Auto-register kernel as an extension

src/Symfony/Component/HttpKernel/CHANGELOG.md

@@ -11,6 +11,7 @@ CHANGELOG
  * content of request parameter `_password` is now also hidden
    in the request profiler raw content section
  * Allowed adding attributes on controller arguments that will be passed to argument resolvers.
+ * kernels implementing the `ExtensionInterface` will now be auto-registered to the container
 
 5.1.0
 -----

src/Symfony/Component/HttpKernel/Kernel.php

@@ -23,6 +23,7 @@ use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\DependencyInjection\Dumper\PhpDumper;
 use Symfony\Component\DependencyInjection\Dumper\Preloader;
+use Symfony\Component\DependencyInjection\Extension\ExtensionInterface;
 use Symfony\Component\DependencyInjection\Loader\ClosureLoader;
 use Symfony\Component\DependencyInjection\Loader\DirectoryLoader;
 use Symfony\Component\DependencyInjection\Loader\GlobFileLoader;
@@ -688,6 +689,9 @@ abstract class Kernel implements KernelInterface, RebootableInterface, Terminabl
         $container = new ContainerBuilder();
         $container->getParameterBag()->add($this->getKernelParameters());
 
+        if ($this instanceof ExtensionInterface) {
+            $container->registerExtension($this);
+        }
         if ($this instanceof CompilerPassInterface) {
             $container->addCompilerPass($this, PassConfig::TYPE_BEFORE_OPTIMIZATION, -10000);
         }

src/Symfony/Component/HttpKernel/Tests/KernelTest.php

@@ -16,6 +16,7 @@ use Symfony\Component\Config\Loader\LoaderInterface;
 use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\DependencyInjection\Extension\ExtensionInterface;
 use Symfony\Component\Filesystem\Filesystem;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
@@ -475,6 +476,34 @@ EOF;
         $this->assertFileExists(\dirname($containerFile).'.legacy');
     }
 
+    public function testKernelExtension()
+    {
+        $kernel = new class() extends CustomProjectDirKernel implements ExtensionInterface {
+            public function load(array $configs, ContainerBuilder $container)
+            {
+                $container->setParameter('test.extension-registered', true);
+            }
+
+            public function getNamespace()
+            {
+                return '';
+            }
+
+            public function getXsdValidationBasePath()
+            {
+                return false;
+            }
+
+            public function getAlias()
+            {
+                return 'test-extension';
+            }
+        };
+        $kernel->boot();
+
+        $this->assertTrue($kernel->getContainer()->getParameter('test.extension-registered'));
+    }
+
     public function testKernelPass()
     {
         $kernel = new PassKernel();