feature #5894 [WIP] Added an article to explain how to upgrade third-…

…party bundles to Symfony 3 (javiereguiluz)

This PR was merged into the 2.3 branch.

Discussion
----------

[WIP] Added an article to explain how to upgrade third-party bundles to Symfony 3

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | yes
| Applies to    | all
| Fixed tickets | #5879

I've just drafted the skeleton of the article to have something to discuss about the contents.

Commits
-------

cb31c16 Added a new section of tips and tricks to upgrade bundles to Symfony 3.0
3697d81 Fixed a lot of issues reported by Wouter
1e2ccd1 Completed the section "Test your Bundle in Symfony 3"
4b13fab Completed the section "Look for Deprecations and Fix Them"
0e585b4 Completed "Allow to Install Symfony 3 Components" section
4e93eb5 Added an article to explain how to upgrade third-party bundles to Symfony 3

cookbook/map.rst.inc

@@ -229,6 +229,7 @@
   * :doc:`/cookbook/upgrade/patch_version`
   * :doc:`/cookbook/upgrade/minor_version`
   * :doc:`/cookbook/upgrade/major_version`
+  * :doc:`/cookbook/upgrade/bundles`
 
 * :doc:`/cookbook/validation/index`
 

cookbook/upgrade/bundles.rst

@@ -0,0 +1,217 @@
+.. index::
+    single: Upgrading; Bundle; Major Version
+
+Upgrading a Third-Party Bundle for a Major Symfony Version
+==========================================================
+
+Symfony 3 was released on November 2015. Although this version doesn't contain
+any new feature, it removes all the backwards compatibility layers included in
+the previous 2.8 version. If your bundle uses any deprecated feature and it's
+published as a third-party bundle, applications upgrading to Symfony 3 will no
+longer be able to use it.
+
+Allowing to Install Symfony 3 Components
+----------------------------------------
+
+Most third-party bundles define their Symfony dependencies using the ``~2.N`` or
+``^2.N`` constraints in the ``composer.json`` file. For example:
+
+.. code-block:: json
+
+    {
+        "require": {
+            "symfony/framework-bundle": "~2.3",
+            "symfony/finder": "~2.3",
+            "symfony/validator": "~2.3"
+        }
+    }
+
+These constraints prevent the bundle from using Symfony 3 components, so it makes
+it impossible to install it in a Symfony 3 based application. This issue is very
+easy to solve thanks to the flexibility of Composer dependencies constraints.
+Just replace ``~2.N`` by ``~2.N|~3.0`` (or ``^2.N`` by ``^2.N|~3.0``).
+
+The above example can be updated to work with Symfony 3 as follows:
+
+.. code-block:: json
+
+    {
+        "require": {
+            "symfony/framework-bundle": "~2.3|~3.0",
+            "symfony/finder": "~2.3|~3.0",
+            "symfony/validator": "~2.3|~3.0"
+        }
+    }
+
+.. tip::
+
+    Another common version constraint found on third-party bundles is ``>=2.N``.
+    You should avoid using that constraint because it's too generic (it means
+    that your bundle is compatible with any future Symfony version). Use instead
+    ``~2.N|~3.0`` or ``^2.N|~3.0`` to make your bundle future-proof.
+
+Looking for Deprecations and Fix Them
+-------------------------------------
+
+Besides allowing to install Symfony 3 packages, your bundle must stop using
+any feature deprecated in 2.8 version, because they are removed (and you'll get
+exceptions or PHP errors). The easiest way to detect deprecations is to install
+the `symfony/phpunit-bridge package`_ and then run the test suite.
+
+First, install the component as a ``dev`` dependency of your bundle:
+
+.. code-block:: bash
+
+    $ composer require --dev symfony/phpunit-bridge
+
+Then, run your test suite and look for the deprecation list displayed after the
+PHPUnit test report:
+
+.. code-block:: bash
+
+    $ phpunit
+
+    # ... PHPUnit output
+
+    Remaining deprecation notices (3)
+
+    The "pattern" option in file ... is deprecated since version 2.2 and will be
+    removed in 3.0. Use the "path" option in the route definition instead ...
+
+    Twig Function "form_enctype" is deprecated. Use "form_start" instead in ...
+
+    The Symfony\Component\Security\Core\SecurityContext class is deprecated since
+    version 2.6 and will be removed in 3.0. Use ...
+
+Fix the reported deprecations, run the test suite again and repeat the process
+until no deprecation usage is reported.
+
+Useful Resources
+~~~~~~~~~~~~~~~~
+
+There are several resources that can help you detect, understand and fix the use
+of deprecated features:
+
+`Official Symfony Guide to Upgrade from 2.x to 3.0`_
+    The full list of changes required to upgrade to Symfony 3.0 and grouped
+    by component.
+`SensioLabs DeprecationDetector`_
+    It runs a static code analysis against your project's source code to find
