Issue #3315088: Added fix to support back Drupal 8.

namespace Drupal\component;

use Drupal\Core\DependencyInjection\ContainerBuilder;

use Drupal\Core\DependencyInjection\ServiceProviderInterface;

use Drupal\Core\DependencyInjection\ServiceProviderBase;

use Symfony\Component\DependencyInjection\Reference;

class ComponentServiceProvider implements ServiceProviderInterface {

class ComponentServiceProvider extends ServiceProviderBase {

  /**

   * {@inheritdoc}

   */

  public function register(ContainerBuilder $container) {

  public function alter(ContainerBuilder $container) {

    // @todo Delete this when dropping Drupal 8 support.

    if ($container->has('component.discovery') && version_compare(\Drupal::VERSION, '9.0', '<')) {

      // @see https://www.drupal.org/project/drupal/issues/3074585

      $container->getDefinition('component.discovery')

        ->setArgument(0, '@app.root');

        ->setArgument(0, new Reference('app.root'));

    }

  }