[ADD] developer: add a tutorial on Owl

This commit adds the introduction and the chapter 1 of the new
Owl/JavaScript framework tutorial.

This new tutorial allows people to discover Owl and the building blocks
of the Odoo JavaScript framework.

closes odoo/documentation#2845

Signed-off-by: Antoine Vandevenne (anv) <anv@odoo.com>
Co-authored-by: Géry Debongnie <ged@odoo.com>
Co-authored-by: Antoine Vandevenne (anv) <anv@odoo.com>

conf.py

@@ -63,6 +63,7 @@ add_function_parentheses = True
 source_read_replace_vals = {
     'GITHUB_PATH': f'https://github.com/odoo/odoo/blob/{version}',
     'GITHUB_ENT_PATH': f'https://github.com/odoo/enterprise/blob/{version}',
+    'OWL_PATH': f'https://github.com/odoo/owl/blob/master',
 }
 
 # Add extensions directory to PYTHONPATH

content/developer/howtos.rst

@@ -8,6 +8,7 @@ Tutorials
     :titlesonly:
 
     howtos/rdtraining
+    howtos/discover_js_framework
     howtos/website
     howtos/backend
     howtos/web_services

content/developer/howtos/discover_js_framework.rst

@@ -0,0 +1,53 @@
+:show-content:
+
+=================================
+Discover the JavaScript Framework
+=================================
+
+.. toctree::
+    :titlesonly:
+    :glob:
+
+    discover_js_framework/*
+
+For this training, we will step into the shoes of the IT staff at the fictional company Awesome
+T-Shirt, which is dedicated to printing custom t-shirts for online customers. The Awesome T-Shirt
+company uses Odoo to manage orders and has created a dedicated Odoo module to manage their workflow.
+The project is currently a simple kanban view, with a few columns.
+
+The usual process is as follows: a customer looking for a nice t-shirt can simply order it from the
+Awesome T-Shirt site and give the url for any image they want. They must also fill in some basic
+information, such as the desired size and quantity of t-shirts. Once they have confirmed their
+order, and once the payment has been validated, the system will create a task in our application.
+
+The big boss of Awesome T-shirt, Bafien Carpink, is unhappy with our implementation. He believes
+that by micromanaging more, he will be able to get more revenue from his employees. As the IT staff
+for Awesome T-shirt, we are responsible with improving the system. Various independent tasks must be
+performed.
+
+Let us now practice our Odoo skills!
+
+.. _howtos/discover_js_framework/setup:
+
+Setup
+=====
+
+To follow the training, it is necessary to have basic knowledge on Git and a recent version of Odoo
+installed. If you have not installed it yet, we recommend installing it from :ref:`source
+<setup/install/source>` (:dfn:`running Odoo from source code`).
+
+To setup your development environment, you can also follow the dedicated chapter in :doc:`Getting
+Started: Development environment setup <rdtraining/02_setup>` tutorial.
+
+The last things to do are:
+
+- Clone the `official Odoo tutorials repository <https://github.com/odoo/tutorials>`_ and switch to
+  the branch `{BRANCH}`.
+- Add the cloned repository to the :option:`--addons-path <odoo-bin --addons-path>`.
+- Start a new Odoo database and install the modules `owl_playground`, `awesome_tshirt`, and
+  `awesome_gallery`.
+
+Exercises
+=========
+
+* :doc:`discover_js_framework/01_components`

