">
-        <h2>Example</h2>
-        <div class="row">
-          <section class="column">
-<pre><code class="javascript">import { mount, Component, useState } from "owl";
-
-class Counter extends Component {
-  setup() {
-    this.state = useState({ value: 0 });
-  }
-
-  increment() {
-    this.state.value++;
-  }
-}
-
-mount(Counter, document.body);</code></pre>
-          </section>
-          <section class="column">
-<pre><code class="xml">&lt;templates&gt;
-  &lt;t t-name=&quot;Counter&quot;&gt;
-    &lt;button t-on-click=&quot;increment&quot;&gt;
-      Click Me! [&lt;t t-esc=&quot;state.value&quot;/&gt;]
-    &lt;/button&gt;
-  &lt;/t&gt;
-&lt;/templates&gt;</code></pre>
-            <div id="app-container"></div>
-            <script>
-const { mount, Component, useState, xml } = owl;
-
-class Counter extends Component {
-  setup() {
-    this.state = useState({ value: 0 });
-  }
-
-  increment() {
-    this.state.value++;
-  }
-}
-Counter.template = xml`<button t-on-click="increment">
-  Click Me! [<t t-esc="state.value"/>]
-</button>`;
-
-mount(Counter, document.getElementById("app-container"));
-            </script>
-          </section>
-        </div>
-      </div>
-    </article>
-  </main>
-  <footer>
-    <p><a href=".">OWL</a> is licensed under LGPLv3.<br>Logo from <a href="https://github.com/googlefonts/noto-emoji">Google Noto Emoji Font</a>, licensed under Apache License 2.0</p>
-  </footer>
-  <script src="assets/highlight.pack.js"></script>
-  <script>hljs.initHighlightingOnLoad();</script>
-</body>
-</html>

package.json

@@ -0,0 +1,85 @@
+{
+  "name": "@odoo/owl",
+  "version": "1.4.10",
+  "description": "Odoo Web Library (OWL)",
+  "main": "dist/owl.cjs.js",
+  "browser": "dist/owl.iife.js",
+  "module": "dist/owl.es.js",
+  "types": "dist/types/index.d.ts",
+  "files": [
+    "dist"
+  ],
+  "engines": {
+    "node": ">=12.18.3"
+  },
+  "scripts": {
+    "build:bundle": "rollup -c",
+    "build": "npm run build:bundle",
+    "test": "jest",
+    "test:watch": "jest --watch",
+    "tools:serve": "python3 tools/server.py || python tools/server.py",
+    "tools": "npm run build && npm run tools:serve",
+    "pretools:watch": "npm run build",
+    "tools:watch": "npm-run-all  --parallel tools:serve \"build:* -- --watch\"",
+    "prettier": "prettier {src/*.ts,src/**/*.ts,tests/*.ts,tests/**/*.ts,doc/*.md,doc/**/*.md} --write",
+    "check-formatting": "prettier {src/*.ts,src/**/*.ts,tests/*.ts,tests/**/*.ts,doc/*.md,doc/**/*.md} --check",
+    "publish": "npm run build && npm publish",
+    "release": "node tools/release.js"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/odoo/owl.git"
+  },
+  "author": "Odoo",
+  "license": "LGPL-3.0-only",
+  "bugs": {
+    "url": "https://github.com/odoo/owl/issues"
+  },
+  "homepage": "https://github.com/odoo/owl#readme",
+  "devDependencies": {
+    "@types/jest": "^27.0.1",
+    "@types/node": "^14.11.8",
+    "chalk": "^3.0.0",
+    "cpx": "^1.5.0",
+    "current-git-branch": "^1.1.0",
+    "git-rev-sync": "^1.12.0",
+    "github-api": "^3.3.0",
+    "jest": "^27.1.0",
+    "jest-environment-jsdom": "^27.1.0",
+    "live-server": "^1.2.1",
+    "npm-run-all": "^4.1.5",
+    "prettier": "^2.0.4",
+    "rollup": "^2.56.3",
+    "rollup-plugin-terser": "^7.0.2",
+    "rollup-plugin-typescript2": "^0.30.0",
+    "sass": "^1.16.1",
+    "source-map-support": "^0.5.10",
+    "ts-jest": "^27.0.5",
+    "typescript": "^3.7.2",
+    "uglify-es": "^3.3.9"
+  },
+  "jest": {
+    "testEnvironment": "jsdom",
+    "roots": [
+      "<rootDir>/src",
+      "<rootDir>/tests"
+    ],
+    "transform": {
+      "^.+\\.ts?$": "ts-jest"
+    },
+    "verbose": false,
+    "testRegex": "(/tests/.*(test|spec))\\.ts?$",
+    "moduleFileExtensions": [
+      "ts",
+      "tsx",
+      "js",
+      "jsx",
+      "json",
+      "node"
+    ]
+  },
+  "prettier": {
+    "printWidth": 100,
+    "endOfLine": "auto"
+  }
+}

playground/export_snippet.js

@@ -1,123 +0,0 @@
-import { loadJS } from "./utils.js";
-
-const sourceCache = new Map();
-async function getSourceCode(filePath) {
-    if (sourceCache.has(filePath)) {
-        return sourceCache.get(filePath);
-    }
-    let source = await fetch(`${filePath}.js`);
-    source = await source.text();
-    sourceCache.set(filePath, source);
-    return source;
-}
-
-const DEFAULT_HTML = `<!DOCTYPE html>
-<html lang="en">
-  <head>
-    <meta charset="utf-8">
-    <title>OWL App</title>
-    <link rel="icon" href="data:,">
-
-    <script src="owl.js"></script>
-    <link rel="stylesheet" href="app.css">
-    <script type="module" src="app.js"></script>
-    <script type="module" src="utils.js"></script>
-  </head>
-  <body>
-  </body>
-</html>
-`;
-
-const APP_PY = `#!/usr/bin/env python3
-
-import threading
-import time
-
-from http.server import SimpleHTTPRequestHandler, HTTPServer
-
-def start_server():
-    SimpleHTTPRequestHandler.extensions_map['.js'] = 'application/javascript'
-    httpd = HTTPServer(('0.0.0.0', 3600), SimpleHTTPRequestHandler)
-    httpd.serve_forever()
-
-url = 'http://127.0.0.1:3600'
-
-if __name__ == "__main__":
-    print("Owl Application")
-    print("---------------")
-    print("Server running on: {}".format(url))
-    threading.Thread(target=start_server, daemon=True).start()
-
-    while True:
-        try:
-            time.sleep(1)
-        except KeyboardInterrupt:
-            httpd.server_close()
-            quit(0)
-`;
-
-/**
- * Make a zip file containing a functioning application
- */
-export async function exportStandaloneApp(js, css, xml) {
-  await loadJS("libs/jszip.min.js");
-
-  const zip = new JSZip();
-  const processedJS = js
-    .split("\n")
-    .map(l => (l === "" ? "" : "  " + l))
-    .join("\n");
-
-  const JS = `
-/**
- * This is the javascript code defined in the playground.
- * In a larger application, this code should probably be moved in different
- * sub files.
- */
-import * as utils from "./utils.js";
-async function app() {
-${processedJS}
-}
-
-/**
- * Initialization code
- * This code load templates, and make sure everything is properly connected.
- */
-function prepareOWLApp(templates) {
-  const _configure = owl.App.prototype.configure;
-  owl.App.prototype.configure = function configureOverriden(config) {
-    config = Object.assign({ dev: true }, config); 
-    this.addTemplates(templates);
-    return _configure.call(this, config);
-  }
-}
-
-async function start() {
-  let templates;
-  try {
-    templates = await owl.loadFile('app.xml');
-  } catch(e) {
-    console.error(\`This app requires a static server.  If you have python installed, try 'python app.py'\`);
-    return;
-  }
-  prepareOWLApp(templates);
-  app();
-}
-
-start();
-`;
-
-  const [owlSrc, utilsSrc] = await Promise.all([
-    getSourceCode("../owl"),
-    getSourceCode("./utils"),
-  ]);
-
-  zip.file("app.js", JS);
-  zip.file("utils.js", utilsSrc);
-  zip.file("app.css", css);
-  zip.file("app.py", APP_PY);
-  zip.file("app.xml", xml);
-  zip.file("index.html", DEFAULT_HTML);
-  zip.file("owl.js", owlSrc);
-  return zip.generateAsync({ type: "blob" });
-}

playground/utils.js

@@ -1,49 +0,0 @@
-export function debounce(func, wait, immediate) {
-  let timeout;
-  return function () {
-    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 useBus(bus, evName, cb) {
-  bus.addEventListener(evName, cb);
-  owl.onWillUnmount(() => {
-    bus.removeEventListener(evName, cb);
-  });
-}
-
-const loadedScripts = {};
-
-export function loadJS(url) {
-  if (url in loadedScripts) {
-    return loadedScripts[url];
-  }
-  const promise = new Promise(function (resolve, reject) {
-    const script = document.createElement("script");
-    script.type = "text/javascript";
-    script.src = url;
-    script.onload = function () {
-      resolve();
-    };
-    script.onerror = function () {
-      reject(`Error loading file '${url}'`);
-    };
-    const head = document.head || document.getElementsByTagName("head")[0];
-    head.appendChild(script);
-  });
-  loadedScripts[url] = promise;
-  return promise;
-}

release-notes.md

@@ -1,8 +0,0 @@
-# v1.0.5
-
-- lots of doc improvements
-- qweb: ignore comments between t-if/t-elif/t-else
-- qweb: support attributes with inside quotes
-- component: concurrency bug fix
-- component: cancel previous mounting operations if necessary
-- transition: no crash if element added/removed quickly

roadmap.md

@@ -0,0 +1,28 @@
+# 🦉 OWL Roadmap 🦉
+
+- Current version: 1.4.10
+- Status: stable
+
+This roadmap is only an attempt at predicting Owl's future.  Everything may
+change!
+
+
+### 1.x
+
+- add chrome and firefox devtools,
+- fix every bugs,
+- improve documentation,
+- small backward compatible improvements.
+
+### 2.x (2020? 2021? 2022?)
+
+- stop support for `t-set` directive to define the content of a slot
+
+Maybe:
+
+- reimplement vdom to use *block* system, like Vue 3, which should make Owl
+  much faster
+- refactor `QWeb` to use an intermediate representation (some kind of AST) to
+  allow additional optimisations.
+
+

rollup.config.js

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

src/browser.ts

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

src/component/component.ts

@@ -0,0 +1,781 @@
+import { Observer } from "../core/observer";
+import { OwlEvent } from "../core/owl_event";
+import { CompiledTemplate, QWeb } from "../qweb/index";
+import { patch, VNode } from "../vdom/index";
+import "./directive";
+import { Fiber } from "./fiber";
+import "./props_validation";
+import { Scheduler, scheduler } from "./scheduler";
+import { activateSheet } from "./styles";
+import { Browser, browser } from "../browser";
+
+/**
+ * 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
+//------------------------------------------------------------------------------
+
+/**
+ * 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;
+  browser: Browser;
+}
+
+export type MountPosition = "first-child" | "last-child" | "self";
+
+interface MountOptions {
+  position?: MountPosition;
+}
+
+export const enum STATUS {
+  CREATED,
+  WILLSTARTED, // willstart has been called
+  RENDERED, // first render is completed (so, vnode is now defined)
+  MOUNTED, // is ready, and in DOM. It has a valid el
+  UNMOUNTED, // has a valid el, but is not in DOM
+  DESTROYED,
+}
+
+/**
+ * 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> {
+  // each component has a unique id, useful mostly to handle parent/child
+  // relationships
+  readonly id: number;
+  depth: number;
+  vnode: VNode | null;
+  pvnode: VNode | null;
+  status: STATUS;
+
+  // parent and children keys are obviously useful to setup the parent-children
+  // relationship.
+  parent: Component<any, T> | null;
+  children: { [key: number]: Component<any, T> };
+  // children mapping: from templateID to componentID. templateID identifies a
+  // place in a template. The t-component directive needs it to be able to get
+  // the component instance back whenever the template is rerendered.
+  cmap: { [key: number]: number };
+
+  currentFiber: Fiber | null;
+  // parentLastFiberId is there to help the parent component to detect, among
+  // its children, those that are not used anymore and thus can be destroyed
+  parentLastFiberId: number;
+
+  // when a rendering is initiated by a parent, it may set variables in 'scope'
+  // (typically when the component is rendered in a slot). We need to
+  // store that information in case the component would be re-rendered later on.
+  scope: any;
+
+  boundHandlers: { [key: number]: any };
+  observer: Observer | null;
+  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<any, T> | HTMLElement | undefined } | null;
+}
+
+export const portalSymbol = Symbol("portal"); // FIXME
+
+//------------------------------------------------------------------------------
+// Component
+//------------------------------------------------------------------------------
+let nextId = 1;
+
+export class Component<Props extends {} = any, T extends Env = Env> {
+  readonly __owl__: Internal<T>;
+  static template?: string | null = null;
+  static _template?: string | null = null;
+  static current: Component | null = null;
+  static components = {};
+  static props?: any;
+  static defaultProps?: any;
+  static env: any = {};
+  // expose scheduler s.t. it can be mocked for testing purposes
+  static scheduler: Scheduler = scheduler;
+
+  /**
+   * The `el` is the root element of the component.  Note that it could be null:
+   * 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.
+   *
+   * 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<any, T> | null, props?: Props) {
+    Component.current = this;
+
+    let constr = this.constructor as any;
+    const defaultProps = constr.defaultProps;
+    if (defaultProps) {
+      props = props || ({} as Props);
+      this.__applyDefaultProps(props, defaultProps);
+    }
+    this.props = <Props>props;
+    if (QWeb.dev) {
+      QWeb.utils.validateProps(constr, this.props);
+    }
+
+    const id: number = nextId++;
+    let depth;
+    if (parent) {
+      this.env = parent.env;
+      const __powl__ = parent.__owl__;
+      __powl__.children[id] = this;
+      depth = __powl__.depth + 1;
+    } else {
+      // we are the root component
+      this.env = (this.constructor as any).env;
+      if (!this.env.qweb) {
+        this.env.qweb = new QWeb();
+      }
+      // TODO: remove this in owl 2.0
+      if (!this.env.browser) {
+        this.env.browser = browser;
+      }
+      this.env.qweb.on("update", this, () => {
+        switch (this.__owl__.status) {
+          case STATUS.MOUNTED:
+            this.render(true);
+            break;
+          case STATUS.DESTROYED:
+            // this is unlikely to happen, but if a root widget is destroyed,
+            // we want to remove our subscription.  The usual way to do that
+            // would be to perform some check in the destroy method, but since
+            // it is very performance sensitive, and since this is a rare event,
+            // we simply do it lazily
+            this.env.qweb.off("update", this);
+            break;
+        }
+      });
+      depth = 0;
+    }
+
+    const qweb = this.env.qweb;
+    const template = constr.template || this.__getTemplate(qweb);
+    this.__owl__ = {
+      id: id,
+      depth: depth,
+      vnode: null,
+      pvnode: null,
+      status: STATUS.CREATED,
+      parent: parent || null,
+      children: {},
+      cmap: {},
+      currentFiber: null,
+      parentLastFiberId: 0,
+      boundHandlers: {},
+      mountedCB: null,
+      willUnmountCB: null,
+      willPatchCB: null,
+      patchedCB: null,
+      willStartCB: null,
+      willUpdatePropsCB: null,
+      observer: null,
+      renderFn: qweb.render.bind(qweb, template),
+      classObj: null,
+      refs: null,
+      scope: null,
+    };
+    if (constr.style) {
+      this.__applyStyles(constr);
+    }
+    this.setup();
+  }
+
+  /**
+   * setup is run just after the component is constructed. This is the standard
+   * location where the component can setup its hooks. It has some advantages
+   * over the constructor:
+   *  - it can be patched (useful in odoo ecosystem)
+   *  - it does not need to propagate the arguments to the super call
+   *
+   * Note: this method should not be called manually.
+   */
+  setup() {}
+
+  /**
+   * willStart is an asynchronous hook that can be implemented to perform some
+   * action before the initial rendering of a component.
+   *
+   * 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 | DocumentFragment, options: MountOptions = {}): Promise<void> {
+    if (!(target instanceof HTMLElement || target instanceof DocumentFragment)) {
+      let message = `Component '${this.constructor.name}' cannot be mounted: the target is not a valid DOM node.`;
+      message += `\nMaybe the DOM is not ready yet? (in that case, you can use owl.utils.whenReady)`;
+      throw new Error(message);
+    }
+    const position = options.position || "last-child";
+    const __owl__ = this.__owl__;
+    const currentFiber = __owl__.currentFiber;
+
+    switch (__owl__.status) {
+      case STATUS.CREATED: {
+        const fiber = new Fiber(null, this, true, target, position);
+        fiber.shouldPatch = false;
+        this.__prepareAndRender(fiber, () => {});
+        return scheduler.addFiber(fiber);
+      }
+      case STATUS.WILLSTARTED:
+      case STATUS.RENDERED:
+        currentFiber.target = target;
+        currentFiber.position = position;
+        return scheduler.addFiber(currentFiber);
+
+      case STATUS.UNMOUNTED: {
+        const fiber = new Fiber(null, this, true, target, position);
+        fiber.shouldPatch = false;
+        this.__render(fiber);
+        return scheduler.addFiber(fiber);
+      }
+
+      case STATUS.MOUNTED: {
+        if (position !== "self" && this.el!.parentNode !== target) {
+          const fiber = new Fiber(null, this, true, target, position);
+          fiber.shouldPatch = false;
+          this.__render(fiber);
+          return scheduler.addFiber(fiber);
+        } else {
+          return Promise.resolve();
+        }
+      }
+
+      case STATUS.DESTROYED:
+        throw new Error("Cannot mount a destroyed component");
+    }
+  }
+
+  /**
+   * 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__.status === STATUS.MOUNTED) {
+      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__;
+    const currentFiber = __owl__.currentFiber;
+    if (!__owl__.vnode && !currentFiber) {
+      return;
+    }
+    if (currentFiber && !currentFiber.isRendered && !currentFiber.isCompleted) {
+      return scheduler.addFiber(currentFiber.root);
+    }
+
+    // if we aren't mounted at this point, it implies that there is a
+    // currentFiber that is already rendered (isRendered is true), so we are
+    // about to be mounted
+    const status = __owl__.status;
+    const fiber = new Fiber(null, this, force, null, null);
+    Promise.resolve().then(() => {
+      if (__owl__.status === STATUS.MOUNTED || status !== STATUS.MOUNTED) {
+        if (fiber.isCompleted || fiber.isRendered) {
+          return;
+        }
+        this.__render(fiber);
+      } else {
+        // we were mounted when render was called, but we aren't anymore, so we
+        // were actually about to be unmounted ; we can thus forget about this
+        // fiber
+        fiber.isCompleted = true;
+        __owl__.currentFiber = null;
+      }
+    });
+    return scheduler.addFiber(fiber);
+  }
+
+  /**
+   * 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__.status !== STATUS.DESTROYED) {
+      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<T = any>(eventType: string, payload?: T) {
+    this.__trigger<T>(this, eventType, payload);
+  }
+
+  //--------------------------------------------------------------------------
+  // 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 | null) {
+    const __owl__ = this.__owl__;
+    if (__owl__.status === STATUS.MOUNTED) {
+      if (__owl__.willUnmountCB) {
+        __owl__.willUnmountCB();
+      }
+      this.willUnmount();
+      __owl__.status = STATUS.UNMOUNTED;
+    }
+    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__.status = STATUS.DESTROYED;
+    delete __owl__.vnode;
+    if (__owl__.currentFiber) {
+      __owl__.currentFiber.isCompleted = true;
+    }
+  }
+
+  __callMounted() {
+    const __owl__ = this.__owl__;
+
+    __owl__.status = STATUS.MOUNTED;
+    this.mounted();
+    if (__owl__.mountedCB) {
+      __owl__.mountedCB();
+    }
+  }
+
+  __callWillUnmount() {
+    const __owl__ = this.__owl__;
+    if (__owl__.willUnmountCB) {
+      __owl__.willUnmountCB();
+    }
+    this.willUnmount();
+    __owl__.status = STATUS.UNMOUNTED;
+    if (__owl__.currentFiber) {
+      __owl__.currentFiber.isCompleted = true;
+      __owl__.currentFiber.root.counter = 0;
+    }
+    const children = __owl__.children;
+    for (let id in children) {
+      const comp = children[id];
+      if (comp.__owl__.status === STATUS.MOUNTED) {
+        comp.__callWillUnmount();
+      }
+    }
+  }
+  /**
+   * Private trigger method, allows to choose the component which triggered
+   * the event in the first place
+   */
+  __trigger<T>(component: Component, eventType: string, payload?: T) {
+    if (this.el) {
+      const ev = new OwlEvent<T>(component, eventType, {
+        bubbles: true,
+        cancelable: true,
+        detail: payload,
+      });
+      const triggerHook = this.env[portalSymbol as any];
+      if (triggerHook) {
+        triggerHook(ev);
+      }
+      this.el.dispatchEvent(ev);
+    }
+  }
+  /**
+   * The __updateProps method is called by the t-component directive whenever
+   * it updates a component (so, when the parent template is rerendered).
+   */
+  async __updateProps(nextProps: Props, parentFiber: Fiber, scope: any): Promise<void> {
+    this.__owl__.scope = scope;
+    const shouldUpdate = parentFiber.force || this.shouldUpdate(nextProps);
+    if (shouldUpdate) {
+      const __owl__ = this.__owl__;
+      const fiber = new Fiber(parentFiber, this, parentFiber.force, null, null);
+      if (!parentFiber.child) {
+        parentFiber.child = fiber;
+      } else {
+        parentFiber.lastChild!.sibling = fiber;
+      }
+      parentFiber.lastChild = fiber;
+
+      const defaultProps = (<any>this.constructor).defaultProps;
+      if (defaultProps) {
+        this.__applyDefaultProps(nextProps, defaultProps);
+      }
+      if (QWeb.dev) {
+        QWeb.utils.validateProps(this.constructor, nextProps);
+      }
+      await Promise.all([
+        this.willUpdateProps(nextProps),
+        __owl__.willUpdatePropsCB && __owl__.willUpdatePropsCB(nextProps),
+      ]);
+      if (fiber.isCompleted) {
+        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(target: HTMLElement | VNode | DocumentFragment, vnode: VNode) {
+    this.__owl__.vnode = patch(target as any, vnode);
+  }
+
+  /**
+   * The __prepare method is only called by the t-component directive, when a
+   * subcomponent is created. It gets its scope, if any, from the
+   * parent template.
+   */
+  __prepare(parentFiber: Fiber, scope: any, cb: CallableFunction): Fiber {
+    this.__owl__.scope = scope;
+    const fiber = new Fiber(parentFiber, this, parentFiber.force, null, null);
+    fiber.shouldPatch = false;
+    if (!parentFiber.child) {
+      parentFiber.child = fiber;
+    } else {
+      parentFiber.lastChild!.sibling = fiber;
+    }
+    parentFiber.lastChild = fiber;
+    this.__prepareAndRender(fiber, cb);
+    return fiber;
+  }
+
+  /**
+   * Apply the stylesheets defined by the component. Note that we need to make
+   * sure all inherited stylesheets are applied as well.  We then delete the
+   * `style` key from the constructor to make sure we do not apply it again.
+   */
+  private __applyStyles(constr) {
+    while (constr && constr.style) {
+      if (constr.hasOwnProperty("style")) {
+        activateSheet(constr.style, constr.name);
+        delete constr.style;
+      }
+      constr = constr.__proto__;
+    }
+  }
+  __getTemplate(qweb: QWeb): string {
+    let p = (<any>this).constructor;
+    if (!p.hasOwnProperty("_template")) {
+      // 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 = p.name;
+      while (!(template in qweb.templates) && p !== Component) {
+        p = p.__proto__;
+        template = p.name;
+      }
+      if (p === Component) {
+        throw new Error(`Could not find template for component "${this.constructor.name}"`);
+      } else {
+        p._template = template;
+      }
+    }
+    return p._template;
+  }
+
+  async __prepareAndRender(fiber: Fiber, cb: CallableFunction) {
+    try {
+      const proms = Promise.all([
+        this.willStart(),
+        this.__owl__.willStartCB && this.__owl__.willStartCB(),
+      ]);
+      this.__owl__.status = STATUS.WILLSTARTED;
+      await proms;
+      if (this.__owl__.status === <any>STATUS.DESTROYED) {
+        return Promise.resolve();
+      }
+    } catch (e) {
+      fiber.handleError(e);
+      return Promise.resolve();
+    }
+    if (!fiber.isCompleted) {
+      this.__render(fiber);
+      this.__owl__.status = STATUS.RENDERED;
+      cb();
+    }
+  }
+
+  __render(fiber: Fiber) {
+    const __owl__ = this.__owl__;
+    if (__owl__.observer) {
+      __owl__.observer.allowMutations = false;
+    }
+    let error;
+    try {
+      let vnode = __owl__.renderFn!(this, {
+        handlers: __owl__.boundHandlers,
+        fiber: fiber,
+      });
+      // we iterate over the children to detect those that no longer belong to the
+      // current rendering: those ones, if not mounted yet, can (and have to) be
+      // destroyed right now, because they are not in the DOM, and thus we won't
+      // be notified later on (when patching), that they are removed from the DOM
+      for (let childKey in __owl__.children) {
+        const child = __owl__.children[childKey];
+        const childOwl = child.__owl__;
+        if (childOwl.status !== STATUS.MOUNTED && childOwl.parentLastFiberId < fiber.id) {
+          // we only do here a "soft" destroy, meaning that we leave the child
+          // dom node alone, without removing it.  Most of the time, it does not
+          // matter, because the child component is already unmounted.  However,
+          // if some of its parent have been unmounted, the child could actually
+          // still be attached to its parent, and this may be important if we
+          // want to remount the parent, because the vdom need to match the
+          // actual DOM
+          child.__destroy(childOwl.parent);
+          if (childOwl.pvnode) {
+            // we remove the key here to make sure that the patching algorithm
+            // is able to make the difference between this pvnode and an eventual
+            // other instance of the same component
+            delete childOwl.pvnode.key;
+            // Since the component has been unmounted, we do not want to actually
+            // call a remove hook.  This is pretty important, since the t-component
+            // directive actually disabled it, so the vdom algorithm will just
+            // not remove the child elm if we don't remove the hook.
+            delete childOwl.pvnode.data!.hook!.remove;
+          }
+        }
+      }
+      if (!vnode) {
+        throw new Error(`Rendering '${this.constructor.name}' did not return anything`);
+      }
+      fiber.vnode = vnode;
+      // we apply here the class information described on the component by the
+      // template (so, something like <MyComponent class="..."/>) to the actual
+      // root vnode
+      if (__owl__.classObj) {
+        const data = vnode.data!;
+        data.class = Object.assign(data.class || {}, __owl__.classObj);
+      }
+    } catch (e) {
+      error = e;
+    }
+    if (__owl__.observer) {
+      __owl__.observer.allowMutations = true;
+    }
+
+    fiber.root.counter--;
+    fiber.isRendered = true;
+    if (error) {
+      fiber.handleError(error);
+    }
+  }
+
+  /**
+   * Apply default props (only top level).
+   *
+   * Note that this method does modify in place the props
+   */
+  __applyDefaultProps(props: Object, defaultProps: Object) {
+    for (let propName in defaultProps) {
+      if (props![propName] === undefined) {
+        props![propName] = defaultProps[propName];
+      }
+    }
+  }
+}
+
+interface MountParameters {
+  env?: Env;
+  target: HTMLElement | DocumentFragment;
+  props?: any;
+  position?: MountOptions["position"];
+}
+
+interface Type<T> extends Function {
+  new (...args: any[]): T;
+}
+
+export async function mount<T extends Type<Component>>(
+  C: T,
+  params: MountParameters
+): Promise<InstanceType<T>> {
+  const { env, props, target } = params;
+  let origEnv = C.hasOwnProperty("env") ? (C as any).env : null;
+  if (env) {
+    (C as any as typeof Component).env = env;
+  }
+  const component: Component = new C(null, props);
+  if (origEnv) {
+    (C as any).env = origEnv;
+  } else {
+    delete (C as any).env;
+  }
+  const position = params.position || "last-child";
+  await component.mount(target, { position });
+  return component as any;
+}

