feature #8892 The New Quick Tour (weaverryan)

This PR was squashed before being merged into the 4.0 branch (closes #8892).

Discussion
----------

The New Quick Tour

Fixes #8884

Hi guys!

The quick tour will now be 3 parts (instead of 4), and I've finished the first 2 parts. I'm purposely using the first person point of view and more conversational language.

Cheers!

Commits
-------

e2a9b82 tweaks thanks to Javier
3beccde Comments thanks to Javier and fixing build issues
a1b02e9 adding progress
b0d46e5 WIP - 2/3 parts of the quick tour finished

Author: weaverryan

_build/redirection_map

@@ -381,3 +381,5 @@
 /testing/simulating_authentication /testing/http_authentication
 /validation/group_service_resolver /form/validation_group_service_resolver
 /request/load_balancer_reverse_proxy /deployment/proxies
+/quick_tour/the_controller /quick_tour/the_big_picture
+/quick_tour/the_view /quick_tour/flex_recipes

_images/quick_tour/no_routes_page.png

@@ -14,8 +14,7 @@ Get started fast with the Symfony :doc:`Quick Tour <quick_tour/index>`:
     quick_tour/index
 
 * :doc:`quick_tour/the_big_picture`
-* :doc:`quick_tour/the_view`
-* :doc:`quick_tour/the_controller`
+* :doc:`quick_tour/flex_recipes`
 * :doc:`quick_tour/the_architecture`
 
