bug #18426 [EventDispatcher] Try first if the event is Stopped (lyrixx)

This PR was merged into the 2.3 branch.

Discussion
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[EventDispatcher] Try first if the event is Stopped

| Q             | A
| ------------- | ---
| Branch?       | 2.3
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

If you trigger 2 events with the same instance of Event and if a listener in the first dispatch stop the propagation, then the very first listener of the second dispatch is called. It should not IMHO.

Commits
-------

a30e166 [EventDispatcher] Try first if the event is Stopped

src/Symfony/Component/EventDispatcher/EventDispatcher.php

@@ -155,10 +155,10 @@ class EventDispatcher implements EventDispatcherInterface
     protected function doDispatch($listeners, $eventName, Event $event)
     {
         foreach ($listeners as $listener) {
-            call_user_func($listener, $event);
             if ($event->isPropagationStopped()) {
                 break;
             }
+            call_user_func($listener, $event);
         }
     }
 

src/Symfony/Component/HttpKernel/Debug/TraceableEventDispatcher.php

@@ -136,6 +136,10 @@ class TraceableEventDispatcher implements EventDispatcherInterface, TraceableEve
             $event = new Event();
         }
 
+        if (null !== $this->logger && $event->isPropagationStopped()) {
+            $this->logger->debug(sprintf('The "%s" event is already stopped. No listeners have been called.', $eventName));
+        }
+
         $eventId = ++$this->lastEventId;
 
         $this->preDispatch($eventName, $eventId, $event);