src/component/directive.ts

@@ -0,0 +1,516 @@
+import { QWeb } from "../qweb/index";
+import { INTERP_REGEXP } from "../qweb/compilation_context";
+import { makeHandlerCode, MODS_CODE } from "../qweb/extensions";
+import { STATUS } from "./component";
+
+//------------------------------------------------------------------------------
+// t-component
+//------------------------------------------------------------------------------
+
+const T_COMPONENT_MODS_CODE = Object.assign({}, MODS_CODE, {
+  self: "if (e.target !== vn.elm) {return}",
+});
+
+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;
+      },
+    });
+  }
+};
+
+QWeb.utils.assignHooks = function assignHooks(dataObj, hooks) {
+  if ("hook" in dataObj) {
+    const hookObject = dataObj.hook;
+    for (let name in hooks) {
+      const current = hookObject[name];
+      const fn = hooks[name];
+      if (current) {
+        hookObject[name] = (...args) => {
+          current(...args);
+          fn(...args);
+        };
+      } else {
+        hookObject[name] = fn;
+      }
+    }
+  } else {
+    dataObj.hook = hooks;
+  }
+};
+
+/**
+ * The t-component directive is certainly a complicated and hard to maintain piece
+ * of code.  To help you, fellow developer, if you have to maintain it, I offer
+ * 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"],
+  priority: 100,
+  atNodeEncounter({ ctx, value, node, qweb }): boolean {
+    ctx.addLine(`// Component '${value}'`);
+    ctx.rootContext.shouldDefineQWeb = true;
+    ctx.rootContext.shouldDefineParent = true;
+    ctx.rootContext.shouldDefineUtils = true;
+    ctx.rootContext.shouldDefineScope = true;
+    let hasDynamicProps = node.getAttribute("t-props") ? true : false;
+
+    // t-on- events and t-transition
+    const events: [string, string][] = [];
+    let transition: string = "";
+    const attributes = (<Element>node).attributes;
+    const props: { [key: string]: string } = {};
+    for (let i = 0; i < attributes.length; i++) {
+      const name = attributes[i].name;
+      const value = attributes[i].textContent!;
+      if (name.startsWith("t-on-")) {
+        events.push([name, value]);
+      } else if (name === "t-transition") {
+        if (QWeb.enableTransitions) {
+          transition = value;
+        }
+      } else if (!name.startsWith("t-")) {
+        if (name !== "class" && name !== "style") {
+          // this is a prop!
+          if (value.includes("=>")) {
+            props[name] = ctx.captureExpression(value);
+          } else {
+            props[name] = ctx.formatExpression(value) || "undefined";
+          }
+        }
+      }
+    }
+
+    // computing the props string representing the props object
+    let propStr = Object.keys(props)
+      .map((k) => k + ":" + props[k])
+      .join(",");
+    let componentID = ctx.generateID();
+
+    let hasDefinedKey = false;
+    let templateKey;
+    if (node.tagName === "t" && !node.hasAttribute("t-key") && value.match(INTERP_REGEXP)) {
+      defineComponentKey();
+      const id = ctx.generateID();
+      // the ___ is to make sure we have no possible conflict with normal
+      // template keys
+      ctx.addLine(`let k${id} = '___' + componentKey${componentID}`);
+      templateKey = `k${id}`;
+    } else {
+      templateKey = ctx.generateTemplateKey();
+    }
+    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${componentID};`;
+    }
+    let finalizeComponentCode = `w${componentID}.destroy();`;
+    if (ref) {
+      finalizeComponentCode += `delete context.__owl__.refs[${refKey}];`;
+    }
+    if (transition) {
+      finalizeComponentCode = `let finalize = () => {
+          ${finalizeComponentCode}
+        };
+        delete w${componentID}.__owl__.transitionInserted;
+        utils.transitionRemove(vn, '${transition}', finalize);`;
+    }
+
+    let createHook = "";
+    let classAttr = node.getAttribute("class");
+    let tattClass = node.getAttribute("t-att-class");
+    let styleAttr = node.getAttribute("style");
+    let tattStyle = node.getAttribute("t-att-style");
+    if (tattStyle) {
+      const attVar = `_${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.toClassObj(${tattExpr})`;
+        }
+        if (classAttr) {
+          ctx.addLine(`Object.assign(${classObj}, ${tattExpr})`);
+        } else {
+          classObj = `_${ctx.generateID()}`;
+          ctx.addLine(`let ${classObj} = ${tattExpr};`);
+        }
+      }
+      let eventsCode = events
+        .map(function ([name, value]) {
+          const capture = name.match(/\.capture/);
+          name = capture ? name.replace(/\.capture/, "") : name;
+          const { event, handler } = makeHandlerCode(
+            ctx,
+            name,
+            value,
+            false,
+            T_COMPONENT_MODS_CODE
+          );
+          if (capture) {
+            return `vn.elm.addEventListener('${event}', ${handler}, true);`;
+          }
+          return `vn.elm.addEventListener('${event}', ${handler});`;
+        })
+        .join("");
+      const styleExpr = tattStyle || (styleAttr ? `'${styleAttr}'` : false);
+      const styleCode = styleExpr ? `vn.elm.style = ${styleExpr};` : "";
+      createHook = `utils.assignHooks(vnode.data, {create(_, vn){${styleCode}${eventsCode}}});`;
+    }
+
+    ctx.addLine(
+      `let w${componentID} = ${templateKey} in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap[${templateKey}]] : false;`
+    );
+    let shouldProxy = !ctx.parentNode;
+    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({}, ${dynamicProp}, {${propStr}});`);
+    } 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 hasSlots = node.childNodes.length;
+
+    let scope = hasSlots ? `utils.combine(context, scope)` : "undefined";
+
+    ctx.addIf(`w${componentID}`);
+
+    // need to update component
+    let styleCode = "";
+    if (tattStyle) {
+      styleCode = `.then(()=>{if (w${componentID}.__owl__.status === ${STATUS.DESTROYED}) {return};w${componentID}.el.style=${tattStyle};});`;
+    }
+    ctx.addLine(
+      `w${componentID}.__updateProps(props${componentID}, extra.fiber, ${scope})${styleCode};`
+    );
+    ctx.addLine(`let pvnode = w${componentID}.__owl__.pvnode;`);
+    if (registerCode) {
+      ctx.addLine(registerCode);
+    }
+    if (ctx.parentNode) {
+      ctx.addLine(`c${ctx.parentNode}.push(pvnode);`);
+    }
+
+    ctx.addElse();
+
+    // new component
+    function defineComponentKey() {
+      if (!hasDefinedKey) {
+        const interpValue = ctx.interpolate(value);
+        ctx.addLine(`let componentKey${componentID} = ${interpValue};`);
+        hasDefinedKey = true;
+      }
+    }
+    defineComponentKey();
+    const contextualValue = value.match(INTERP_REGEXP) ? "false" : ctx.formatExpression(value);
+    ctx.addLine(
+      `let W${componentID} = ${contextualValue} || context.constructor.components[componentKey${componentID}] || QWeb.components[componentKey${componentID}];`
+    );
+
+    // maybe only do this in dev mode...
+    ctx.addLine(
+      `if (!W${componentID}) {throw new Error('Cannot find the definition of component "' + componentKey${componentID} + '"')}`
+    );
+    ctx.addLine(`w${componentID} = new W${componentID}(parent, props${componentID});`);
+    if (transition) {
+      ctx.addLine(`const __patch${componentID} = w${componentID}.__patch;`);
+      ctx.addLine(
+        `w${componentID}.__patch = (t, vn) => {__patch${componentID}.call(w${componentID}, t, vn); if(!w${componentID}.__owl__.transitionInserted){w${componentID}.__owl__.transitionInserted = true;utils.transitionInsert(w${componentID}.__owl__.vnode, '${transition}');}};`
+      );
+    }
+    ctx.addLine(`parent.__owl__.cmap[${templateKey}] = w${componentID}.__owl__.id;`);
+
+    if (hasSlots) {
+      const clone = <Element>node.cloneNode(true);
+
+      // The next code is a fallback for compatibility reason. It accepts t-set
+      // elements that are direct children with a non empty body as nodes defining
+      // the content of a slot.
+      //
+      // This is wrong, but is necessary to prevent breaking all existing Owl
+      // code using slots. This will be removed in v2.0 someday. Meanwhile,
+      // please use t-set-slot everywhere you need to set the content of a
+      // slot.
+      for (let node of clone.children) {
+        if (node.hasAttribute("t-set") && node.hasChildNodes()) {
+          node.setAttribute("t-set-slot", node.getAttribute("t-set")!);
+          node.removeAttribute("t-set");
+        }
+      }
+      const slotNodes = Array.from(clone.querySelectorAll("[t-set-slot]"));
+      const slotNames = new Set<string>();
+      const slotId = QWeb.nextSlotId++;
+      ctx.addLine(`w${componentID}.__owl__.slotId = ${slotId};`);
+      if (slotNodes.length) {
+        for (let i = 0, length = slotNodes.length; i < length; i++) {
+          const slotNode = slotNodes[i];
+          // check if this is defined in a sub component (in which case it should
+          // be ignored)
+          let el = slotNode.parentElement;
+          let isInSubComponent = false;
+          while (el !== clone) {
+            if (
+              el!.hasAttribute("t-component") ||
+              el!.tagName[0] === el!.tagName[0].toUpperCase()
+            ) {
+              isInSubComponent = true;
+              break;
+            }
+            el = el.parentElement;
+          }
+          if (isInSubComponent) {
+            continue;
+          }
+          let key = slotNode.getAttribute("t-set-slot")!;
+          if (slotNames.has(key)) {
+            continue;
+          }
+          slotNames.add(key);
+          slotNode.removeAttribute("t-set-slot");
+          slotNode.parentElement!.removeChild(slotNode);
+
+          const slotFn = qweb._compile(`slot_${key}_template`, { elem: slotNode, hasParent: true });
+          QWeb.slots[`${slotId}_${key}`] = slotFn;
+        }
+      }
+      if (clone.childNodes.length) {
+        let hasContent = false;
+        const t = clone.ownerDocument!.createElement("t");
+        for (let child of Object.values(clone.childNodes)) {
+          hasContent =
+            hasContent || (child instanceof Text ? Boolean(child.textContent.trim().length) : true);
+          t.appendChild(child);
+        }
+        if (hasContent) {
+          const slotFn = qweb._compile(`slot_default_template`, { elem: t, hasParent: true });
+          QWeb.slots[`${slotId}_default`] = slotFn;
+        }
+      }
+    }
+
+    ctx.addLine(
+      `let fiber = w${componentID}.__prepare(extra.fiber, ${scope}, () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; ${createHook}});`
+    );
+    // hack: specify empty remove hook to prevent the node from being removed from the DOM
+    const insertHook = refExpr ? `insert(vn) {${refExpr}},` : "";
+    ctx.addLine(
+      `let pvnode = h('dummy', {key: ${templateKey}, hook: {${insertHook}remove() {},destroy(vn) {${finalizeComponentCode}}}});`
+    );
+    if (registerCode) {
+      ctx.addLine(registerCode);
+    }
+    if (ctx.parentNode) {
+      ctx.addLine(`c${ctx.parentNode}.push(pvnode);`);
+    }
+    ctx.addLine(`w${componentID}.__owl__.pvnode = pvnode;`);
+
+    ctx.closeIf();
+
+    if (classObj) {
+      ctx.addLine(`w${componentID}.__owl__.classObj=${classObj};`);
+    }
+
+    ctx.addLine(`w${componentID}.__owl__.parentLastFiberId = extra.fiber.id;`);
+
+    return true;
+  },
+});

src/component/fiber.ts

@@ -0,0 +1,366 @@
+import { h, VNode } from "../vdom/index";
+import { Component, MountPosition, STATUS } from "./component";
+import { scheduler } from "./scheduler";
+
+/**
+ * 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 {
+  static nextId: number = 1;
+  id: number = Fiber.nextId++;
+
+  // The force attribute determines if a rendering should bypass the `shouldUpdate`
+  // method potentially implemented by a component. It is usually set to false.
+  force: boolean;
+
+  // isCompleted means that the rendering corresponding to this fiber's work is
+  // done, either because the component has been mounted or patched, or because
+  // fiber has been cancelled.
+  isCompleted: boolean = false;
+
+  // the fibers corresponding to component updates (updateProps) need to call
+  // the willPatch and patched hooks from the corresponding component. However,
+  // 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;
+
+  target: HTMLElement | DocumentFragment | null;
+  position: MountPosition | null;
+
+  scope: any;
+
+  component: Component;
+  vnode: VNode | null = null;
+
+  root: Fiber;
+  child: Fiber | null = null;
+  sibling: Fiber | null = null;
+  lastChild: Fiber | null = null;
+  parent: Fiber | null = null;
+
+  error?: Error;
+
+  constructor(
+    parent: Fiber | null,
+    component: Component,
+    force: boolean,
+    target: HTMLElement | DocumentFragment | null,
+    position: MountPosition | null
+  ) {
+    this.component = component;
+    this.force = force;
+    this.target = target;
+    this.position = position;
+
+    const __owl__ = component.__owl__;
+    this.scope = __owl__.scope;
+
+    this.root = parent ? parent.root : this;
+    this.parent = parent;
+
+    let oldFiber = __owl__.currentFiber;
+    if (oldFiber && !oldFiber.isCompleted) {
+      this.force = true;
+      if (oldFiber.root === oldFiber && !parent) {
+        // both oldFiber and this fiber are root fibers
+        this._reuseFiber(oldFiber);
+        return oldFiber;
+      } else {
+        this._remapFiber(oldFiber);
+      }
+    }
+
+    this.root.counter++;
+
+    __owl__.currentFiber = this;
+  }
+
+  /**
+   * When the oldFiber is not completed yet, and both oldFiber and this fiber
+   * are root fibers, we want to reuse the oldFiber instead of creating a new
+   * one. Doing so will guarantee that the initiator(s) of those renderings will
+   * be notified (the promise will resolve) when the last rendering will be done.
+   *
+   * This function thus assumes that oldFiber is a root fiber.
+   */
+  _reuseFiber(oldFiber: Fiber) {
+    oldFiber.cancel(); // cancel children fibers
+    oldFiber.target = this.target || oldFiber.target;
+    oldFiber.position = this.position || oldFiber.position;
+    oldFiber.isCompleted = false; // keep the root fiber alive
+    oldFiber.isRendered = false; // the fiber has to be re-rendered
+    if (oldFiber.child) {
+      // remove relation to children
+      oldFiber.child.parent = null;
+      oldFiber.child = null;
+      oldFiber.lastChild = null;
+    }
+    oldFiber.counter = 1; // re-initialize counter
+    oldFiber.id = Fiber.nextId++;
+  }
+
+  /**
+   * 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();
+    this.shouldPatch = oldFiber.shouldPatch;
+    if (oldFiber === oldFiber.root) {
+      oldFiber.counter++;
+    }
+    if (oldFiber.parent && !this.parent) {
+      // re-map links
+      this.parent = oldFiber.parent;
+      this.root = this.parent.root;
+      this.sibling = oldFiber.sibling;
+      if (this.parent.lastChild === oldFiber) {
+        this.parent.lastChild = this;
+      }
+      if (this.parent.child === oldFiber) {
+        this.parent.child = this;
+      } else {
+        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;
+    }
+  }
+
+  /**
+   * Successfully complete the work of the fiber: call the mount or patch hooks
+   * and patch the DOM. This function is called once the fiber and its children
+   * are ready, and the scheduler decides to process it.
+   */
+  complete() {
+    let component = this.component;
+    this.isCompleted = true;
+    const status = component.__owl__.status;
+    if (status === STATUS.DESTROYED) {
+      return;
+    }
+
+    // build patchQueue
+    const patchQueue: Fiber[] = [];
+    const doWork: (Fiber) => Fiber | null = function (f) {
+      f.component.__owl__.currentFiber = null;
+      patchQueue.push(f);
+      return f.child;
+    };
+    this._walk(doWork);
+    const patchLen = patchQueue.length;
+
+    // call willPatch hook on each fiber of patchQueue
+    if (status === STATUS.MOUNTED) {
+      for (let i = 0; i < patchLen; i++) {
+        const fiber = patchQueue[i];
+        if (fiber.shouldPatch) {
+          component = fiber.component;
+          if (component.__owl__.willPatchCB) {
+            component.__owl__.willPatchCB();
+          }
+          component.willPatch();
+        }
+      }
+    }
+
+    // call __patch on each fiber of (reversed) patchQueue
+    for (let i = patchLen - 1; i >= 0; i--) {
+      const fiber = patchQueue[i];
+      component = fiber.component;
+      if (fiber.target && i === 0) {
+        let target;
+        if (fiber.position === "self") {
+          target = fiber.target;
+          if ((target as HTMLElement).tagName.toLowerCase() !== fiber.vnode!.sel) {
+            throw new Error(
+              `Cannot attach '${component.constructor.name}' to target node (not same tag name)`
+            );
+          }
+          // In self mode, we *know* we are to take possession of the target
+          // Hence we manually create the corresponding VNode and copy the "key" in data
+          const selfVnodeData = fiber.vnode!.data ? { key: fiber.vnode!.data.key } : {};
+          const selfVnode = h(fiber.vnode!.sel, selfVnodeData);
+          selfVnode.elm = target;
+          target = selfVnode;
+        } else {
+          target = component.__owl__.vnode || document.createElement(fiber.vnode!.sel!);
+        }
+        component.__patch(target!, fiber.vnode!);
+      } else {
+        const vnode = component.__owl__.vnode;
+        if (fiber.shouldPatch && vnode) {
+          component.__patch(vnode, fiber.vnode!);
+          // When updating a Component's props (in directive),
+          // the component has a pvnode AND should be patched.
+          // However, its pvnode.elm may have changed if it is a High Order Component
+          if (component.__owl__.pvnode) {
+            component.__owl__.pvnode.elm = component.__owl__.vnode!.elm;
+          }
+        } else {
+          component.__patch(document.createElement(fiber.vnode!.sel!), fiber.vnode!);
+          component.__owl__.pvnode!.elm = component.__owl__.vnode!.elm;
+        }
+      }
+    }
+
+    // insert into the DOM (mount case)
+    let inDOM = false;
+    if (this.target) {
+      switch (this.position) {
+        case "first-child":
+          this.target.prepend(this.component.el!);
+          break;
+        case "last-child":
+          this.target.appendChild(this.component.el!);
+          break;
+      }
+      inDOM = document.body.contains(this.component.el);
+      this.component.env.qweb.trigger("dom-appended");
+    }
+
+    // call patched/mounted hook on each fiber of (reversed) patchQueue
+    if (status === STATUS.MOUNTED || inDOM) {
+      for (let i = patchLen - 1; i >= 0; i--) {
+        const fiber = patchQueue[i];
+        component = fiber.component;
+        if (fiber.shouldPatch && !this.target) {
+          component.patched();
+          if (component.__owl__.patchedCB) {
+            component.__owl__.patchedCB();
+          }
+        } else {
+          component.__callMounted();
+        }
+      }
+    } else {
+      for (let i = patchLen - 1; i >= 0; i--) {
+        const fiber = patchQueue[i];
+        component = fiber.component;
+        component.__owl__.status = STATUS.UNMOUNTED;
+      }
+    }
+  }
+
+  /**
+   * Cancel a fiber and all its children.
+   */
+  cancel() {
+    this._walk((f) => {
+      if (!f.isRendered) {
+        f.root.counter--;
+      }
+      f.isCompleted = 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 component = this.component;
+    this.vnode = component.__owl__.vnode || h("div");
+
+    const qweb = component.env.qweb;
+    let root = component;
+
+    function handle(error) {
+      let canCatch = false;
+      qweb.trigger("error", error);
+      while (component && !(canCatch = !!component.catchError)) {
+        root = component;
+        component = component.__owl__.parent!;
+      }
+      if (canCatch) {
+        try {
+          component.catchError!(error);
+        } catch (e) {
+          root = component;
+          component = component.__owl__.parent!;
+          return handle(e);
+        }
+        return true;
+      }
+      return false;
+    }
+
+    let isHandled = handle(error);
+
+    if (!isHandled) {
+      // the 3 next lines aim to mark the root fiber as being in error, and
+      // to force it to end, without waiting for its children
+      this.root.counter = 0;
+      this.root.error = error;
+      scheduler.flush();
+      // at this point, the state of the application is corrupted and we could
+      // have a lot of issues or crashes. So we destroy the application in a try
+      // catch and swallow these errors because the fiber is already in error,
+      // and this is the actual issue that needs to be solved, not those followup
+      // errors.
+      try {
+        root.destroy();
+      } catch (e) {}
+    }
+  }
+}

src/component/props_validation.ts

@@ -0,0 +1,115 @@
+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 {
+          continue;
+        }
+      }
+      let isValid;
+      try {
+        isValid = isValidProp(props[propName], propsDef[propName]);
+      } catch (e) {
+        e.message = `Invalid prop '${propName}' in component ${Widget.name} (${e.message})`;
+        throw e;
+      }
+      if (!isValid) {
+        throw new Error(`Invalid Prop '${propName}' in component '${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
+  if (propDef.optional && prop === undefined) {
+    return true;
+  }
+  let result = propDef.type ? isValidProp(prop, propDef.type) : true;
+  if (propDef.validate) {
+    result = result && propDef.validate(prop);
+  }
+  if (propDef.type === Array && propDef.element) {
+    for (let i = 0, iLen = prop.length; i < iLen; i++) {
+      result = result && isValidProp(prop[i], propDef.element);
+    }
+  }
+  if (propDef.type === Object && propDef.shape) {
+    const shape = propDef.shape;
+    for (let key in shape) {
+      result = result && isValidProp(prop[key], shape[key]);
+    }
+    if (result) {
+      for (let propName in prop) {
+        if (!(propName in shape)) {
+          throw new Error(`unknown prop '${propName}'`);
+        }
+      }
+    }
+  }
+  return result;
+}

src/component/scheduler.ts

@@ -0,0 +1,113 @@
+import { Fiber } from "./fiber";
+import { browser } from "../browser";
+
+/**
+ * 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: Window["requestAnimationFrame"];
+
+  constructor(requestAnimationFrame: Window["requestAnimationFrame"]) {
+    this.requestAnimationFrame = requestAnimationFrame;
+  }
+
+  start() {
+    this.isRunning = true;
+    this.scheduleTasks();
+  }
+
+  stop() {
+    this.isRunning = false;
+  }
+
+  addFiber(fiber: Fiber): Promise<void> {
+    // if the fiber was remapped into a larger rendering fiber, it may not be a
+    // root fiber.  But we only want to register root fibers
+    fiber = fiber.root;
+    return new Promise((resolve, reject) => {
+      if (fiber.error) {
+        return reject(fiber.error);
+      }
+      this.tasks.push({
+        fiber,
+        callback: () => {
+          if (fiber.error) {
+            return reject(fiber.error);
+          }
+          resolve();
+        },
+      });
+      if (!this.isRunning) {
+        this.start();
+      }
+    });
+  }
+
+  rejectFiber(fiber: Fiber, reason: string) {
+    fiber = fiber.root;
+    const index = this.tasks.findIndex((t) => t.fiber === fiber);
+    if (index >= 0) {
+      const [task] = this.tasks.splice(index, 1);
+      fiber.cancel();
+      fiber.error = new Error(reason);
+      task.callback();
+    }
+  }
+
+  /**
+   * Process all current tasks. This only applies to the fibers that are ready.
+   * Other tasks are left unchanged.
+   */
+  flush() {
+    let tasks = this.tasks;
+    this.tasks = [];
+    tasks = tasks.filter((task) => {
+      if (task.fiber.isCompleted) {
+        task.callback();
+        return false;
+      }
+      if (task.fiber.counter === 0) {
+        if (!task.fiber.error) {
+          try {
+            task.fiber.complete();
+          } catch (e) {
+            task.fiber.handleError(e);
+          }
+        }
+        task.callback();
+        return false;
+      }
+      return true;
+    });
+    this.tasks = tasks.concat(this.tasks);
+    if (this.tasks.length === 0) {
+      this.stop();
+    }
+  }
+
+  scheduleTasks() {
+    this.requestAnimationFrame(() => {
+      this.flush();
+      if (this.isRunning) {
+        this.scheduleTasks();
+      }
+    });
+  }
+}
+
+export const scheduler = new Scheduler(browser.requestAnimationFrame);

