Issue #2318281 by tim.plunkett, dawehner | kim.pepper: Provide a standard way...

Issue #2318281 by tim.plunkett, dawehner | kim.pepper: Provide a standard way to check a plugin is an instance of the required interface.

core/lib/Drupal/Component/Plugin/Factory/DefaultFactory.php

@@ -8,7 +8,6 @@
 
 use Drupal\Component\Plugin\Discovery\DiscoveryInterface;
 use Drupal\Component\Plugin\Exception\PluginException;
-use Drupal\Component\Plugin\Derivative\DeriverInterface;
 
 /**
  * Default plugin factory.
@@ -30,11 +29,24 @@ class DefaultFactory implements FactoryInterface {
    */
   protected $discovery;
 
+  /**
+   * Defines an interface each plugin should implement.
+   *
+   * @var string|null
+   */
+  protected $interface;
+
   /**
    * Constructs a Drupal\Component\Plugin\Factory\DefaultFactory object.
+   *
+   * @param \Drupal\Component\Plugin\Discovery\DiscoveryInterface $discovery
+   *   The plugin discovery.
+   * @param string|null $plugin_interface
+   *   (optional) The interface each plugin should implement.
    */
-  public function __construct(DiscoveryInterface $discovery) {
+  public function __construct(DiscoveryInterface $discovery, $plugin_interface = NULL) {
     $this->discovery = $discovery;
+    $this->interface = $plugin_interface;
   }
 
   /**
@@ -42,7 +54,7 @@ public function __construct(DiscoveryInterface $discovery) {
    */
   public function createInstance($plugin_id, array $configuration = array()) {
     $plugin_definition = $this->discovery->getDefinition($plugin_id);
-    $plugin_class = static::getPluginClass($plugin_id, $plugin_definition);
+    $plugin_class = static::getPluginClass($plugin_id, $plugin_definition, $this->interface);
     return new $plugin_class($configuration, $plugin_id, $plugin_definition);
   }
 
@@ -53,13 +65,18 @@ public function createInstance($plugin_id, array $configuration = array()) {
    *   The id of a plugin.
    * @param mixed $plugin_definition
    *   The plugin definition associated with the plugin ID.
+   * @param string $required_interface
+   *   (optional) THe required plugin interface.
    *
    * @return string
    *   The appropriate class name.
    *
    * @throws \Drupal\Component\Plugin\Exception\PluginException
+   *   Thrown when there is no class specified, the class doesn't exist, or
+   *   the class does not implement the specified required interface.
+   *
    */
-  public static function getPluginClass($plugin_id, $plugin_definition = NULL) {
+  public static function getPluginClass($plugin_id, $plugin_definition = NULL, $required_interface = NULL) {
     if (empty($plugin_definition['class'])) {
       throw new PluginException(sprintf('The plugin (%s) did not specify an instance class.', $plugin_id));
     }
@@ -70,6 +87,10 @@ public static function getPluginClass($plugin_id, $plugin_definition = NULL) {
       throw new PluginException(sprintf('Plugin (%s) instance class "%s" does not exist.', $plugin_id, $class));
     }
 
+    if ($required_interface && !is_subclass_of($plugin_definition['class'], $required_interface)) {
+      throw new PluginException(sprintf('Plugin "%s" (%s) in %s should implement interface %s.', $plugin_id, $plugin_definition['class'], $plugin_definition['provider'], $required_interface));
+    }
+
     return $class;
   }
 }

core/lib/Drupal/Component/Plugin/Factory/ReflectionFactory.php

@@ -19,7 +19,7 @@ class ReflectionFactory extends DefaultFactory {
    */
   public function createInstance($plugin_id, array $configuration = array()) {
     $plugin_definition = $this->discovery->getDefinition($plugin_id);
-    $plugin_class = static::getPluginClass($plugin_id, $plugin_definition);
+    $plugin_class = static::getPluginClass($plugin_id, $plugin_definition, $this->interface);
 
     // Lets figure out of there's a constructor for this class and pull
     // arguments from the $options array if so to populate it.

