feature #13761 Automatically process extensions when they implement C…

…ompilerPassInterface (WouterJ)

This PR was merged into the 2.7 branch.

Discussion
----------

Automatically process extensions when they implement CompilerPassInterface

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | todo (if people are in favor of this PR)

Compiler passes are very powerfull, but also quite strange to work with. Especially when you just need a very simple compiler pass (like https://github.com/symfony-cmf/RoutingBundle/blob/master/DependencyInjection/Compiler/SetRouterPass.php). For 3 lines of code, you need to tweak your bundle class and create a new class.

When using the DI component standalone, compiler passes are even harder to work with, as DI extensions can't register them. I believe that's why libraries like Behat make their extensions compiler passes by default.

I think it would be very easy to just implement an interface and have a `compile` method for the simple compiler pass stuff. If a bundle needs multiple compiler passes or need compiler passes to be executed at other times in the compile process, a bundle can use the normal compiler passes. But if it's just one simple thing, like replacing a definition or getting services with a specific tag, I think this method will be very usefull.

Commits
-------

6c50013 Allowed extensions to inline compiler passes

src/Symfony/Component/DependencyInjection/Compiler/ExtensionCompilerPass.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace Symfony\Component\DependencyInjection\Compiler;
+
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+
+/**
+ * A pass to automatically process extensions if they implement 
+ * CompilerPassInterface.
+ *
+ * @author Wouter J <wouter@wouterj.nl>
+ */
+class ExtensionCompilerPass implements CompilerPassInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function process(ContainerBuilder $container)
+    {
+        foreach ($container->getExtensions() as $extension) {
+            if (!$extension instanceof CompilerPassInterface) {
+                continue;
+            }
+
+            $extension->process($container);
+        }
+    }
+}

src/Symfony/Component/DependencyInjection/Compiler/PassConfig.php

@@ -45,6 +45,7 @@ public function __construct()
         $this->mergePass = new MergeExtensionConfigurationPass();
 
         $this->optimizationPasses = array(
+            new ExtensionCompilerPass(),
             new ResolveDefinitionTemplatesPass(),
             new DecoratorServicePass(),
             new ResolveParameterPlaceHoldersPass(),

src/Symfony/Component/DependencyInjection/Tests/Compiler/ExtensionCompilerPassTest.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace Symfony\Component\DependencyInjection\Tests\Compiler;
+
+use Symfony\Component\DependencyInjection\Compiler\ExtensionCompilerPass;
+
+/**
+ * @author Wouter J <wouter@wouterj.nl>
+ */
+class ExtensionCompilerPassTest extends \PHPUnit_Framework_TestCase
+{
+    private $container;
+    private $pass;
+
+    public function setUp()
+    {
+        $this->container = $this->getMock('Symfony\Component\DependencyInjection\ContainerBuilder');
+        $this->pass = new ExtensionCompilerPass();
+    }
+
+    public function testProcess()
+    {
+        $extension1 = $this->createExtensionMock(true);
+        $extension1->expects($this->once())->method('process');
+        $extension2 = $this->createExtensionMock(false);
+        $extension3 = $this->createExtensionMock(false);
+        $extension4 = $this->createExtensionMock(true);
+        $extension4->expects($this->once())->method('process');
+
+        $this->container->expects($this->any())
+            ->method('getExtensions')
+            ->will($this->returnValue(array($extension1, $extension2, $extension3, $extension4)))
+        ;
+
+        $this->pass->process($this->container);
+    }
+
+    private function createExtensionMock($hasInlineCompile)
+    {
+        return $this->getMock('Symfony\Component\DependencyInjection\\'.(
+            $hasInlineCompile
+            ? 'Compiler\CompilerPassInterface'
+            : 'Extension\ExtensionInterface'
+        ));
+    }
+}