src/component/styles.ts

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

src/config.ts

@@ -0,0 +1,42 @@
+import { QWeb } from "./qweb/index";
+import { TRANSLATABLE_ATTRS } from "./qweb/qweb";
+
+/**
+ * This file creates and exports the OWL 'config' object, with keys:
+ *  - 'mode': 'prod' or 'dev',
+ *  - 'env': the environment to use in root components.
+ */
+
+interface Config {
+  mode: string;
+  enableTransitions: boolean;
+  translatableAttributes: string[];
+}
+
+export const config = {
+  translatableAttributes: TRANSLATABLE_ATTRS,
+} as Config;
+
+Object.defineProperty(config, "mode", {
+  get() {
+    return QWeb.dev ? "dev" : "prod";
+  },
+  set(mode: string) {
+    QWeb.dev = mode === "dev";
+    if (QWeb.dev) {
+      console.info(`Owl is running in 'dev' mode.
+
+This is not suitable for production use.
+See https://github.com/odoo/owl/blob/master/doc/reference/config.md#mode for more information.`);
+    }
+  },
+});
+
+Object.defineProperty(config, "enableTransitions", {
+  get() {
+    return QWeb.enableTransitions;
+  },
+  set(value: boolean) {
+    QWeb.enableTransitions = value;
+  },
+});

src/context.ts

@@ -0,0 +1,138 @@
+import { Component } from "./component/component";
+import { scheduler } from "./component/scheduler";
+import { EventBus } from "./core/event_bus";
+import { Observer } from "./core/observer";
+
+/**
+ * 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.
+ */
+
+function partitionBy<T>(arr: T[], fn: (t: T) => boolean) {
+  let lastGroup: T[] | false = false;
+  let lastValue;
+  return arr.reduce((acc: T[][], cur) => {
+    let curVal = fn(cur);
+    if (lastGroup) {
+      if (curVal === lastValue) {
+        lastGroup.push(cur);
+      } else {
+        lastGroup = false;
+      }
+    }
+    if (!lastGroup) {
+      lastGroup = [cur];
+      acc.push(lastGroup);
+    }
+    lastValue = curVal;
+    return acc;
+  }, []);
+}
+
+export class Context extends EventBus {
+  state: any;
+  observer: Observer;
+  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 = () => {
+      // notify components in the next microtask tick to ensure that subscribers
+      // are notified only once for all changes that occur in the same micro tick
+      let rev = this.rev;
+      return Promise.resolve().then(() => {
+        if (rev === this.rev) {
+          this.__notifyComponents();
+        }
+      });
+    };
+    this.state = this.observer.observe(state);
+    this.subscriptions.update = [];
+  }
+
+  /**
+   * Instead of using trigger to emit an update event, we actually implement
+   * our own function to do that.  The reason is that we need to be smarter than
+   * a simple trigger function: we need to wait for parent components to be
+   * done before doing children components.  More precisely, if an update
+   * as an effect of destroying a children, we do not want to call any code
+   * from the child, and certainly not render it.
+   *
+   * This method implements a simple grouping algorithm by depth. If we have
+   * connected components of depths [2, 4,4,4,4, 3,8,8], the Context will notify
+   * them in the following groups: [2], [4,4,4,4], [3], [8,8]. Each group will
+   * be updated sequentially, but each components in a given group will be done in
+   * parallel.
+   *
+   * This is a very simple algorithm, but it avoids checking if a given
+   * component is a child of another.
+   */
+  async __notifyComponents() {
+    const rev = ++this.rev;
+    const subscriptions = this.subscriptions.update;
+    const groups = partitionBy(subscriptions, (s) => (s.owner ? s.owner.__owl__.depth : -1));
+    for (let group of groups) {
+      const proms = group.map((sub) => sub.callback.call(sub.owner, rev));
+      // at this point, each component in the current group has registered a
+      // top level fiber in the scheduler. It could happen that rendering these
+      // components is done (if they have no children).  This is why we manually
+      // flush the scheduler.  This will force the scheduler to check
+      // immediately if they are done, which will cause their rendering
+      // promise to resolve earlier, which means that there is a chance of
+      // processing the next group in the same frame.
+      scheduler.flush();
+      await Promise.all(proms);
+    }
+  }
+}
+
+/**
+ * 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 = Component.current!;
+  return useContextWithCB(ctx, component, component.render.bind(component));
+}
+
+export function useContextWithCB(ctx: Context, component: Component, 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);
+  }
+
+  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();
+    }
+  });
+  const __destroy = component.__destroy;
+  component.__destroy = (parent) => {
+    ctx.off("update", component);
+    delete mapping[id];
+    __destroy.call(component, parent);
+  };
+  return ctx.state;
+}

src/core/event_bus.ts

@@ -0,0 +1,79 @@
+/**
+ * We define here a simple event bus: it can
+ * - emit events
+ * - add/remove listeners.
+ *
+ * This is a useful pattern of communication in many cases.  For OWL, each
+ * components and stores are event buses.
+ */
+
+//------------------------------------------------------------------------------
+// Types
+//------------------------------------------------------------------------------
+
+export type Callback = (...args: any[]) => void;
+
+export interface Subscription {
+  owner: any;
+  callback: Callback;
+}
+
+//------------------------------------------------------------------------------
+// EventBus
+//------------------------------------------------------------------------------
+
+export class EventBus {
+  subscriptions: { [eventType: string]: Subscription[] } = {};
+
+  /**
+   * Add a listener for the 'eventType' events.
+   *
+   * Note that the 'owner' of this event can be anything, but will more likely
+   * 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
+   * listener.
+   */
+  on(eventType: string, owner: any, callback: Callback) {
+    if (!callback) {
+      throw new Error("Missing callback");
+    }
+    if (!this.subscriptions[eventType]) {
+      this.subscriptions[eventType] = [];
+    }
+    this.subscriptions[eventType].push({
+      owner,
+      callback,
+    });
+  }
+
+  /**
+   * Remove a listener
+   */
+  off(eventType: string, owner: any) {
+    const subs = this.subscriptions[eventType];
+    if (subs) {
+      this.subscriptions[eventType] = subs.filter((s) => s.owner !== owner);
+    }
+  }
+
+  /**
+   * Emit an event of type 'eventType'.  Any extra arguments will be passed to
+   * the listeners callback.
+   */
+  trigger(eventType: string, ...args: any[]) {
+    const subs = this.subscriptions[eventType] || [];
+    for (let i = 0, iLen = subs.length; i < iLen; i++) {
+      const sub = subs[i];
+      sub.callback.call(sub.owner, ...args);
+    }
+  }
+
+  /**
+   * Remove all subscriptions.
+   */
+  clear() {
+    this.subscriptions = {};
+  }
+}

src/core/observer.ts

@@ -0,0 +1,99 @@
+/**
+ * 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;
+  weakMap: WeakMap<any, any> = new WeakMap();
+
+  notifyCB() {}
+
+  observe<T>(value: T, parent?: any): T {
+    if (
+      value === null ||
+      typeof value !== "object" ||
+      value instanceof Date ||
+      value instanceof Promise
+    ) {
+      // 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;
+  }
+
+  _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.notifyCB();
+        }
+        return true;
+      },
+      deleteProperty(target, key) {
+        if (key in target) {
+          delete target[key];
+          self._updateRevNumber(target);
+          self.notifyCB();
+        }
+        return true;
+      },
+    });
+
+    const metadata = {
+      value,
+      proxy,
+      rev: 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);
+    let parent = target;
+    do {
+      metadata = this.weakMap.get(parent);
+      metadata.rev++;
+    } while ((parent = metadata.parent) && parent !== target);
+  }
+}

src/core/owl_event.ts

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

src/hooks.ts

@@ -0,0 +1,182 @@
+import { Component, Env } 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 = 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 = 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 = 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 = 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<C extends Component = Component> {
+  el: HTMLElement | null;
+  comp: C | null;
+}
+
+export function useRef<C extends Component = Component>(name: string): Ref<C> {
+  const __owl__ = Component.current!.__owl__;
+  return {
+    get el(): HTMLElement | null {
+      const val = __owl__.refs && __owl__.refs[name];
+      if (val instanceof HTMLElement) {
+        return val;
+      } else if (val instanceof Component) {
+        return val.el;
+      }
+      return null;
+    },
+    get comp(): C | null {
+      const val = __owl__.refs && __owl__.refs[name];
+      return val instanceof Component ? (val as C) : null;
+    },
+  };
+}
+
+// -----------------------------------------------------------------------------
+// "Builder" hooks
+// -----------------------------------------------------------------------------
+
+/**
+ * This hook is useful as a building block for some customized hooks, that may
+ * need a reference to the component calling them.
+ */
+export function useComponent<P, E extends Env>(): Component<P, E> {
+  return Component.current as any;
+}
+
+/**
+ * This hook is useful as a building block for some customized hooks, that may
+ * need a reference to the env of the component calling them.
+ */
+export function useEnv<E extends Env>(): E {
+  return Component.current.env as any;
+}
+
+// -----------------------------------------------------------------------------
+// useSubEnv
+// -----------------------------------------------------------------------------
+
+/**
+ * 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);
+}
+
+// -----------------------------------------------------------------------------
+// useExternalListener
+// -----------------------------------------------------------------------------
+
+/**
+ * When a component needs to listen to DOM Events on element(s) that are not
+ * part of his hierarchy, we can use the `useExternalListener` hook.
+ * It will correctly add and remove the event listener, whenever the
+ * component is mounted and unmounted.
+ *
+ * Example:
+ *  a menu needs to listen to the click on window to be closed automatically
+ *
+ * Usage:
+ *  in the constructor of the OWL component that needs to be notified,
+ *  `useExternalListener(window, 'click', this._doSomething);`
+ * */
+export function useExternalListener(
+  target: HTMLElement | typeof window,
+  eventName: string,
+  handler,
+  eventParams?
+) {
+  const boundHandler = handler.bind(Component.current);
+
+  onMounted(() => target.addEventListener(eventName, boundHandler, eventParams));
+  onWillUnmount(() => target.removeEventListener(eventName, boundHandler, eventParams));
+}

src/index.ts

@@ -0,0 +1,42 @@
+/**
+ * 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 { config } from "./config";
+import * as _store from "./store";
+import * as _utils from "./utils";
+import * as _tags from "./tags";
+import { AsyncRoot } from "./misc/async_root";
+import { Portal } from "./misc/portal";
+import * as _hooks from "./hooks";
+import * as _context from "./context";
+import { Link } from "./router/link";
+import { RouteComponent } from "./router/route_component";
+import { Router } from "./router/router";
+
+export { Component, mount } from "./component/component";
+export { QWeb };
+export { config };
+export { browser } from "./browser";
+
+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, Portal };
+export const hooks = Object.assign({}, _hooks, {
+  useContext: _context.useContext,
+  useDispatch: _store.useDispatch,
+  useGetters: _store.useGetters,
+  useStore: _store.useStore,
+});
+
+export const __info__ = {};

src/misc/async_root.ts

@@ -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 {
+  static template = xml`<t t-slot="default"/>`;
+
+  async __updateProps(nextProps, parentFiber) {
+    this.render(parentFiber.force);
+  }
+}

src/misc/portal.ts

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

src/qweb/base_directives.ts

@@ -0,0 +1,395 @@
+import { CompilationContext, INTERP_REGEXP } from "./compilation_context";
+import { QWeb } from "./qweb";
+import { htmlToVDOM } from "../vdom/html_to_vdom";
+import { QWebVar } from "./expression_parser";
+
+/**
+ * Owl QWeb Directives
+ *
+ * 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.htmlToVDOM = htmlToVDOM;
+
+function compileValueNode(value: any, node: Element, qweb: QWeb, ctx: CompilationContext) {
+  ctx.rootContext.shouldDefineScope = true;
+  if (value === "0") {
+    if (ctx.parentNode) {
+      // the 'zero' magical symbol is where we can find the result of the rendering
+      // of  the body of the t-call.
+      ctx.rootContext.shouldDefineUtils = true;
+      const zeroArgs = ctx.escaping
+        ? `{text: utils.vDomToString(scope[utils.zero])}`
+        : `...scope[utils.zero]`;
+      ctx.addLine(`c${ctx.parentNode}.push(${zeroArgs});`);
+    }
+    return;
+  }
+
+  let exprID: string;
+  if (typeof value === "string") {
+    exprID = `_${ctx.generateID()}`;
+    ctx.addLine(`let ${exprID} = ${ctx.formatExpression(value)};`);
+  } else {
+    exprID = `scope.${value.id}`;
+  }
+  ctx.addIf(`${exprID} != null`);
+
+  if (ctx.escaping) {
+    let protectID;
+    if (value.hasBody) {
+      ctx.rootContext.shouldDefineUtils = true;
+      protectID = ctx.startProtectScope();
+      ctx.addLine(
+        `${exprID} = ${exprID} instanceof utils.VDomArray ? utils.vDomToString(${exprID}) : ${exprID};`
+      );
+    }
+    if (ctx.parentTextNode) {
+      ctx.addLine(`vn${ctx.parentTextNode}.text += ${exprID};`);
+    } else if (ctx.parentNode) {
+      ctx.addLine(`c${ctx.parentNode}.push({text: ${exprID}});`);
+    } else {
+      let nodeID = ctx.generateID();
+      ctx.rootContext.rootNode = nodeID;
+      ctx.rootContext.parentTextNode = nodeID;
+      ctx.addLine(`let vn${nodeID} = {text: ${exprID}};`);
+      if (ctx.rootContext.shouldDefineResult) {
+        ctx.addLine(`result = vn${nodeID}`);
+      }
+    }
+    if (value.hasBody) {
+      ctx.stopProtectScope(protectID);
+    }
+  } else {
+    ctx.rootContext.shouldDefineUtils = true;
+    if (value.hasBody) {
+      ctx.addLine(
+        `const vnodeArray = ${exprID} instanceof utils.VDomArray ? ${exprID} : utils.htmlToVDOM(${exprID});`
+      );
+      ctx.addLine(`c${ctx.parentNode}.push(...vnodeArray);`);
+    } else {
+      ctx.addLine(`c${ctx.parentNode}.push(...utils.htmlToVDOM(${exprID}));`);
+    }
+  }
+  if (node.childNodes.length) {
+    ctx.addElse();
+    qweb._compileChildren(node, ctx);
+  }
+
+  ctx.closeIf();
+}
+
+QWeb.addDirective({
+  name: "esc",
+  priority: 70,
+  atNodeEncounter({ node, qweb, ctx }): boolean {
+    let value = ctx.getValue(node.getAttribute("t-esc")!);
+    compileValueNode(value, node, qweb, ctx.subContext("escaping", true));
+    return true;
+  },
+});
+
+QWeb.addDirective({
+  name: "raw",
+  priority: 80,
+  atNodeEncounter({ node, qweb, ctx }): boolean {
+    let value = ctx.getValue(node.getAttribute("t-raw")!);
+    compileValueNode(value, node, qweb, ctx);
+    return true;
+  },
+});
+
+//------------------------------------------------------------------------------
+// t-set
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "set",
+  extraNames: ["value"],
+  priority: 60,
+  atNodeEncounter({ node, qweb, ctx }): boolean {
+    ctx.rootContext.shouldDefineScope = true;
+    const variable = node.getAttribute("t-set")!;
+    let value = node.getAttribute("t-value")!;
+    ctx.variables[variable] = ctx.variables[variable] || ({} as QWebVar);
+    let qwebvar = ctx.variables[variable];
+    const hasBody = node.hasChildNodes();
+
+    qwebvar.id = variable;
+    qwebvar.expr = `scope.${variable}`;
+    if (value) {
+      const formattedValue = ctx.formatExpression(value);
+      let scopeExpr = `scope`;
+      if (ctx.protectedScopeNumber) {
+        ctx.rootContext.shouldDefineUtils = true;
+        scopeExpr = `utils.getScope(scope, '${variable}')`;
+      }
+      ctx.addLine(`${scopeExpr}.${variable} = ${formattedValue};`);
+      qwebvar.value = formattedValue;
+    }
+
+    if (hasBody) {
+      ctx.rootContext.shouldDefineUtils = true;
+      if (value) {
+        ctx.addIf(`!(${qwebvar.expr})`);
+      }
+      const tempParentNodeID = ctx.generateID();
+      const _parentNode = ctx.parentNode;
+      ctx.parentNode = tempParentNodeID;
+
+      ctx.addLine(`let c${tempParentNodeID} = new utils.VDomArray();`);
+      const nodeCopy = node.cloneNode(true) as Element;
+      for (let attr of ["t-set", "t-value", "t-if", "t-else", "t-elif"]) {
+        nodeCopy.removeAttribute(attr);
+      }
+      qweb._compileNode(nodeCopy, ctx);
+
+      ctx.addLine(`${qwebvar.expr} = c${tempParentNodeID}`);
+      qwebvar.value = `c${tempParentNodeID}`;
+      qwebvar.hasBody = true;
+
+      ctx.parentNode = _parentNode;
+      if (value) {
+        ctx.closeIf();
+      }
+    }
+    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) : `scope.${cond.id!}`);
+    return false;
+  },
+  finalize({ ctx }) {
+    ctx.closeIf();
+  },
+});
+
+QWeb.addDirective({
+  name: "elif",
+  priority: 30,
+  atNodeEncounter({ node, ctx }): boolean {
+    let cond = ctx.getValue(node.getAttribute("t-elif")!);
+    ctx.addLine(
+      `else if (${typeof cond === "string" ? ctx.formatExpression(cond) : `scope.${cond.id}`}) {`
+    );
+    ctx.indent();
+    return false;
+  },
+  finalize({ ctx }) {
+    ctx.closeIf();
+  },
+});
+
+QWeb.addDirective({
+  name: "else",
+  priority: 40,
+  atNodeEncounter({ ctx }): boolean {
+    ctx.addLine(`else {`);
+    ctx.indent();
+    return false;
+  },
+  finalize({ ctx }) {
+    ctx.closeIf();
+  },
+});
+
+//------------------------------------------------------------------------------
+// t-call
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "call",
+  priority: 50,
+  atNodeEncounter({ node, qweb, ctx }): boolean {
+    // Step 1: sanity checks
+    // ------------------------------------------------
+    ctx.rootContext.shouldDefineScope = true;
+    ctx.rootContext.shouldDefineUtils = true;
+    const subTemplate = node.getAttribute("t-call")!;
+    const isDynamic = INTERP_REGEXP.test(subTemplate);
+    const nodeTemplate = qweb.templates[subTemplate];
+    if (!isDynamic && !nodeTemplate) {
+      throw new Error(`Cannot find template "${subTemplate}" (t-call)`);
+    }
+
+    // Step 2: compile target template in sub templates
+    // ------------------------------------------------
+    let subIdstr: string;
+    if (isDynamic) {
+      const _id = ctx.generateID();
+      ctx.addLine(`let tname${_id} = ${ctx.interpolate(subTemplate)};`);
+      ctx.addLine(`let tid${_id} = this.subTemplates[tname${_id}];`);
+      ctx.addIf(`!tid${_id}`);
+      ctx.addLine(`tid${_id} = this.constructor.nextId++;`);
+      ctx.addLine(`this.subTemplates[tname${_id}] = tid${_id};`);
+      ctx.addLine(
+        `this.constructor.subTemplates[tid${_id}] = this._compile(tname${_id}, {hasParent: true, defineKey: true});`
+      );
+      ctx.closeIf();
+      subIdstr = `tid${_id}`;
+    } else {
+      let subId = qweb.subTemplates[subTemplate];
+      if (!subId) {
+        subId = QWeb.nextId++;
+        qweb.subTemplates[subTemplate] = subId;
+        const subTemplateFn = qweb._compile(subTemplate, { hasParent: true, defineKey: true });
+        QWeb.subTemplates[subId] = subTemplateFn;
+      }
+      subIdstr = `'${subId}'`;
+    }
+
+    // Step 3: compile t-call body if necessary
+    // ------------------------------------------------
+    let hasBody = node.hasChildNodes();
+    const protectID = ctx.startProtectScope();
+    if (hasBody) {
+      // we add a sub scope to protect the ambient scope
+      ctx.addLine(`{`);
+      ctx.indent();
+      const nodeCopy = node.cloneNode(true) as Element;
+      for (let attr of ["t-if", "t-else", "t-elif", "t-call"]) {
+        nodeCopy.removeAttribute(attr);
+      }
+      // this local scope is intended to trap c__0
+      ctx.addLine(`{`);
+      ctx.indent();
+      ctx.addLine("let c__0 = [];");
+      qweb._compileNode(nodeCopy, ctx.subContext("parentNode", "__0"));
+      ctx.rootContext.shouldDefineUtils = true;
+      ctx.addLine("scope[utils.zero] = c__0;");
+      ctx.dedent();
+      ctx.addLine(`}`);
+    }
+
+    // Step 4: add the appropriate function call to current component
+    // ------------------------------------------------
+    const parentComponent = ctx.rootContext.shouldDefineParent
+      ? `parent`
+      : `utils.getComponent(context)`;
+    const key = ctx.generateTemplateKey();
+    const parentNode = ctx.parentNode ? `c${ctx.parentNode}` : "result";
+    const extra = `Object.assign({}, extra, {parentNode: ${parentNode}, parent: ${parentComponent}, key: ${key}})`;
+    if (ctx.parentNode) {
+      ctx.addLine(`this.constructor.subTemplates[${subIdstr}].call(this, scope, ${extra});`);
+    } else {
+      // this is a t-call with no parentnode, we need to extract the result
+      ctx.rootContext.shouldDefineResult = true;
+      ctx.addLine(`result = []`);
+      ctx.addLine(`this.constructor.subTemplates[${subIdstr}].call(this, scope, ${extra});`);
+      ctx.addLine(`result = result[0]`);
+    }
+
+    // Step 5: restore previous scope
+    // ------------------------------------------------
+    if (hasBody) {
+      ctx.dedent();
+      ctx.addLine(`}`);
+    }
+    ctx.stopProtectScope(protectID);
+
+    return true;
+  },
+});
+
+//------------------------------------------------------------------------------
+// t-foreach
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "foreach",
+  extraNames: ["as"],
+  priority: 10,
+  atNodeEncounter({ node, qweb, ctx }): boolean {
+    ctx.rootContext.shouldDefineScope = true;
+    ctx = ctx.subContext("loopNumber", ctx.loopNumber + 1);
+    const elems = node.getAttribute("t-foreach")!;
+    const name = node.getAttribute("t-as")!;
+    let arrayID = ctx.generateID();
+    ctx.addLine(`let _${arrayID} = ${ctx.formatExpression(elems)};`);
+    ctx.addLine(`if (!_${arrayID}) { throw new Error('QWeb error: Invalid loop expression')}`);
+    let keysID = ctx.generateID();
+    let valuesID = ctx.generateID();
+    ctx.addLine(`let _${keysID} = _${arrayID};`);
+    ctx.addLine(`let _${valuesID} = _${arrayID};`);
+    ctx.addIf(`!(_${arrayID} instanceof Array)`);
+    ctx.addLine(`_${keysID} = Object.keys(_${arrayID});`);
+    ctx.addLine(`_${valuesID} = Object.values(_${arrayID});`);
+    ctx.closeIf();
+    ctx.addLine(`let _length${keysID} = _${keysID}.length;`);
+    let varsID = ctx.startProtectScope(true);
+    const loopVar = `i${ctx.loopNumber}`;
+    ctx.addLine(`for (let ${loopVar} = 0; ${loopVar} < _length${keysID}; ${loopVar}++) {`);
+    ctx.indent();
+
+    ctx.addLine(`scope.${name}_first = ${loopVar} === 0`);
+    ctx.addLine(`scope.${name}_last = ${loopVar} === _length${keysID} - 1`);
+    ctx.addLine(`scope.${name}_index = ${loopVar}`);
+    ctx.addLine(`scope.${name} = _${keysID}[${loopVar}]`);
+    ctx.addLine(`scope.${name}_value = _${valuesID}[${loopVar}]`);
+    const nodeCopy = <Element>node.cloneNode(true);
+    let shouldWarn =
+      !nodeCopy.hasAttribute("t-key") &&
+      node.children.length === 1 &&
+      node.children[0].tagName !== "t" &&
+      !node.children[0].hasAttribute("t-key");
+    if (shouldWarn) {
+      console.warn(
+        `Directive t-foreach should always be used with a t-key! (in template: '${ctx.templateName}')`
+      );
+    }
+    if (nodeCopy.hasAttribute("t-key")) {
+      const expr = ctx.formatExpression(nodeCopy.getAttribute("t-key")!);
+      ctx.addLine(`let key${ctx.loopNumber} = ${expr};`);
+      nodeCopy.removeAttribute("t-key");
+    } else {
+      ctx.addLine(`let key${ctx.loopNumber} = i${ctx.loopNumber};`);
+    }
+
+    nodeCopy.removeAttribute("t-foreach");
+    qweb._compileNode(nodeCopy, ctx);
+    ctx.dedent();
+    ctx.addLine("}");
+    ctx.stopProtectScope(varsID);
+    return true;
+  },
+});
+
+//------------------------------------------------------------------------------
+// t-debug
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "debug",
+  priority: 1,
+  atNodeEncounter({ ctx }) {
+    ctx.addLine("debugger;");
+  },
+});
+
+//------------------------------------------------------------------------------
+// t-log
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "log",
+  priority: 1,
+  atNodeEncounter({ ctx, value }) {
+    const expr = ctx.formatExpression(value);
+    ctx.addLine(`console.log(${expr})`);
+  },
+});