core/lib/Drupal/Core/Action/ActionManager.php

@@ -33,7 +33,7 @@ class ActionManager extends DefaultPluginManager {
    *   The module handler to invoke the alter hook with.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
-    parent::__construct('Plugin/Action', $namespaces, $module_handler, 'Drupal\Core\Annotation\Action');
+    parent::__construct('Plugin/Action', $namespaces, $module_handler, 'Drupal\Core\Action\ActionInterface', 'Drupal\Core\Annotation\Action');
     $this->alterInfo('action_info');
     $this->setCacheBackend($cache_backend, 'action_info');
   }

core/lib/Drupal/Core/Archiver/ArchiverManager.php

 <?php
 
 /**
+ * @file
  * Contains \Drupal\Core\Archiver\ArchiverManager.
  */
 
@@ -32,7 +33,7 @@ class ArchiverManager extends DefaultPluginManager {
    *   The module handler to invoke the alter hook with.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
-    parent::__construct('Plugin/Archiver', $namespaces, $module_handler, 'Drupal\Core\Archiver\Annotation\Archiver');
+    parent::__construct('Plugin/Archiver', $namespaces, $module_handler, 'Drupal\Core\Archiver\ArchiverInterface', 'Drupal\Core\Archiver\Annotation\Archiver');
     $this->alterInfo('archiver_info');
     $this->setCacheBackend($cache_backend, 'archiver_info_plugins');
   }
@@ -42,7 +43,7 @@ public function __construct(\Traversable $namespaces, CacheBackendInterface $cac
    */
   public function createInstance($plugin_id, array $configuration = array()) {
     $plugin_definition = $this->getDefinition($plugin_id);
-    $plugin_class = DefaultFactory::getPluginClass($plugin_id, $plugin_definition);
+    $plugin_class = DefaultFactory::getPluginClass($plugin_id, $plugin_definition, 'Drupal\Core\Archiver\ArchiverInterface');
     return new $plugin_class($configuration['filepath']);
   }
 

core/lib/Drupal/Core/Block/BlockManager.php

@@ -44,7 +44,7 @@ class BlockManager extends DefaultPluginManager implements BlockManagerInterface
    *   The module handler to invoke the alter hook with.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
-    parent::__construct('Plugin/Block', $namespaces, $module_handler, 'Drupal\Core\Block\Annotation\Block');
+    parent::__construct('Plugin/Block', $namespaces, $module_handler, 'Drupal\Core\Block\BlockPluginInterface', 'Drupal\Core\Block\Annotation\Block');
 
     $this->alterInfo('block');
     $this->setCacheBackend($cache_backend, 'block_plugins');

core/lib/Drupal/Core/Condition/ConditionManager.php

@@ -42,7 +42,7 @@ public function __construct(\Traversable $namespaces, CacheBackendInterface $cac
     $this->alterInfo('condition_info');
     $this->setCacheBackend($cache_backend, 'condition_plugins');
 
-    parent::__construct('Plugin/Condition', $namespaces, $module_handler, 'Drupal\Core\Condition\Annotation\Condition');
+    parent::__construct('Plugin/Condition', $namespaces, $module_handler, 'Drupal\Core\Condition\ConditionInterface', 'Drupal\Core\Condition\Annotation\Condition');
   }
 
   /**

core/lib/Drupal/Core/Display/VariantManager.php

@@ -31,7 +31,7 @@ class VariantManager extends DefaultPluginManager {
    *   The module handler to invoke the alter hook with.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
-    parent::__construct('Plugin/DisplayVariant', $namespaces, $module_handler, 'Drupal\Core\Display\Annotation\DisplayVariant');
+    parent::__construct('Plugin/DisplayVariant', $namespaces, $module_handler, 'Drupal\Core\Display\VariantInterface', 'Drupal\Core\Display\Annotation\DisplayVariant');
 
     $this->setCacheBackend($cache_backend, 'variant_plugins');
     $this->alterInfo('display_variant_plugin');

core/lib/Drupal/Core/Entity/EntityManager.php

@@ -171,7 +171,7 @@ class EntityManager extends DefaultPluginManager implements EntityManagerInterfa
    *   The class resolver.
    */
   public function __construct(\Traversable $namespaces, ModuleHandlerInterface $module_handler, CacheBackendInterface $cache, LanguageManagerInterface $language_manager, TranslationInterface $translation_manager, ClassResolverInterface $class_resolver, TypedDataManager $typed_data_manager) {
-    parent::__construct('Entity', $namespaces, $module_handler, 'Drupal\Core\Entity\Annotation\EntityType');
+    parent::__construct('Entity', $namespaces, $module_handler, 'Drupal\Core\Entity\EntityInterface', 'Drupal\Core\Entity\Annotation\EntityType');
 