 Getting Started

_images/quick_tour/profiler.png

@@ -0,0 +1,249 @@
+Flex: Compose your Application
+==============================
+
+After reading the first part of this tutorial, you have decided that Symfony was
+worth another 10 minutes. Great choice! In this second part, you'll learn about
+Symfony Flex: the amazing tool that makes adding new features as simple as running
+one command. It's also the reason why Symfony is ideal for a small micro-service
+or a huge application. Curious? Perfect!
+
+Symfony: Start Micro!
+---------------------
+
+Unless you're building a pure API (more on that soon!), you'll probably want to
+render HTML. To do that, you'll use `Twig`_. Twig is a flexible, fast, and secure
+template engine for PHP. It makes your templates more readable and concise; it also
+makes them more friendly for web designers.
+
+Is Twig already installed in our application? Actually, not yet! And that's great!
+When you start a new Symfony project, it's *small*:  only the most critical dependencies
+are included in your ``composer.json`` file:
+
+.. code-block:: text
+
+    "require": {
+        "...",
+        "symfony/console": "^4.1",
+        "symfony/flex": "^1.0",
+        "symfony/framework-bundle": "^4.1",
+        "symfony/yaml": "^4.1"
+    }
+
+This makes Symfony different than any other PHP framework! Instead of starting with
+a *bulky* app with *every* possible feature you might ever need, a Symfony app is
+small, simple and *fast*. And you're in total control of what you add.
+
+Flex Recipes and Aliases
+------------------------
+
+So how can we install and configure Twig? Just run one command:
+
+.. code-block:: terminal
+
+    $ composer require twig
+
+Two *very* interesting things happen behind the scenes thanks to Symfony Flex: a
+Composer plugin that is already installed in our project.
+
+First, ``twig`` is not the name of a Composer package: it's a Flex *alias* that
+points to ``symfony/twig-bundle``. Flex resolves that alias for Composer.
+
+And second, Flex installs a *recipe* for ``symfony/twig-bundle``. What's a recipe?
+It's a way for a library to automatically configure itself by adding and modifying
+files. Thanks to recipes, adding features is seamless and automated: install a package
+and you're done!
+
+You can find a full list of recipes and aliases by going to `https://symfony.sh`_.
+
+What did this recipe do? In addition to automatically enabling the feature in
+``config/bundles.php``, it added 3 things:
+
+``config/packages/twig.yaml``
+    A configuration file that sets up Twig with sensible defaults.
+
+``config/routes/dev/twig.yaml``
+    A route that helps you debug your error pages.
+
+``templates/``
+    This is the directory where template files will live. The recipe also added
+    a ``base.html.twig`` layout file.
+
+Twig: Rendering a Template
+--------------------------
+
+Thanks to Flex, after one command, you can start using Twig immediately::
+
+    // src/Controller/DefaultController.php
+    // ...
+
+    + use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+ 
+    -class DefaultController
+    +class DefaultController extends AbstractController
+     {
+         /**
+          * @Route("/hello/{name}")
+          */
+         public function index($name)
+         {
+    -        return new Response("Hello $name!");
+    +        return $this->render('default/index.html.twig', [
+    +            'name' => $name,
+    +        ]);
+         }
+
+By extending ``AbstractController``, you now have access to a number of shortcut
+methods and tools, like ``render()``. Create the new template:
+
+.. code-block:: twig
+
+    {# templates/default/index.html.twig #}
+    <h1>Hello {{ name }}</h1>
+
+That's it! The ``{{ name }}`` syntax will print the ``name`` variable that's passed
+in from the controller. If you're new to Twig, welcome! You'll learn more about
+its syntax and power later.
+
+But, right now, the page *only* contains the ``h1`` tag. To give it an HTML layout,
+extend ``base.html.twig``:
+
+.. code-block:: twig
+
+    {# templates/default/index.html.twig #}
+    {% extends 'base.html.twig' %}
+
+    {% block body %}
+        <h1>Hello {{ name }}</h1>
+    {% endblock %}
+
+This is called template inheritance: our page now inherits the HTML structure from
+``base.html.twig``.
+
+Profiler: Debugging Paradise
+----------------------------
+
+One of the *coolest* features of Symfony isn't even installed yet! Let's fix that:
+
+.. code-block:: terminal
+
+    $ composer require profiler
+
+Yes! This is another alias! And Flex *also* installs another recipe, which automates
+the configuration of Symfony's Profiler. What's the result? Refresh!
+
+See that black bar on the bottom? That's the web debug toolbar, and it's your new
+best friend. By hovering over each icon, you can get information about what controller
+was executed, performance information, cache hits & misses and a lot more. Click
+any icon to go into the *profiler* where you have even *more* detailed debugging
+and performance data!
+
+Oh, and as you install more libraries, you'll get more tools (like a web debug toolbar
+icon that shows database queries).
+
+Using the profiler is easy because it configured *itself* thanks to the recipe.
+What else can we install this easily?
+
+Rich API Support
+----------------
+
+Are you building an API? You can already return JSON easily from any controller::
+
+    /**
+     * @Route("/api/hello/{name}")
+     */
+    public function apiExample($name)
+    {
+        return $this->json([
+            'name' => $name,
+            'symfony' => 'rocks',
+        ]);
+    }
+
+But for a *truly* rich API, try installing `Api Platform`_:
+
+.. code-block:: terminal
+
+    $ composer require api
+
+This is an alias to ``api-platform/api-pack``, which has dependencies on several
+other packages, like Symfony's Validator and Security components, as well as the Doctrine
+ORM. In fact, Flex installed *5* recipes!
+
+But like usual, we can immediately start using the new library. Want to create a
+rich API for a ``product`` table? Create a ``Product`` entity and give it the
+``@ApiResource()`` annotation::
+
+    // src/Entity/Product.php
+    // ...
+
+    use ApiPlatform\Core\Annotation\ApiResource;
+
+    /**
+     * @ORM\Entity()
+     * @ApiResource()
+     */
+    class Product
+    {
+        /**
+         * @ORM\Id
+         * @ORM\GeneratedValue(strategy="AUTO")
+         * @ORM\Column(type="integer")
+         */
+        private $id;
+
+        /**
+         * @ORM\Column(type="string")
+         */
+        private $name;
+
+        /**
+         * @ORM\Column(type="string")
+         */
+        private $price;
+
+        // ...
+    }
+
+Done! You now have endpoints to list, add, update and delete products! Don't believe
+me? List your routes by running:
+
+.. code-block:: terminal
+
+    $ php bin/console debug:router
+
+.. code-block:: text
+
+    ------------------------------ -------- ------------------------------------- 
+     Name                           Method   Path                                 
+    ------------------------------ -------- ------------------------------------- 
+     api_products_get_collection    GET      /api/products.{_format}              
+     api_products_post_collection   POST     /api/products.{_format}              
+     api_products_get_item          GET      /api/products/{id}.{_format}         
+     api_products_put_item          PUT      /api/products/{id}.{_format}         
+     api_products_delete_item       DELETE   /api/products/{id}.{_format}         
+     ...
+    ------------------------------ -------- ------------------------------------- 
+
+Easily Remove Recipes
+---------------------
+
+Not convinced yet? No problem: remove the library:
+
+.. code-block:: terminal
+
+    $ composer remove api
+
+Flex will *uninstall* the recipes: removing files and un-doing changes to put your
+app back in its original state. Experiment without worry.
+
+More Features, Architecture and Speed
+-------------------------------------
+
+I hope you're as excited about Flex as I am! But we still have *one* more chapter,
+and it's the most important yet. I want to show you how Symfony empowers you to quickly
+build features *without* sacrificing code quality or performance. It's all about
+the service container, and it's Symfony's super power.
+
+.. _`https://symfony.sh`: https://symfony.sh
+.. _`Api Platform`: https://api-platform.com/
+.. _`Twig`: https://twig.symfony.com/

_images/quick_tour/web_debug_toolbar.png

@@ -5,6 +5,5 @@ The Quick Tour
    :maxdepth: 1
 
    the_big_picture
-   the_view
-   the_controller
+   flex_recipes
    the_architecture