src/qweb/compilation_context.ts

@@ -0,0 +1,229 @@
+import { compileExpr, compileExprToArray, QWebVar } from "./expression_parser";
+
+export const INTERP_REGEXP = /\{\{.*?\}\}/g;
+//------------------------------------------------------------------------------
+// Compilation Context
+//------------------------------------------------------------------------------
+
+export class CompilationContext {
+  static nextID: number = 1;
+  code: string[] = [];
+  variables: { [key: string]: QWebVar } = {};
+  escaping: boolean = false;
+  parentNode: number | null | string = null;
+  parentTextNode: number | null = null;
+  rootNode: number | null = null;
+  indentLevel: number = 0;
+  rootContext: CompilationContext;
+  shouldDefineParent: boolean = false;
+  shouldDefineScope: boolean = false;
+  protectedScopeNumber: number = 0;
+  shouldDefineQWeb: boolean = false;
+  shouldDefineUtils: boolean = false;
+  shouldDefineRefs: boolean = false;
+  shouldDefineResult: boolean = true;
+  loopNumber: number = 0;
+  inPreTag: boolean = false;
+  templateName: string;
+  allowMultipleRoots: boolean = false;
+  hasParentWidget: boolean = false;
+  hasKey0: boolean = false;
+  keyStack: boolean[] = [];
+
+  constructor(name?: string) {
+    this.rootContext = this;
+    this.templateName = name || "noname";
+    this.addLine("let h = this.h;");
+  }
+
+  generateID(): number {
+    return CompilationContext.nextID++;
+  }
+
+  /**
+   * This method generates a "template key", which is basically a unique key
+   * which depends on the currently set keys, and on the iteration numbers (if
+   * we are in a loop).
+   *
+   * Such a key is necessary when we need to associate an id to some element
+   * generated by a template (for example, a component)
+   */
+  generateTemplateKey(prefix: string = ""): string {
+    const id = this.generateID();
+    if (this.loopNumber === 0 && !this.hasKey0) {
+      return `'${prefix}__${id}__'`;
+    }
+    let key = `\`${prefix}__${id}__`;
+    let start = this.hasKey0 ? 0 : 1;
+    for (let i = start; i < this.loopNumber + 1; i++) {
+      key += `\${key${i}}__`;
+    }
+    this.addLine(`let k${id} = ${key}\`;`);
+    return `k${id}`;
+  }
+
+  generateCode(): string[] {
+    if (this.shouldDefineResult) {
+      this.code.unshift("    let result;");
+    }
+
+    if (this.shouldDefineScope) {
+      this.code.unshift("    let scope = Object.create(context);");
+    }
+    if (this.shouldDefineRefs) {
+      this.code.unshift("    context.__owl__.refs = context.__owl__.refs || {};");
+    }
+    if (this.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${node};`);
+    }
+    return this.subContext("parentNode", node);
+  }
+
+  subContext(key: keyof CompilationContext, value: any): CompilationContext {
+    const newContext = Object.create(this);
+    newContext[key] = value;
+    return newContext;
+  }
+
+  indent() {
+    this.rootContext.indentLevel++;
+  }
+
+  dedent() {
+    this.rootContext.indentLevel--;
+  }
+
+  addLine(line: string): number {
+    const prefix = new Array(this.indentLevel + 2).join("    ");
+    this.code.push(prefix + line);
+    return this.code.length - 1;
+  }
+
+  addIf(condition: string) {
+    this.addLine(`if (${condition}) {`);
+    this.indent();
+  }
+
+  addElse() {
+    this.dedent();
+    this.addLine("} else {");
+    this.indent();
+  }
+
+  closeIf() {
+    this.dedent();
+    this.addLine("}");
+  }
+
+  getValue(val: any): QWebVar | 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 {
+    this.rootContext.shouldDefineScope = true;
+    return compileExpr(expr, this.variables);
+  }
+  captureExpression(expr: string): string {
+    this.rootContext.shouldDefineScope = true;
+    const argId = this.generateID();
+    const tokens = compileExprToArray(expr, this.variables);
+    const done = new Set();
+    return tokens
+      .map((tok, i) => {
+        // "this" in captured expressions should be the current component
+        if (tok.value === "this") {
+          if (!done.has("this")) {
+            done.add("this");
+            this.addLine(`const this_${argId} = utils.getComponent(context);`);
+          }
+          tok.value = `this_${argId}`;
+        }
+        // Variables that should be looked up in the scope. isLocal is for arrow
+        // function arguments that should stay untouched (eg "ev => ev" should
+        // not become "const ev_1 = scope['ev']; ev_1 => ev_1")
+        if (
+          tok.varName &&
+          !tok.isLocal &&
+          // HACK: for backwards compatibility, we don't capture bare methods
+          // this allows them to be called with the rendering context/scope
+          // as their this value.
+          (!tokens[i + 1] || tokens[i + 1].type !== "LEFT_PAREN")
+        ) {
+          if (!done.has(tok.varName)) {
+            done.add(tok.varName);
+            this.addLine(`const ${tok.varName}_${argId} = ${tok.value};`);
+          }
+          tok.value = `${tok.varName}_${argId}`;
+        }
+        return tok.value;
+      })
+      .join("");
+  }
+
+  /**
+   * Perform string interpolation on the given string. Note that if the whole
+   * 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) => "${" + this.formatExpression(s.slice(2, -2)) + "}");
+    return "`" + r + "`";
+  }
+  startProtectScope(codeBlock?: boolean): number {
+    const protectID = this.generateID();
+    this.rootContext.protectedScopeNumber++;
+    this.rootContext.shouldDefineScope = true;
+    const scopeExpr = `Object.create(scope);`;
+    this.addLine(`let _origScope${protectID} = scope;`);
+    this.addLine(`scope = ${scopeExpr}`);
+    if (!codeBlock) {
+      this.addLine(`scope.__access_mode__ = 'ro';`);
+    }
+    return protectID;
+  }
+  stopProtectScope(protectID: number) {
+    this.rootContext.protectedScopeNumber--;
+    this.addLine(`scope = _origScope${protectID};`);
+  }
+}

src/qweb/expression_parser.ts

@@ -0,0 +1,348 @@
+/**
+ * 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,eval,void,Math,RegExp,Array,Object,Date".split(
+    ","
+  );
+
+const WORD_REPLACEMENT = Object.assign(Object.create(null), {
+  and: "&&",
+  or: "||",
+  gt: ">",
+  gte: ">=",
+  lt: "<",
+  lte: "<=",
+});
+
+export interface QWebVar {
+  id: string; // foo
+  expr: string; // scope.foo (local variables => only foo)
+  value?: string; // 1 + 3
+  hasBody?: boolean;
+}
+
+//------------------------------------------------------------------------------
+// Tokenizer
+//------------------------------------------------------------------------------
+type TKind =
+  | "LEFT_BRACE"
+  | "RIGHT_BRACE"
+  | "LEFT_BRACKET"
+  | "RIGHT_BRACKET"
+  | "LEFT_PAREN"
+  | "RIGHT_PAREN"
+  | "COMMA"
+  | "VALUE"
+  | "TEMPLATE_STRING"
+  | "SYMBOL"
+  | "OPERATOR"
+  | "COLON";
+
+interface Token {
+  type: TKind;
+  value: string;
+  originalValue?: string;
+  size?: number;
+  varName?: string;
+  replace?: Function;
+  isLocal?: boolean;
+}
+
+const STATIC_TOKEN_MAP: { [key: string]: TKind } = Object.assign(Object.create(null), {
+  "{": "LEFT_BRACE",
+  "}": "RIGHT_BRACE",
+  "[": "LEFT_BRACKET",
+  "]": "RIGHT_BRACKET",
+  ":": "COLON",
+  ",": "COMMA",
+  "(": "LEFT_PAREN",
+  ")": "RIGHT_PAREN",
+});
+
+// note that the space after typeof is relevant. It makes sure that the formatted
+// expression has a space after typeof
+const OPERATORS = "...,.,===,==,+,!==,!=,!,||,&&,>=,>,<=,<,?,-,*,/,%,typeof ,=>,=,;,in ".split(",");
+
+type Tokenizer = (expr: string) => Token | false;
+
+let tokenizeString: Tokenizer = function (expr) {
+  let s = expr[0];
+  let start = s;
+  if (s !== "'" && 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;
+  if (start === "`") {
+    return {
+      type: "TEMPLATE_STRING",
+      value: s,
+      replace(replacer) {
+        return s.replace(/\$\{(.*?)\}/g, (match, group) => {
+          return "${" + replacer(group) + "}";
+        });
+      },
+    };
+  }
+  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,
+  tokenizeOperator,
+  tokenizeSymbol,
+  tokenizeStatic,
+];
+
+/**
+ * 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"
+//------------------------------------------------------------------------------
+
+const isLeftSeparator = (token) => token && (token.type === "LEFT_BRACE" || token.type === "COMMA");
+const isRightSeparator = (token) =>
+  token && (token.type === "RIGHT_BRACE" || token.type === "COMMA");
+
+/**
+ * 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}`)
+ *
+ * Some specific code is also required to support arrow functions. If we detect
+ * the arrow operator, then we add the current (or some previous tokens) token to
+ * the list of variables so it does not get replaced by a lookup in the context
+ */
+export function compileExprToArray(expr: string, scope: { [key: string]: QWebVar }): Token[] {
+  const localVars = new Set<string>();
+  scope = Object.create(scope);
+  const tokens = tokenize(expr);
+
+  let i = 0;
+  let stack = []; // to track last opening [ or {
+
+  while (i < tokens.length) {
+    let token = tokens[i];
+    let prevToken = tokens[i - 1];
+    let nextToken = tokens[i + 1];
+    let groupType = stack[stack.length - 1];
+
+    switch (token.type) {
+      case "LEFT_BRACE":
+      case "LEFT_BRACKET":
+        stack.push(token.type);
+        break;
+      case "RIGHT_BRACE":
+      case "RIGHT_BRACKET":
+        stack.pop();
+    }
+
+    let isVar = token.type === "SYMBOL" && !RESERVED_WORDS.includes(token.value);
+    if (token.type === "SYMBOL" && !RESERVED_WORDS.includes(token.value)) {
+      if (prevToken) {
+        // normalize missing tokens: {a} should be equivalent to {a:a}
+        if (
+          groupType === "LEFT_BRACE" &&
+          isLeftSeparator(prevToken) &&
+          isRightSeparator(nextToken)
+        ) {
+          tokens.splice(i + 1, 0, { type: "COLON", value: ":" }, { ...token });
+          nextToken = tokens[i + 1];
+        }
+
+        if (prevToken.type === "OPERATOR" && prevToken.value === ".") {
+          isVar = false;
+        } else if (prevToken.type === "LEFT_BRACE" || prevToken.type === "COMMA") {
+          if (nextToken && nextToken.type === "COLON") {
+            isVar = false;
+          }
+        }
+      }
+    }
+    if (token.type === "TEMPLATE_STRING") {
+      token.value = token.replace((expr) => compileExpr(expr, scope));
+    }
+    if (nextToken && nextToken.type === "OPERATOR" && nextToken.value === "=>") {
+      if (token.type === "RIGHT_PAREN") {
+        let j = i - 1;
+        while (j > 0 && tokens[j].type !== "LEFT_PAREN") {
+          if (tokens[j].type === "SYMBOL" && tokens[j].originalValue) {
+            tokens[j].value = tokens[j].originalValue!;
+            scope[tokens[j].value] = { id: tokens[j].value, expr: tokens[j].value };
+            localVars.add(tokens[j].value);
+          }
+          j--;
+        }
+      } else {
+        scope[token.value] = { id: token.value, expr: token.value };
+        localVars.add(token.value);
+      }
+    }
+
+    if (isVar) {
+      token.varName = token.value;
+      if (token.value in scope && "id" in scope[token.value]) {
+        token.value = scope[token.value].expr!;
+      } else {
+        token.originalValue = token.value;
+        token.value = `scope['${token.value}']`;
+      }
+    }
+    i++;
+  }
+  // Mark all variables that have been used locally.
+  // This assumes the expression has only one scope (incorrect but "good enough for now")
+  for (const token of tokens) {
+    if (token.type === "SYMBOL" && localVars.has(token.value)) {
+      token.isLocal = true;
+    }
+  }
+  return tokens;
+}
+
+export function compileExpr(expr: string, scope: { [key: string]: QWebVar }): string {
+  return compileExprToArray(expr, scope)
+    .map((t) => t.value)
+    .join("");
+}

src/qweb/extensions.ts

@@ -0,0 +1,377 @@
+import { STATUS } from "../component/component";
+import { VNode } from "../vdom/index";
+import { INTERP_REGEXP } from "./compilation_context";
+import { QWeb } from "./qweb";
+import { browser } from "../browser";
+
+/**
+ * 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();",
+};
+
+interface HandlerInfo {
+  event: string;
+  handler: string;
+}
+
+const FNAMEREGEXP = /^[$A-Z_][0-9A-Z_$]*$/i;
+
+export function makeHandlerCode(
+  ctx,
+  fullName,
+  value,
+  putInCache: boolean,
+  modcodes = MODS_CODE
+): HandlerInfo {
+  let [event, ...mods] = fullName.slice(5).split(".");
+  if (mods.includes("capture")) {
+    event = "!" + event;
+  }
+  if (!event) {
+    throw new Error("Missing event name with t-on directive");
+  }
+  let code: string;
+  // check if it is a method with no args, a method with args or an expression
+  let args: string = "";
+  const name: string = value.replace(/\(.*\)/, function (_args) {
+    args = _args.slice(1, -1);
+    return "";
+  });
+  const isMethodCall = name.match(FNAMEREGEXP);
+
+  // then generate code
+  if (isMethodCall) {
+    ctx.rootContext.shouldDefineUtils = true;
+    const comp = `utils.getComponent(context)`;
+    if (args) {
+      const argId = ctx.generateID();
+      ctx.addLine(`let args${argId} = [${ctx.formatExpression(args)}];`);
+      code = `${comp}['${name}'](...args${argId}, e);`;
+      putInCache = false;
+    } else {
+      code = `${comp}['${name}'](e);`;
+    }
+  } else {
+    // if we get here, then it is an expression
+    // we need to capture every variable in it
+    putInCache = false;
+    code = ctx.captureExpression(value);
+    code = `const res = (() => { return ${code} })(); if (typeof res === 'function') { res(e) }`;
+  }
+  const modCode = mods.map((mod) => modcodes[mod]).join("");
+  let handler = `function (e) {if (context.__owl__.status === ${STATUS.DESTROYED}){return}${modCode}${code}}`;
+  if (putInCache) {
+    const key = ctx.generateTemplateKey(event);
+    ctx.addLine(`extra.handlers[${key}] = extra.handlers[${key}] || ${handler};`);
+    handler = `extra.handlers[${key}]`;
+  }
+  return { event, handler };
+}
+
+QWeb.addDirective({
+  name: "on",
+  priority: 90,
+  atNodeCreation({ ctx, fullName, value, nodeID }) {
+    const { event, handler } = makeHandlerCode(ctx, fullName, value, true);
+    ctx.addLine(`p${nodeID}.on['${event}'] = ${handler};`);
+  },
+});
+
+//------------------------------------------------------------------------------
+// t-ref
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "ref",
+  priority: 95,
+  atNodeCreation({ ctx, value, addNodeHook }) {
+    ctx.rootContext.shouldDefineRefs = true;
+    const refKey = `ref${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");
+  elm.classList.remove(name + "-leave-active");
+  elm.classList.remove(name + "-leave-to");
+  const finalize = () => {
+    elm.classList.remove(name + "-enter-active");
+    elm.classList.remove(name + "-enter-to");
+  };
+  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 = () => {
+    if (!elm.classList.contains(name + "-leave-active")) {
+      return;
+    }
+    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) {
+  if (!elm.parentNode) {
+    // if we get here, this means that the element was removed for some other
+    // reasons, and in that case, we don't want to work on animation since nothing
+    // will be displayed anyway.
+    return;
+  }
+
+  const styles = window.getComputedStyle(elm);
+  const delays: Array<string> = (styles.transitionDelay || "").split(", ");
+  const durations: Array<string> = (styles.transitionDuration || "").split(", ");
+  const timeout: number = getTimeout(delays, durations);
+  if (timeout > 0) {
+    const transitionEndCB = () => {
+      if (!elm.parentNode) return;
+      cb();
+      browser.clearTimeout(fallbackTimeout);
+      elm.removeEventListener("transitionend", transitionEndCB);
+    };
+    elm.addEventListener("transitionend", transitionEndCB, { once: true });
+    const fallbackTimeout = browser.setTimeout(transitionEndCB, timeout + 1);
+  } else {
+    cb();
+  }
+}
+
+QWeb.addDirective({
+  name: "transition",
+  priority: 96,
+  atNodeCreation({ ctx, value, addNodeHook }) {
+    if (!QWeb.enableTransitions) {
+      return;
+    }
+    ctx.rootContext.shouldDefineUtils = true;
+    let name = value;
+    const hooks = {
+      insert: `utils.transitionInsert(vn, '${name}');`,
+      remove: `utils.transitionRemove(vn, '${name}', rm);`,
+    };
+    for (let hookName in hooks) {
+      addNodeHook(hookName, hooks[hookName]);
+    }
+  },
+});
+
+//------------------------------------------------------------------------------
+// t-slot
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "slot",
+  priority: 80,
+  atNodeEncounter({ ctx, value, node, qweb }): boolean {
+    const slotKey = ctx.generateID();
+    const valueExpr = value.match(INTERP_REGEXP) ? ctx.interpolate(value) : `'${value}'`;
+    ctx.addLine(
+      `const slot${slotKey} = this.constructor.slots[context.__owl__.slotId + '_' + ${valueExpr}];`
+    );
+    ctx.addIf(`slot${slotKey}`);
+    let parentNode = `c${ctx.parentNode}`;
+    if (!ctx.parentNode) {
+      ctx.rootContext.shouldDefineResult = true;
+      ctx.rootContext.shouldDefineUtils = true;
+      parentNode = `children${ctx.generateID()}`;
+      ctx.addLine(`let ${parentNode}= []`);
+      ctx.addLine(`result = {}`);
+    }
+    ctx.addLine(
+      `slot${slotKey}.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: ${parentNode}, parent: extra.parent || context}));`
+    );
+    if (!ctx.parentNode) {
+      ctx.addLine(`utils.defineProxy(result, ${parentNode}[0]);`);
+    }
+    if (node.hasChildNodes()) {
+      ctx.addElse();
+      const nodeCopy = <Element>node.cloneNode(true);
+      nodeCopy.removeAttribute("t-slot");
+      qweb._compileNode(nodeCopy, ctx);
+    }
+    ctx.closeIf();
+    return true;
+  },
+});
+
+//------------------------------------------------------------------------------
+// t-model
+//------------------------------------------------------------------------------
+QWeb.utils.toNumber = function (val: string): number | string {
+  const n = parseFloat(val);
+  return isNaN(n) ? val : n;
+};
+
+const hasDotAtTheEnd = /\.[\w_]+\s*$/;
+const hasBracketsAtTheEnd = /\[[^\[]+\]\s*$/;
+
+QWeb.addDirective({
+  name: "model",
+  priority: 42,
+  atNodeCreation({ ctx, nodeID, value, node, fullName, addNodeHook }) {
+    const type = node.getAttribute("type");
+    let handler;
+    let event = fullName.includes(".lazy") ? "change" : "input";
+
+    // First step: we need to understand the structure of the expression, and
+    // from it, extract a base expression (that we can capture, which is
+    // important because it will be used in a handler later) and a formatted
+    // expression (which uses the captured base expression)
+    //
+    // Also, we support 2 kinds of values: some.expr.value or some.expr[value]
+    // For the first one, we have:
+    // - base expression = scope[some].expr
+    // - expression = exprX.value (where exprX is the var that captures the base expr)
+    // and for the expression with brackets:
+    // - base expression = scope[some].expr
+    // - expression = exprX[keyX] (where exprX is the var that captures the base expr
+    //        and keyX captures scope[value])
+    let expr: string;
+    let baseExpr: string;
+
+    if (hasDotAtTheEnd.test(value)) {
+      // we manage the case where the expr has a dot: some.expr.value
+      const index = value.lastIndexOf(".");
+      baseExpr = value.slice(0, index);
+      ctx.addLine(`let expr${nodeID} = ${ctx.formatExpression(baseExpr)};`);
+      expr = `expr${nodeID}${value.slice(index)}`;
+    } else if (hasBracketsAtTheEnd.test(value)) {
+      // we manage here the case where the expr ends in a bracket expression:
+      //    some.expr[value]
+      const index = value.lastIndexOf("[");
+      baseExpr = value.slice(0, index);
+      ctx.addLine(`let expr${nodeID} = ${ctx.formatExpression(baseExpr)};`);
+      let exprKey = value.trimRight().slice(index + 1, -1);
+      ctx.addLine(`let exprKey${nodeID} = ${ctx.formatExpression(exprKey)};`);
+      expr = `expr${nodeID}[exprKey${nodeID}]`;
+    } else {
+      throw new Error(`Invalid t-model expression: "${value}" (it should be assignable)`);
+    }
+
+    const key = ctx.generateTemplateKey();
+    if (node.tagName === "select") {
+      ctx.addLine(`p${nodeID}.props = {value: ${expr}};`);
+      addNodeHook("create", `n.elm.value=${expr};`);
+      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} = ${valueCode}}`;
+    }
+    ctx.addLine(`extra.handlers[${key}] = extra.handlers[${key}] || (${handler});`);
+    ctx.addLine(`p${nodeID}.on['${event}'] = extra.handlers[${key}];`);
+  },
+});
+
+//------------------------------------------------------------------------------
+// t-key
+//------------------------------------------------------------------------------
+QWeb.addDirective({
+  name: "key",
+  priority: 45,
+  atNodeEncounter({ ctx, value, node }) {
+    if (ctx.loopNumber === 0) {
+      ctx.keyStack.push(ctx.rootContext.hasKey0);
+      ctx.rootContext.hasKey0 = true;
+    }
+    ctx.addLine("{");
+    ctx.indent();
+    ctx.addLine(`let key${ctx.loopNumber} = ${ctx.formatExpression(value)};`);
+  },
+  finalize({ ctx }) {
+    ctx.dedent();
+    ctx.addLine("}");
+    if (ctx.loopNumber === 0) {
+      ctx.rootContext.hasKey0 = ctx.keyStack.pop() as boolean;
+    }
+  },
+});

src/qweb/index.ts

@@ -0,0 +1,4 @@
+import "./base_directives";
+import "./extensions";
+
+export { CompiledTemplate, QWeb } from "./qweb";

