Issue #3416826 by longwave, smustgrave, solideogloria, fgm: Queue factory services do not conform to an interface

core/lib/Drupal/Core/Queue/QueueDatabaseFactory.php

@@ -5,9 +5,9 @@ namespace Drupal\Core\Queue;
 use Drupal\Core\Database\Connection;
 
 /**
- * Defines the key/value store factory for the database backend.
+ * Defines the queue factory for the database backend.
  */
-class QueueDatabaseFactory {
+class QueueDatabaseFactory implements QueueFactoryInterface {
 
   /**
    * The database connection.
@@ -20,20 +20,14 @@ class QueueDatabaseFactory {
    * Constructs this factory object.
    *
    * @param \Drupal\Core\Database\Connection $connection
-   *   The Connection object containing the key-value tables.
+   *   The Connection object containing the queue table.
    */
   public function __construct(Connection $connection) {
     $this->connection = $connection;
   }
 
   /**
-   * Constructs a new queue object for a given name.
-   *
-   * @param string $name
-   *   The name of the collection holding key and value pairs.
-   *
-   * @return \Drupal\Core\Queue\DatabaseQueue
-   *   A key/value store implementation for the given $collection.
+   * {@inheritdoc}
    */
   public function get($name) {
     return new DatabaseQueue($name, $this->connection);

core/lib/Drupal/Core/Queue/QueueFactory.php

@@ -58,7 +58,11 @@ class QueueFactory implements ContainerAwareInterface {
       if (empty($service_name)) {
         $service_name = $this->settings->get('queue_service_' . $name, $this->settings->get('queue_default', 'queue.database'));
       }
-      $this->queues[$name] = $this->container->get($service_name)->get($name);
+      $factory = $this->container->get($service_name);
+      if (!$factory instanceof QueueFactoryInterface) {
+        @trigger_error(sprintf('Not implementing %s in %s is deprecated in drupal:10.3.0 and the factory will not be discovered in drupal:11.0.0. Implement the interface in your factory class. See https://www.drupal.org/node/3417034', QueueFactoryInterface::class, $factory::class), E_USER_DEPRECATED);
+      }
+      $this->queues[$name] = $factory->get($name);
     }
     return $this->queues[$name];
   }

core/lib/Drupal/Core/Queue/QueueFactoryInterface.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace Drupal\Core\Queue;
+
+/**
+ * An interface defining queue factory classes.
+ */
+interface QueueFactoryInterface {
+
+  /**
+   * Constructs a new queue object for a given name.
+   *
+   * @param string $name
+   *   The name of the queue.
+   *
+   * @return \Drupal\Core\Queue\QueueInterface
+   *   The queue object.
+   */
+  public function get($name);
+
+}