+    usages of deprecated methods, classes and interfaces. It works for any PHP
+    application, but it includes special detectors for Symfony applications,
+    where it can also detect usages of deprecated services.
+`Symfony Upgrade Fixer`_
+    It analyzes Symfony projects to find deprecations. In addition it solves
+    automatically some of them thanks to the growing list of supported "fixers".
+
+Testing your Bundle in Symfony 3
+--------------------------------
+
+Now that your bundle has removed all deprecations, it's time to test it for real
+in a Symfony 3 application. Assuming that you already have a Symfony 3 application,
+you can test the updated bundle locally without having to install it through
+Composer.
+
+If your operating system supports symbolic links, just point the appropriate
+vendor directory to your local bundle root directory:
+
+.. code-block:: bash
+
+    $ ln -s /path/to/your/local/bundle/ vendor/you-vendor-name/your-bundle-name
+
+If your operating system doesn't support symbolic links, you'll need to copy
+your local bundle directory into the appropriate directory inside ``vendor/``.
+
+Update the Travis CI Configuration
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+In addition to running tools locally, it's recommended to set-up Travis CI service
+to run the tests of your bundle using different Symfony configurations. Use the
+following recommended configuration as the starting point of your own configuration:
+
+.. code-block:: yaml
+
+    language: php
+    sudo: false
+    php:
+        - 5.3
+        - 5.6
+        - 7.0
+
+    matrix:
+        include:
+            - php: 5.3.3
+              env: COMPOSER_FLAGS='--prefer-lowest --prefer-stable' SYMFONY_DEPRECATIONS_HELPER=weak
+            - php: 5.6
+              env: SYMFONY_VERSION='2.3.*'
+            - php: 5.6
+              env: DEPENDENCIES='dev' SYMFONY_VERSION='2.8.*@dev'
+            - php: 5.6
+              env: SYMFONY_VERSION='3.0.*@dev'
+
+    before_install:
+        - composer self-update
+        - if [ "$DEPENDENCIES" == "dev" ]; then perl -pi -e 's/^}$/,"minimum-stability":"dev"}/' composer.json; fi;
+        - if [ "$SYMFONY_VERSION" != "" ]; then composer --no-update require symfony/symfony:${SYMFONY_VERSION}; fi;
+
+    install: composer update $COMPOSER_FLAGS
+
+    script: phpunit
+
+Updating your Code to Support Symfony 2.x and 3.x at the Same Time
+------------------------------------------------------------------
+
+The real challenge of adding Symfony 3 support for your bundles is when you want
+to support both Symfony 2.x and 3.x simultaneously using the same code. There
+are some edge cases where you'll need to deal with the API differences.
+
+Before diving into the specifics of the most common edge cases, the general
+recommendation is to **not rely on the Symfony Kernel version** to decide which
+code to use::
+
+    if (Kernel::VERSION_ID <= 20800) {
+        // code for Symfony 2.x
+    } else {
+        // code for Symfony 3.x
+    }
+
+Instead of checking the Symfony Kernel version, check the version of the specific
+component. For example, the OptionsResolver API changed in its 2.6 version by
+adding a ``setDefined()`` method. The recommended check in this case would be::
+
+    if (!method_exists('Symfony\Component\OptionsResolver\OptionsResolver', 'setDefined')) {
+        // code for the old OptionsResolver API
+    } else {
+        // code for the new OptionsResolver API
+    }
+
+Form Name Refactoring
+~~~~~~~~~~~~~~~~~~~~~
+
+.. TODO
+
+  - how to check which version to use
+  - how to update FormType classes
+  - how to update type service definitions
+  - how to update FormTypeExtension classes & service definition
+
+OptionsResolver API Refactoring
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. TODO
+
+  - how to check which version to use
+  - how to both APIs
+
+Service Factory Refactoring
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. TODO
+
+  - how to support both APIs ==> Is there a nice way except from (a) doing
+    it in the DI extension or (b) creating 2 service definition files?
+
+.. _`symfony/phpunit-bridge package`: https://github.com/symfony/phpunit-bridge
+.. _`Official Symfony Guide to Upgrade from 2.x to 3.0`: https://github.com/symfony/symfony/blob/2.8/UPGRADE-3.0.md
+.. _`SensioLabs DeprecationDetector`: https://github.com/sensiolabs-de/deprecation-detector
+.. _`Symfony Upgrade Fixer`: https://github.com/umpirsky/Symfony-Upgrade-Fixer

cookbook/upgrade/index.rst

@@ -16,3 +16,4 @@ There are three types of upgrades, all needing a little different preparation:
     /cookbook/upgrade/patch_version
     /cookbook/upgrade/minor_version
     /cookbook/upgrade/major_version
+    /cookbook/upgrade/bundles