src/qweb/qweb.ts

@@ -0,0 +1,930 @@
+import { EventBus } from "../core/event_bus";
+import { h, patch, VNode } from "../vdom/index";
+import { CompilationContext } from "./compilation_context";
+import { shallowEqual, escape } 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
+//------------------------------------------------------------------------------
+
+export const TRANSLATABLE_ATTRS = ["label", "title", "placeholder", "alt"];
+
+const lineBreakRE = /[\r\n]/;
+const whitespaceRE = /\s+/g;
+const translationRE = /^(\s*)([\s\S]+?)(\s*)$/;
+
+const NODE_HOOKS_PARAMS = {
+  create: "(_, n)",
+  insert: "vn",
+  remove: "(vn, rm)",
+  destroy: "()",
+};
+
+interface Utils {
+  toClassObj(expr: any): Object;
+  shallowEqual(p1: Object, p2: Object): boolean;
+  [key: string]: any;
+}
+
+function isComponent(obj): boolean {
+  return obj && obj.hasOwnProperty("__owl__");
+}
+
+class VDomArray extends Array {
+  toString() {
+    return vDomToString(this);
+  }
+}
+
+function vDomToString(vdom: VNode[]): string {
+  return vdom
+    .map((vnode) => {
+      if (vnode.sel) {
+        const node = document.createElement(vnode.sel);
+        const result = patch(node, vnode);
+        return (<HTMLElement>result.elm).outerHTML;
+      } else {
+        return vnode.text;
+      }
+    })
+    .join("");
+}
+
+const UTILS: Utils = {
+  zero: Symbol("zero"),
+  toClassObj(expr) {
+    const result = {};
+    if (typeof expr === "string") {
+      // we transform here a list of classes into an object:
+      //  'hey you' becomes {hey: true, you: true}
+      expr = expr.trim();
+      if (!expr) {
+        return {};
+      }
+      let words = expr.split(/\s+/);
+      for (let i = 0; i < words.length; i++) {
+        result[words[i]] = true;
+      }
+      return result;
+    }
+    // this is already an object, but we may need to split keys:
+    // {'a b': true, 'a c': false} should become {a: true, b: true, c: false}
+    for (let key in expr) {
+      const value = expr[key];
+      const words = key.split(/\s+/);
+      for (let word of words) {
+        result[word] = result[word] || value;
+      }
+    }
+    return result;
+  },
+  /**
+   * This method combines the current context with the variables defined in a
+   * scope for use in a slot.
+   *
+   * The implementation is kind of tricky because we want to preserve the
+   * prototype chain structure of the cloned result. So we need to traverse the
+   * prototype chain, cloning each level respectively.
+   */
+  combine(context, scope) {
+    let clone = context;
+    const scopeStack = [];
+    while (!isComponent(scope)) {
+      scopeStack.push(scope);
+      scope = scope.__proto__;
+    }
+    while (scopeStack.length) {
+      let scope = scopeStack.pop();
+      clone = Object.create(clone);
+      Object.assign(clone, scope);
+    }
+    return clone;
+  },
+  shallowEqual,
+  addNameSpace(vnode) {
+    addNS(vnode.data, vnode.children, vnode.sel);
+  },
+  VDomArray,
+  vDomToString,
+  getComponent(obj) {
+    while (obj && !isComponent(obj)) {
+      obj = obj.__proto__;
+    }
+    return obj;
+  },
+  getScope(obj, property: string) {
+    const obj0 = obj;
+    while (
+      obj &&
+      !obj.hasOwnProperty(property) &&
+      !(obj.hasOwnProperty("__access_mode__") && obj.__access_mode__ === "ro")
+    ) {
+      const newObj = obj.__proto__;
+      if (!newObj || isComponent(newObj)) {
+        return obj0;
+      }
+      obj = newObj;
+    }
+    return obj;
+  },
+};
+
+function parseXML(xml: string): Document {
+  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;
+}
+
+function escapeQuotes(str: string): string {
+  return str.replace(/\'/g, "\\'");
+}
+
+//------------------------------------------------------------------------------
+// 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,
+    tag: 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;
+  static enableTransitions: boolean = true;
+
+  // slots contains sub templates defined with t-set inside t-component nodes, and
+  // are meant to be used by the t-slot directive.
+  static slots = {};
+  static nextSlotId = 1;
+
+  // subTemplates are stored in two objects: a (local) mapping from a name to an
+  // id, and a (global) mapping from an id to the compiled function.  This is
+  // necessary to ensure that global templates can be called with more than one
+  // QWeb instance.
+  subTemplates: { [key: string]: number } = {};
+  static subTemplates: { [id: number]: Function } = {};
+
+  isUpdating: boolean = false;
+  translateFn?: QWebConfig["translateFn"];
+
+  constructor(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) {
+    if (!xmlstr) {
+      return;
+    }
+    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);
+        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 (with only spaces) and comment nodes (nodeType 8) between
+        // branch nodes are removed
+        let textNode;
+        while ((textNode = node.previousSibling) !== prevElem) {
+          if (textNode.nodeValue.trim().length && textNode.nodeType !== 8) {
+            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 elem = patch(node, vnode).elm as HTMLElement;
+    function escapeTextNodes(node) {
+      if (node.nodeType === 3) {
+        node.textContent = escape(node.textContent);
+      }
+      for (let n of node.childNodes) {
+        escapeTextNodes(n);
+      }
+    }
+    escapeTextNodes(elem);
+    return elem.outerHTML;
+  }
+
+  /**
+   * 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,
+    options: {
+      elem?: Element;
+      hasParent?: boolean;
+      defineKey?: boolean;
+    } = {}
+  ): CompiledTemplate {
+    const elem = options.elem || this.templates[name].elem;
+    const isDebug = elem.attributes.hasOwnProperty("t-debug");
+    const ctx = new CompilationContext(name);
+    if (elem.tagName !== "t") {
+      ctx.shouldDefineResult = false;
+    }
+    if (options.hasParent) {
+      ctx.variables = Object.create(null);
+      ctx.parentNode = ctx.generateID();
+      ctx.allowMultipleRoots = true;
+      ctx.shouldDefineParent = true;
+      ctx.hasParentWidget = true;
+      ctx.shouldDefineResult = false;
+      ctx.addLine(`let c${ctx.parentNode} = extra.parentNode;`);
+      if (options.defineKey) {
+        ctx.addLine(`let key0 = extra.key || "";`);
+        ctx.hasKey0 = true;
+      }
+    }
+    this._compileNode(elem, ctx);
+
+    if (!options.hasParent) {
+      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();
+    const templateName = ctx.templateName.replace(/`/g, "'").slice(0, 200);
+    code.unshift(`    // Template name: "${templateName}"`);
+
+    let template;
+    try {
+      template = new Function("context, extra", code.join("\n")) as CompiledTemplate;
+    } catch (e) {
+      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") {
+          const match = translationRE.exec(text);
+          text = match[1] + this.translateFn(match[2]) + match[3];
+        }
+      }
+      if (ctx.parentNode) {
+        if (node.nodeType === 3) {
+          ctx.addLine(`c${ctx.parentNode}.push({text: \`${text}\`});`);
+        } 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(`let vn${nodeID} = {text: \`${text}\`};`);
+        ctx.addLine(`result = vn${nodeID};`);
+        ctx.rootContext.rootNode = nodeID;
+        ctx.rootContext.parentTextNode = nodeID;
+      }
+      return;
+    }
+
+    if (node.tagName !== "t" && node.hasAttribute("t-call")) {
+      const tCallNode = document.implementation.createDocument(
+        "http://www.w3.org/1999/xhtml",
+        "t",
+        null
+      ).documentElement;
+      tCallNode.setAttribute("t-call", node.getAttribute("t-call")!);
+      node.removeAttribute("t-call");
+      node.prepend(tCallNode);
+    }
+
+    const firstLetter = node.tagName[0];
+    if (firstLetter === firstLetter.toUpperCase()) {
+      // this is a component, we modify in place the xml document to change
+      // <SomeComponent ... /> to <SomeComponent t-component="SomeComponent" ... />
+      node.setAttribute("t-component", node.tagName);
+    } else if (node.tagName !== "t" && node.hasAttribute("t-component")) {
+      throw new Error(
+        `Directive 't-component' can only be used on <t> nodes (used on a <${node.tagName}>)`
+      );
+    }
+    const attributes = (<Element>node).attributes;
+
+    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.implementation.createDocument(
+            "http://www.w3.org/1999/xhtml",
+            "t",
+            null
+          ).documentElement;
+          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" || node.hasAttribute("t-tag")) {
+      let nodeHooks = {};
+      let addNodeHook = function (hook, handler) {
+        nodeHooks[hook] = nodeHooks[hook] || [];
+        nodeHooks[hook].push(handler);
+      };
+      if (node.tagName === "select" && node.hasAttribute("t-att-value")) {
+        const value = node.getAttribute("t-att-value");
+        let exprId = ctx.generateID();
+        ctx.addLine(`let expr${exprId} = ${ctx.formatExpression(value)};`);
+        let expr = `expr${exprId}`;
+        node.setAttribute("t-att-value", expr);
+        addNodeHook("create", `n.elm.value=${expr};`);
+      }
+      let nodeID = this._compileGenericNode(node, ctx, withHandlers);
+      ctx = ctx.withParent(nodeID);
+
+      for (let { directive, value, fullName } of validDirectives) {
+        if (directive.atNodeCreation) {
+          directive.atNodeCreation({
+            node,
+            qweb: this,
+            ctx,
+            fullName,
+            value,
+            nodeID,
+            addNodeHook,
+          });
+        }
+      }
+
+      if (Object.keys(nodeHooks).length) {
+        ctx.addLine(`p${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 handleProperties(key, val) {
+      let isProp = false;
+      switch (node.nodeName) {
+        case "input":
+          let type = (<Element>node).getAttribute("type");
+          if (type === "checkbox" || type === "radio") {
+            if (key === "checked" || key === "indeterminate") {
+              isProp = true;
+            }
+          }
+          if (key === "value" || key === "readonly" || key === "disabled") {
+            isProp = true;
+          }
+          break;
+        case "option":
+          isProp = key === "selected" || key === "disabled";
+          break;
+        case "textarea":
+          isProp = key === "readonly" || key === "disabled" || key === "value";
+          break;
+        case "select":
+          isProp = key === "disabled" || key === "value";
+          break;
+        case "button":
+        case "optgroup":
+          isProp = key === "disabled";
+          break;
+      }
+      if (isProp) {
+        props.push(`${key}: ${val}`);
+      }
+    }
+    let classObj = "";
+
+    for (let i = 0; i < attributes.length; i++) {
+      let name = attributes[i].name;
+      let value = attributes[i].textContent!;
+
+      if (this.translateFn && TRANSLATABLE_ATTRS.includes(name)) {
+        value = this.translateFn(value);
+      }
+
+      // regular attributes
+      if (!name.startsWith("t-") && !(<Element>node).getAttribute("t-attf-" + name)) {
+        const attID = ctx.generateID();
+        if (name === "class") {
+          if ((value = value.trim())) {
+            let classDef = value
+              .split(/\s+/)
+              .map((a) => `'${escapeQuotes(a)}':true`)
+              .join(",");
+            if (classObj) {
+              ctx.addLine(`Object.assign(${classObj}, {${classDef}})`);
+            } else {
+              classObj = `_${ctx.generateID()}`;
+              ctx.addLine(`let ${classObj} = {${classDef}};`);
+            }
+          }
+        } else {
+          ctx.addLine(`let _${attID} = '${escapeQuotes(value)}';`);
+          if (!name.match(/^[a-zA-Z]+$/)) {
+            // attribute contains 'non letters' => we want to quote it
+            name = '"' + name + '"';
+          }
+          attrs.push(`${name}: _${attID}`);
+          handleProperties(name, `_${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) : `scope.${v.id}`;
+
+        if (attName === "class") {
+          ctx.rootContext.shouldDefineUtils = true;
+          formattedValue = `utils.toClassObj(${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(`let _${attValueID} = ${formattedValue};`);
+            formattedValue = `'${attValue}' + (_${attValueID} ? ' ' + _${attValueID} : '')`;
+            const attrIndex = attrs.findIndex((att) => att.startsWith(attName + ":"));
+            attrs.splice(attrIndex, 1);
+          }
+          if (node.nodeName === "select" && attName === "value") {
+            attrs.push(`${attName}: ${v}`);
+            handleProperties(attName, v);
+          } else {
+            ctx.addLine(`let _${attID} = ${formattedValue};`);
+            attrs.push(`${attName}: _${attID}`);
+            handleProperties(attName, "_" + attID);
+          }
+        }
+      }
+
+      if (name.startsWith("t-attf-")) {
+        let attName = name.slice(7);
+        if (!attName.match(/^[a-zA-Z]+$/)) {
+          // 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(`let _${attID} = '${staticVal} ' + ${formattedExpr};`);
+        } else {
+          ctx.addLine(`let _${attID} = ${formattedExpr};`);
+        }
+        attrs.push(`${attName}: _${attID}`);
+      }
+
+      // t-att= attributes
+      if (name === "t-att") {
+        let id = ctx.generateID();
+        ctx.addLine(`let _${id} = ${ctx.formatExpression(value!)};`);
+        tattrs.push(id);
+      }
+    }
+    let nodeID = ctx.generateID();
+    let key = ctx.loopNumber || ctx.hasKey0 ? `\`\${key${ctx.loopNumber}}_${nodeID}\`` : nodeID;
+    const parts = [`key:${key}`];
+    if (attrs.length + tattrs.length > 0) {
+      parts.push(`attrs:{${attrs.join(",")}}`);
+    }
+    if (props.length > 0) {
+      parts.push(`props:{${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] = _${id}[key];`);
+      ctx.dedent();
+      ctx.addLine(`}`);
+      ctx.closeIf();
+    }
+    let nodeName = `'${node.nodeName}'`;
+    if ((<Element>node).hasAttribute("t-tag")) {
+      const tagExpr = (<Element>node).getAttribute("t-tag");
+      (<Element>node).removeAttribute("t-tag");
+      nodeName = `tag${ctx.generateID()}`;
+      ctx.addLine(`let ${nodeName} = ${ctx.formatExpression(tagExpr)};`);
+    }
+    ctx.addLine(`let vn${nodeID} = h(${nodeName}, p${nodeID}, c${nodeID});`);
+    if (ctx.parentNode) {
+      ctx.addLine(`c${ctx.parentNode}.push(vn${nodeID});`);
+    } else if (ctx.loopNumber || ctx.hasKey0) {
+      ctx.rootContext.shouldDefineResult = true;
+      ctx.addLine(`result = vn${nodeID};`);
+    }
+
+    return nodeID;
+  }
+
+  _compileChildren(node: ChildNode, ctx: CompilationContext) {
+    if (node.childNodes.length > 0) {
+      for (let child of Array.from(node.childNodes)) {
+        this._compileNode(child, ctx);
+      }
+    }
+  }
+}

src/router/link.ts

@@ -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<Props, Env> {
+  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);
+  }
+}

src/router/route_component.ts

@@ -0,0 +1,19 @@
+import { Component } from "../component/component";
+import { xml } from "../tags";
+import { EnvWithRouter } from "./router";
+
+export class RouteComponent extends Component<{}, EnvWithRouter> {
+  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;
+  }
+}

src/router/router.ts

@@ -0,0 +1,294 @@
+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;
+  extractionRegExp: RegExp;
+  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"];
+}
+
+export interface EnvWithRouter extends Env {
+  router: Router;
+}
+
+const paramRegexp = /\{\{(.*?)\}\}/;
+const globalParamRegexp = new RegExp(paramRegexp.source, "g");
+
+export class Router {
+  currentRoute: Route | null = null;
+  currentParams: RouteParams | null = null;
+  mode: "history" | "hash";
+
+  routes: { [id: string]: Route };
+  routeIds: string[];
+  env: RouterEnv;
+
+  constructor(
+    env: Partial<EnvWithRouter>,
+    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) : [];
+      partialRoute.extractionRegExp = makeExtractionRegExp(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") {
+      let finalPath = this.routeToPath(result.route, result.params);
+      if (path.indexOf("?") > -1) {
+        finalPath += "?" + path.split("?")[1];
+      }
+      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 prefix = this.mode === "hash" ? "#" : "";
+    return (
+      prefix +
+      route.path.replace(globalParamRegexp, (match, param) => {
+        const [key] = param.split(".");
+        return <string>params[key];
+      })
+    );
+  }
+
+  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.indexOf("?") > -1) {
+      path = path.split("?")[0];
+    }
+    if (path.startsWith("#")) {
+      path = path.slice(1);
+    }
+    const paramsMatch = path.match(route.extractionRegExp);
+    if (!paramsMatch) {
+      return false;
+    }
+    const result = {};
+    route.params.forEach((param, index) => {
+      const [key, suffix] = param.split(".");
+      const paramValue = paramsMatch[index + 1];
+      if (suffix === "number") {
+        return (result[key] = parseInt(paramValue, 10));
+      }
+      return (result[key] = paramValue);
+    });
+    return result;
+  }
+}
+
+function findParams(str: string): string[] {
+  const result: string[] = [];
+  let m;
+  do {
+    m = globalParamRegexp.exec(str);
+    if (m) {
+      result.push(m[1]);
+    }
+  } while (m);
+  return result;
+}
+
+function escapeRegExp(str: string) {
+  return str.replace(/[-[\]{}()*+?.,\\^$|#\s]/g, "\\$&");
+}
+
+function makeExtractionRegExp(path: string) {
+  // replace param strings with capture groups so that we can build a regex to match over the path
+  const extractionString = path
+    .split(paramRegexp)
+    .map((part, index) => {
+      return index % 2 ? "(.*)" : escapeRegExp(part);
+    })
+    .join("");
+  // Example: /home/{{param1}}/{{param2}} => ^\/home\/(.*)\/(.*)$
+  return new RegExp(`^${extractionString}$`);
+}

src/store.ts

@@ -0,0 +1,173 @@
+import { Component, 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 interface EnvWithStore extends Env {
+  store: Store;
+}
+
+export type Action = ({ state, dispatch, env, getters }, ...payload: any) => any;
+export type Getter = ({ state: any, getters }, payload?) => any;
+
+interface StoreConfig {
+  env?: Env;
+  state?: any;
+  actions?: { [name: string]: Action };
+  getters?: { [name: string]: Getter };
+}
+
+export class Store extends Context {
+  actions: any;
+  env: any;
+  getters: { [name: string]: (payload?) => any };
+  updateFunctions: { [key: number]: (() => boolean)[] };
+
+  constructor(config: StoreConfig) {
+    super(config.state);
+    this.actions = config.actions;
+    this.env = config.env;
+    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);
+      }
+    }
+  }
+
+  dispatch(action: string, ...payload: any): Promise<void> | void {
+    if (!this.actions[action]) {
+      throw new Error(`[Error] action ${action} is undefined`);
+    }
+    const result = this.actions[action](
+      {
+        dispatch: this.dispatch.bind(this),
+        env: this.env,
+        state: this.state,
+        getters: this.getters,
+      },
+      ...payload
+    );
+    return result;
+  }
+
+  __notifyComponents(): Promise<void> {
+    this.trigger("before-update");
+    return super.__notifyComponents();
+  }
+}
+
+interface SelectorOptions {
+  store?: Store;
+  isEqual?: (a: any, b: any) => boolean;
+  onUpdate?: (result: any) => any;
+}
+
+const isStrictEqual = (a, b) => a === b;
+
+export function useStore(selector, options: SelectorOptions = {}): any {
+  const component = Component.current as Component<any, EnvWithStore>;
+  const componentId = component.__owl__.id;
+  const store = options.store || (component.env.store as Store);
+  if (!(store instanceof Store)) {
+    throw new Error(`No store found when connecting '${component.constructor.name}'`);
+  }
+  let result = selector(store.state, component.props);
+  const hashFn = store.observer.revNumber.bind(store.observer);
+  let revNumber = hashFn(result);
+  const isEqual = options.isEqual || isStrictEqual;
+  if (!store.updateFunctions[componentId]) {
+    store.updateFunctions[componentId] = [];
+  }
+  function selectCompareUpdate(state, props): boolean {
+    const oldResult = result;
+    result = selector(state, props);
+    const newRevNumber = hashFn(result);
+    if ((newRevNumber > 0 && revNumber !== newRevNumber) || !isEqual(oldResult, result)) {
+      revNumber = newRevNumber;
+      return true;
+    }
+    return false;
+  }
+  if (options.onUpdate) {
+    store.on("before-update", component, () => {
+      const newValue = selector(store!.state, component.props!);
+      options.onUpdate(newValue);
+    });
+  }
+  store.updateFunctions[componentId].push(function (): boolean {
+    return selectCompareUpdate(store!.state, component.props);
+  });
+
+  useContextWithCB(store, component, function (): Promise<void> | void {
+    let shouldRender = false;
+    for (let fn of store.updateFunctions[componentId]) {
+      shouldRender = fn() || shouldRender;
+    }
+    if (shouldRender) {
+      return component.render();
+    }
+  });
+  onWillUpdateProps((props) => {
+    selectCompareUpdate(store.state, props);
+  });
+
+  const __destroy = component.__destroy;
+  component.__destroy = (parent) => {
+    delete store.updateFunctions[componentId];
+    if (options.onUpdate) {
+      store.off("before-update", component);
+    }
+    __destroy.call(component, parent);
+  };
+
+  if (typeof result !== "object" || result === null) {
+    return result;
+  }
+  return new Proxy(result, {
+    get(target, k) {
+      return result[k];
+    },
+    set(target, k, v) {
+      throw new Error("Store state should only be modified through actions");
+    },
+    has(target, k) {
+      return k in result;
+    },
+  });
+}
+
+export function useDispatch(store?: Store): Store["dispatch"] {
+  store = store || (Component.current!.env as EnvWithStore).store;
+  return store.dispatch.bind(store);
+}
+
+export function useGetters(store?: Store): Store["getters"] {
+  store = store || (Component.current!.env as EnvWithStore).store;
+  return store.getters;
+}

src/tags.ts

@@ -0,0 +1,44 @@
+import { QWeb } from "./qweb/index";
+import { registerSheet } from "./component/styles";
+
+/**
+ * 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__${QWeb.nextId++}`;
+  const value = String.raw(strings, ...args);
+  QWeb.registerTemplate(name, value);
+  return name;
+}
+
+/**
+ * CSS tag helper for defining inline stylesheets.  With this, one can simply define
+ * an inline stylesheet with just the following code:
+ * ```js
+ *   class A extends Component {
+ *     static style = css`.component-a { color: red; }`;
+ *   }
+ * ```
+ */
+export function css(strings, ...args) {
+  const name = `__sheet__${QWeb.nextId++}`;
+  const value = String.raw(strings, ...args);
+  registerSheet(name, value);
+  return name;
+}

src/utils.ts

@@ -0,0 +1,103 @@
+/**
+ * Owl Utils
+ *
+ * We have here a small collection of utility functions:
+ *
+ * - whenReady
+ * - loadJS
+ * - loadFile
+ * - escape
+ * - debounce
+ */
+
+import { browser } from "./browser";
+
+export function whenReady(fn?: any) {
+  return new Promise(function (resolve) {
+    if (document.readyState !== "loading") {
+      resolve();
+    } else {
+      document.addEventListener("DOMContentLoaded", resolve, false);
+    }
+  }).then(fn || function () {});
+}
+
+const loadedScripts: { [key: string]: Promise<void> } = {};
+
+export function loadJS(url: string): Promise<void> {
+  if (url in loadedScripts) {
+    return loadedScripts[url];
+  }
+  const promise: Promise<void> = new Promise(function (resolve, reject) {
+    const script = document.createElement("script");
+    script.type = "text/javascript";
+    script.src = url;
+    script.onload = function () {
+      resolve();
+    };
+    script.onerror = function () {
+      reject(`Error loading file '${url}'`);
+    };
+    const head = document.head || document.getElementsByTagName("head")[0];
+    head.appendChild(script);
+  });
+  loadedScripts[url] = promise;
+  return promise;
+}
+
+export async function loadFile(url: string): Promise<string> {
+  const result = await browser.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);
+  }
+  const p = document.createElement("p");
+  p.textContent = str;
+  return p.innerHTML;
+}
+
+/**
+ * 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;
+    browser.clearTimeout(timeout);
+    timeout = browser.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;
+}

src/vdom/html_to_vdom.ts

@@ -0,0 +1,34 @@
+import { VNode, h, addNS } 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)) {
+    if (node instanceof Comment) {
+      return h("!", node.textContent);
+    }
+    return { text: node.textContent! } as VNode;
+  }
+  const attrs = {};
+  for (let attr of node.attributes) {
+    attrs[attr.name] = attr.textContent;
+  }
+  const children: VNode[] = [];
+  for (let c of node.childNodes) {
+    children.push(htmlToVNode(c));
+  }
+  const vnode = h((node as Element).tagName, { attrs }, children);
+  if (vnode.sel === "svg") {
+    addNS(vnode.data, (vnode as any).children, vnode.sel);
+  }
+  return vnode;
+}

src/vdom/index.ts

@@ -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]);

src/vdom/modules.ts

@@ -0,0 +1,247 @@
+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) {
+    if (on[name]) {
+      invokeHandler(on[name], vnode, event);
+    } else if (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
+        const capture = name.charAt(0) === "!";
+        name = capture ? name.slice(1) : name;
+        oldElm.removeEventListener(name, oldListener, capture);
+      }
+    } else {
+      for (name in oldOn) {
+        // remove listener if existing listener removed
+        if (!on[name]) {
+          const capture = name.charAt(0) === "!";
+          name = capture ? name.slice(1) : name;
+          oldElm.removeEventListener(name, oldListener, capture);
+        }
+      }
+    }
+  }
+
+  // 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
+        const capture = name.charAt(0) === "!";
+        name = capture ? name.slice(1) : name;
+        elm.addEventListener(name, listener, capture);
+      }
+    } else {
+      for (name in on) {
+        // add listener if new listener added
+        if (!oldOn[name]) {
+          const capture = name.charAt(0) === "!";
+          name = capture ? name.slice(1) : name;
+          elm.addEventListener(name, listener, capture);
+        }
+      }
+    }
+  }
+}
+
+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 (name && !klass[name] && !Object.prototype.hasOwnProperty.call(klass, name)) {
+      // was `true` and now not provided
+      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;

