Merge branch '2.8' into 3.4

* 2.8:
  Update dependency_injection.rst
  Fix some misspellings
  Explained how the URL trailing slash redirection works

Author: javiereguiluz

changelog.rst

@@ -2622,7 +2622,7 @@ Fixed Documentation
 - `e385d28 <https://github.com/symfony/symfony-docs/commit/e385d28bee7c7418c8175d43befc4954a43a300c>`_ #3503 file extension correction xfliff to xliff (nixilla)
 - `6d34aa6 <https://github.com/symfony/symfony-docs/commit/6d34aa6038b8317259d2e8fffd186ad24fef5bc5>`_ #3478 Update custom_password_authenticator.rst (piotras-s)
 - `a171700 <https://github.com/symfony/symfony-docs/commit/a171700fb8d9695947bc1b16c6f61c183f296657>`_ #3477 Api key user provider should use "implements" instead of "extends" (skowi)
-- `7fe0de3 <https://github.com/symfony/symfony-docs/commit/7fe0de330b2d72155b6b7ec87c59f5a7e7ee4881>`_ #3475 Fixed doc for framework.session.cookie_lifetime refrence. (tyomo4ka)
+- `7fe0de3 <https://github.com/symfony/symfony-docs/commit/7fe0de330b2d72155b6b7ec87c59f5a7e7ee4881>`_ #3475 Fixed doc for framework.session.cookie_lifetime reference. (tyomo4ka)
 - `8155e4c <https://github.com/symfony/symfony-docs/commit/8155e4cab70e481962a4775274a4412a4465ecdc>`_ #3473 Update proxy_examples.rst (AZielinski)
 
 Minor Documentation Changes

components/validator.rst

@@ -23,7 +23,7 @@ Usage
 
 The Validator component behavior is based on two concepts:
 
-* Contraints, which define the rules to be validated;
+* Constraints, which define the rules to be validated;
 * Validators, which are the classes that contain the actual validation logic.
 
 The following example shows how to validate that a string is at least 10

create_framework/dependency_injection.rst

@@ -196,7 +196,7 @@ Now, here is how you can register a custom listener in the front controller::
     // ...
     use Simplex\StringResponseListener;
 
-    $container->register('listener.string_response', StringResposeListener::class);
+    $container->register('listener.string_response', StringResponseListener::class);
     $container->getDefinition('dispatcher')
         ->addMethodCall('addSubscriber', array(new Reference('listener.string_response')))
     ;

http_cache.rst

@@ -291,7 +291,7 @@ two things:
   (e.g. deleting a blog post). Caching them would prevent certain requests from hitting
   and mutating your application.
 
-* POST requests are generally considered uncachable, but `they can be cached`_
+* POST requests are generally considered uncacheable, but `they can be cached`_
   when they include explicit freshness information. However POST caching is not
   widely implemented, so you should avoid it if possible.
 

routing.rst

@@ -494,6 +494,30 @@ that are special: each adds a unique piece of functionality inside your applicat
 ``_locale``
     Used to set the locale on the request (:ref:`read more <translation-locale-url>`).
 
+Redirecting URLs with Trailing Slashes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Historically, URLs have followed the UNIX convention of adding trailing slashes
+for directories (e.g. ``https://example.com/foo/``) and removing them to refer
+to files (``https://example.com/foo``). Although serving different contents for
+both URLs is OK, nowadays it's common to treat both URLs as the same URL and
+redirect between them.
+
+Symfony follows this logic to redirect between URLs with and without trailing
+slashes (but only for ``GET`` and ``HEAD`` requests):
+
+----------  ----------------------------------------  ------------------------------------------
+Route path  If the requested URL is ``/foo``          If the requested URL is ``/foo/``
+----------  ----------------------------------------  ------------------------------------------
+``/foo``    It matches (``200`` status response)      It doesn't match (``404`` status response)
+``/foo/``   It makes a ``301`` redirect to ``/foo/``  It matches (``200`` status response)
+----------  ----------------------------------------  ------------------------------------------
+
+In summary, adding a trailing slash in the route path is the best way to ensure
+that both URLs work. Read the :doc:`/routing/redirect_trailing_slash` article to
+learn how to avoid the ``404`` error when the request URL contains a trailing
+slash and the route path does not.
+
 .. index::
    single: Routing; Controllers
    single: Controller; String naming format