Restore container-aware event dispatcher

for supported Symfony versions.

The container aware variant has been deprecated (3.4) and removed (4.0),
but is still required to keep the RegisterListenersPass happy (2.8).

resources/config/services.yml

@@ -11,7 +11,10 @@ services:
         public: true
 
     event_dispatcher:
-        class: Symfony\Component\EventDispatcher\EventDispatcher
+        class: Symfony\Component\EventDispatcher\EventDispatcherInterface
+        factory: GrumPHP\Event\EventDispatcherFactory::create
+        arguments:
+          - '@service_container'
         public: true
 
     filesystem:

spec/Event/EventDispatcherFactorySpec.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace spec\GrumPHP\Event;
+
+use PhpSpec\Exception\Example\SkippingException;
+use PhpSpec\ObjectBehavior;
+use GrumPHP\Event\EventDispatcherFactory;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher;
+use Symfony\Component\EventDispatcher\EventDispatcher;
+
+class EventDispatcherFactorySpec extends ObjectBehavior
+{
+    function it_is_initializable()
+    {
+        $this->shouldHaveType(EventDispatcherFactory::class);
+    }
+
+    function it_creates_an_event_dispatcher(
+        ContainerInterface $container
+    ) {
+        $eventDispatcher = self::create($container);
+        $eventDispatcher->shouldBeAnInstanceOf(EventDispatcher::class);
+    }
+
+    function it_creates_a_container_aware_event_dispatcher_instead_when_available(
+        ContainerInterface $container
+    ) {
+        if (!class_exists(ContainerAwareEventDispatcher::class)) {
+            throw new SkippingException('A container-aware implementation of the event dispatcher is no longer available.');
+        }
+
+        $eventDispatcher = self::create($container);
+        $eventDispatcher->shouldBeAnInstanceOf(ContainerAwareEventDispatcher::class);
+        $eventDispatcher->getContainer()->shouldReturn($container);
+    }
+}

src/Event/EventDispatcherFactory.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace GrumPHP\Event;
+
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\EventDispatcher\EventDispatcherInterface;
+use Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher;
+use Symfony\Component\EventDispatcher\EventDispatcher;
+
+class EventDispatcherFactory
+{
+    /**
+     * @param ContainerInterface $container
+     *
+     * @return EventDispatcherInterface
+     */
+    public static function create(ContainerInterface $container)
+    {
+        if (class_exists(ContainerAwareEventDispatcher::class)) {
+            return new ContainerAwareEventDispatcher($container);
+        }
+
+        return new EventDispatcher();
+    }
+}