feature #23812 [FrameworkBundle] Allow micro kernel to subscribe events easily (ogizanagi)

This PR was merged into the 3.4 branch.

Discussion
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[FrameworkBundle] Allow micro kernel to subscribe events easily

| Q             | A
| ------------- | ---
| Branch?       | 3.4 <!-- see comment below -->
| Bug fix?      | no
| New feature?  | yes <!-- don't forget updating src/**/CHANGELOG.md files -->
| BC breaks?    | no
| Deprecations? | no <!-- don't forget updating UPGRADE-*.md files -->
| Tests pass?   | yes
| Fixed tickets | #16982 <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | N/A

just by implementing `EventSubscriberInterface`. See related issue for other implementation suggestions.

Commits
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b31542eb22 [FrameworkBundle] Allow micro kernel to subscribe events easily

src/Symfony/Bundle/FrameworkBundle/Kernel/MicroKernelTrait.php

@@ -13,6 +13,7 @@ namespace Symfony\Bundle\FrameworkBundle\Kernel;
 
 use Symfony\Component\Config\Loader\LoaderInterface;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 use Symfony\Component\Routing\RouteCollectionBuilder;
 
 /**
@@ -68,6 +69,13 @@ trait MicroKernelTrait
                 ),
             ));
 
+            if ($this instanceof EventSubscriberInterface) {
+                $container->register('kernel', static::class)
+                    ->setSynthetic(true)
+                    ->addTag('kernel.event_subscriber')
+                ;
+            }
+
             $this->configureContainer($container, $loader);
 
             $container->addObjectResource($this);

src/Symfony/Bundle/FrameworkBundle/Tests/Kernel/ConcreteMicroKernel.php

@@ -15,22 +15,37 @@ use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
 use Symfony\Bundle\FrameworkBundle\FrameworkBundle;
 use Symfony\Component\Config\Loader\LoaderInterface;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 use Symfony\Component\Filesystem\Filesystem;
 use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent;
 use Symfony\Component\HttpKernel\Kernel;
+use Symfony\Component\HttpKernel\KernelEvents;
 use Symfony\Component\Routing\RouteCollectionBuilder;
 
-class ConcreteMicroKernel extends Kernel
+class ConcreteMicroKernel extends Kernel implements EventSubscriberInterface
 {
     use MicroKernelTrait;
 
     private $cacheDir;
 
+    public function onKernelException(GetResponseForExceptionEvent $event)
+    {
+        if ($event->getException() instanceof Danger) {
+            $event->setResponse(Response::create('It\'s dangerous to go alone. Take this ⚔'));
+        }
+    }
+
     public function halloweenAction()
     {
         return new Response('halloween');
     }
 
+    public function dangerousAction()
+    {
+        throw new Danger();
+    }
+
     public function registerBundles()
     {
         return array(
@@ -57,6 +72,7 @@ class ConcreteMicroKernel extends Kernel
     protected function configureRoutes(RouteCollectionBuilder $routes)
     {
         $routes->add('/', 'kernel:halloweenAction');
+        $routes->add('/danger', 'kernel:dangerousAction');
     }
 
     protected function configureContainer(ContainerBuilder $c, LoaderInterface $loader)
@@ -68,4 +84,18 @@ class ConcreteMicroKernel extends Kernel
         $c->setParameter('halloween', 'Have a great day!');
         $c->register('halloween', 'stdClass');
     }
+
+    /**
+     * {@inheritdoc}
+     */
+    public static function getSubscribedEvents()
+    {
+        return array(
+            KernelEvents::EXCEPTION => 'onKernelException',
+        );
+    }
+}
+
+class Danger extends \RuntimeException
+{
 }

src/Symfony/Bundle/FrameworkBundle/Tests/Kernel/MicroKernelTraitTest.php

@@ -28,4 +28,15 @@ class MicroKernelTraitTest extends TestCase
         $this->assertEquals('Have a great day!', $kernel->getContainer()->getParameter('halloween'));
         $this->assertInstanceOf('stdClass', $kernel->getContainer()->get('halloween'));
     }
+
+    public function testAsEventSubscriber()
+    {
+        $kernel = new ConcreteMicroKernel('test', true);
+        $kernel->boot();
+
+        $request = Request::create('/danger');
+        $response = $kernel->handle($request);
+
+        $this->assertSame('It\'s dangerous to go alone. Take this ⚔', $response->getContent());
+    }
 }