BackendCompilerPass.php in Service Container 7.2

Contains \Drupal\Core\DependencyInjection\Compiler\BackendCompilerPass.

Namespace

Drupal\Core\DependencyInjection\Compiler

File

lib/Drupal/Core/DependencyInjection/Compiler/BackendCompilerPass.php

<?php

/**
 * @file
 * Contains \Drupal\Core\DependencyInjection\Compiler\BackendCompilerPass.
 */
namespace Drupal\Core\DependencyInjection\Compiler;

use Symfony\Component\DependencyInjection\Alias;
use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
use Symfony\Component\DependencyInjection\ContainerBuilder;

/**
 * Defines a compiler pass to allow automatic override per backend.
 *
 * A module developer has to tag his backend service with "backend_overridable":
 * @code
 * custom_service:
 *   class: ...
 *   tags:
 *     - { name: backend_overridable }
 * @endcode
 *
 * As a site admin you set the 'default_backend' in your services.yml file:
 * @code
 * parameters:
 *   default_backend: sqlite
 * @endcode
 *
 * As a developer for alternative storage engines you register a service with
 * $yourbackend.$original_service:
 *
 * @code
 * sqlite.custom_service:
 *   class: ...
 * @endcode
 */
class BackendCompilerPass implements CompilerPassInterface {

  /**
   * {@inheritdoc}
   */
  public function process(ContainerBuilder $container) {
    if ($container
      ->hasParameter('default_backend')) {
      $default_backend = $container
        ->getParameter('default_backend');

      // Opt out from the default backend.
      if (!$default_backend) {
        return;
      }
    }
    else {
      try {
        $default_backend = $container
          ->get('database')
          ->driver();
        $container
          ->set('database', NULL);
      } catch (\Exception $e) {

        // If Drupal is not installed or a test doesn't define database there
        // is nothing to override.
        return;
      }
    }
    foreach ($container
      ->findTaggedServiceIds('backend_overridable') as $id => $attributes) {

      // If the service is already an alias it is not the original backend, so
      // we don't want to fallback to other storages any longer.
      if ($container
        ->hasAlias($id)) {
        continue;
      }
      if ($container
        ->hasDefinition("{$default_backend}.{$id}") || $container
        ->hasAlias("{$default_backend}.{$id}")) {
        $container
          ->setAlias($id, new Alias("{$default_backend}.{$id}"));
      }
    }
  }

}

Classes

Name	Description
BackendCompilerPass	Defines a compiler pass to allow automatic override per backend.