Merge branch '3.4' into 4.3

* 3.4:
  Add container.hot_path to built-in service tags
  Removed the Debug component
  BC promise: only optional arguments can be removed

Author: OskarStark

_build/redirection_map

@@ -428,6 +428,7 @@
 /contributing/community/other /contributing/community
 /profiler/storage /profiler
 /setup/composer /setup
+<<<<<<< HEAD
 /security/security_checker /setup
 /service_container/parameters /configuration
 /routing/generate_url_javascript /routing
@@ -473,3 +474,4 @@
 /best_practices/security /best_practices
 /best_practices/web-assets /best_practices
 /best_practices/tests /best_practices
+/components/debug https://github.com/symfony/debug

components/debug.rst

@@ -42,7 +42,7 @@ to `decorate`_ the kernel with additional features. Examples include:
 * Configuring the autoloader or adding additional autoloading mechanisms;
 * Adding HTTP level caching by wrapping the kernel with an instance of
   :ref:`HttpCache <symfony-gateway-cache>`;
-* Enabling the :doc:`Debug Component </components/debug>`.
+* Enabling the `Debug component`_.
 
 You can choose the front controller that's used by adding it in the URL, like:
 
@@ -264,3 +264,4 @@ includes the following:
 
 .. _`front controller`: https://en.wikipedia.org/wiki/Front_Controller_pattern
 .. _`decorate`: https://en.wikipedia.org/wiki/Decorator_pattern
+.. _Debug component: https://github.com/symfony/debug

configuration/front_controllers_and_kernel.rst

@@ -204,7 +204,7 @@ Change name                                     No
 Move to parent interface                        Yes
 Add argument without a default value            No
 Add argument with a default value               No
-Remove argument                                 Yes [3]_
+Remove argument                                 No [3]_
 Add default value to an argument                No
 Remove default value of an argument             No
 Add type hint to an argument                    No
@@ -272,7 +272,7 @@ Make final                                          No [6]_
 Move to parent class                                Yes
 Add argument without a default value                No
 Add argument with a default value                   No [7]_ [8]_
-Remove argument                                     Yes [3]_
+Remove argument                                     No [3]_
 Add default value to an argument                    No [7]_ [8]_
 Remove default value of an argument                 No
 Add type hint to an argument                        No [7]_ [8]_
@@ -291,7 +291,7 @@ Make public                                         No [7]_ [8]_
 Move to parent class                                Yes
 Add argument without a default value                No [7]_
 Add argument with a default value                   No [7]_ [8]_
-Remove argument                                     Yes [3]_
+Remove argument                                     No [3]_
 Add default value to an argument                    No [7]_ [8]_
 Remove default value of an argument                 No [7]_
 Add type hint to an argument                        No [7]_ [8]_
@@ -416,8 +416,8 @@ Turn static into non static                         No
 .. [2] The added parent interface must not introduce any new methods that don't
        exist in the interface already.
 
-.. [3] Only the last argument(s) of a method may be removed, as PHP does not
-       care about additional arguments that you pass to a method.
+.. [3] Only the last optional argument(s) of a method may be removed, as PHP
+       does not care about additional arguments that you pass to a method.
 
 .. [4] When changing the parent class, the original parent class must remain an
        ancestor of the class.

contributing/code/bc.rst

@@ -13,6 +13,7 @@ Tag Name                                  Usage
 ========================================  ========================================================================
 `auto_alias`_                             Define aliases based on the value of container parameters
 `console.command`_                        Add a command
+`container.hot_path`_                     Add to list of always needed services
 `controller.argument_value_resolver`_     Register a value resolver for controller arguments such as ``Request``
 `data_collector`_                         Create a class that collects custom data for the profiler
 `doctrine.event_listener`_                Add a Doctrine event listener
@@ -181,6 +182,27 @@ console.command
 For details on registering your own commands in the service container, read
 :doc:`/console/commands_as_services`.
 
+container.hot_path
+------------------
+
+.. versionadded:: 3.4
+
+    The ``container.hot_path`` tag was introduced in Symfony 3.4.
+
+**Purpose**: Add to list of always needed services
+
+This tag identifies the services that are always needed. It is only applied to 
+a very short list of bootstrapping services (like ``router``, ``event_dispatcher``, 
+``http_kernel``, ``request_stack``, etc.). Then, it is propagated to all dependencies 
+of these services, with a special case for event listeners, where only listed events 
+are propagated to their related listeners.
+
+It will replace, in cache for generated service factories, the PHP autoload by 
+plain inlined ``include_once``. The benefit is a complete bypass of the autoloader 
+for services and their class hierarchy. The result is as significant performance improvement.
+
+Use this tag with great caution, you have to be sure that the tagged service is always used.
+
 controller.argument_value_resolver
 ----------------------------------