     $this->setCacheBackend($cache, 'entity_type', array('entity_types' => TRUE));
     $this->alterInfo('entity_type');

core/lib/Drupal/Core/Field/FieldTypePluginManager.php

@@ -31,7 +31,7 @@ class FieldTypePluginManager extends DefaultPluginManager implements FieldTypePl
    *   The module handler.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
-    parent::__construct('Plugin/Field/FieldType', $namespaces, $module_handler, 'Drupal\Core\Field\Annotation\FieldType');
+    parent::__construct('Plugin/Field/FieldType', $namespaces, $module_handler, 'Drupal\Core\Field\FieldItemInterface', 'Drupal\Core\Field\Annotation\FieldType');
     $this->alterInfo('field_info');
     $this->setCacheBackend($cache_backend, 'field_types_plugins');
   }

core/lib/Drupal/Core/Field/FormatterPluginManager.php

@@ -47,8 +47,7 @@ class FormatterPluginManager extends DefaultPluginManager {
    *   The 'field type' plugin manager.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler, FieldTypePluginManagerInterface $field_type_manager) {
-
-    parent::__construct('Plugin/Field/FieldFormatter', $namespaces, $module_handler, 'Drupal\Core\Field\Annotation\FieldFormatter');
+    parent::__construct('Plugin/Field/FieldFormatter', $namespaces, $module_handler, 'Drupal\Core\Field\FormatterInterface', 'Drupal\Core\Field\Annotation\FieldFormatter');
 
     $this->setCacheBackend($cache_backend, 'field_formatter_types_plugins');
     $this->alterInfo('field_formatter_info');

core/lib/Drupal/Core/Field/WidgetFactory.php

@@ -19,7 +19,7 @@ class WidgetFactory extends DefaultFactory {
    */
   public function createInstance($plugin_id, array $configuration = array()) {
     $plugin_definition = $this->discovery->getDefinition($plugin_id);
-    $plugin_class = static::getPluginClass($plugin_id, $plugin_definition);
+    $plugin_class = static::getPluginClass($plugin_id, $plugin_definition, $this->interface);
     return new $plugin_class($plugin_id, $plugin_definition, $configuration['field_definition'], $configuration['settings']);
   }
 }

core/lib/Drupal/Core/Field/WidgetPluginManager.php

@@ -47,7 +47,7 @@ class WidgetPluginManager extends DefaultPluginManager {
    *   The 'field type' plugin manager.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler, FieldTypePluginManagerInterface $field_type_manager) {
-    parent::__construct('Plugin/Field/FieldWidget', $namespaces, $module_handler, 'Drupal\Core\Field\Annotation\FieldWidget');
+    parent::__construct('Plugin/Field/FieldWidget', $namespaces, $module_handler, 'Drupal\Core\Field\WidgetInterface', 'Drupal\Core\Field\Annotation\FieldWidget');
 
     $this->setCacheBackend($cache_backend, 'field_widget_types_plugins');
     $this->alterInfo('field_widget_info');

core/lib/Drupal/Core/ImageToolkit/ImageToolkitManager.php

@@ -43,7 +43,7 @@ class ImageToolkitManager extends DefaultPluginManager {
    *   The config factory.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler, ConfigFactoryInterface $config_factory) {
-    parent::__construct('Plugin/ImageToolkit', $namespaces, $module_handler, 'Drupal\Core\ImageToolkit\Annotation\ImageToolkit');
+    parent::__construct('Plugin/ImageToolkit', $namespaces, $module_handler, 'Drupal\Core\ImageToolkit\ImageToolkitInterface', 'Drupal\Core\ImageToolkit\Annotation\ImageToolkit');
 
     $this->setCacheBackend($cache_backend, 'image_toolkit_plugins');
     $this->configFactory = $config_factory;

core/lib/Drupal/Core/ImageToolkit/ImageToolkitOperationManager.php

@@ -46,7 +46,7 @@ class ImageToolkitOperationManager extends DefaultPluginManager implements Image
    *   A logger instance.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler, LoggerInterface $logger) {
-    parent::__construct('Plugin/ImageToolkit/Operation', $namespaces, $module_handler, 'Drupal\Core\ImageToolkit\Annotation\ImageToolkitOperation');
+    parent::__construct('Plugin/ImageToolkit/Operation', $namespaces, $module_handler, 'Drupal\Core\ImageToolkit\ImageToolkitOperationInterface', 'Drupal\Core\ImageToolkit\Annotation\ImageToolkitOperation');
 
     $this->alterInfo('image_toolkit_operation');
     $this->setCacheBackend($cache_backend, 'image_toolkit_operation_plugins');

core/lib/Drupal/Core/Mail/MailManager.php

@@ -12,8 +12,6 @@
 use Drupal\Core\Cache\CacheBackendInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\Config\ConfigFactoryInterface;
-use Drupal\Component\Utility\String;
-use Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException;
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 use Drupal\Core\StringTranslation\TranslationInterface;
 
