Have a method to add tags to the TagSubscriber directly, for when the request does not exist yet

Author: dbu

EventListener/TagSubscriber.php

@@ -36,6 +36,13 @@ class TagSubscriber extends AbstractRuleSubscriber implements EventSubscriberInt
      */
     private $expressionLanguage;
 
+    /**
+     * List of tags to add to response.
+     *
+     * @var string[]
+     */
+    private $tags = array();
+
     /**
      * Constructor
      *
@@ -50,6 +57,22 @@ public function __construct(
         $this->expressionLanguage = $expressionLanguage;
     }
 
+    /**
+     * Add tags to set on the response to the current request.
+     *
+     * Contrary to CacheManager::tagResponse, this method can be called before
+     * the response object exists.
+     *
+     * Adding a tag during an unsafe request is forbidden and leads to an
+     * error. Use CacheManager::invalidateTags directly.
+     *
+     * @param array $tags List of tags to add.
+     */
+    public function addTags(array $tags)
+    {
+        $this->tags = array_merge($this->tags, $tags);
+    }
+
     /**
      * Process the _tags request attribute, which is set when using the Tag
      * annotation
@@ -63,12 +86,16 @@ public function onKernelResponse(FilterResponseEvent $event)
     {
         $request = $event->getRequest();
         $response = $event->getResponse();
-
-        $tags = array();
+        if ($request->isMethodSafe()) {
+            $tags = $this->tags;
+            $this->tags = array();
+        } else {
+            $tags = array();
+        }
 
         // Only set cache tags or invalidate them if response is successful
         if ($response->isSuccessful()) {
-            $tags = $this->getAnnotationTags($request);
+            $tags = array_merge($tags, $this->getAnnotationTags($request));
         }
 
         $configuredTags = $this->matchRule($request, $response);

Resources/doc/features/tagging.rst

@@ -35,15 +35,22 @@ Setting and Invalidating Tags
 You can tag responses in three ways: with the cache manager, configuration and
 annotations.
 
-Cache Manager
-~~~~~~~~~~~~~
+Tagging from code
+~~~~~~~~~~~~~~~~~
 
-Use ``tagResponse($response, $tags)`` to set tags on a response::
+Inject the ``CacheManager`` (service ``fos_http_cache.cache_manager``) and
+use ``tagResponse($response, $tags)`` to set tags on a response::
 
     use Symfony\Component\HttpFoundation\Response;
+    use FOS\HttpCacheBundle\CacheManager;
 
     class NewsController
     {
+        /**
+         * @var CacheManager
+         */
+        private $cacheManager;
+
         public function articleAction($id)
         {
             $response = new Response('Some news article');
@@ -53,7 +60,28 @@ Use ``tagResponse($response, $tags)`` to set tags on a response::
         }
     }
 
-Then call ``invalidateTags($tags)`` to invalidate the tags you set::
+Or inject the ``TagSubscriber`` (service ``fos_http_cache.event_listener.tag``)
+and call ``addTags($tags)`` to set tags that will be added to the response once
+it exists::
+
+    use FOS\HttpCacheBundle\EventListener\TagSubscriber;
+
+    class Service
+    {
+        /**
+         * @var TagSubscriber
+         */
+        private $tagSubscriber;
+
+        public function doStuff($thing)
+        {
+            $this->tagSubscriber->addTags(array('news', 'news-' . $thing->getId()));
+
+            // ...
+        }
+    }
+
+To invalidate tags, call ``CacheManager::invalidateTags($tags)``::
 
     class NewsController
     {

Resources/doc/reference/cache-manager.rst

@@ -95,6 +95,12 @@ option to true::
 
     $cacheManager->tagResponse($response, array('different'), true);
 
+.. tip::
+
+    If you do not yet have the response available, you can use the
+    ``TagSubscriber::addTags($tags)`` method to have your tags added once the
+    response is being sent.
+
 ``invalidateTags()``
 --------------------
 

Tests/Unit/EventListener/TagSubscriberTest.php

@@ -124,6 +124,33 @@ public function testOnKernelResponsePost()
         $this->listener->onKernelResponse($event);
     }
 
+    public function testAddTagsGet()
+    {
+        $request = new Request();
+        $request->setMethod('GET');
+
+        $this->listener->addTags(array('a', 'b'));
+        $event = $this->getEvent($request);
+        $this->listener->onKernelResponse($event);
+
+        $this->assertEquals(
+            'a,b',
+            $event->getResponse()->headers->get($this->cacheManager->getTagsHeader())
+        );
+    }
+
+    public function testAddTagsPost()
+    {
+        $request = new Request();
+        $request->setMethod('POST');
+
+        $this->listener->addTags(array('a', 'b'));
+        $event = $this->getEvent($request);
+        $this->listener->onKernelResponse($event);
+
+        $this->assertFalse($event->getResponse()->headers->has($this->cacheManager->getTagsHeader()));
+    }
+
     protected function getEvent(Request $request, Response $response = null)
     {
         return new FilterResponseEvent(