Update to Drupal 8.2.0. For more information, see https://www.drupal.org/project/drupal/releases/8.2.0

core/lib/Drupal/Core/Routing/AccessAwareRouter.php

@@ -3,6 +3,7 @@
 namespace Drupal\Core\Routing;
 
 use Drupal\Core\Access\AccessManagerInterface;
+use Drupal\Core\Access\AccessResultReasonInterface;
 use Drupal\Core\Session\AccountInterface;
 use Symfony\Cmf\Component\Routing\ChainRouter;
 use Symfony\Component\HttpFoundation\Request;
@@ -105,7 +106,7 @@ class AccessAwareRouter implements AccessAwareRouterInterface {
       $request->attributes->set(AccessAwareRouterInterface::ACCESS_RESULT, $access_result);
     }
     if (!$access_result->isAllowed()) {
-      throw new AccessDeniedHttpException();
+      throw new AccessDeniedHttpException($access_result instanceof AccessResultReasonInterface ? $access_result->getReason() : NULL);
     }
   }
 

core/lib/Drupal/Core/Routing/MethodFilter.php

@@ -0,0 +1,57 @@
+<?php
+
+namespace Drupal\Core\Routing;
+
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\Routing\Exception\MethodNotAllowedException;
+use Symfony\Component\Routing\Route;
+use Symfony\Component\Routing\RouteCollection;
+
+/**
+ * Filters routes based on the HTTP method.
+ */
+class MethodFilter implements RouteFilterInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function filter(RouteCollection $collection, Request $request) {
+    $method = $request->getMethod();
+
+    $all_supported_methods = [];
+
+    foreach ($collection->all() as $name => $route) {
+      $supported_methods = $route->getMethods();
+
+      // A route not restricted to specific methods allows any method. If this
+      // is the case, we'll also have at least one route left in the collection,
+      // hence we don't need to calculate the set of all supported methods.
+      if (empty($supported_methods)) {
+        continue;
+      }
+
+      // If the GET method is allowed we also need to allow the HEAD method
+      // since HEAD is a GET method that doesn't return the body.
+      if (in_array('GET', $supported_methods, TRUE)) {
+        $supported_methods[] = 'HEAD';
+      }
+
+      if (!in_array($method, $supported_methods, TRUE)) {
+        $all_supported_methods = array_merge($supported_methods, $all_supported_methods);
+        $collection->remove($name);
+      }
+    }
+    if (count($collection)) {
+      return $collection;
+    }
+    throw new MethodNotAllowedException(array_unique($all_supported_methods));
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function applies(Route $route) {
+    return !empty($route->getMethods());
+  }
+
+}

core/lib/Drupal/Core/Routing/RouteBuilder.php

@@ -2,9 +2,9 @@
 
 namespace Drupal\Core\Routing;
 
-use Drupal\Component\Discovery\YamlDiscovery;
 use Drupal\Core\Access\CheckProviderInterface;
 use Drupal\Core\Controller\ControllerResolverInterface;
+use Drupal\Core\Discovery\YamlDiscovery;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\Lock\LockBackendInterface;
 use Drupal\Core\DestructableInterface;

core/lib/Drupal/Core/Routing/StackedRouteMatchInterface.php

@@ -28,7 +28,7 @@ interface StackedRouteMatchInterface extends RouteMatchInterface {
   /**
    * Returns the parent route match of the current.
    *
-   * @return \Drupal\Core\Routing\RouteMatchInterface|NULL
+   * @return \Drupal\Core\Routing\RouteMatchInterface|null
    *   The parent route match or NULL, if it the master route match.
    */
   public function getParentRouteMatch();
@@ -36,10 +36,10 @@ interface StackedRouteMatchInterface extends RouteMatchInterface {
   /**
    * Returns a route match from a given request, if possible.
    *
-   * @param \Symfony\Component\HttpFoundation\Request
+   * @param \Symfony\Component\HttpFoundation\Request $request
    *   The request.
    *
-   * @return \Drupal\Core\Routing\RouteMatchInterface|NULL
+   * @return \Drupal\Core\Routing\RouteMatchInterface|null
    *   THe matching route match, or NULL if there is no matching one.
    */
   public function getRouteMatchFromRequest(Request $request);