@@ -67,7 +65,7 @@ class MailManager extends DefaultPluginManager implements MailManagerInterface {
    *   The string translation service.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler, ConfigFactoryInterface $config_factory, LoggerChannelFactoryInterface $logger_factory, TranslationInterface $string_translation) {
-    parent::__construct('Plugin/Mail', $namespaces, $module_handler, 'Drupal\Core\Annotation\Mail');
+    parent::__construct('Plugin/Mail', $namespaces, $module_handler, 'Drupal\Core\Mail\MailInterface', 'Drupal\Core\Annotation\Mail');
     $this->alterInfo('mail_backend_info');
     $this->setCacheBackend($cache_backend, 'mail_backend_plugins');
     $this->configFactory = $config_factory;
@@ -149,16 +147,7 @@ public function getInstance(array $options) {
     }
 
     if (empty($this->instances[$plugin_id])) {
-      $plugin = $this->createInstance($plugin_id);
-      if (is_subclass_of($plugin, '\Drupal\Core\Mail\MailInterface')) {
-        $this->instances[$plugin_id] = $plugin;
-      }
-      else {
-        throw new InvalidPluginDefinitionException($plugin_id, String::format('Class %class does not implement interface %interface', array(
-          '%class' => get_class($plugin),
-          '%interface' => 'Drupal\Core\Mail\MailInterface',
-        )));
-      }
+      $this->instances[$plugin_id] = $this->createInstance($plugin_id);
     }
     return $this->instances[$plugin_id];
   }

core/lib/Drupal/Core/Menu/ContextualLinkManager.php

@@ -105,7 +105,7 @@ class ContextualLinkManager extends DefaultPluginManager implements ContextualLi
   public function __construct(ControllerResolverInterface $controller_resolver, ModuleHandlerInterface $module_handler, CacheBackendInterface $cache_backend, LanguageManagerInterface $language_manager, AccessManagerInterface $access_manager, AccountInterface $account, RequestStack $request_stack) {
     $this->discovery = new YamlDiscovery('links.contextual', $module_handler->getModuleDirectories());
     $this->discovery = new ContainerDerivativeDiscoveryDecorator($this->discovery);
-    $this->factory = new ContainerFactory($this);
+    $this->factory = new ContainerFactory($this, '\Drupal\Core\Menu\ContextualLinkInterface');
 
     $this->controllerResolver = $controller_resolver;
     $this->accessManager = $access_manager;

core/lib/Drupal/Core/Menu/LocalActionManager.php

@@ -116,7 +116,7 @@ public function __construct(ControllerResolverInterface $controller_resolver, Re
     // discovery.
     $this->discovery = new YamlDiscovery('links.action', $module_handler->getModuleDirectories());
     $this->discovery = new ContainerDerivativeDiscoveryDecorator($this->discovery);
-    $this->factory = new ContainerFactory($this);
+    $this->factory = new ContainerFactory($this, 'Drupal\Core\Menu\LocalActionInterface');
     $this->controllerResolver = $controller_resolver;
     $this->requestStack = $request_stack;
     $this->routeProvider = $route_provider;

core/lib/Drupal/Core/Menu/LocalTaskManager.php

@@ -126,7 +126,7 @@ class LocalTaskManager extends DefaultPluginManager implements LocalTaskManagerI
   public function __construct(ControllerResolverInterface $controller_resolver, RequestStack $request_stack, RouteProviderInterface $route_provider, RouteBuilderInterface $route_builder, ModuleHandlerInterface $module_handler, CacheBackendInterface $cache, LanguageManagerInterface $language_manager, AccessManagerInterface $access_manager, AccountInterface $account) {
     $this->discovery = new YamlDiscovery('links.task', $module_handler->getModuleDirectories());
     $this->discovery = new ContainerDerivativeDiscoveryDecorator($this->discovery);
-    $this->factory = new ContainerFactory($this);
+    $this->factory = new ContainerFactory($this, '\Drupal\Core\Menu\LocalTaskInterface');
     $this->controllerResolver = $controller_resolver;
     $this->requestStack = $request_stack;
     $this->routeProvider = $route_provider;

core/lib/Drupal/Core/Plugin/DefaultPluginManager.php

@@ -9,7 +9,6 @@
 
 use Drupal\Component\Plugin\Discovery\CachedDiscoveryInterface;
 use Drupal\Component\Plugin\Discovery\DiscoveryCachedTrait;
-use Drupal\Component\Plugin\Exception\PluginNotFoundException;
 use Drupal\Core\Plugin\Discovery\ContainerDerivativeDiscoveryDecorator;
 use Drupal\Component\Plugin\PluginManagerBase;
 use Drupal\Component\Plugin\PluginManagerInterface;
@@ -17,7 +16,6 @@
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Cache\CacheBackendInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
-use Drupal\Core\Language\LanguageManagerInterface;
 use Drupal\Core\Plugin\Discovery\AnnotatedClassDiscovery;
 use Drupal\Core\Plugin\Factory\ContainerFactory;
 
