class RegisterEntityResolversCompilerPass

class RegisterEntityResolversCompilerPass implements CompilerPassInterface {

  /**
   * Adds services to the Serializer.
   *
   * @param \Symfony\Component\DependencyInjection\ContainerBuilder $container
   *   The container to process.
   */
  public function process(ContainerBuilder $container) {
    $definition = $container
      ->getDefinition('serializer.entity_resolver');

    // Retrieve registered Normalizers and Encoders from the container.
    foreach ($container
      ->findTaggedServiceIds('entity_resolver') as $id => $attributes) {
      $priority = isset($attributes[0]['priority']) ? $attributes[0]['priority'] : 0;
      $resolvers[$priority][] = new Reference($id);
    }

    // Add the registered concrete EntityResolvers to the ChainEntityResolver.
    if (!empty($resolvers)) {
      $definition
        ->replaceArgument(0, $this
        ->sort($resolvers));
    }
  }

  /**
   * Sorts by priority.
   *
   * Order services from highest priority number to lowest (reverse sorting).
   *
   * @param array $services
   *   A nested array keyed on priority number. For each priority number, the
   *   value is an array of Symfony\Component\DependencyInjection\Reference
   *   objects, each a reference to a normalizer or encoder service.
   *
   * @return array
   *   A flattened array of Reference objects from $services, ordered from high
   *   to low priority.
   */
  protected function sort($services) {
    $sorted = array();
    krsort($services);

    // Flatten the array.
    foreach ($services as $a) {
      $sorted = array_merge($sorted, $a);
    }
    return $sorted;
  }

}