Issue #3309334 by el7cosmos, smustgrave: Service collector won't collect child services

(cherry picked from commit 9e52085b)

core/lib/Drupal/Core/DependencyInjection/Compiler/TaggedHandlersPass.php

@@ -3,8 +3,10 @@
 namespace Drupal\Core\DependencyInjection\Compiler;
 
 use Drupal\Component\Utility\Reflection;
+use Symfony\Component\DependencyInjection\ChildDefinition;
 use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Definition;
 use Symfony\Component\DependencyInjection\Exception\LogicException;
 use Symfony\Component\DependencyInjection\Reference;
 
@@ -180,7 +182,8 @@ protected function processServiceCollectorPass(array $pass, $consumer_id, Contai
     foreach ($this->tagCache[$tag] ?? [] as $id => $attributes) {
       // Validate the interface.
       $handler = $container->getDefinition($id);
-      if (!is_a($handler->getClass(), $interface, TRUE)) {
+      $class = $this->resolveDefinitionClass($handler, $container);
+      if (!is_a($class, $interface, TRUE)) {
         throw new LogicException("Service '$id' for consumer '$consumer_id' does not implement $interface.");
       }
       $handlers[$id] = $attributes[0]['priority'] ?? 0;
@@ -251,4 +254,33 @@ protected function processServiceIdCollectorPass(array $pass, $consumer_id, Cont
     $consumer->addArgument(array_keys($handlers));
   }
 
+  /**
+   * Resolves the definition class.
+   *
+   * @param \Symfony\Component\DependencyInjection\Definition $definition
+   *   The service definition.
+   * @param \Symfony\Component\DependencyInjection\ContainerBuilder $container
+   *   The service container.
+   *
+   * @return class-string|null
+   *   The resolved class-string or null if the class cannot be resolved.
+   */
+  protected function resolveDefinitionClass(Definition $definition, ContainerBuilder $container): ?string {
+    $class = $definition->getClass();
+    if ($class) {
+      return $class;
+    }
+
+    if (!$definition instanceof ChildDefinition) {
+      return NULL;
+    }
+
+    if (!$container->hasDefinition($definition->getParent())) {
+      return NULL;
+    }
+
+    $parent = $container->getDefinition($definition->getParent());
+    return $this->resolveDefinitionClass($parent, $container);
+  }
+
 }

core/tests/Drupal/Tests/Core/DependencyInjection/Compiler/TaggedHandlersPassTest.php

@@ -6,6 +6,7 @@
 
 use Drupal\Core\DependencyInjection\Compiler\TaggedHandlersPass;
 use Drupal\Tests\UnitTestCase;
+use Symfony\Component\DependencyInjection\ChildDefinition;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Exception\LogicException;
 use Symfony\Component\DependencyInjection\Reference;
@@ -306,6 +307,31 @@ public function testProcessInterfaceMismatch(): void {
     $handler_pass->process($container);
   }
 
+  /**
+   * Tests child handler with parent service.
+   *
+   * @covers ::process
+   */
+  public function testProcessChildDefinition(): void {
+    $container = $this->buildContainer();
+
+    $container
+      ->register('consumer_id', __NAMESPACE__ . '\ValidConsumer')
+      ->addTag('service_collector');
+    $container
+      ->register('root_handler', __NAMESPACE__ . '\ValidHandler');
+    $container->addDefinitions([
+      'parent_handler' => new ChildDefinition('root_handler'),
+      'child_handler' => (new ChildDefinition('parent_handler'))->addTag('consumer_id'),
+    ]);
+
+    $handler_pass = new TaggedHandlersPass();
+    $handler_pass->process($container);
+
+    $method_calls = $container->getDefinition('consumer_id')->getMethodCalls();
+    $this->assertCount(1, $method_calls);
+  }
+
   /**
    * Tests consumer method with extra parameters.
    *