@@ -92,15 +90,17 @@ class DefaultPluginManager extends PluginManagerBase implements PluginManagerInt
    *   keyed by the corresponding namespace to look for plugin implementations.
    * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
    *   The module handler.
+   * @param string|null $plugin_interface
+   *   (optional) The interface each plugin should implement.
    * @param string $plugin_definition_annotation_name
    *   (optional) The name of the annotation that contains the plugin definition.
    *   Defaults to 'Drupal\Component\Annotation\Plugin'.
    */
-  public function __construct($subdir, \Traversable $namespaces, ModuleHandlerInterface $module_handler, $plugin_definition_annotation_name = 'Drupal\Component\Annotation\Plugin') {
+  public function __construct($subdir, \Traversable $namespaces, ModuleHandlerInterface $module_handler, $plugin_interface = NULL, $plugin_definition_annotation_name = 'Drupal\Component\Annotation\Plugin') {
     $this->subdir = $subdir;
     $this->discovery = new AnnotatedClassDiscovery($subdir, $namespaces, $plugin_definition_annotation_name);
     $this->discovery = new ContainerDerivativeDiscoveryDecorator($this->discovery);
-    $this->factory = new ContainerFactory($this);
+    $this->factory = new ContainerFactory($this, $plugin_interface);
     $this->moduleHandler = $module_handler;
   }
 

core/lib/Drupal/Core/Plugin/Factory/ContainerFactory.php

@@ -18,7 +18,7 @@ class ContainerFactory extends DefaultFactory {
    */
   public function createInstance($plugin_id, array $configuration = array()) {
     $plugin_definition = $this->discovery->getDefinition($plugin_id);
-    $plugin_class = static::getPluginClass($plugin_id, $plugin_definition);
+    $plugin_class = static::getPluginClass($plugin_id, $plugin_definition, $this->interface);
 
     // If the plugin provides a factory method, pass the container to it.
     if (is_subclass_of($plugin_class, 'Drupal\Core\Plugin\ContainerFactoryPluginInterface')) {

core/lib/Drupal/Core/Render/Element/Page.php

@@ -12,7 +12,7 @@
  *
  * @RenderElement("page")
  */
-class Page {
+class Page extends RenderElement {
 
   /**
    * {@inheritdoc}

core/lib/Drupal/Core/Render/ElementInfoManager.php

@@ -46,7 +46,7 @@ class ElementInfoManager extends DefaultPluginManager implements ElementInfoMana
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
     $this->setCacheBackend($cache_backend, 'element_info');
 
-    parent::__construct('Element', $namespaces, $module_handler, 'Drupal\Core\Render\Annotation\RenderElement');
+    parent::__construct('Element', $namespaces, $module_handler, 'Drupal\Core\Render\Element\ElementInterface', 'Drupal\Core\Render\Annotation\RenderElement');
   }
 
   /**

core/lib/Drupal/Core/TypedData/TypedDataManager.php

@@ -59,7 +59,7 @@ public function __construct(\Traversable $namespaces, CacheBackendInterface $cac
     $this->alterInfo('data_type_info');
     $this->setCacheBackend($cache_backend, 'typed_data_types_plugins');
 
-    parent::__construct('Plugin/DataType', $namespaces, $module_handler, 'Drupal\Core\TypedData\Annotation\DataType');
+    parent::__construct('Plugin/DataType', $namespaces, $module_handler, NULL, 'Drupal\Core\TypedData\Annotation\DataType');
   }
 
   /**

core/modules/aggregator/src/Plugin/AggregatorPluginManager.php

@@ -44,8 +44,13 @@ public function __construct($type, \Traversable $namespaces, CacheBackendInterfa
       'parser' => 'Drupal\aggregator\Annotation\AggregatorParser',
       'processor' => 'Drupal\aggregator\Annotation\AggregatorProcessor',
     );
+    $plugin_interfaces = array(
+      'fetcher' => 'Drupal\aggregator\Plugin\FetcherInterface',
+      'parser' => 'Drupal\aggregator\Plugin\ParserInterface',
+      'processor' => 'Drupal\aggregator\Plugin\ProcessorInterface',
+    );
 