src/vdom/vdom.ts

@@ -0,0 +1,616 @@
+/**
+ * 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;
+  }
+}
+
+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
+//------------------------------------------------------------------------------
+type Key = string | number;
+
+export interface VNode {
+  sel: string | undefined;
+  data: VNodeData | undefined;
+  children: Array<VNode | string> | undefined;
+  elm: Node | undefined;
+  text: string | undefined;
+  key: Key | undefined;
+}
+
+export interface VNodeData {
+  props?: Props;
+  attrs?: Attrs;
+  on?: On;
+  hook?: Hooks;
+  key?: Key;
+  ns?: string; // for SVGs
+  [key: string]: any; // for any other 3rd party module
+}
+
+function vnode(
+  sel: string | undefined,
+  data: any | undefined,
+  children: Array<VNode | string> | undefined,
+  text: string | undefined,
+  elm: Element | Text | undefined
+): VNode {
+  let key = data === undefined ? undefined : data.key;
+  return { sel, data, children, text, elm, key };
+}
+
+//------------------------------------------------------------------------------
+// snabbdom.ts
+//------------------------------------------------------------------------------
+function isUndef(s: any): boolean {
+  return s === undefined;
+}
+function isDef(s: any): boolean {
+  return s !== undefined;
+}
+
+type VNodeQueue = Array<VNode>;
+
+const emptyNode = vnode("", {}, [], undefined, undefined);
+
+function sameVnode(vnode1: VNode, vnode2: VNode): boolean {
+  return vnode1.key === vnode2.key && vnode1.sel === vnode2.sel;
+}
+
+function isVnode(vnode: any): vnode is VNode {
+  return vnode.sel !== undefined;
+}
+
+type KeyToIndexMap = { [key: string]: number };
+
+type ArraysOf<T> = { [K in keyof T]: T[K][] };
+
+type ModuleHooks = ArraysOf<Module>;
+
+function createKeyToOldIdx(
+  children: Array<VNode>,
+  beginIdx: number,
+  endIdx: number
+): KeyToIndexMap {
+  let i: number,
+    map: KeyToIndexMap = {},
+    key: Key | undefined,
+    ch;
+  for (i = beginIdx; i <= endIdx; ++i) {
+    ch = children[i];
+    if (ch != null) {
+      key = ch.key;
+      if (key !== undefined) map[key] = i;
+    }
+  }
+  return map;
+}
+
+const hooks: (keyof Module)[] = ["create", "update", "remove", "destroy", "pre", "post"];
+
+export function init(modules: Array<Partial<Module>>, domApi?: DOMAPI) {
+  let i: number,
+    j: number,
+    cbs = {} as ModuleHooks;
+
+  const api: DOMAPI = domApi !== undefined ? domApi : htmlDomApi;
+
+  for (i = 0; i < hooks.length; ++i) {
+    cbs[hooks[i]] = [];
+    for (j = 0; j < modules.length; ++j) {
+      const hook = modules[j][hooks[i]];
+      if (hook !== undefined) {
+        (cbs[hooks[i]] as Array<any>).push(hook);
+      }
+    }
+  }
+
+  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);
+  }
+
+  function createRmCb(childElm: Node, listeners: number) {
+    return function rmCb() {
+      if (--listeners === 0) {
+        const parent = api.parentNode(childElm);
+        api.removeChild(parent, childElm);
+      }
+    };
+  }
+
+  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))) {
+        i(vnode);
+        data = vnode.data;
+      }
+    }
+    let children = vnode.children,
+      sel = vnode.sel;
+    if (sel === "!") {
+      if (isUndef(vnode.text)) {
+        vnode.text = "";
+      }
+      vnode.elm = api.createComment(vnode.text as string);
+    } else if (sel !== undefined) {
+      const elm =
+        vnode.elm ||
+        (vnode.elm =
+          isDef(data) && isDef((i = (data as VNodeData).ns))
+            ? api.createElementNS(i, sel)
+            : api.createElement(sel));
+      for (i = 0, iLen = cbs.create.length; i < iLen; ++i) cbs.create[i](emptyNode, vnode);
+      if (array(children)) {
+        for (i = 0, iLen = children.length; i < iLen; ++i) {
+          const ch = children[i];
+          if (ch != null) {
+            api.appendChild(elm, createElm(ch as VNode, insertedVnodeQueue));
+          }
+        }
+      } else if (primitive(vnode.text)) {
+        api.appendChild(elm, api.createTextNode(vnode.text));
+      }
+      i = (vnode.data as VNodeData).hook; // Reuse variable
+      if (isDef(i)) {
+        if (i.create) i.create(emptyNode, vnode);
+        if (i.insert) insertedVnodeQueue.push(vnode);
+      }
+    } else {
+      vnode.elm = api.createTextNode(vnode.text as string);
+    }
+    return vnode.elm;
+  }
+
+  function addVnodes(
+    parentElm: Node,
+    before: Node | null,
+    vnodes: Array<VNode>,
+    startIdx: number,
+    endIdx: number,
+    insertedVnodeQueue: VNodeQueue
+  ) {
+    for (; startIdx <= endIdx; ++startIdx) {
+      const ch = vnodes[startIdx];
+      if (ch != null) {
+        api.insertBefore(parentElm, createElm(ch, insertedVnodeQueue), before);
+      }
+    }
+  }
+
+  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, iLen = cbs.destroy.length; i < iLen; ++i) cbs.destroy[i](vnode);
+      if (vnode.children !== undefined) {
+        for (j = 0, jLen = vnode.children.length; j < jLen; ++j) {
+          i = vnode.children[j];
+          if (i != null && typeof i !== "string") {
+            invokeDestroyHook(i);
+          }
+        }
+      }
+    }
+  }
+
+  function removeVnodes(
+    parentElm: Node,
+    vnodes: Array<VNode>,
+    startIdx: number,
+    endIdx: number
+  ): void {
+    for (; startIdx <= endIdx; ++startIdx) {
+      let i: any,
+        iLen: number,
+        listeners: number,
+        rm: () => void,
+        ch = vnodes[startIdx];
+      if (ch != null) {
+        if (isDef(ch.sel)) {
+          invokeDestroyHook(ch);
+          listeners = cbs.remove.length + 1;
+          rm = createRmCb(ch.elm as Node, listeners);
+          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();
+          }
+        } else {
+          // Text node
+          api.removeChild(parentElm, ch.elm as Node);
+        }
+      }
+    }
+  }
+
+  function updateChildren(
+    parentElm: Node,
+    oldCh: Array<VNode>,
+    newCh: Array<VNode>,
+    insertedVnodeQueue: VNodeQueue
+  ) {
+    let oldStartIdx = 0,
+      newStartIdx = 0;
+    let oldEndIdx = oldCh.length - 1;
+    let oldStartVnode = oldCh[0];
+    let oldEndVnode = oldCh[oldEndIdx];
+    let newEndIdx = newCh.length - 1;
+    let newStartVnode = newCh[0];
+    let newEndVnode = newCh[newEndIdx];
+    let oldKeyToIdx: any;
+    let idxInOld: number;
+    let elmToMove: VNode;
+    let before: any;
+
+    while (oldStartIdx <= oldEndIdx && newStartIdx <= newEndIdx) {
+      if (oldStartVnode == null) {
+        oldStartVnode = oldCh[++oldStartIdx]; // Vnode might have been moved left
+      } else if (oldEndVnode == null) {
+        oldEndVnode = oldCh[--oldEndIdx];
+      } else if (newStartVnode == null) {
+        newStartVnode = newCh[++newStartIdx];
+      } else if (newEndVnode == null) {
+        newEndVnode = newCh[--newEndIdx];
+      } else if (sameVnode(oldStartVnode, newStartVnode)) {
+        patchVnode(oldStartVnode, newStartVnode, insertedVnodeQueue);
+        oldStartVnode = oldCh[++oldStartIdx];
+        newStartVnode = newCh[++newStartIdx];
+      } else if (sameVnode(oldEndVnode, newEndVnode)) {
+        patchVnode(oldEndVnode, newEndVnode, insertedVnodeQueue);
+        oldEndVnode = oldCh[--oldEndIdx];
+        newEndVnode = newCh[--newEndIdx];
+      } else if (sameVnode(oldStartVnode, newEndVnode)) {
+        // Vnode moved right
+        patchVnode(oldStartVnode, newEndVnode, insertedVnodeQueue);
+        api.insertBefore(
+          parentElm,
+          oldStartVnode.elm as Node,
+          api.nextSibling(oldEndVnode.elm as Node)
+        );
+        oldStartVnode = oldCh[++oldStartIdx];
+        newEndVnode = newCh[--newEndIdx];
+      } else if (sameVnode(oldEndVnode, newStartVnode)) {
+        // Vnode moved left
+        patchVnode(oldEndVnode, newStartVnode, insertedVnodeQueue);
+        api.insertBefore(parentElm, oldEndVnode.elm as Node, oldStartVnode.elm as Node);
+        oldEndVnode = oldCh[--oldEndIdx];
+        newStartVnode = newCh[++newStartIdx];
+      } else {
+        if (oldKeyToIdx === undefined) {
+          oldKeyToIdx = createKeyToOldIdx(oldCh, oldStartIdx, oldEndIdx);
+        }
+        idxInOld = oldKeyToIdx[newStartVnode.key as string];
+        if (isUndef(idxInOld)) {
+          // New element
+          api.insertBefore(
+            parentElm,
+            createElm(newStartVnode, insertedVnodeQueue),
+            oldStartVnode.elm as Node
+          );
+          newStartVnode = newCh[++newStartIdx];
+        } else {
+          elmToMove = oldCh[idxInOld];
+          if (elmToMove.sel !== newStartVnode.sel) {
+            api.insertBefore(
+              parentElm,
+              createElm(newStartVnode, insertedVnodeQueue),
+              oldStartVnode.elm as Node
+            );
+          } else {
+            patchVnode(elmToMove, newStartVnode, insertedVnodeQueue);
+            oldCh[idxInOld] = undefined as any;
+            api.insertBefore(parentElm, elmToMove.elm as Node, oldStartVnode.elm as Node);
+          }
+          newStartVnode = newCh[++newStartIdx];
+        }
+      }
+    }
+    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);
+      } else {
+        removeVnodes(parentElm, oldCh, oldStartIdx, oldEndIdx);
+      }
+    }
+  }
+
+  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);
+    let oldCh = oldVnode.children;
+    let ch = vnode.children;
+    if (oldVnode === vnode) return;
+    if (vnode.data !== undefined) {
+      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);
+      } else if (isDef(ch)) {
+        if (isDef(oldVnode.text)) api.setTextContent(elm, "");
+        addVnodes(
+          elm,
+          null,
+          ch as Array<VNode>,
+          0,
+          (ch as Array<VNode>).length - 1,
+          insertedVnodeQueue
+        );
+      } else if (isDef(oldCh)) {
+        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);
+      }
+      api.setTextContent(elm, vnode.text as string);
+    }
+    if (isDef(hook) && isDef((i = hook.postpatch))) {
+      i(oldVnode, vnode);
+    }
+  }
+
+  return function patch(oldVnode: VNode | Element, vnode: VNode): VNode {
+    let i: number, iLen: number, elm: Node, parent: Node;
+    const insertedVnodeQueue: VNodeQueue = [];
+    for (i = 0, iLen = cbs.pre.length; i < iLen; ++i) cbs.pre[i]();
+
+    if (!isVnode(oldVnode)) {
+      oldVnode = emptyNodeAt(oldVnode);
+    }
+
+    if (sameVnode(oldVnode, vnode)) {
+      patchVnode(oldVnode, vnode, insertedVnodeQueue);
+    } else {
+      elm = oldVnode.elm as Node;
+      parent = api.parentNode(elm);
+
+      createElm(vnode, insertedVnodeQueue);
+
+      if (parent !== null) {
+        api.insertBefore(parent, vnode.elm as Node, api.nextSibling(elm));
+        removeVnodes(parent, [oldVnode], 0, 0);
+      }
+    }
+
+    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, iLen = cbs.post.length; i < iLen; ++i) cbs.post[i]();
+    return vnode;
+  };
+}
+
+//------------------------------------------------------------------------------
+// is.ts
+//------------------------------------------------------------------------------
+const array = Array.isArray;
+function primitive(s: any): s is string | number {
+  return typeof s === "string" || typeof s === "number";
+}
+
+//------------------------------------------------------------------------------
+// htmldomapi.ts
+//------------------------------------------------------------------------------
+interface DOMAPI {
+  createElement: (tagName: any) => HTMLElement;
+  createElementNS: (namespaceURI: string, qualifiedName: string) => Element;
+  createTextNode: (text: string) => Text;
+  createComment: (text: string) => Comment;
+  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;
+}
+
+function createElement(tagName: any): HTMLElement {
+  return document.createElement(tagName);
+}
+
+function createElementNS(namespaceURI: string, qualifiedName: string): Element {
+  return document.createElementNS(namespaceURI, qualifiedName);
+}
+
+function createTextNode(text: string): Text {
+  return document.createTextNode(text);
+}
+
+function createComment(text: string): Comment {
+  return document.createComment(text);
+}
+
+function insertBefore(parentNode: Node, newNode: Node, referenceNode: Node | null): void {
+  parentNode.insertBefore(newNode, referenceNode);
+}
+
+function removeChild(node: Node, child: Node): void {
+  node.removeChild(child);
+}
+
+function appendChild(node: Node, child: Node): void {
+  node.appendChild(child);
+}
+
+function parentNode(node: Node): Node | null {
+  return node.parentNode;
+}
+
+function nextSibling(node: Node): Node | null {
+  return node.nextSibling;
+}
+
+function tagName(elm: Element): string {
+  return elm.tagName;
+}
+
+function setTextContent(node: Node, text: string | null): void {
+  node.textContent = text;
+}
+
+const htmlDomApi = {
+  createElement,
+  createElementNS,
+  createTextNode,
+  createComment,
+  insertBefore,
+  removeChild,
+  appendChild,
+  parentNode,
+  nextSibling,
+  tagName,
+  setTextContent,
+} as DOMAPI;
+
+//------------------------------------------------------------------------------
+// hooks.ts
+//------------------------------------------------------------------------------
+type PreHook = () => any;
+type InitHook = (vNode: VNode) => any;
+type CreateHook = (emptyVNode: VNode, vNode: VNode) => any;
+type InsertHook = (vNode: VNode) => any;
+type PrePatchHook = (oldVNode: VNode, vNode: VNode) => any;
+type UpdateHook = (oldVNode: VNode, vNode: VNode) => any;
+type PostPatchHook = (oldVNode: VNode, vNode: VNode) => any;
+type DestroyHook = (vNode: VNode) => any;
+type RemoveHook = (vNode: VNode, removeCallback: () => void) => any;
+type PostHook = () => any;
+
+interface Hooks {
+  pre?: PreHook;
+  init?: InitHook;
+  create?: CreateHook;
+  insert?: InsertHook;
+  prepatch?: PrePatchHook;
+  update?: UpdateHook;
+  postpatch?: PostPatchHook;
+  destroy?: DestroyHook;
+  remove?: RemoveHook;
+  post?: PostHook;
+}
+
+//------------------------------------------------------------------------------
+// h.ts
+//------------------------------------------------------------------------------
+type VNodes = Array<VNode>;
+type VNodeChildElement = VNode | string | number | undefined | null;
+type ArrayOrElement<T> = T | T[];
+type VNodeChildren = ArrayOrElement<VNodeChildElement>;
+
+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, iLen = children.length; i < iLen; ++i) {
+      const child = children[i];
+      let childData = child.data;
+      if (childData !== undefined) {
+        addNS(childData, (child as VNode).children as VNodes, child.sel);
+      }
+    }
+  }
+}
+
+export function h(sel: string): VNode;
+export function h(sel: string, data: VNodeData): VNode;
+export function h(sel: string, children: VNodeChildren): VNode;
+export function h(sel: string, data: VNodeData, children: VNodeChildren): VNode;
+export function h(sel: any, b?: any, c?: any): VNode {
+  var data: VNodeData = {},
+    children: any,
+    text: any,
+    i: number,
+    iLen: number;
+  if (c !== undefined) {
+    data = b;
+    if (array(c)) {
+      children = c;
+    } else if (primitive(c)) {
+      text = c;
+    } else if (c && c.sel) {
+      children = [c];
+    }
+  } else if (b !== undefined) {
+    if (array(b)) {
+      children = b;
+    } else if (primitive(b)) {
+      text = b;
+    } else if (b && b.sel) {
+      children = [b];
+    } else {
+      data = b;
+    }
+  }
+  if (children !== undefined) {
+    for (i = 0, iLen = children.length; i < iLen; ++i) {
+      if (primitive(children[i]))
+        children[i] = vnode(undefined, undefined, undefined, children[i], undefined);
+    }
+  }
+  return vnode(sel, data, children, text, undefined);
+}

tests/__snapshots__/animations.test.ts.snap

@@ -0,0 +1,200 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`animations t-transition combined with component 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"Parent\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    // Component 'Child'
+    let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+    let props2 = {};
+    if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+        w2.destroy();
+        w2 = false;
+    }
+    if (w2) {
+        w2.__updateProps(props2, extra.fiber, undefined);
+        let pvnode = w2.__owl__.pvnode;
+        c1.push(pvnode);
+    } else {
+        let componentKey2 = \`Child\`;
+        let W2 = scope['Child'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+        if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+        w2 = new W2(parent, props2);
+        const __patch2 = w2.__patch;
+        w2.__patch = (t, vn) => {__patch2.call(w2, t, vn); if(!w2.__owl__.transitionInserted){w2.__owl__.transitionInserted = true;utils.transitionInsert(w2.__owl__.vnode, 'chimay');}};
+        parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+        let fiber = w2.__prepare(extra.fiber, undefined, () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {let finalize = () => {
+          w2.destroy();
+        };
+        delete w2.__owl__.transitionInserted;
+        utils.transitionRemove(vn, 'chimay', finalize);}}});
+        c1.push(pvnode);
+        w2.__owl__.pvnode = pvnode;
+    }
+    w2.__owl__.parentLastFiberId = extra.fiber.id;
+    return vn1;
+}"
+`;
+
+exports[`animations t-transition combined with t-component and t-if 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"Parent\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    if (scope['state'].display) {
+        // Component 'Child'
+        let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+        let props2 = {};
+        if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+            w2.destroy();
+            w2 = false;
+        }
+        if (w2) {
+            w2.__updateProps(props2, extra.fiber, undefined);
+            let pvnode = w2.__owl__.pvnode;
+            c1.push(pvnode);
+        } else {
+            let componentKey2 = \`Child\`;
+            let W2 = scope['Child'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+            if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+            w2 = new W2(parent, props2);
+            const __patch2 = w2.__patch;
+            w2.__patch = (t, vn) => {__patch2.call(w2, t, vn); if(!w2.__owl__.transitionInserted){w2.__owl__.transitionInserted = true;utils.transitionInsert(w2.__owl__.vnode, 'chimay');}};
+            parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+            let fiber = w2.__prepare(extra.fiber, undefined, () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {let finalize = () => {
+          w2.destroy();
+        };
+        delete w2.__owl__.transitionInserted;
+        utils.transitionRemove(vn, 'chimay', finalize);}}});
+            c1.push(pvnode);
+            w2.__owl__.pvnode = pvnode;
+        }
+        w2.__owl__.parentLastFiberId = extra.fiber.id;
+    }
+    return vn1;
+}"
+`;
+
+exports[`animations t-transition combined with t-component, remove and re-add before transitionend 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__2\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    if (scope['state'].flag) {
+        // Component 'Child'
+        let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+        let props2 = {};
+        if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+            w2.destroy();
+            w2 = false;
+        }
+        if (w2) {
+            w2.__updateProps(props2, extra.fiber, undefined);
+            let pvnode = w2.__owl__.pvnode;
+            c1.push(pvnode);
+        } else {
+            let componentKey2 = \`Child\`;
+            let W2 = scope['Child'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+            if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+            w2 = new W2(parent, props2);
+            const __patch2 = w2.__patch;
+            w2.__patch = (t, vn) => {__patch2.call(w2, t, vn); if(!w2.__owl__.transitionInserted){w2.__owl__.transitionInserted = true;utils.transitionInsert(w2.__owl__.vnode, 'chimay');}};
+            parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+            let fiber = w2.__prepare(extra.fiber, undefined, () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {let finalize = () => {
+          w2.destroy();
+        };
+        delete w2.__owl__.transitionInserted;
+        utils.transitionRemove(vn, 'chimay', finalize);}}});
+            c1.push(pvnode);
+            w2.__owl__.pvnode = pvnode;
+        }
+        w2.__owl__.parentLastFiberId = extra.fiber.id;
+    }
+    return vn1;
+}"
+`;
+
+exports[`animations t-transition with no delay/duration 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let utils = this.constructor.utils;
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('span', p1, c1);
+    p1.hook = {
+      insert: vn => {
+        utils.transitionInsert(vn, '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
+) {
+    // Template name: \\"test\\"
+    let utils = this.constructor.utils;
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('span', p1, c1);
+    p1.hook = {
+      insert: vn => {
+        utils.transitionInsert(vn, 'chimay');
+      },
+      remove: (vn, rm) => {
+        utils.transitionRemove(vn, 'chimay', rm);
+      },
+    };
+    c1.push({text: \`blue\`});
+    return vn1;
+}"
+`;
+
+exports[`animations t-transition, on a simple node, not in the DOM 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let utils = this.constructor.utils;
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('span', p1, c1);
+    p1.hook = {
+      insert: vn => {
+        utils.transitionInsert(vn, 'chimay');
+      },
+      remove: (vn, rm) => {
+        utils.transitionRemove(vn, 'chimay', rm);
+      },
+    };
+    c1.push({text: \`blue\`});
+    return vn1;
+}"
+`;

tests/__snapshots__/store_hooks.test.ts.snap

@@ -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>"`;

tests/animations.test.ts

@@ -0,0 +1,452 @@
+import { Component, Env } from "../src/component/component";
+import { useRef, useState } from "../src/hooks";
+import { QWeb } from "../src/qweb/index";
+import { xml } from "../src/tags";
+import {
+  makeDeferred,
+  makeTestEnv,
+  makeTestFixture,
+  nextFrame,
+  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();
+  Component.env = env;
+  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");
+    fixture.appendChild(node);
+
+    expect(node.className).toBe("chimay-enter chimay-enter-active");
+    await def; // wait for the mocked repaint to be done
+    node.dispatchEvent(new Event("transitionend")); // mock end of css transition
+    expect(node.className).toBe("");
+  });
+
+  test("t-transition, on a simple node, not in the DOM", async () => {
+    expect.assertions(5);
+    qweb.addTemplate("test", `<span t-transition="chimay">blue</span>`);
+
+    let def = makeDeferred();
+    patchNextFrame((cb) => {
+      expect(node.className).toBe("chimay-enter chimay-enter-active");
+      cb();
+      expect(node.className).toBe("chimay-enter-active chimay-enter-to");
+      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"));
+    // we check here that the css classes have not been removed, since the
+    // element is not in the dom, we actually do not want to do anything.
+    expect(node.className).toBe("chimay-enter-active chimay-enter-to");
+  });
+
+  test("t-transition with no delay/duration", async () => {
+    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");
+    fixture.appendChild(node);
+    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();
+
+    // 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();
+
+    // 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();
+
+    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();
+
+    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="__3__">blue</span></div>'
+      );
+      cb();
+      expect(fixture.innerHTML).toBe(
+        '<div><span class="chimay-leave-active chimay-leave-to" data-owl-key="__3__">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();
+    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(12);
+
+    class Child extends Widget {
+      static template = xml`<span>blue</span>`;
+    }
+    class Parent extends Widget {
+      static template = xml`
+        <div t-name="Parent">
+          <t t-if="state.flag" t-component="Child" t-transition="chimay"/>
+        </div>`;
+      static components = { Child };
+      state = useState({ flag: false });
+    }
+
+    const widget = new Parent();
+    await widget.mount(fixture);
+    expect(env.qweb.templates[Parent.template].fn.toString()).toMatchSnapshot();
+
+    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();
+    });
+
+    // display the span
+    widget.state.flag = true;
+    await def; // wait for the mocked repaint to be done
+    widget.el!.querySelector("span")!.dispatchEvent(new Event("transitionend")); // mock end of css transition
+    expect(fixture.innerHTML).toBe('<div><span class="">blue</span></div>');
+
+    // click to remove the span, and click again to re-add it before transitionend
+    def = makeDeferred();
+    phase = "leave";
+
+    widget.state.flag = false;
+
+    await def; // wait for the mocked repaint to be done
+    def = makeDeferred();
+    phase = "enter";
+    widget.state.flag = true;
+
+    await def; // wait for the mocked repaint to be done
+    widget.el!.querySelector("span")!.dispatchEvent(new Event("transitionend")); // mock end of css transition
+    expect(fixture.innerHTML).toBe('<div><span class="" data-owl-key="__3__">blue</span></div>');
+  });
+
+  test("transitionInsert is called the correct amount of times", async () => {
+    const oldTransitionInsert = QWeb.utils.transitionInsert;
+    QWeb.utils.transitionInsert = jest.fn(oldTransitionInsert);
+
+    class Child extends Widget {
+      static template = xml`<span>blue</span>`;
+    }
+    class Parent extends Widget {
+      static template = xml`
+        <div t-name="Parent">
+          <Child t-if="state.flag" t-transition="chimay"/>
+        </div>`;
+      static components = { Child };
+      state = useState({ flag: false });
+    }
+
+    patchNextFrame((cb) => cb());
+
+    const widget = new Parent();
+    await widget.mount(fixture);
+
+    widget.state.flag = true;
+
+    await nextFrame();
+    widget.el!.querySelector("span")!.dispatchEvent(new Event("transitionend"));
+    expect(fixture.innerHTML).toBe('<div><span class="">blue</span></div>');
+    expect(QWeb.utils.transitionInsert).toBeCalledTimes(1);
+
+    widget.state.flag = false;
+    await nextFrame();
+    expect(fixture.innerHTML).toBe(
+      '<div><span class="chimay-leave-active chimay-leave-to" data-owl-key="__3__">blue</span></div>'
+    );
+    expect(QWeb.utils.transitionInsert).toBeCalledTimes(1);
+
+    widget.state.flag = true;
+    await nextFrame();
+    expect(fixture.innerHTML).toBe(
+      '<div><span class="chimay-enter-active chimay-enter-to" data-owl-key="__3__">blue</span></div>'
+    );
+    expect(QWeb.utils.transitionInsert).toBeCalledTimes(2);
+
+    widget.state.flag = false;
+    await nextFrame();
+    widget.state.flag = true;
+    await nextFrame();
+
+    expect(QWeb.utils.transitionInsert).toBeCalledTimes(3);
+    widget.el!.querySelector("span")!.dispatchEvent(new Event("transitionend"));
+    expect(fixture.innerHTML).toBe('<div><span class="" data-owl-key="__3__">blue</span></div>');
+    QWeb.utils.transitionInsert = oldTransitionInsert;
+  });
+});

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

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

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

@@ -0,0 +1,39 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`props validation props are validated in dev mode (code snapshot) 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"App\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    // Component 'Child'
+    let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+    let props2 = {message:1};
+    if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+        w2.destroy();
+        w2 = false;
+    }
+    if (w2) {
+        w2.__updateProps(props2, extra.fiber, undefined);
+        let pvnode = w2.__owl__.pvnode;
+        c1.push(pvnode);
+    } else {
+        let componentKey2 = \`Child\`;
+        let W2 = scope['Child'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+        if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+        w2 = new W2(parent, props2);
+        parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+        let fiber = w2.__prepare(extra.fiber, undefined, () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {w2.destroy();}}});
+        c1.push(pvnode);
+        w2.__owl__.pvnode = pvnode;
+    }
+    w2.__owl__.parentLastFiberId = extra.fiber.id;
+    return vn1;
+}"
+`;

