Documented upgrading path for a major version

contributing/code/bc.rst

@@ -1,4 +1,4 @@
-Our backwards Compatibility Promise
+Our Backwards Compatibility Promise
 ===================================
 
 Ensuring smooth upgrades of your projects is our first priority. That's why

cookbook/index.rst

@@ -28,7 +28,7 @@ The Cookbook
     symfony1
     templating/index
     testing/index
-    upgrading
+    upgrade/index
     validation/index
     web_server/index
     web_services/index

cookbook/map.rst.inc

@@ -201,9 +201,11 @@
   * (email) :doc:`/cookbook/email/testing`
   * (form) :doc:`/cookbook/form/unit_testing`
 
-* **Upgrading**
+* :doc:`/cookbook/upgrade/index`
 
-  * :doc:`/cookbook/upgrading`
+  * :doc:`/cookbook/upgrade/patch_version`
+  * :doc:`/cookbook/upgrade/minor_version`
+  * :doc:`/cookbook/upgrade/major_version`
 
 * :doc:`/cookbook/validation/index`
 

cookbook/upgrade/_update_all_packages.rst.inc

@@ -0,0 +1,16 @@
+You may also want to upgrade the rest of your libraries. If you've done a
+good job with your `version constraints`_ in ``composer.json``, you can do
+this safely by running:
+
+.. code-block:: bash
+
+    $ composer update
+
+.. caution::
+
+    Beware, if you have some unspecific `version constraints`_ in your
+    ``composer.json`` (e.g. ``dev-master``), this could upgrade some
+    non-Symfony libraries to new versions that contain backwards-compatibility
+    breaking changes.
+
+.. _`version constraints`: https://getcomposer.org/doc/01-basic-usage.md#package-versions

cookbook/upgrade/index.rst

@@ -0,0 +1,18 @@
+.. index::
+    single: Upgrading
+
+Upgrading
+=========
+
+So a new Symfony release has come out and you want to upgrade, great! Fortunately,
+because Symfony protects backwards-compatibility very closely, this *should*
+be quite easy.
+
+There are three types of upgrades, all needing a little different preparation:
+
+.. toctree::
+    :maxdepth: 2
+
+    /cookbook/upgrade/patch_version
+    /cookbook/upgrade/minor_version
+    /cookbook/upgrade/major_version

cookbook/upgrade/major_version.rst

@@ -0,0 +1,114 @@
+.. index::
+    single: Upgrading; Major Version
+
+Upgrading a Major Version (e.g. 2.7.0 to 3.0.0)
+===============================================
+
+Every few years, Symfony releases a new major version release (the first number
+changes). These releases are the trickiest to upgrade, as they are allowed to
+contain BC breaks. However, Symfony tries to make this upgrade process as
+smooth as possible.
+
+This means that you can update most of your code before the major release is
+actually released. This is called making your code *future compatible*.
+
+There are a couple of steps to upgrading a major version:
+
+#. :ref:`Make your code deprecation free <upgrade-major-symfony-deprecations>`;
+#. :ref:`Update to the new major version via Composer <upgrade-major-symfony-composer>`.
+#. :ref:`Update your code to work with the new version <upgrade-major-symfony-after>`
+
+.. _upgrade-major-symfony-deprecations:
+
+1) Make your Code Deprecation Free
+----------------------------------
+
+During the lifecycle of a major release, new features are added and method
+signatures and public API usages are changed. However, minor versions should
+not contain any backwards compatibility changes. It is made sure that there is
+a so-called *backwards compatibility layer* (or BC layer). This means that the
+old API will still work, while the new feature is used internally. This BC
+layer is then marked as *deprecated*, indicating that it will be
+removed/changed in the future.
+
+The major version is the only time all existing BC layers are removed. However,
+if you make sure you've fixed all deprecated usages in the last version of the
+previous major version, you should be able to upgrade to the new major version
+without problems. To help you with this, the last minor releases will trigger
+deprecated notices. For example, 2.7 and 2.8 trigger deprecated notices and if
+you do not have any notice while using 2.8, you can savely upgrade to 3.0.
+
+When visiting your application in the
+:doc:`dev environment </cookbook/configuration/environments>` in your browser,
+these notices are shown in the web dev toolbar:
+
+.. image:: /images/cookbook/deprecations-in-profiler.png
+
+Deprecations in PHPUnit
+~~~~~~~~~~~~~~~~~~~~~~~
+
+By default, PHPUnit will handle deprecation notices as real errors. This means
+that all tests are aborted because it uses a BC layer.
+
+To make sure this doesn't happen, you can install the PHPUnit bridge:
+
+.. code-block:: bash
+
+    $ composer require symfony/phpunit-bridge
+
+Now, your tests execute normally and a nice summary of the deprecation notices
+is displayed at the end of the test report:
+
+.. code-block:: text
+
+    $ phpunit
+    ...
+
+    OK (10 tests, 20 assertions)
+
+    Remaining deprecation notices (6)
+
+    The "request" service is deprecated and will be removed in 3.0. Add a typehint for
+    Symfony\Component\HttpFoundation\Request to your controller parameters to retrieve the
+    request instead: 6x
+        3x in PageAdminTest::testPageShow from Symfony\Cmf\SimpleCmsBundle\Tests\WebTest\Admin
+        2x in PageAdminTest::testPageList from Symfony\Cmf\SimpleCmsBundle\Tests\WebTest\Admin
+        1x in PageAdminTest::testPageEdit from Symfony\Cmf\SimpleCmsBundle\Tests\WebTest\Admin
+
+.. _upgrade-major-symfony-composer:
+
+2) Update to the New Major Version via Composer
+-----------------------------------------------
+
+If your code is deprecation free, you can update the Symfony library via
+Composer by modifying your ``composer.json`` file:
+
+.. code-block:: json
+
+    {
+        "...": "...",
+
+        "require": {
+            "symfony/symfony": "3.0.*",
+        },
+        "...": "...",
+    }
+
+Next, use Composer to download new versions of the libraries:
+
+.. code-block:: bash
+
+    $ composer update symfony/symfony
+
+.. include:: /cookbook/upgrade/_update_all_packages.rst.inc
+
+.. _upgrade-major-symfony-after:
+
+3) Update your Code to Work with the New Version
+------------------------------------------------
+
+There is a high chance that you're done now! However, the next major version
+*may* also contain new BC breaks as a BC layer is not always a possibility.
+Make sure you read the ``UPGRADE-X.0.md`` (where X is the new major version)
+included in the Symfony repository for any BC break that you need to be aware
+of.

