Chris@0: <?php
Chris@0: 
Chris@0: namespace Drupal\Core\EventSubscriber;
Chris@0: 
Chris@0: use Drupal\Core\Cache\CacheableMetadata;
Chris@0: use Drupal\Core\Cache\CacheableResponseInterface;
Chris@0: use Drupal\Core\Session\AccountInterface;
Chris@0: use Symfony\Component\HttpKernel\Event\FilterResponseEvent;
Chris@0: use Symfony\Component\HttpKernel\KernelEvents;
Chris@0: use Symfony\Component\EventDispatcher\EventSubscriberInterface;
Chris@0: 
Chris@0: /**
Chris@0:  * Response subscriber to handle finished responses for the anonymous user.
Chris@0:  */
Chris@0: class AnonymousUserResponseSubscriber implements EventSubscriberInterface {
Chris@0: 
Chris@0:   /**
Chris@0:    * The current user.
Chris@0:    *
Chris@0:    * @var \Drupal\Core\Session\AccountInterface
Chris@0:    */
Chris@0:   protected $currentUser;
Chris@0: 
Chris@0:   /**
Chris@0:    * Constructs an AnonymousUserResponseSubscriber object.
Chris@0:    *
Chris@0:    * @param \Drupal\Core\Session\AccountInterface $current_user
Chris@0:    *   The current user.
Chris@0:    */
Chris@0:   public function __construct(AccountInterface $current_user) {
Chris@0:     $this->currentUser = $current_user;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Adds a cache tag if the 'user.permissions' cache context is present.
Chris@0:    *
Chris@0:    * @param \Symfony\Component\HttpKernel\Event\FilterResponseEvent $event
Chris@0:    *   The event to process.
Chris@0:    */
Chris@0:   public function onRespond(FilterResponseEvent $event) {
Chris@0:     if (!$event->isMasterRequest()) {
Chris@0:       return;
Chris@0:     }
Chris@0: 
Chris@0:     if (!$this->currentUser->isAnonymous()) {
Chris@0:       return;
Chris@0:     }
Chris@0: 
Chris@0:     $response = $event->getResponse();
Chris@0:     if (!$response instanceof CacheableResponseInterface) {
Chris@0:       return;
Chris@0:     }
Chris@0: 
Chris@0:     // The 'user.permissions' cache context ensures that if the permissions for
Chris@0:     // a role are modified, users are not served stale render cache content.
Chris@0:     // But, when entire responses are cached in reverse proxies, the value for
Chris@0:     // the cache context is never calculated, causing the stale response to not
Chris@0:     // be invalidated. Therefore, when varying by permissions and the current
Chris@0:     // user is the anonymous user, also add the cache tag for the 'anonymous'
Chris@0:     // role.
Chris@0:     if (in_array('user.permissions', $response->getCacheableMetadata()->getCacheContexts())) {
Chris@0:       $per_permissions_response_for_anon = new CacheableMetadata();
Chris@0:       $per_permissions_response_for_anon->setCacheTags(['config:user.role.anonymous']);
Chris@0:       $response->addCacheableDependency($per_permissions_response_for_anon);
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Registers the methods in this class that should be listeners.
Chris@0:    *
Chris@0:    * @return array
Chris@0:    *   An array of event listener definitions.
Chris@0:    */
Chris@0:   public static function getSubscribedEvents() {
Chris@0:     // Priority 5, so that it runs before FinishResponseSubscriber, but after
Chris@0:     // event subscribers that add the associated cacheability metadata (which
Chris@0:     // have priority 10). This one is conditional, so must run after those.
Chris@0:     $events[KernelEvents::RESPONSE][] = ['onRespond', 5];
Chris@0:     return $events;
Chris@0:   }
Chris@0: 
Chris@0: }