feature #30772 [Contracts][EventDispatcher] move the Event class to symfony/contracts (nicolas-grekas)

This PR was merged into the 4.3-dev branch.

Discussion
----------

[Contracts][EventDispatcher] move the Event class to symfony/contracts

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

Will allow decoupling more components in 5.0

Commits
-------

a4ce08ec30 [Contracts][EventDispatcher] move the Event class to symfony/contracts

UPGRADE-4.3.md

@@ -42,6 +42,7 @@ EventDispatcher
 ---------------
 
  * The signature of the `EventDispatcherInterface::dispatch()` method should be updated to `dispatch($event, string $eventName = null)`, not doing so is deprecated
+ * The `Event` class has been deprecated, use `Symfony\Contracts\EventDispatcher\Event` instead
 
 Form
 ----

UPGRADE-5.0.md

@@ -71,6 +71,7 @@ EventDispatcher
 
  * The `TraceableEventDispatcherInterface` has been removed.
  * The signature of the `EventDispatcherInterface::dispatch()` method has been updated to `dispatch($event, string $eventName = null)`
+ * The `Event` class has been removed, use `Symfony\Contracts\EventDispatcher\Event` instead
 
 DependencyInjection
 -------------------

src/Symfony/Component/EventDispatcher/CHANGELOG.md

@@ -5,6 +5,7 @@ CHANGELOG
 -----
 
  * The signature of the `EventDispatcherInterface::dispatch()` method should be updated to `dispatch($event, string $eventName = null)`, not doing so is deprecated
+ * deprecated the `Event` class, use `Symfony\Contracts\EventDispatcher\Event` instead
 
 4.1.0
 -----

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

@@ -18,6 +18,7 @@ use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 use Symfony\Component\EventDispatcher\LegacyEventDispatcherProxy;
 use Symfony\Component\Stopwatch\Stopwatch;
+use Symfony\Contracts\EventDispatcher\Event as ContractsEvent;
 
 /**
  * Collects some data about event listeners.
@@ -147,7 +148,7 @@ class TraceableEventDispatcher implements TraceableEventDispatcherInterface
             }
         }
 
-        if (null !== $this->logger && ($event instanceof Event || $event instanceof StoppableEventInterface) && $event->isPropagationStopped()) {
+        if (null !== $this->logger && ($event instanceof Event || $event instanceof ContractsEvent || $event instanceof StoppableEventInterface) && $event->isPropagationStopped()) {
             $this->logger->debug(sprintf('The "%s" event is already stopped. No listeners have been called.', $eventName));
         }
 

src/Symfony/Component/EventDispatcher/Debug/WrappedListener.php

@@ -16,6 +16,7 @@ use Symfony\Component\EventDispatcher\Event;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 use Symfony\Component\Stopwatch\Stopwatch;
 use Symfony\Component\VarDumper\Caster\ClassStub;
+use Symfony\Contracts\EventDispatcher\Event as ContractsEvent;
 
 /**
  * @author Fabien Potencier <fabien@symfony.com>
@@ -123,7 +124,7 @@ class WrappedListener
             $e->stop();
         }
 
-        if (($event instanceof Event || $event instanceof StoppableEventInterface) && $event->isPropagationStopped()) {
+        if (($event instanceof Event || $event instanceof ContractsEvent || $event instanceof StoppableEventInterface) && $event->isPropagationStopped()) {
             $this->stoppedPropagation = true;
         }
     }

src/Symfony/Component/EventDispatcher/Event.php

@@ -12,32 +12,16 @@
 namespace Symfony\Component\EventDispatcher;
 
 /**
- * Event is the base class for classes containing event data.
- *
- * This class contains no event data. It is used by events that do not pass
- * state information to an event handler when an event is raised.
- *
- * You can call the method stopPropagation() to abort the execution of
- * further listeners in your event listener.
- *
- * @author Guilherme Blanco <guilhermeblanco@hotmail.com>
- * @author Jonathan Wage <jonwage@gmail.com>
- * @author Roman Borschel <roman@code-factory.org>
- * @author Bernhard Schussek <bschussek@gmail.com>
+ * @deprecated since Symfony 4.3, use "Symfony\Contracts\EventDispatcher\Event" instead
  */
 class Event
 {
-    /**
-     * @var bool Whether no further event listeners should be triggered
-     */
     private $propagationStopped = false;
 
     /**
-     * Returns whether further event listeners should be triggered.
-     *
-     * @see Event::stopPropagation()
-     *
      * @return bool Whether propagation was already stopped for this event
+     *
+     * @deprecated since Symfony 4.3, use "Symfony\Contracts\EventDispatcher\Event" instead
      */
     public function isPropagationStopped()
     {
@@ -45,11 +29,7 @@ class Event
     }
 
     /**
-     * Stops the propagation of the event to further event listeners.
-     *
-     * If multiple event listeners are connected to the same event, no
-     * further event listener will be triggered once any trigger calls
-     * stopPropagation().
+     * @deprecated since Symfony 4.3, use "Symfony\Contracts\EventDispatcher\Event" instead
      */
     public function stopPropagation()
     {

src/Symfony/Component/EventDispatcher/EventDispatcher.php

@@ -12,6 +12,7 @@
 namespace Symfony\Component\EventDispatcher;
 
 use Psr\EventDispatcher\StoppableEventInterface;
+use Symfony\Contracts\EventDispatcher\Event as ContractsEvent;
 
