Issue #3130341 by jungle, longwave, catch, xjm: [backport] Remove...

use Drupal\Core\Site\Settings;

use Drupal\Core\StackMiddleware\ReverseProxyMiddleware;

use Symfony\Cmf\Component\Routing\RouteObjectInterface;

use Symfony\Component\DependencyInjection\ContainerInterface;

use Symfony\Component\HttpFoundation\ParameterBag;

use Symfony\Component\HttpFoundation\Request;

use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;

    }

  }

  /**

   * {@inheritdoc}

   */

  public function loadLegacyIncludes() {

    parent::loadLegacyIncludes();

    static::fixSerializedExtensionObjects($this->container);

  }

  /**

   * Fixes caches and theme info if they contain old Extension objects.

   *

   * @param \Symfony\Component\DependencyInjection\ContainerInterface $container

   *   The container.

   *

   * @internal

   *   This function is only to be called by the Drupal core update process.

   *   Additionally, this function will be removed in minor release of Drupal.

   *

   * @todo https://www.drupal.org/project/drupal/issues/3031322 Remove once

   *   Drupal 8.6.x is not supported.

   */

  public static function fixSerializedExtensionObjects(ContainerInterface $container) {

    // Create a custom error handler that will clear caches if a warning occurs

    // while getting 'system.theme.data' from state. If this state value was

    // created by Drupal <= 8.6.7 then when it is read by Drupal >= 8.6.8 there

    // will be PHP warnings. This silently fixes Drupal so that the update can

    // continue.

    $clear_caches = FALSE;

    $callable = function ($errno, $errstr) use ($container, &$clear_caches) {

      if ($errstr === 'Class Drupal\Core\Extension\Extension has no unserializer') {

        $clear_caches = TRUE;

      }

    };

    set_error_handler($callable, E_ERROR | E_WARNING);

    $container->get('state')->get('system.theme.data', []);

    restore_error_handler();

    if ($clear_caches) {

      // Reset static caches in profile list so the module list is rebuilt

      // correctly.

      $container->get('extension.list.profile')->reset();

      foreach ($container->getParameter('cache_bins') as $service_id => $bin) {

        $container->get($service_id)->deleteAll();

      }

      // The system.theme.data key is no longer used in Drupal 8.7.x.

      $container->get('state')->delete('system.theme.data');

      // Also rebuild themes because it uses state as cache.

      $container->get('theme_handler')->refreshInfo();

    }

  }

}

   */

  public function testUpdate() {

    $connection = Database::getConnection();

    // Ensure \Drupal\Core\Update\UpdateKernel::fixSerializedExtensionObjects()

    // does not clear the cache.

    $connection->delete('key_value')

      ->condition('collection', 'state')

      ->condition('name', 'system.theme.data')

      ->execute();

    // Create broken element info caches entries.

    $insert = $connection->upsert('cache_discovery');