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

@@ -0,0 +1,758 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`t-slot directive can define and call slots 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"Parent\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    // Component 'Dialog'
+    let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+    let props2 = {};
+    if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+        w2.destroy();
+        w2 = false;
+    }
+    if (w2) {
+        w2.__updateProps(props2, extra.fiber, utils.combine(context, scope));
+        let pvnode = w2.__owl__.pvnode;
+        c1.push(pvnode);
+    } else {
+        let componentKey2 = \`Dialog\`;
+        let W2 = scope['Dialog'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+        if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+        w2 = new W2(parent, props2);
+        parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+        w2.__owl__.slotId = 1;
+        let fiber = w2.__prepare(extra.fiber, utils.combine(context, scope), () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {w2.destroy();}}});
+        c1.push(pvnode);
+        w2.__owl__.pvnode = pvnode;
+    }
+    w2.__owl__.parentLastFiberId = extra.fiber.id;
+    return vn1;
+}"
+`;
+
+exports[`t-slot directive can define and call slots 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"Dialog\\"
+    let h = this.h;
+    let c8 = [], p8 = {key:8};
+    let vn8 = h('div', p8, c8);
+    let c9 = [], p9 = {key:9};
+    let vn9 = h('div', p9, c9);
+    c8.push(vn9);
+    const slot10 = this.constructor.slots[context.__owl__.slotId + '_' + 'header'];
+    if (slot10) {
+        slot10.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c9, parent: extra.parent || context}));
+    }
+    let c11 = [], p11 = {key:11};
+    let vn11 = h('div', p11, c11);
+    c8.push(vn11);
+    const slot12 = this.constructor.slots[context.__owl__.slotId + '_' + 'footer'];
+    if (slot12) {
+        slot12.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c11, parent: extra.parent || context}));
+    }
+    return vn8;
+}"
+`;
+
+exports[`t-slot directive can define and call slots 3`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_header_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c4 = extra.parentNode;
+    let c5 = [], p5 = {key:5};
+    let vn5 = h('span', p5, c5);
+    c4.push(vn5);
+    c5.push({text: \`header\`});
+}"
+`;
+
+exports[`t-slot directive can define and call slots 4`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_footer_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c6 = extra.parentNode;
+    let c7 = [], p7 = {key:7};
+    let vn7 = h('span', p7, c7);
+    c6.push(vn7);
+    c7.push({text: \`footer\`});
+}"
+`;
+
+exports[`t-slot directive can define and call slots using old t-set keyword 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__2\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    // Component 'Dialog'
+    let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+    let props2 = {};
+    if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+        w2.destroy();
+        w2 = false;
+    }
+    if (w2) {
+        w2.__updateProps(props2, extra.fiber, utils.combine(context, scope));
+        let pvnode = w2.__owl__.pvnode;
+        c1.push(pvnode);
+    } else {
+        let componentKey2 = \`Dialog\`;
+        let W2 = scope['Dialog'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+        if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+        w2 = new W2(parent, props2);
+        parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+        w2.__owl__.slotId = 1;
+        let fiber = w2.__prepare(extra.fiber, utils.combine(context, scope), () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {w2.destroy();}}});
+        c1.push(pvnode);
+        w2.__owl__.pvnode = pvnode;
+    }
+    w2.__owl__.parentLastFiberId = extra.fiber.id;
+    return vn1;
+}"
+`;
+
+exports[`t-slot directive can define and call slots using old t-set keyword 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__1\\"
+    let h = this.h;
+    let c8 = [], p8 = {key:8};
+    let vn8 = h('div', p8, c8);
+    let c9 = [], p9 = {key:9};
+    let vn9 = h('div', p9, c9);
+    c8.push(vn9);
+    const slot10 = this.constructor.slots[context.__owl__.slotId + '_' + 'header'];
+    if (slot10) {
+        slot10.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c9, parent: extra.parent || context}));
+    }
+    let c11 = [], p11 = {key:11};
+    let vn11 = h('div', p11, c11);
+    c8.push(vn11);
+    const slot12 = this.constructor.slots[context.__owl__.slotId + '_' + 'footer'];
+    if (slot12) {
+        slot12.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c11, parent: extra.parent || context}));
+    }
+    return vn8;
+}"
+`;
+
+exports[`t-slot directive can define and call slots using old t-set keyword 3`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_header_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c4 = extra.parentNode;
+    let c5 = [], p5 = {key:5};
+    let vn5 = h('span', p5, c5);
+    c4.push(vn5);
+    c5.push({text: \`header\`});
+}"
+`;
+
+exports[`t-slot directive can define and call slots using old t-set keyword 4`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_footer_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c6 = extra.parentNode;
+    let c7 = [], p7 = {key:7};
+    let vn7 = h('span', p7, c7);
+    c6.push(vn7);
+    c7.push({text: \`footer\`});
+}"
+`;
+
+exports[`t-slot directive content is the default slot 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_default_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c4 = extra.parentNode;
+    let c5 = [], p5 = {key:5};
+    let vn5 = h('span', p5, c5);
+    c4.push(vn5);
+    c5.push({text: \`sts rocks\`});
+}"
+`;
+
+exports[`t-slot directive dafault slots can define a default content 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__1\\"
+    let h = this.h;
+    let c4 = [], p4 = {key:4};
+    let vn4 = h('span', p4, c4);
+    const slot5 = this.constructor.slots[context.__owl__.slotId + '_' + 'default'];
+    if (slot5) {
+        slot5.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c4, parent: extra.parent || context}));
+    } else {
+        c4.push({text: \`default content\`});
+    }
+    return vn4;
+}"
+`;
+
+exports[`t-slot directive default slot next to named slot, with default content 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__2\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    // Component 'Dialog'
+    let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+    let props2 = {};
+    if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+        w2.destroy();
+        w2 = false;
+    }
+    if (w2) {
+        w2.__updateProps(props2, extra.fiber, utils.combine(context, scope));
+        let pvnode = w2.__owl__.pvnode;
+        c1.push(pvnode);
+    } else {
+        let componentKey2 = \`Dialog\`;
+        let W2 = scope['Dialog'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+        if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+        w2 = new W2(parent, props2);
+        parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+        w2.__owl__.slotId = 1;
+        let fiber = w2.__prepare(extra.fiber, utils.combine(context, scope), () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {w2.destroy();}}});
+        c1.push(pvnode);
+        w2.__owl__.pvnode = pvnode;
+    }
+    w2.__owl__.parentLastFiberId = extra.fiber.id;
+    return vn1;
+}"
+`;
+
+exports[`t-slot directive default slot work with text nodes 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_default_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c4 = extra.parentNode;
+    c4.push({text: \`sts rocks\`});
+}"
+`;
+
+exports[`t-slot directive dynamic t-slot call 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__1\\"
+    let utils = this.constructor.utils;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c9 = [], p9 = {key:9,on:{}};
+    let vn9 = h('button', p9, c9);
+    extra.handlers['click__10__'] = extra.handlers['click__10__'] || function (e) {if (context.__owl__.status === 5){return}utils.getComponent(context)['toggle'](e);};
+    p9.on['click'] = extra.handlers['click__10__'];
+    const slot11 = this.constructor.slots[context.__owl__.slotId + '_' + (scope['current'].slot)];
+    if (slot11) {
+        slot11.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c9, parent: extra.parent || context}));
+    }
+    return vn9;
+}"
+`;
+
+exports[`t-slot directive multiple roots are allowed in a default slot 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_default_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c4 = extra.parentNode;
+    let c5 = [], p5 = {key:5};
+    let vn5 = h('span', p5, c5);
+    c4.push(vn5);
+    c5.push({text: \`sts\`});
+    let c6 = [], p6 = {key:6};
+    let vn6 = h('span', p6, c6);
+    c4.push(vn6);
+    c6.push({text: \`rocks\`});
+}"
+`;
+
+exports[`t-slot directive multiple roots are allowed in a named slot 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_content_template\\"
+    let parent = extra.parent;
+    let h = this.h;
+    let c4 = extra.parentNode;
+    let c5 = [], p5 = {key:5};
+    let vn5 = h('span', p5, c5);
+    c4.push(vn5);
+    c5.push({text: \`sts\`});
+    let c6 = [], p6 = {key:6};
+    let vn6 = h('span', p6, c6);
+    c4.push(vn6);
+    c6.push({text: \`rocks\`});
+}"
+`;
+
+exports[`t-slot directive named slots can define a default content 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__1\\"
+    let h = this.h;
+    let c4 = [], p4 = {key:4};
+    let vn4 = h('span', p4, c4);
+    const slot5 = this.constructor.slots[context.__owl__.slotId + '_' + 'header'];
+    if (slot5) {
+        slot5.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c4, parent: extra.parent || context}));
+    } else {
+        c4.push({text: \`default content\`});
+    }
+    return vn4;
+}"
+`;
+
+exports[`t-slot directive refs are properly bound in slots 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_footer_template\\"
+    let utils = this.constructor.utils;
+    let parent = extra.parent;
+    context.__owl__.refs = context.__owl__.refs || {};
+    let h = this.h;
+    let c8 = extra.parentNode;
+    let c9 = [], p9 = {key:9,on:{}};
+    let vn9 = h('button', p9, c9);
+    c8.push(vn9);
+    extra.handlers['click__10__'] = extra.handlers['click__10__'] || function (e) {if (context.__owl__.status === 5){return}utils.getComponent(context)['doSomething'](e);};
+    p9.on['click'] = extra.handlers['click__10__'];
+    const ref11 = \`myButton\`;
+    p9.hook = {
+      create: (_, n) => {
+        context.__owl__.refs[ref11] = n.elm;
+      },
+      destroy: () => {
+        delete context.__owl__.refs[ref11];
+      },
+    };
+    c9.push({text: \`do something\`});
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_footer_template\\"
+    let utils = this.constructor.utils;
+    let parent = extra.parent;
+    let h = this.h;
+    let c8 = extra.parentNode;
+    let c9 = [], p9 = {key:9,on:{}};
+    let vn9 = h('button', p9, c9);
+    c8.push(vn9);
+    extra.handlers['click__10__'] = extra.handlers['click__10__'] || function (e) {if (context.__owl__.status === 5){return}utils.getComponent(context)['doSomething'](e);};
+    p9.on['click'] = extra.handlers['click__10__'];
+    c9.push({text: \`do something\`});
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 2 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"Link\\"
+    let scope = Object.create(context);
+    let h = this.h;
+    let _12 = scope['props'].to;
+    let c13 = [], p13 = {key:13,attrs:{href: _12}};
+    let vn13 = h('a', p13, c13);
+    const slot14 = this.constructor.slots[context.__owl__.slotId + '_' + 'default'];
+    if (slot14) {
+        slot14.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c13, parent: extra.parent || context}));
+    }
+    return vn13;
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 2 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"App\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    let c2 = [], p2 = {key:2};
+    let vn2 = h('u', p2, c2);
+    c1.push(vn2);
+    let _3 = scope['state'].users;
+    if (!_3) { throw new Error('QWeb error: Invalid loop expression')}
+    let _4 = _3;
+    let _5 = _3;
+    if (!(_3 instanceof Array)) {
+        _4 = Object.keys(_3);
+        _5 = Object.values(_3);
+    }
+    let _length4 = _4.length;
+    let _origScope6 = scope;
+    scope = Object.create(scope);
+    for (let i1 = 0; i1 < _length4; i1++) {
+        scope.user_first = i1 === 0
+        scope.user_last = i1 === _length4 - 1
+        scope.user_index = i1
+        scope.user = _4[i1]
+        scope.user_value = _5[i1]
+        let key1 = scope['user'].id;
+        let c7 = [], p7 = {key:\`\${key1}_7\`};
+        let vn7 = h('li', p7, c7);
+        c2.push(vn7);
+        // Component 'Link'
+        let k9 = \`__9__\${key1}__\`;
+        let w8 = k9 in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap[k9]] : false;
+        let props8 = {to:'/user/'+scope['user'].id};
+        if (w8 && w8.__owl__.currentFiber && !w8.__owl__.vnode) {
+            w8.destroy();
+            w8 = false;
+        }
+        if (w8) {
+            w8.__updateProps(props8, extra.fiber, utils.combine(context, scope));
+            let pvnode = w8.__owl__.pvnode;
+            c7.push(pvnode);
+        } else {
+            let componentKey8 = \`Link\`;
+            let W8 = scope['Link'] || context.constructor.components[componentKey8] || QWeb.components[componentKey8];
+            if (!W8) {throw new Error('Cannot find the definition of component \\"' + componentKey8 + '\\"')}
+            w8 = new W8(parent, props8);
+            parent.__owl__.cmap[k9] = w8.__owl__.id;
+            w8.__owl__.slotId = 1;
+            let fiber = w8.__prepare(extra.fiber, utils.combine(context, scope), () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            let pvnode = h('dummy', {key: k9, hook: {remove() {},destroy(vn) {w8.destroy();}}});
+            c7.push(pvnode);
+            w8.__owl__.pvnode = pvnode;
+        }
+        w8.__owl__.parentLastFiberId = extra.fiber.id;
+    }
+    scope = _origScope6;
+    return vn1;
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 2 3`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_default_template\\"
+    let parent = extra.parent;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c10 = extra.parentNode;
+    c10.push({text: \`User \`});
+    let _11 = scope['user'].name;
+    if (_11 != null) {
+        c10.push({text: _11});
+    }
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 3 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"Link\\"
+    let scope = Object.create(context);
+    let h = this.h;
+    let _12 = scope['props'].to;
+    let c13 = [], p13 = {key:13,attrs:{href: _12}};
+    let vn13 = h('a', p13, c13);
+    const slot14 = this.constructor.slots[context.__owl__.slotId + '_' + 'default'];
+    if (slot14) {
+        slot14.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c13, parent: extra.parent || context}));
+    }
+    return vn13;
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 3 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"App\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    let c2 = [], p2 = {key:2};
+    let vn2 = h('u', p2, c2);
+    c1.push(vn2);
+    let _3 = scope['state'].users;
+    if (!_3) { throw new Error('QWeb error: Invalid loop expression')}
+    let _4 = _3;
+    let _5 = _3;
+    if (!(_3 instanceof Array)) {
+        _4 = Object.keys(_3);
+        _5 = Object.values(_3);
+    }
+    let _length4 = _4.length;
+    let _origScope6 = scope;
+    scope = Object.create(scope);
+    for (let i1 = 0; i1 < _length4; i1++) {
+        scope.user_first = i1 === 0
+        scope.user_last = i1 === _length4 - 1
+        scope.user_index = i1
+        scope.user = _4[i1]
+        scope.user_value = _5[i1]
+        let key1 = scope['user'].id;
+        let c7 = [], p7 = {key:\`\${key1}_7\`};
+        let vn7 = h('li', p7, c7);
+        c2.push(vn7);
+        utils.getScope(scope, 'userdescr').userdescr = 'User '+scope['user'].name;
+        // Component 'Link'
+        let k9 = \`__9__\${key1}__\`;
+        let w8 = k9 in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap[k9]] : false;
+        let props8 = {to:'/user/'+scope['user'].id};
+        if (w8 && w8.__owl__.currentFiber && !w8.__owl__.vnode) {
+            w8.destroy();
+            w8 = false;
+        }
+        if (w8) {
+            w8.__updateProps(props8, extra.fiber, utils.combine(context, scope));
+            let pvnode = w8.__owl__.pvnode;
+            c7.push(pvnode);
+        } else {
+            let componentKey8 = \`Link\`;
+            let W8 = scope['Link'] || context.constructor.components[componentKey8] || QWeb.components[componentKey8];
+            if (!W8) {throw new Error('Cannot find the definition of component \\"' + componentKey8 + '\\"')}
+            w8 = new W8(parent, props8);
+            parent.__owl__.cmap[k9] = w8.__owl__.id;
+            w8.__owl__.slotId = 1;
+            let fiber = w8.__prepare(extra.fiber, utils.combine(context, scope), () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+            let pvnode = h('dummy', {key: k9, hook: {remove() {},destroy(vn) {w8.destroy();}}});
+            c7.push(pvnode);
+            w8.__owl__.pvnode = pvnode;
+        }
+        w8.__owl__.parentLastFiberId = extra.fiber.id;
+    }
+    scope = _origScope6;
+    return vn1;
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 3 3`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_default_template\\"
+    let parent = extra.parent;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c10 = extra.parentNode;
+    let _11 = scope['userdescr'];
+    if (_11 != null) {
+        c10.push({text: _11});
+    }
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 4 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"App\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    scope.userdescr = 'User '+scope['state'].user.name;
+    // Component 'Link'
+    let w2 = '__3__' in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap['__3__']] : false;
+    let props2 = {to:'/user/'+scope['state'].user.id};
+    if (w2 && w2.__owl__.currentFiber && !w2.__owl__.vnode) {
+        w2.destroy();
+        w2 = false;
+    }
+    if (w2) {
+        w2.__updateProps(props2, extra.fiber, utils.combine(context, scope));
+        let pvnode = w2.__owl__.pvnode;
+        c1.push(pvnode);
+    } else {
+        let componentKey2 = \`Link\`;
+        let W2 = scope['Link'] || context.constructor.components[componentKey2] || QWeb.components[componentKey2];
+        if (!W2) {throw new Error('Cannot find the definition of component \\"' + componentKey2 + '\\"')}
+        w2 = new W2(parent, props2);
+        parent.__owl__.cmap['__3__'] = w2.__owl__.id;
+        w2.__owl__.slotId = 1;
+        let fiber = w2.__prepare(extra.fiber, utils.combine(context, scope), () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+        let pvnode = h('dummy', {key: '__3__', hook: {remove() {},destroy(vn) {w2.destroy();}}});
+        c1.push(pvnode);
+        w2.__owl__.pvnode = pvnode;
+    }
+    w2.__owl__.parentLastFiberId = extra.fiber.id;
+    return vn1;
+}"
+`;
+
+exports[`t-slot directive slots are rendered with proper context, part 4 2`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"slot_default_template\\"
+    let parent = extra.parent;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c4 = extra.parentNode;
+    let _5 = scope['userdescr'];
+    if (_5 != null) {
+        c4.push({text: _5});
+    }
+}"
+`;
+
+exports[`t-slot directive slots in t-foreach in t-foreach 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__2\\"
+    let utils = this.constructor.utils;
+    let QWeb = this.constructor;
+    let parent = context;
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('div', p1, c1);
+    let _2 = scope['tree'];
+    if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
+    let _3 = _2;
+    let _4 = _2;
+    if (!(_2 instanceof Array)) {
+        _3 = Object.keys(_2);
+        _4 = Object.values(_2);
+    }
+    let _length3 = _3.length;
+    let _origScope5 = scope;
+    scope = Object.create(scope);
+    for (let i1 = 0; i1 < _length3; i1++) {
+        scope.node1_first = i1 === 0
+        scope.node1_last = i1 === _length3 - 1
+        scope.node1_index = i1
+        scope.node1 = _3[i1]
+        scope.node1_value = _4[i1]
+        let key1 = scope['node1'].key;
+        let c6 = [], p6 = {key:\`\${key1}_6\`};
+        let vn6 = h('div', p6, c6);
+        c1.push(vn6);
+        let _7 = scope['node1'].value;
+        if (_7 != null) {
+            c6.push({text: _7});
+        }
+        let c8 = [], p8 = {key:\`\${key1}_8\`};
+        let vn8 = h('ul', p8, c8);
+        c1.push(vn8);
+        let _9 = scope['node1'].nodes;
+        if (!_9) { throw new Error('QWeb error: Invalid loop expression')}
+        let _10 = _9;
+        let _11 = _9;
+        if (!(_9 instanceof Array)) {
+            _10 = Object.keys(_9);
+            _11 = Object.values(_9);
+        }
+        let _length10 = _10.length;
+        let _origScope12 = scope;
+        scope = Object.create(scope);
+        for (let i2 = 0; i2 < _length10; i2++) {
+            scope.node2_first = i2 === 0
+            scope.node2_last = i2 === _length10 - 1
+            scope.node2_index = i2
+            scope.node2 = _10[i2]
+            scope.node2_value = _11[i2]
+            let key2 = scope['node2'].key;
+            // Component 'Child'
+            let k14 = \`__14__\${key1}__\${key2}__\`;
+            let w13 = k14 in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap[k14]] : false;
+            let props13 = {};
+            if (w13 && w13.__owl__.currentFiber && !w13.__owl__.vnode) {
+                w13.destroy();
+                w13 = false;
+            }
+            if (w13) {
+                w13.__updateProps(props13, extra.fiber, utils.combine(context, scope));
+                let pvnode = w13.__owl__.pvnode;
+                c8.push(pvnode);
+            } else {
+                let componentKey13 = \`Child\`;
+                let W13 = scope['Child'] || context.constructor.components[componentKey13] || QWeb.components[componentKey13];
+                if (!W13) {throw new Error('Cannot find the definition of component \\"' + componentKey13 + '\\"')}
+                w13 = new W13(parent, props13);
+                parent.__owl__.cmap[k14] = w13.__owl__.id;
+                w13.__owl__.slotId = 1;
+                let fiber = w13.__prepare(extra.fiber, utils.combine(context, scope), () => { const vnode = fiber.vnode; pvnode.sel = vnode.sel; });
+                let pvnode = h('dummy', {key: k14, hook: {remove() {},destroy(vn) {w13.destroy();}}});
+                c8.push(pvnode);
+                w13.__owl__.pvnode = pvnode;
+            }
+            w13.__owl__.parentLastFiberId = extra.fiber.id;
+        }
+        scope = _origScope12;
+    }
+    scope = _origScope5;
+    return vn1;
+}"
+`;
+
+exports[`t-slot directive t-set t-value in a slot 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__1\\"
+    let h = this.h;
+    let c5 = [], p5 = {key:5};
+    let vn5 = h('span', p5, c5);
+    const slot6 = this.constructor.slots[context.__owl__.slotId + '_' + 'default'];
+    if (slot6) {
+        slot6.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: c5, parent: extra.parent || context}));
+    }
+    return vn5;
+}"
+`;
+
+exports[`t-slot directive template can just return a slot 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"__template__2\\"
+    let utils = this.constructor.utils;
+    let result;
+    let h = this.h;
+    const slot7 = this.constructor.slots[context.__owl__.slotId + '_' + 'default'];
+    if (slot7) {
+        let children8= []
+        result = {}
+        slot7.call(this, context.__owl__.scope, Object.assign({}, extra, {parentNode: children8, parent: extra.parent || context}));
+        utils.defineProxy(result, children8[0]);
+    }
+    return result;
+}"
+`;

tests/component/class_style.test.ts

@@ -0,0 +1,273 @@
+import { Component, Env } from "../../src/component/component";
+import { QWeb } from "../../src/qweb/qweb";
+import { xml } from "../../src/tags";
+import { useState, useRef } from "../../src/hooks";
+import { makeTestFixture, makeTestEnv, nextTick } from "../helpers";
+
+//------------------------------------------------------------------------------
+// Setup and helpers
+//------------------------------------------------------------------------------
+
+// We create before each test:
+// - fixture: a div, appended to the DOM, intended to be the target of dom
+//   manipulations.  Note that it is removed after each test.
+// - env: a WEnv, necessary to create new components
+
+let fixture: HTMLElement;
+let env: Env;
+
+beforeEach(() => {
+  fixture = makeTestFixture();
+  env = makeTestEnv();
+  Component.env = env;
+});
+
+afterEach(() => {
+  fixture.remove();
+});
+
+describe("class and style attributes with t-component", () => {
+  test("class is properly added on widget root el", async () => {
+    class Child extends Component {
+      static template = xml`<div class="c"/>`;
+    }
+    class ParentWidget extends Component {
+      static template = xml`<div><Child class="a b"/></div>`;
+      static components = { Child };
+    }
+    const widget = new ParentWidget();
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe(`<div><div class="c a b"></div></div>`);
+  });
+
+  test("empty class attribute is not added on widget root el", async () => {
+    class Child extends Component {
+      static template = xml`<span/>`;
+    }
+    class Parent extends Component {
+      static template = xml`<div><Child class=""/></div>`;
+      static components = { Child };
+    }
+    const widget = new Parent();
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe(`<div><span></span></div>`);
+  });
+
+  test("t-att-class is properly added/removed on widget root el", async () => {
+    class Child extends Component {
+      static template = xml`<div class="c"/>`;
+    }
+    class ParentWidget extends Component {
+      static template = xml`<div><Child t-att-class="{a:state.a, b:state.b}"/></div>`;
+      static components = { Child };
+      state = useState({ a: true, b: false });
+    }
+    const widget = new ParentWidget();
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe(`<div><div class="c a"></div></div>`);
+    expect(QWeb.TEMPLATES[ParentWidget.template].fn.toString());
+
+    widget.state.a = false;
+    widget.state.b = true;
+    await nextTick();
+    expect(fixture.innerHTML).toBe(`<div><div class="c b"></div></div>`);
+  });
+
+  test("class with extra whitespaces", async () => {
+    env.qweb.addTemplate(
+      "ParentWidget",
+      `<div>
+              <Child class="a  b c   d"/>
+        </div>`
+    );
+    class Child extends Component {}
+    class ParentWidget extends Component {
+      static components = { Child };
+    }
+    env.qweb.addTemplate("Child", `<div/>`);
+    const widget = new ParentWidget();
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe(`<div><div class="a b c d"></div></div>`);
+  });
+
+  test("t-att-class is properly added/removed on widget root el (v2)", async () => {
+    env.qweb.addTemplates(`
+        <templates>
+          <div t-name="ParentWidget">
+            <Child class="a" t-att-class="{ b: state.b }" t-ref="child"/>
+          </div>
+          <span t-name="Child" class="c" t-att-class="{ d: state.d }"/>
+        </templates>`);
+
+    class Child extends Component {
+      state = useState({ d: true });
+    }
+    class ParentWidget extends Component {
+      static components = { Child };
+      state = useState({ b: true });
+      child = useRef("child");
+    }
+    const widget = new ParentWidget();
+    await widget.mount(fixture);
+
+    const span = fixture.querySelector("span")!;
+    expect(span.className).toBe("c d a b");
+
+    widget.state.b = false;
+    await nextTick();
+    expect(span.className).toBe("c d a");
+
+    (widget.child.comp as Child).state.d = false;
+    await nextTick();
+    expect(span.className).toBe("c a");
+
+    widget.state.b = true;
+    await nextTick();
+    expect(span.className).toBe("c a b");
+
+    (widget.child.comp as Child).state.d = true;
+    await nextTick();
+    expect(span.className).toBe("c a b d");
+    expect(env.qweb.templates.ParentWidget.fn.toString()).toMatchSnapshot();
+    expect(env.qweb.templates.Child.fn.toString()).toMatchSnapshot();
+  });
+
+  test("t-att-class is properly added/removed on widget root el (v3)", async () => {
+    env.qweb.addTemplates(`
+        <templates>
+          <div t-name="ParentWidget">
+            <Child class="a" t-att-class="state.b ? 'b' : ''" t-ref="child"/>
+          </div>
+          <span t-name="Child" class="c" t-att-class="state.d ? 'd' : ''"/>
+        </templates>`);
+
+    class Child extends Component {
+      state = useState({ d: true });
+    }
+    class ParentWidget extends Component {
+      static components = { Child };
+      state = useState({ b: true });
+      child = useRef("child");
+    }
+    const widget = new ParentWidget();
+    await widget.mount(fixture);
+
+    const span = fixture.querySelector("span")!;
+    expect(span.className).toBe("c d a b");
+
+    widget.state.b = false;
+    await nextTick();
+    expect(span.className).toBe("c d a");
+
+    (widget.child.comp as Child).state.d = false;
+    await nextTick();
+    expect(span.className).toBe("c a");
+
+    widget.state.b = true;
+    await nextTick();
+    expect(span.className).toBe("c a b");
+
+    (widget.child.comp as Child).state.d = true;
+    await nextTick();
+    expect(span.className).toBe("c a b d");
+    expect(env.qweb.templates.ParentWidget.fn.toString()).toMatchSnapshot();
+    expect(env.qweb.templates.Child.fn.toString()).toMatchSnapshot();
+  });
+
+  test("class on components do not interfere with user defined classes", async () => {
+    env.qweb.addTemplates(`
+        <templates>
+          <div t-name="App" t-att-class="{ c: state.c }" />
+        </templates>`);
+
+    class App extends Component {
+      state = useState({ c: true });
+      mounted() {
+        this.el!.classList.add("user");
+      }
+    }
+
+    const widget = new App();
+    await widget.mount(fixture);
+
+    expect(fixture.innerHTML).toBe('<div class="c user"></div>');
+
+    widget.state.c = false;
+    await nextTick();
+
+    expect(fixture.innerHTML).toBe('<div class="user"></div>');
+  });
+
+  test("style is properly added on widget root el", async () => {
+    env.qweb.addTemplate(
+      "ParentWidget",
+      `
+          <div>
+              <t t-component="child" style="font-weight: bold;"/>
+          </div>`
+    );
+
+    class SomeComponent extends Component {
+      static template = xml`<div/>`;
+    }
+
+    class ParentWidget extends Component {
+      static components = { child: SomeComponent };
+    }
+    const widget = new ParentWidget();
+    await widget.mount(fixture);
+    expect(fixture.innerHTML).toBe(`<div><div style="font-weight: bold;"></div></div>`);
+  });
+
+  test("dynamic t-att-style is properly added and updated on widget root el", async () => {
+    env.qweb.addTemplate(
+      "ParentWidget",
+      `
+          <div>
+              <t t-component="child" t-att-style="state.style"/>
+          </div>`
+    );
+
+    class SomeComponent extends Component {
+      static template = xml`<div/>`;
+    }
+
+    class ParentWidget extends Component {
+      static components = { child: SomeComponent };
+      state = useState({ style: "font-size: 20px" });
+    }
+    const widget = new ParentWidget();
+    await widget.mount(fixture);
+
+    expect(env.qweb.templates.ParentWidget.fn.toString()).toMatchSnapshot();
+
+    expect(fixture.innerHTML).toBe(`<div><div style="font-size: 20px;"></div></div>`);
+
+    widget.state.style = "font-size: 30px";
+    await nextTick();
+
+    expect(fixture.innerHTML).toBe(`<div><div style="font-size: 30px;"></div></div>`);
+  });
+
+  test("error in subcomponent with class", async () => {
+    class Child extends Component {
+      static template = xml`<div t-esc="this.will.crash"/>`;
+    }
+    class ParentWidget extends Component {
+      static template = xml`<div><Child class="a"/></div>`;
+      static components = { Child };
+    }
+    const widget = new ParentWidget();
+    let error;
+    try {
+      await widget.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    const regexp =
+      /Cannot read properties of undefined \(reading 'crash'\)|Cannot read property 'crash' of undefined/g;
+    expect(error.message).toMatch(regexp);
+    expect(fixture.innerHTML).toBe("");
+  });
+});