-    parent::__construct("Plugin/aggregator/$type", $namespaces, $module_handler, $type_annotations[$type]);
+    parent::__construct("Plugin/aggregator/$type", $namespaces, $module_handler, $plugin_interfaces[$type], $type_annotations[$type]);
     $this->setCacheBackend($cache_backend, 'aggregator_' . $type . '_plugins');
   }
 

core/modules/ckeditor/src/CKEditorPluginManager.php

@@ -39,7 +39,7 @@ class CKEditorPluginManager extends DefaultPluginManager {
    *   The module handler to invoke the alter hook with.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
-    parent::__construct('Plugin/CKEditorPlugin', $namespaces, $module_handler, 'Drupal\ckeditor\Annotation\CKEditorPlugin');
+    parent::__construct('Plugin/CKEditorPlugin', $namespaces, $module_handler, 'Drupal\ckeditor\CKEditorPluginInterface', 'Drupal\ckeditor\Annotation\CKEditorPlugin');
     $this->alterInfo('ckeditor_plugin_info');
     $this->setCacheBackend($cache_backend, 'ckeditor_plugins');
   }

core/modules/config_translation/src/ConfigMapperManager.php

@@ -90,7 +90,7 @@ public function __construct(CacheBackendInterface $cache_backend, LanguageManage
     $this->discovery = new InfoHookDecorator($this->discovery, 'config_translation_info');
     $this->discovery = new ContainerDerivativeDiscoveryDecorator($this->discovery);
 
-    $this->factory = new ContainerFactory($this);
+    $this->factory = new ContainerFactory($this, '\Drupal\config_translation\ConfigMapperInterface');
 
     // Let others alter definitions with hook_config_translation_info_alter().
     $this->moduleHandler = $module_handler;

core/modules/editor/src/Plugin/EditorManager.php

@@ -33,7 +33,7 @@ class EditorManager extends DefaultPluginManager {
    *   The module handler to invoke the alter hook with.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
-    parent::__construct('Plugin/Editor', $namespaces, $module_handler, 'Drupal\editor\Annotation\Editor');
+    parent::__construct('Plugin/Editor', $namespaces, $module_handler, 'Drupal\editor\Plugin\EditorPluginInterface', 'Drupal\editor\Annotation\Editor');
     $this->alterInfo('editor_info');
     $this->setCacheBackend($cache_backend, 'editor_plugins');
   }

core/modules/entity_reference/src/Plugin/Type/SelectionPluginManager.php

@@ -36,7 +36,7 @@ public function __construct(\Traversable $namespaces, CacheBackendInterface $cac
 
     // We're not using the parent constructor because we use a different factory
     // method and don't need the derivative discovery decorator.
-    $this->factory = new ReflectionFactory($this);
+    $this->factory = new ReflectionFactory($this, '\Drupal\entity_reference\Plugin\Type\Selection\SelectionInterface');
 
     $this->moduleHandler = $module_handler;
     $this->alterInfo('entity_reference_selection');

core/modules/filter/src/FilterPluginManager.php

@@ -34,7 +34,7 @@ class FilterPluginManager extends DefaultPluginManager {
    *   The module handler to invoke the alter hook with.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
-    parent::__construct('Plugin/Filter', $namespaces, $module_handler, 'Drupal\filter\Annotation\Filter');
+    parent::__construct('Plugin/Filter', $namespaces, $module_handler, 'Drupal\filter\Plugin\FilterInterface', 'Drupal\filter\Annotation\Filter');
     $this->alterInfo('filter_info');
     $this->setCacheBackend($cache_backend, 'filter_plugins', array('filter_formats' => TRUE));
   }

core/modules/image/src/ImageEffectManager.php

@@ -36,7 +36,7 @@ class ImageEffectManager extends DefaultPluginManager {
    *   The module handler.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
-    parent::__construct('Plugin/ImageEffect', $namespaces, $module_handler, 'Drupal\image\Annotation\ImageEffect');
+    parent::__construct('Plugin/ImageEffect', $namespaces, $module_handler, 'Drupal\image\ImageEffectInterface', 'Drupal\image\Annotation\ImageEffect');
 