 /**
  * The EventDispatcherInterface is the central point of Symfony's event listener system.
@@ -237,7 +238,7 @@ class EventDispatcher implements EventDispatcherInterface
      */
     protected function doDispatch($listeners, $eventName, Event $event)
     {
-        $stoppable = $event instanceof Event || $event instanceof StoppableEventInterface;
+        $stoppable = $event instanceof Event || $event instanceof ContractsEvent || $event instanceof StoppableEventInterface;
 
         foreach ($listeners as $listener) {
             if ($stoppable && $event->isPropagationStopped()) {

src/Symfony/Component/EventDispatcher/LegacyEventDispatcherProxy.php

@@ -12,6 +12,7 @@
 namespace Symfony\Component\EventDispatcher;
 
 use Psr\EventDispatcher\StoppableEventInterface;
+use Symfony\Contracts\EventDispatcher\Event as ContractsEvent;
 use Symfony\Contracts\EventDispatcher\EventDispatcherInterface;
 
 /**
@@ -68,7 +69,7 @@ final class LegacyEventDispatcherProxy implements EventDispatcherInterface
         }
 
         $listeners = $this->getListeners($eventName);
-        $stoppable = $event instanceof Event || $event instanceof StoppableEventInterface;
+        $stoppable = $event instanceof Event || $event instanceof ContractsEvent || $event instanceof StoppableEventInterface;
 
         foreach ($listeners as $listener) {
             if ($stoppable && $event->isPropagationStopped()) {

src/Symfony/Component/EventDispatcher/Tests/EventTest.php

@@ -15,7 +15,7 @@ use PHPUnit\Framework\TestCase;
 use Symfony\Component\EventDispatcher\Event;
 
 /**
- * Test class for Event.
+ * @group legacy
  */
 class EventTest extends TestCase
 {

src/Symfony/Contracts/CHANGELOG.md

@@ -5,8 +5,8 @@ CHANGELOG
 -----
 
  * added `HttpClient` namespace with contracts for implementing flexible HTTP clients
- * added `EventDispatcher\EventDispatcherInterface`
- * added `ServiceProviderInterface`
+ * added `EventDispatcherInterface` and `Event` in namespace `EventDispatcher`
+ * added `ServiceProviderInterface` in namespace `Service`
 
 1.0.0
 -----

src/Symfony/Contracts/EventDispatcher/Event.php

@@ -0,0 +1,96 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Contracts\EventDispatcher;
+
+use Psr\EventDispatcher\StoppableEventInterface;
+
+if (interface_exists(StoppableEventInterface::class)) {
+    /**
+     * Event is the base class for classes containing event data.
+     *
+     * This class contains no event data. It is used by events that do not pass
+     * state information to an event handler when an event is raised.
+     *
+     * You can call the method stopPropagation() to abort the execution of
+     * further listeners in your event listener.
+     *
+     * @author Guilherme Blanco <guilhermeblanco@hotmail.com>
+     * @author Jonathan Wage <jonwage@gmail.com>
+     * @author Roman Borschel <roman@code-factory.org>
+     * @author Bernhard Schussek <bschussek@gmail.com>
+     * @author Nicolas Grekas <p@tchwork.com>
+     */
+    class Event implements StoppableEventInterface
+    {
+        private $propagationStopped = false;
+
+        /**
+         * Returns whether further event listeners should be triggered.
+         */
+        public function isPropagationStopped(): bool
+        {
+            return $this->propagationStopped;
+        }
+
+        /**
+         * Stops the propagation of the event to further event listeners.
+         *
+         * If multiple event listeners are connected to the same event, no
+         * further event listener will be triggered once any trigger calls
+         * stopPropagation().
+         */
+        public function stopPropagation(): void
+        {
+            $this->propagationStopped = true;
+        }
+    }
+} else {
+    /**
+     * Event is the base class for classes containing event data.
+     *
+     * This class contains no event data. It is used by events that do not pass
+     * state information to an event handler when an event is raised.
+     *
+     * You can call the method stopPropagation() to abort the execution of
+     * further listeners in your event listener.
+     *
+     * @author Guilherme Blanco <guilhermeblanco@hotmail.com>
+     * @author Jonathan Wage <jonwage@gmail.com>
+     * @author Roman Borschel <roman@code-factory.org>
+     * @author Bernhard Schussek <bschussek@gmail.com>
+     * @author Nicolas Grekas <p@tchwork.com>
+     */
+    class Event
+    {
+        private $propagationStopped = false;
+
+        /**
+         * Returns whether further event listeners should be triggered.
+         */
+        public function isPropagationStopped(): bool
+        {
+            return $this->propagationStopped;
+        }
+
+        /**
+         * Stops the propagation of the event to further event listeners.
+         *
+         * If multiple event listeners are connected to the same event, no
+         * further event listener will be triggered once any trigger calls
+         * stopPropagation().
+         */
+        public function stopPropagation(): void
+        {
+            $this->propagationStopped = true;
+        }
+    }
+}