tests/component/error_handling.test.ts

@@ -0,0 +1,620 @@
+import { Component, Env, mount, STATUS } from "../../src/component/component";
+import { useState } from "../../src/hooks";
+import { xml } from "../../src/tags";
+import { makeTestEnv, makeTestFixture, nextTick } from "../helpers";
+
+//------------------------------------------------------------------------------
+// Setup and helpers
+//------------------------------------------------------------------------------
+
+// We create before each test:
+// - fixture: a div, appended to the DOM, intended to be the target of dom
+//   manipulations.  Note that it is removed after each test.
+// - env: a WEnv, necessary to create new components
+
+let fixture: HTMLElement;
+let env: Env;
+
+beforeEach(() => {
+  fixture = makeTestFixture();
+  env = makeTestEnv();
+  Component.env = env;
+});
+
+afterEach(() => {
+  fixture.remove();
+});
+
+describe("component error handling (catchError)", () => {
+  /**
+   * This test suite requires often to wait for 3 ticks. Here is why:
+   * - First tick is to let the app render and crash.
+   * - When we crash, we call the catchError handler in a setTimeout (because we
+   *   need to wait for the previous rendering to be completely stopped). So, we
+   *   need to wait for the second tick.
+   * - Then, when the handler changes the state, we need to wait for the interface
+   *   to be rerendered.
+   *  */
+
+  test("can catch an error in a component render function", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn();
+    const handler = jest.fn();
+    env.qweb.on("error", null, handler);
+    class ErrorComponent extends Component {
+      static template = xml`<div>hey<t t-esc="props.flag and state.this.will.crash"/></div>`;
+    }
+    class ErrorBoundary extends Component {
+      static template = xml`
+          <div>
+            <t t-if="state.error">Error handled</t>
+            <t t-else=""><t t-slot="default" /></t>
+          </div>`;
+      state = useState({ error: false });
+
+      catchError() {
+        this.state.error = true;
+      }
+    }
+    class App extends Component {
+      static template = xml`
+          <div>
+            <ErrorBoundary><ErrorComponent flag="state.flag"/></ErrorBoundary>
+          </div>`;
+      state = useState({ flag: false });
+      static components = { ErrorBoundary, ErrorComponent };
+    }
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div><div>heyfalse</div></div></div>");
+    app.state.flag = true;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><div>Error handled</div></div>");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+    expect(handler).toBeCalledTimes(1);
+  });
+
+  test("no component catching error lead to full app destruction", async () => {
+    expect.assertions(6);
+    const handler = jest.fn();
+    env.qweb.on("error", null, handler);
+    const consoleError = console.error;
+    console.error = jest.fn();
+
+    class ErrorComponent extends Component {
+      static template = xml`<div>hey<t t-esc="props.flag and state.this.will.crash"/></div>`;
+    }
+
+    class App extends Component {
+      static template = xml`<div><ErrorComponent flag="state.flag"/></div>`;
+      static components = { ErrorComponent };
+      state = useState({ flag: false });
+      async render() {
+        try {
+          await super.render();
+        } catch (e) {
+          expect(e.message).toMatch(
+            /Cannot read properties of undefined \(reading 'this'\)|Cannot read property 'this' of undefined/
+          );
+        }
+      }
+    }
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>heyfalse</div></div>");
+    app.state.flag = true;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+    expect(app.__owl__.status).toBe(STATUS.DESTROYED);
+    expect(handler).toBeCalledTimes(1);
+  });
+
+  test("can catch an error in the initial call of a component render function (parent mounted)", async () => {
+    const handler = jest.fn();
+    env.qweb.on("error", null, handler);
+    const consoleError = console.error;
+    console.error = jest.fn();
+    class ErrorComponent extends Component {
+      static template = xml`<div>hey<t t-esc="state.this.will.crash"/></div>`;
+    }
+    class ErrorBoundary extends Component {
+      static template = xml`
+          <div>
+            <t t-if="state.error">Error handled</t>
+            <t t-else=""><t t-slot="default" /></t>
+          </div>`;
+      state = useState({ error: false });
+
+      catchError() {
+        this.state.error = true;
+      }
+    }
+    class App extends Component {
+      static template = xml`
+          <div>
+              <ErrorBoundary><ErrorComponent /></ErrorBoundary>
+          </div>`;
+      static components = { ErrorBoundary, ErrorComponent };
+    }
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>Error handled</div></div>");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+    expect(handler).toBeCalledTimes(1);
+  });
+
+  test("can catch an error in the initial call of a component render function (parent updated)", async () => {
+    const handler = jest.fn();
+    env.qweb.on("error", null, handler);
+    const consoleError = console.error;
+    console.error = jest.fn();
+    class ErrorComponent extends Component {
+      static template = xml`<div>hey<t t-esc="state.this.will.crash"/></div>`;
+    }
+    class ErrorBoundary extends Component {
+      static template = xml`
+          <div>
+            <t t-if="state.error">Error handled</t>
+            <t t-else=""><t t-slot="default" /></t>
+          </div>`;
+      state = useState({ error: false });
+
+      catchError() {
+        this.state.error = true;
+      }
+    }
+    class App extends Component {
+      static template = xml`
+          <div>
+              <ErrorBoundary t-if="state.flag"><ErrorComponent /></ErrorBoundary>
+          </div>`;
+      state = useState({ flag: false });
+      static components = { ErrorBoundary, ErrorComponent };
+    }
+    const app = new App();
+    await app.mount(fixture);
+    app.state.flag = true;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><div>Error handled</div></div>");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+    expect(handler).toBeCalledTimes(1);
+  });
+
+  test("can catch an error in the constructor call of a component render function", async () => {
+    const handler = jest.fn();
+    env.qweb.on("error", null, handler);
+    const consoleError = console.error;
+    console.error = jest.fn();
+    env.qweb.addTemplates(`
+        <templates>
+          <div t-name="ErrorBoundary">
+              <t t-if="state.error">Error handled</t>
+              <t t-else=""><t t-slot="default" /></t>
+          </div>
+          <div t-name="ErrorComponent">Some text</div>
+          <div t-name="App">
+              <ErrorBoundary><ErrorComponent /></ErrorBoundary>
+          </div>
+        </templates>`);
+    class ErrorComponent extends Component {
+      constructor(parent) {
+        super(parent);
+        throw new Error("NOOOOO");
+      }
+    }
+    class ErrorBoundary extends Component {
+      state = useState({ error: false });
+
+      catchError() {
+        this.state.error = true;
+      }
+    }
+    class App extends Component {
+      static components = { ErrorBoundary, ErrorComponent };
+    }
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>Error handled</div></div>");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+    expect(handler).toBeCalledTimes(1);
+  });
+
+  test("can catch an error in the willStart call", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn();
+    class ErrorComponent extends Component {
+      static template = xml`<div t-name="ErrorComponent">Some text</div>`;
+      async willStart() {
+        // we wait a little bit to be in a different stack frame
+        await nextTick();
+        throw new Error("NOOOOO");
+      }
+    }
+    class ErrorBoundary extends Component {
+      static template = xml`
+          <div>
+            <t t-if="state.error">Error handled</t>
+            <t t-else=""><t t-slot="default" /></t>
+          </div>`;
+      state = useState({ error: false });
+
+      catchError() {
+        this.state.error = true;
+      }
+    }
+    class App extends Component {
+      static template = xml`<div><ErrorBoundary><ErrorComponent /></ErrorBoundary></div>`;
+      static components = { ErrorBoundary, ErrorComponent };
+    }
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>Error handled</div></div>");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test.skip("can catch an error in the mounted call", async () => {
+    // we do not catch error in mounted anymore
+    console.error = jest.fn();
+    env.qweb.addTemplates(`
+        <templates>
+          <div t-name="ErrorBoundary">
+              <t t-if="state.error">Error handled</t>
+              <t t-else=""><t t-slot="default" /></t>
+          </div>
+          <div t-name="ErrorComponent">Some text</div>
+          <div t-name="App">
+              <ErrorBoundary><ErrorComponent /></ErrorBoundary>
+          </div>
+        </templates>`);
+    class ErrorComponent extends Component {
+      mounted() {
+        throw new Error("NOOOOO");
+      }
+    }
+    class ErrorBoundary extends Component {
+      state = useState({ error: false });
+
+      catchError() {
+        this.state.error = true;
+      }
+    }
+    class App extends Component {
+      static components = { ErrorBoundary, ErrorComponent };
+    }
+    const app = new App();
+    await app.mount(fixture);
+    await nextTick();
+    await nextTick();
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><div>Error handled</div></div>");
+  });
+
+  test.skip("can catch an error in the willPatch call", async () => {
+    // we do not catch error in willPatch anymore
+    const consoleError = console.error;
+    console.error = jest.fn();
+    class ErrorComponent extends Component {
+      static template = xml`<div><t t-esc="props.message"/></div>`;
+      willPatch() {
+        throw new Error("NOOOOO");
+      }
+    }
+    class ErrorBoundary extends Component {
+      static template = xml`
+          <div>
+            <t t-if="state.error">Error handled</t>
+            <t t-else=""><t t-slot="default" /></t>
+          </div>`;
+      state = useState({ error: false });
+
+      catchError() {
+        this.state.error = true;
+      }
+    }
+    class App extends Component {
+      static template = xml`
+          <div>
+              <span><t t-esc="state.message"/></span>
+            <ErrorBoundary><ErrorComponent message="state.message" /></ErrorBoundary>
+          </div>`;
+      state = useState({ message: "abc" });
+      static components = { ErrorBoundary, ErrorComponent };
+    }
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><span>abc</span><div><div>abc</div></div></div>");
+    app.state.message = "def";
+    await nextTick();
+    await nextTick();
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><span>def</span><div>Error handled</div></div>");
+    expect(console.error).toHaveBeenCalledTimes(1);
+    console.error = consoleError;
+  });
+
+  test("a rendering error will reject the mount promise", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+    // we do not catch error in willPatch anymore
+    class App extends Component {
+      static template = xml`<div><t t-esc="this.will.crash"/></div>`;
+    }
+
+    const app = new App();
+    let error;
+    try {
+      await app.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    const regexp =
+      /Cannot read properties of undefined \(reading 'crash'\)|Cannot read property 'crash' of undefined/g;
+    expect(error.message).toMatch(regexp);
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test("an error in mounted call will reject the mount promise", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+
+    class App extends Component {
+      static template = xml`<div>abc</div>`;
+      mounted() {
+        throw new Error("boom");
+      }
+    }
+
+    const app = new App();
+    let error;
+    try {
+      await app.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("boom");
+    expect(fixture.innerHTML).toBe("");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test("an error in willPatch call will reject the render promise", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+
+    class App extends Component {
+      static template = xml`<div><t t-esc="val"/></div>`;
+      val = 3;
+      willPatch() {
+        throw new Error("boom");
+      }
+    }
+
+    const app = new App();
+    await app.mount(fixture);
+    app.val = 4;
+    let error;
+    try {
+      await app.render();
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("boom");
+    expect(fixture.innerHTML).toBe("");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test("an error in patched call will reject the render promise", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+
+    class App extends Component {
+      static template = xml`<div><t t-esc="val"/></div>`;
+      val = 3;
+      patched() {
+        throw new Error("boom");
+      }
+    }
+
+    const app = new App();
+    await app.mount(fixture);
+    app.val = 4;
+    let error;
+    try {
+      await app.render();
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("boom");
+    expect(fixture.innerHTML).toBe("");
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test("a rendering error in a sub component will reject the mount promise", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+    // we do not catch error in willPatch anymore
+    class Child extends Component {
+      static template = xml`<div><t t-esc="this.will.crash"/></div>`;
+    }
+    class App extends Component {
+      static template = xml`<div><Child/></div>`;
+      static components = { Child };
+    }
+
+    const app = new App();
+    let error;
+    try {
+      await app.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    const regexp =
+      /Cannot read properties of undefined \(reading 'crash'\)|Cannot read property 'crash' of undefined/g;
+    expect(error.message).toMatch(regexp);
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test("a rendering error will reject the render promise", async () => {
+    const consoleError = console.error;
+    console.error = jest.fn(() => {});
+    // we do not catch error in willPatch anymore
+    class App extends Component {
+      static template = xml`<div><t t-if="flag" t-esc="this.will.crash"/></div>`;
+      flag = false;
+    }
+
+    const app = new App();
+    await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div></div>");
+    app.flag = true;
+    let error;
+    try {
+      await app.render();
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    const regexp =
+      /Cannot read properties of undefined \(reading 'crash'\)|Cannot read property 'crash' of undefined/g;
+    expect(error.message).toMatch(regexp);
+
+    expect(console.error).toBeCalledTimes(0);
+    console.error = consoleError;
+  });
+
+  test("a rendering error will reject the render promise (with sub components)", async () => {
+    class Child extends Component {
+      static template = xml`<span></span>`;
+    }
+    class Parent extends Component {
+      static template = xml`<div><Child/><t t-esc="x.y"/></div>`;
+      static components = { Child };
+    }
+
+    let error;
+    try {
+      const parent = new Parent();
+      await parent.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    const regexp =
+      /Cannot read properties of undefined \(reading 'y'\)|Cannot read property 'y' of undefined/g;
+    expect(error.message).toMatch(regexp);
+  });
+
+  test("simple catchError", async () => {
+    class Boom extends Component {
+      static template = xml`<div t-esc="a.b.c"/>`;
+    }
+
+    class Parent extends Component {
+      static template = xml`
+        <div>
+          <t t-if="error">Error</t>
+          <t t-else="">
+            <Boom />
+          </t>
+        </div>`;
+      static components = { Boom };
+
+      error = false;
+
+      catchError(error) {
+        this.error = error;
+        this.render();
+      }
+    }
+
+    await mount(Parent, { target: fixture });
+    expect(fixture.innerHTML).toBe("<div>Error</div>");
+  });
+
+  test("catchError in catchError", async () => {
+    class Boom extends Component {
+      static template = xml`<div t-esc="a.b.c"/>`;
+    }
+
+    class Child extends Component {
+      static template = xml`
+        <div>
+          <Boom />
+        </div>`;
+      static components = { Boom };
+
+      catchError(error) {
+        throw error;
+      }
+    }
+
+    class Parent extends Component {
+      static template = xml`
+        <div>
+          <t t-if="error">Error</t>
+          <t t-else="">
+            <Child />
+          </t>
+        </div>`;
+      static components = { Child };
+
+      error = false;
+
+      catchError(error) {
+        this.error = error;
+        this.render();
+      }
+    }
+
+    await mount(Parent, { target: fixture });
+    expect(fixture.innerHTML).toBe("<div>Error</div>");
+  });
+
+  test("errors in mounted and in willUnmount", async () => {
+    expect.assertions(1);
+    class Example extends Component {
+      static template = xml`<div/>`;
+      val;
+      mounted() {
+        throw new Error("Error in mounted");
+        this.val = { foo: "bar" };
+      }
+      willUnmount() {
+        console.log(this.val.foo);
+      }
+    }
+
+    try {
+      await mount(Example, { target: fixture });
+    } catch (e) {
+      expect(e.message).toBe("Error in mounted");
+    }
+  });
+});

tests/component/props_validation.test.ts

@@ -0,0 +1,868 @@
+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();
+  Component.env = env;
+  dev = QWeb.dev;
+  QWeb.dev = true;
+});
+
+afterEach(() => {
+  fixture.remove();
+  QWeb.dev = dev;
+});
+
+class Widget extends Component {}
+
+//------------------------------------------------------------------------------
+// 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>`;
+    }
+    class Parent extends Widget {
+      static components = { TestWidget };
+      static template = xml`<div><TestWidget /></div>`;
+    }
+
+    let error;
+    QWeb.dev = true;
+    try {
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe(`Missing props 'message' (component 'TestWidget')`);
+
+    error = undefined;
+
+    QWeb.dev = false;
+    try {
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+  });
+
+  test("props: list of strings", async () => {
+    class TestWidget extends Widget {
+      static props = ["message"];
+      static template = xml`<div>hey</div>`;
+    }
+    class Parent extends Widget {
+      static components = { TestWidget };
+      static template = xml`<div><TestWidget /></div>`;
+    }
+
+    let error;
+    try {
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe(`Missing props 'message' (component 'TestWidget')`);
+  });
+
+  test("validate simple types", async () => {
+    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" },
+    ];
+
+    let props;
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      get p() {
+        return props.p;
+      }
+    }
+    for (let test of Tests) {
+      let TestWidget = class extends Widget {
+        static template = xml`<div>hey</div>`;
+        static props = { p: test.type };
+      };
+      Parent.components = { TestWidget };
+
+      let error;
+      props = {};
+      try {
+        const p = new Parent();
+        await p.mount(fixture);
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeDefined();
+      expect(error.message).toBe(`Missing props 'p' (component '_a')`);
+
+      error = undefined;
+      props = { p: test.ok };
+      try {
+        const p = new Parent();
+        await p.mount(fixture);
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeUndefined();
+
+      props = { p: test.ko };
+      try {
+        const p = new Parent();
+        await p.mount(fixture);
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeDefined();
+      expect(error.message).toBe("Invalid Prop 'p' in component '_a'");
+    }
+  });
+
+  test("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" },
+    ];
+
+    let props;
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      get p() {
+        return props.p;
+      }
+    }
+    for (let test of Tests) {
+      let TestWidget = class extends Component {
+        static props = { p: { type: test.type } };
+        static template = xml`<div>hey</div>`;
+      };
+      Parent.components = { TestWidget };
+
+      let error;
+      props = {};
+      try {
+        const p = new Parent();
+        await p.mount(fixture);
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeDefined();
+      expect(error.message).toBe(`Missing props 'p' (component '_a')`);
+
+      error = undefined;
+      props = { p: test.ok };
+      try {
+        const p = new Parent();
+        await p.mount(fixture);
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeUndefined();
+
+      props = { p: test.ko };
+      try {
+        const p = new Parent();
+        await p.mount(fixture);
+      } catch (e) {
+        error = e;
+      }
+      expect(error).toBeDefined();
+      expect(error.message).toBe("Invalid Prop 'p' in component '_a'");
+    }
+  });
+
+  test("can validate a prop with multiple types", async () => {
+    class TestWidget extends Component {
+      static template = xml`<div>hey</div>`;
+      static props = { p: [String, Boolean] };
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      static components = { TestWidget };
+      get p() {
+        return props.p;
+      }
+    }
+
+    let error;
+    let props;
+    try {
+      props = { p: "string" };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: true };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: 1 };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'p' in component 'TestWidget'");
+  });
+
+  test("can validate an optional props", async () => {
+    class TestWidget extends Component {
+      static template = xml`<div>hey</div>`;
+      static props = { p: { type: String, optional: true } };
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      static components = { TestWidget };
+      get p() {
+        return props.p;
+      }
+    }
+
+    let error;
+    let props;
+    try {
+      props = { p: "key" };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = {};
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: 1 };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'p' in component 'TestWidget'");
+  });
+
+  test("can validate an array with given primitive type", async () => {
+    class TestWidget extends Component {
+      static template = xml`<div>hey</div>`;
+      static props = { p: { type: Array, element: String } };
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      static components = { TestWidget };
+      get p() {
+        return props.p;
+      }
+    }
+
+    let error;
+    let props;
+    try {
+      props = { p: [] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: ["string"] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: [1] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+
+    error = undefined;
+    try {
+      props = { p: ["string", 1] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+  });
+
+  test("can validate an array with multiple sub element types", async () => {
+    class TestWidget extends Component {
+      static template = xml`<div>hey</div>`;
+      static props = { p: { type: Array, element: [String, Boolean] } };
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      static components = { TestWidget };
+      get p() {
+        return props.p;
+      }
+    }
+
+    let error;
+    let props;
+    try {
+      props = { p: [] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: ["string"] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: [false, true, "string"] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: [true, 1] };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'p' in component 'TestWidget'");
+  });
+
+  test("can validate an object with simple shape", async () => {
+    class TestWidget extends Component {
+      static template = xml`<div>hey</div>`;
+      static props = {
+        p: { type: Object, shape: { id: Number, url: String } },
+      };
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      static components = { TestWidget };
+      get p() {
+        return props.p;
+      }
+    }
+
+    let error;
+    let props;
+    try {
+      props = { p: { id: 1, url: "url" } };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: { id: 1, url: "url", extra: true } };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid prop 'p' in component TestWidget (unknown prop 'extra')");
+
+    try {
+      props = { p: { id: "1", url: "url" } };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'p' in component 'TestWidget'");
+
+    error = undefined;
+    try {
+      props = { p: { id: 1 } };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'p' in component 'TestWidget'");
+  });
+
+  test("can validate recursively complicated prop def", async () => {
+    class TestWidget extends Component {
+      static template = xml`<div>hey</div>`;
+      static props = {
+        p: {
+          type: Object,
+          shape: {
+            id: Number,
+            url: [Boolean, { type: Array, element: Number }],
+          },
+        },
+      };
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="p"/></div>`;
+      static components = { TestWidget };
+      get p() {
+        return props.p;
+      }
+    }
+
+    let error;
+    let props;
+    try {
+      props = { p: { id: 1, url: true } };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: { id: 1, url: [12] } };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      props = { p: { id: 1, url: [12, true] } };
+      const p = new Parent();
+      await p.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'p' in component 'TestWidget'");
+  });
+
+  test("can validate optional attributes in nested sub props", () => {
+    class TestComponent extends Component {
+      static props = {
+        myprop: {
+          type: Array,
+          element: {
+            type: Object,
+            shape: {
+              num: { type: Number, optional: true },
+            },
+          },
+        },
+      };
+    }
+    let error;
+    try {
+      QWeb.utils.validateProps(TestComponent, { myprop: [{}] });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      QWeb.utils.validateProps(TestComponent, { myprop: [{ a: 1 }] });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe(
+      "Invalid prop 'myprop' in component TestComponent (unknown prop 'a')"
+    );
+  });
+
+  test("can validate with a custom validator", () => {
+    class TestComponent extends Component {
+      static props = {
+        size: {
+          validate: (e) => ["small", "medium", "large"].includes(e),
+        },
+      };
+    }
+    let error;
+    try {
+      QWeb.utils.validateProps(TestComponent, { size: "small" });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+
+    try {
+      QWeb.utils.validateProps(TestComponent, { size: "abcdef" });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'size' in component 'TestComponent'");
+  });
+
+  test("can validate with a custom validator, and a type", () => {
+    const validator = jest.fn((n) => 0 <= n && n <= 10);
+    class TestComponent extends Component {
+      static props = {
+        n: {
+          type: Number,
+          validate: validator,
+        },
+      };
+    }
+    let error;
+    try {
+      QWeb.utils.validateProps(TestComponent, { n: 3 });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeUndefined();
+    expect(validator).toBeCalledTimes(1);
+
+    try {
+      QWeb.utils.validateProps(TestComponent, { n: "str" });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'n' in component 'TestComponent'");
+    expect(validator).toBeCalledTimes(1);
+
+    error = null;
+    try {
+      QWeb.utils.validateProps(TestComponent, { n: 100 });
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Invalid Prop 'n' in component 'TestComponent'");
+    expect(validator).toBeCalledTimes(2);
+  });
+
+  test("props are validated in dev mode (code snapshot)", async () => {
+    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();
+    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 with type array, and no element", async () => {
+    class TestWidget extends Widget {
+      static props = { myprop: { type: Array } };
+    }
+
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, { myprop: [1] });
+    }).not.toThrow();
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, { myprop: 1 });
+    }).toThrow(`Invalid Prop 'myprop' in component 'TestWidget'`);
+  });
+
+  test("props with type object, and no shape", async () => {
+    class TestWidget extends Widget {
+      static props = { myprop: { type: Object } };
+    }
+
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, { myprop: { a: 3 } });
+    }).not.toThrow();
+    expect(() => {
+      QWeb.utils.validateProps(TestWidget, { myprop: false });
+    }).toThrow(`Invalid Prop 'myprop' in component 'TestWidget'`);
+  });
+
+  test("props: extra props cause an error", async () => {
+    class TestWidget extends Widget {
+      static props = ["message"];
+    }
+
+    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(undefined, {});
+    let error;
+    try {
+      await w.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Missing props 'p' (component 'TestWidget')");
+  });
+
+  test("props are validated whenever component is updated", async () => {
+    let error;
+    class TestWidget extends Component {
+      static props = { p: { type: Number } };
+      static template = xml`<div><t t-esc="props.p"/></div>`;
+
+      async __updateProps() {
+        try {
+          await Component.prototype.__updateProps.apply(this, arguments);
+        } catch (e) {
+          error = e;
+        }
+      }
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="state.p"/></div>`;
+      static components = { TestWidget };
+      state: any = useState({ p: 1 });
+    }
+
+    const w = new Parent();
+    await w.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>1</div></div>");
+
+    w.state.p = undefined;
+    await nextTick();
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Missing props 'p' (component 'TestWidget')");
+  });
+
+  test("default values are applied before validating props at update", async () => {
+    class TestWidget extends Component {
+      static props = { p: { type: Number } };
+      static template = xml`<div><t t-esc="props.p"/></div>`;
+      static defaultProps = { p: 4 };
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget p="state.p"/></div>`;
+      static components = { TestWidget };
+      state: any = useState({ p: 1 });
+    }
+
+    const w = new Parent();
+    await w.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>1</div></div>");
+
+    w.state.p = undefined;
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div><div>4</div></div>");
+  });
+
+  test("mix of optional and mandatory", async () => {
+    class Child extends Component {
+      static props = {
+        optional: { type: String, optional: true },
+        mandatory: Number,
+      };
+      static template = xml` <div><t t-esc="props.mandatory"/></div>`;
+    }
+
+    class App extends Component {
+      static components = { Child };
+      static template = xml`<div><Child/></div>`;
+    }
+
+    const w = new App(undefined, {});
+    let error;
+    try {
+      await w.mount(fixture);
+    } catch (e) {
+      error = e;
+    }
+    expect(error).toBeDefined();
+    expect(error.message).toBe("Missing props 'mandatory' (component 'Child')");
+  });
+});
+
+describe("default props", () => {
+  test("can set default values", async () => {
+    class TestWidget extends Component {
+      static defaultProps = { p: 4 };
+      static template = xml`<div><t t-esc="props.p"/></div>`;
+    }
+    class Parent extends Component {
+      static template = xml`<div><TestWidget /></div>`;
+      static components = { TestWidget };
+    }
+
+    const w = new Parent();
+    await w.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><div>4</div></div>");
+  });
+
+  test("default values are also set whenever component is updated", async () => {
+    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();
+    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(undefined, {});
+    await w.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div><span>heyhey</span></div>");
+  });
+});