content/developer/howtos/discover_js_framework/01_components.rst

@@ -0,0 +1,319 @@
+=====================
+Chapter 1: Components
+=====================
+
+This chapter introduces the `Owl framework <https://github.com/odoo/owl>`_, a tailor-made component
+system for Odoo. The main building blocks of OWL are `components
+<{OWL_PATH}/doc/reference/component.md>`_ and `templates
+<{OWL_PATH}/doc/reference/templates.md>`_.
+
+In Owl, every part of user interface is managed by a component: they hold the logic and define the
+templates that are used to render the user interface. In practice, a component is represented by a
+small JavaScript class subclassing the `Component` class.
+
+.. _jstraining/chapter1/intro_example:
+
+.. example::
+   The `Counter` class implements a component that holds the internal state of a counter and defines
+   how it should be incremented.
+
+   .. code-block:: js
+
+      const { Component, useState } = owl;
+
+       class Counter extends Component {
+           static template = "my_module.Counter";
+
+           state = useState({ value: 0 });
+
+           increment() {
+               this.state.value++;
+           }
+       }
+
+   The `Counter` class specifies the name of the template to render. The template is written in XML
+   and defines a part of user interface.
+
+   .. code-block:: xml
+
+       <templates xml:space="preserve">
+           <t t-name="my_module.Counter" owl="1">
+               <p>Counter: <t t-esc="state.value"/></p>
+               <button class="btn btn-primary" t-on-click="increment">Increment</button>
+           </t>
+       </templates>
+
+   You maybe noticed the `owl="1"` temporary attribute, it allows Odoo to differentiate Owl
+   templates from the old JavaScript framework templates.
+
+Let us take some time to get used to Owl itself. Below, you will find a series of exercises
+intended to quickly understand and practice the basics of Owl.
+
+.. todo:: update screenshot
+
+.. admonition:: Goal
+
+   Here is an overview of what we are going to achieve in this chapter.
+
+   .. image:: 01_components/overview.png
+      :scale: 50%
+      :align: center
+      :alt: Overview of chapter 1.
+
+.. spoiler:: Solutions
+
+   The solutions for each exercise of the chapter are hosted on the `official Odoo tutorials
+   repository <https://github.com/odoo/tutorials/commits/{BRANCH}-solutions/owl_playground>`_.
+
+1. Displaying a counter
+=======================
+
+As a first exercise, let us implement a counter in the `Playground` component located in
+:file:`owl_playground/static/src/`.
+
+.. exercise::
+
+   #. Modify :file:`playground.js` so that it acts as a counter like in :ref:`the example above
+      <jstraining/chapter1/intro_example>`. You will need to use the `useState
+      <{OWL_PATH}/doc/reference/hooks.md#usestate>`_ function so that the component is re-rendered
+      whenever any part of the state object has been read by this component is modified.
+   #. In the same component, create an `increment` method.
+   #. Modify the template in :file:`playground.xml` so that it displays your counter variable. Use
+      `t-esc <{OWL_PATH}/doc/reference/templates.md#outputting-data>`_ to output the data.
+   #. Add a button in the template and specify a `t-on-click
+      <{OWL_PATH}/doc/reference/event_handling.md#event-handling>`_ attribute in the button to
+      trigger the `increment` method whenever the button is clicked.
+
+   .. image:: 01_components/counter.png
+      :scale: 70%
+      :align: center
+      :alt: A counter component.
+
+2. Extract counter in a component
+=================================
+
+For now we have the logic of a counter in the `Playground` component, let us see how to create a
+sub-component from it.
+
+.. exercise::
+
+   #. Extract the counter code from the `Playground` component into a new `Counter` component.
+   #. You can do it in the same file first, but once it's done, update your code to move the
+      `Counter` in its own file.
+   #. Make sure the template is in its own file, with the same name.
+
+.. important::
+   Don't forget :code:`/** @odoo-module **/` in your JavaScript files. More information on this can
+   be found :ref:`here <frontend/modules/native_js>`.
+
+3. A todo component
+===================
+
+We will create new components in :file:`owl_playground/static/src/` to keep track of a list of
+todos. This will be done incrementally in multiple exercises that will introduce various concepts.
+
+.. exercise::
+
+   #. Create a `Todo` component that receive a `todo` object in `props
+      <{OWL_PATH}/doc/reference/props.md>`_, and display it. It should show something like
+      **3. buy milk**.
+   #. Add the Bootstrap classes `text-muted` and `text-decoration-line-through` on the task if it is
+      done. To do that, you can use `dynamic attributes
+      <{OWL_PATH}/doc/reference/templates.md#dynamic-attributes>`_
+   #. Modify :file:`owl_playground/static/src/playground.js` and
+      :file:`owl_playground/static/src/playground.xml` to display your new `Todo` component with
+      some hard-coded props to test it first.
+
+      .. example::
+
+         .. code-block:: javascript
+
+            setup() {
+               ...
+               this.todo = { id: 3, description: "buy milk", done: false };
+            }
+
+   .. image:: 01_components/todo.png
+      :scale: 70%
+      :align: center
+      :alt: A Todo component
+
+.. seealso::
+   `Owl: Dynamic class attributes <{OWL_PATH}/doc/reference/templates.md#dynamic-class-attribute>`_
+
+4. Props validation
+===================
+
+The `Todo` component has an implicit API. It expects to receive in its props the description of a
+todo object in a specified format: `id`, `description` and `done`. Let us make that API more
+explicit. We can add a props definition that will let Owl perform a validation step in :ref:`dev
+mode <developer-mode>`. It is a good practice to do that for every component.