     $this->alterInfo('image_effect_info');
     $this->setCacheBackend($cache_backend, 'image_effect_plugins');

core/modules/language/src/LanguageNegotiationMethodManager.php

@@ -28,7 +28,7 @@ class LanguageNegotiationMethodManager extends DefaultPluginManager {
    *   An object that implements ModuleHandlerInterface
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
-    parent::__construct('Plugin/LanguageNegotiation', $namespaces, $module_handler);
+    parent::__construct('Plugin/LanguageNegotiation', $namespaces, $module_handler, 'Drupal\language\LanguageNegotiationMethodInterface');
     $this->cacheBackend = $cache_backend;
     $this->cacheKeyPrefix = 'language_negotiation_plugins';
     $this->cacheKey = 'language_negotiation_plugins';

core/modules/migrate/src/Plugin/MigratePluginManager.php

@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\migrate\MigraterPluginManager.
+ * Contains \Drupal\migrate\Plugin\MigratePluginManager.
  */
 
 namespace Drupal\migrate\Plugin;
@@ -46,7 +46,15 @@ class MigratePluginManager extends DefaultPluginManager {
    *   The annotation class name.
    */
   public function __construct($type, \Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler, $annotation = 'Drupal\Component\Annotation\PluginID') {
-    parent::__construct("Plugin/migrate/$type", $namespaces, $module_handler, $annotation);
+    $plugin_interface_map = array(
+      'destination' => 'Drupal\migrate\Plugin\MigrateDestinationInterface',
+      'process' => 'Drupal\migrate\Plugin\MigrateProcessInterface',
+      'source' => 'Drupal\migrate\Plugin\MigrateSourceInterface',
+      'id_map' => 'Drupal\migrate\Plugin\MigrateIdMapInterface',
+      'entity_field' => 'Drupal\migrate\Plugin\MigrateEntityDestinationFieldInterface',
+    );
+    $plugin_interface = isset($plugin_interface_map[$type]) ? $plugin_interface_map[$type] : NULL;
+    parent::__construct("Plugin/migrate/$type", $namespaces, $module_handler, $plugin_interface, $annotation);
     $this->alterInfo('migrate_' . $type . '_info');
     $this->setCacheBackend($cache_backend, 'migrate_plugins_' . $type);
   }

core/modules/migrate_drupal/migrate_drupal.services.yml

 services:
   plugin.manager.migrate.load:
-    class: Drupal\migrate\Plugin\MigratePluginManager
+    class: Drupal\migrate_drupal\Plugin\MigratePluginManager
     arguments: [load, '@container.namespaces', '@cache.discovery', '@module_handler']

core/modules/migrate_drupal/src/Plugin/MigrateLoadInterface.php

@@ -2,11 +2,12 @@
 
 /**
  * @file
- * Contains Drupal\migrate\Plugin\MigrateLoadInterface
+ * Contains Drupal\migrate_drupal\Plugin\MigrateLoadInterface
  */
 
 namespace Drupal\migrate_drupal\Plugin;
 
+use Drupal\Component\Plugin\PluginInspectionInterface;
 use Drupal\Core\Entity\EntityStorageInterface;
 
 /**
@@ -16,7 +17,7 @@
  *
  * @ingroup migration
  */
-interface MigrateLoadInterface {
+interface MigrateLoadInterface extends PluginInspectionInterface {
 
   /**
    * Load an additional migration.

core/modules/migrate_drupal/src/Plugin/MigratePluginManager.php

+<?php
+
+/**
+ * @file
+ * Contains \Drupal\migrate_drupal\Plugin\MigratePluginManager.
+ */
+
+namespace Drupal\migrate_drupal\Plugin;
+
+use Drupal\Core\Cache\CacheBackendInterface;
+use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\Plugin\Factory\ContainerFactory;
+use Drupal\migrate\Plugin\MigratePluginManager as BaseMigratePluginManager;
+
+/**
+ * Manages migrate_drupal plugins.
+ *
+ * @see plugin_api
+ *
+ * @ingroup migration
+ */
+class MigratePluginManager extends BaseMigratePluginManager {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function __construct($type, \Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler, $annotation = 'Drupal\Component\Annotation\PluginID') {
+    parent::__construct($type, $namespaces, $cache_backend, $module_handler, $annotation);
+
+    $this->factory = new ContainerFactory($this, 'Drupal\migrate_drupal\Plugin\MigrateLoadInterface');
+  }
+
+
+}

core/modules/quickedit/src/Plugin/InPlaceEditorManager.php

@@ -35,7 +35,7 @@ class InPlaceEditorManager extends DefaultPluginManager {
    *   The module handler to invoke the alter hook with.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
-    parent::__construct('Plugin/InPlaceEditor', $namespaces, $module_handler, 'Drupal\quickedit\Annotation\InPlaceEditor');
+    parent::__construct('Plugin/InPlaceEditor', $namespaces, $module_handler, 'Drupal\quickedit\Plugin\InPlaceEditorInterface', 'Drupal\quickedit\Annotation\InPlaceEditor');
     $this->alterInfo('quickedit_editor');
     $this->setCacheBackend($cache_backend, 'quickedit:editor');
   }

core/modules/rest/src/Plugin/Type/ResourcePluginManager.php

@@ -33,7 +33,7 @@ class ResourcePluginManager extends DefaultPluginManager {
    *   The module handler to invoke the alter hook with.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
-    parent::__construct('Plugin/rest/resource', $namespaces, $module_handler, 'Drupal\rest\Annotation\RestResource');
+    parent::__construct('Plugin/rest/resource', $namespaces, $module_handler, 'Drupal\rest\Plugin\ResourceInterface', 'Drupal\rest\Annotation\RestResource');
 