cookbook/upgrade/minor_version.rst

@@ -0,0 +1,63 @@
+.. index::
+    single: Upgrading; Minor Version
+
+Upgrading a Minor Version (e.g. 2.5.3 to 2.6.1)
+===============================================
+
+If you're upgrading a minor version (where the middle number changes), then
+you should *not* encounter significant backwards compatibility changes. For
+details, see the :doc:`Symfony backwards compatibility promise </contributing/code/bc>`.
+
+However, some backwards-compatibility breaks *are* possible and you'll learn in
+a second how to prepare for them.
+
+There are two steps to upgrading a minor version:
+
+#. :ref:`Update the Symfony library via Composer <upgrade-minor-symfony-composer>`;
+#. :ref:`Update your code to work with the new version <upgrade-minor-symfony-code>`.
+
+.. _`upgrade-minor-symfony-composer`:
+
+1) Update the Symfony Library via Composer
+------------------------------------------
+
+First, you need to update Symfony by modifying your ``composer.json`` file
+to use the new version:
+
+.. code-block:: json
+
+    {
+        "...": "...",
+
+        "require": {
+            "symfony/symfony": "2.6.*",
+        },
+        "...": "...",
+    }
+
+Next, use Composer to download new versions of the libraries:
+
+.. code-block:: bash
+
+    $ composer update symfony/symfony
+
+.. include:: /cookbook/upgrade/_update_all_packages.rst.inc
+
+.. _`upgrade-minor-symfony-code`:
+
+2) Updating your Code to Work with the new Version
+--------------------------------------------------
+
+In theory, you should be done! However, you *may* need to make a few changes
+to your code to get everything working. Additionally, some features you're
+using might still work, but might now be deprecated. While that's just fine,
+if you know about these deprecations, you can start to fix them over time.
+
+Every version of Symfony comes with an UPGRADE file included in the Symfony
+directory that describes these changes. If you follow the instructions in the
+document and update your code accordingly, it should be save to update in the
+future.
+
+These documents can also be found in the `Symfony Repository`_.
+
+.. _`Symfony Repository`: https://github.com/symfony/symfony

cookbook/upgrade/patch_version.rst

@@ -0,0 +1,26 @@
+.. index::
+    single: Upgrading; Patch Version
+
+Upgrading a Patch Version (e.g. 2.6.0 to 2.6.1)
+===============================================
+
+When a new patch version is released (only the last number changed), it is a
+release that only contains bug fixes. This means that upgrading to a new patch
+version is *really* easy:
+
+.. code-block:: bash
+
+    $ composer update symfony/symfony
+
+That's it! You should not encounter any backwards-compatibility breaks or
+need to change anything else in your code. That's because when you started
+your project, your ``composer.json`` included Symfony using a constraint
+like ``2.6.*``, where only the *last* version number will change when you
+update.
+
+.. tip::
+
+    It is recommended to update to a new patch version as soon as possible, as
+    important bugs and security leaks may be fixed in these new releases.
+
+.. include:: /cookbook/upgrade/_update_all_packages.rst.inc