+
+.. exercise::
+
+   #. Add `props validation <{OWL_PATH}/doc/reference/props.md#props-validation>`_ to the `Todo`
+      component.
+   #. Make sure it passes in :ref:`dev mode <developer-mode>`.
+   #. Remove `done` from the props and reload the page. The validation should fail.
+
+5. A list of todos
+==================
+
+Now, let us display a list of todos instead of just one todo. For now, we can still hard-code the
+list.
+
+.. exercise::
+
+   #. Change the code to display a list of todos instead of just one, and use `t-foreach
+      <{OWL_PATH}/doc/reference/templates.md#loops>`_ in the template
+   #. Think about how it should be keyed with the `t-key` directive.
+
+   .. image:: 01_components/todo_list.png
+      :scale: 70%
+      :align: center
+      :alt: A TodoList
+
+6. Adding a todo
+================
+
+So far, the todos in our list are hard-coded. Let us make it more useful by allowing the user to add
+a todo to the list.
+
+.. exercise::
+
+   #. Add an input above the task list with placeholder *Enter a new task*.
+   #. Add an `event handler <{OWL_PATH}/doc/reference/event_handling.md>`_ on the `keyup` event
+      named ``addTodo``.
+   #. Implement `addTodo` to check if enter was pressed (:code:`ev.keyCode === 13`), and in that
+      case, create a new todo with the current content of the input as the description.
+   #. Make sure it has a unique id. It can be just a counter that increments at each todo.
+   #. Then, clear the input of all content.
+   #. Bonus point: don't do anything if the input is empty.
+
+   .. note::
+      Notice that nothing updates in the UI: this is because Owl does not know that it should update
+      the UI. This can be fixed by wrapping the todo list in a `useState` hook.
+
+      .. code-block:: javascript
+
+          this.todos = useState([]);
+
+   .. image:: 01_components/create_todo.png
+      :scale: 70%
+      :align: center
+      :alt: Creating todos
+
+.. seealso::
+   `Owl: Reactivity <{OWL_PATH}/doc/reference/reactivity.md>`_
+
+7. Focusing the input
+=====================
+
+Let's see how we can access the DOM with `t-ref <{OWL_PATH}/doc/reference/refs.md>`_ and `useRef
+<{OWL_PATH}/doc/reference/hooks.md#useref>`_.
+
+.. exercise::
+
+   #. Focus the `input` from the previous exercise when the dashboard is `mounted
+      <{OWL_PATH}/doc/reference/component.md#mounted>`_.
+   #. Bonus point: extract the code into a specialized `hook <{OWL_PATH}/doc/reference/hooks.md>`_
+      `useAutofocus`.
+
+.. seealso::
+   `Owl: Component lifecycle <{OWL_PATH}/doc/reference/component.md#lifecycle>`_
+
+8. Toggling todos
+=================
+
+Now, let's add a new feature: mark a todo as completed. This is actually trickier than one might
+think. The owner of the state is not the same as the component that displays it. So, the `Todo`
+component needs to communicate to its parent that the todo state needs to be toggled. One classic
+way to do this is by using a `callback prop
+<{OWL_PATH}/doc/reference/props.md#binding-function-props>`_ `toggleState`.
+
+.. exercise::
+
+   #. Add an input with the attribute :code:`type="checkbox"` before the id of the task, which must
+      be checked if the state `done` is true.
+   #. Add a callback props `toggleState`.
+   #. Add a `click` event handler on the input in the `Todo` component and make sure it calls the
+      `toggleState` function with the todo id.
+   #. Make it work!
+
+   .. image:: 01_components/toggle_todo.png
+      :scale: 70%
+      :align: center
+      :alt: Toggling todos
+
+9. Deleting todos
+=================
+
+The final touch is to let the user delete a todo.
+
+.. exercise::
+
+   #. Add a new callback prop `removeTodo`.
+   #. Insert :code:`<span class="fa fa-remove">` in the template of the `Todo` component.
+   #. Whenever the user clicks on it, it should call the `removeTodo` method.
+
+   .. image:: 01_components/delete_todo.png
+      :scale: 70%
+      :align: center
+      :alt: Deleting todos
+
+10. Generic components with slots
+=================================
+
+Owl has a powerful `slot <{OWL_PATH}/doc/reference/slots.md>`_ system to allow you to write generic
+components. This is useful to factorize the common layout between different parts of the interface.
+
+.. exercise::
+
+   #. Write a `Card` component using the following Bootstrap HTML structure:
+
+      .. code-block:: html
+
+         <div class="card" style="width: 18rem;">
+             <img src="..." class="card-img-top" alt="..." />
+             <div class="card-body">
+             <h5 class="card-title">Card title</h5>
+             <p class="card-text">
+                 Some quick example text to build on the card title and make up the bulk
+                 of the card's content.
+             </p>
+             <a href="#" class="btn btn-primary">Go somewhere</a>
+             </div>
+         </div>
+
+   #. This component should have two slots: one slot for the title, and one for the content (the
+      default slot).
+
+      .. example::
+         Here is how one could use it:
+
+         .. code-block:: html
+
+               <Card>
+                  <t t-set-slot="title">Card title</t>
+                  <p class="card-text">Some quick example text...</p>
+                  <a href="#" class="btn btn-primary">Go somewhere</a>
+               </Card>
+
+   #. Bonus point: if the `title` slot is not given, the `h5` should not be rendered at all.
+
+    .. image:: 01_components/card.png
+       :scale: 70%
+       :align: center
+       :alt: Creating card with slots
+
+.. seealso::
+   `Bootstrap: documentation on cards <https://getbootstrap.com/docs/5.2/components/card/>`_
+
+11. Go further
+==============
+
+.. exercise::
+
+   #. Add prop validation on the `Card` component.
+   #. Try to express in the props validation system that it requires a `default` slot, and an
+      optional `title` slot.