     $this->setCacheBackend($cache_backend, 'rest_plugins');
     $this->alterInfo('rest_resource');

core/modules/search/src/SearchPluginManager.php

@@ -28,7 +28,7 @@ class SearchPluginManager extends DefaultPluginManager {
    *   The module handler to invoke the alter hook with.
    */
   public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
-    parent::__construct('Plugin/Search', $namespaces, $module_handler, 'Drupal\search\Annotation\SearchPlugin');
+    parent::__construct('Plugin/Search', $namespaces, $module_handler, 'Drupal\search\Plugin\SearchInterface', 'Drupal\search\Annotation\SearchPlugin');
     $this->setCacheBackend($cache_backend, 'search_plugins');
     $this->alterInfo('search_plugin');
   }

core/modules/system/src/Tests/Plugin/Discovery/AnnotatedClassDiscoveryTest.php

@@ -43,6 +43,13 @@ protected function setUp() {
         'class' => 'Drupal\plugin_test\Plugin\plugin_test\fruit\Cherry',
         'provider' => 'plugin_test',
       ),
+      'kale' => array(
+        'id' => 'kale',
+        'label' => 'Kale',
+        'color' => 'green',
+        'class' => 'Drupal\plugin_test\Plugin\plugin_test\fruit\Kale',
+        'provider' => 'plugin_test',
+      ),
       'orange' => array(
         'id' => 'orange',
         'label' => 'Orange',

core/modules/system/src/Tests/Plugin/Discovery/CustomDirectoryAnnotatedClassDiscoveryTest.php

@@ -57,6 +57,13 @@ protected function setUp() {
         'class' => 'Drupal\plugin_test\Plugin\plugin_test\fruit\Cherry',
         'provider' => 'plugin_test',
       ),
+      'kale' => array(
+        'id' => 'kale',
+        'label' => 'Kale',
+        'color' => 'green',
+        'class' => 'Drupal\plugin_test\Plugin\plugin_test\fruit\Kale',
+        'provider' => 'plugin_test',
+      ),
       'orange' => array(
         'id' => 'orange',
         'label' => 'Orange',

core/modules/system/tests/modules/plugin_test/src/Plugin/DefaultsTestPluginManager.php

@@ -29,7 +29,7 @@ public function __construct(ModuleHandlerInterface $module_handler) {
     // discovery implementation, but StaticDiscovery lets us add some simple
     // mock plugins for unit testing.
     $this->discovery = new StaticDiscovery();
-    $this->factory = new DefaultFactory($this);
+    $this->factory = new DefaultFactory($this, 'Drupal\Component\Plugin\PluginInspectionInterface');
     $this->moduleHandler = $module_handler;
 
     // Specify default values.

core/modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/fruit/Apple.php

@@ -14,4 +14,4 @@
  *   color = "green"
  * )
  */
-class Apple {}
+class Apple implements FruitInterface {}

core/modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/fruit/Banana.php

@@ -17,6 +17,6 @@
  *   }
  * )
  */
-class Banana {
+class Banana implements FruitInterface {
 
 }

core/modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/fruit/Cherry.php

@@ -14,4 +14,4 @@
  *   color = "red"
  * )
  */
-class Cherry {}
+class Cherry implements FruitInterface {}

core/modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/fruit/FruitInterface.php

+<?php
+
+/**
+ * @file
+ * Contains \Drupal\plugin_test\Plugin\plugin_test\fruit\FruitInterface.
+ */
+
+namespace Drupal\plugin_test\Plugin\plugin_test\fruit;
+
+/**
+ * Provides an interface for test plugins.
+ */
+interface FruitInterface { }
+

core/modules/system/tests/modules/plugin_test/src/Plugin/plugin_test/fruit/Kale.php

+<?php
+
+/**
+ * @file
+ * Contains \Drupal\plugin_test\Plugin\plugin_test\fruit\Kale.
+ */
+
+namespace Drupal\plugin_test\Plugin\plugin_test\fruit;
+
+/**
+ * @Plugin(