Issue #3368855 by steven jones: Set the admin path option on routes.

  "type": "drupal-module",

  "license": "GPL-2.0-or-later",

  "require": {

    "drupal/csv_serialization": "~1.4 || ~2.0 || ~3 || ~4"

    "drupal/csv_serialization": "~1.4 || ~2.0 || ~3 || ~4",

    "php": ">=8.0"

  },

  "require-dev": {

    "drupal/search_api": "~1.12",

use PhpOffice\PhpSpreadsheet\IOFactory;

use Symfony\Component\HttpFoundation\RedirectResponse;

use Symfony\Component\HttpKernel\Exception\ServiceUnavailableHttpException;

use Symfony\Component\Routing\RouteCollection;

/**

 * Provides a data export display plugin.

 */

class DataExport extends RestExport {

  /**

   * {@inheritdoc}

   */

  public function collectRoutes(RouteCollection $collection) {

    parent::collectRoutes($collection);

    // \Drupal\system\EventSubscriber\AdminRouteSubscriber will not apply the

    // _admin_route to the view as the route is not an HTML route - but the

    // batch should pick up the admin theme for this route if it begins with

    // /admin.

    if ($this->getOption('export_method') === 'batch' && str_starts_with($this->getOption('path') ?? '', 'admin/')) {

      $view_id = $this->view->storage->id();

      $display_id = $this->display['id'];

      if ($route = $collection->get("view.$view_id.$display_id")) {

        $route->setOption('_admin_route', TRUE);

      }

    }

  }

  /**

   * {@inheritdoc}

   */

   */

  protected function getRoute($view_id, $display_id) {

    $route = parent::getRoute($view_id, $display_id);

    $view = Views::getView($view_id);

    $view->setDisplay($display_id);

    // If this display is going to perform a redirect to the batch url

    // make sure thr redirect response is never cached.

    if ($view->display_handler->getOption('export_method') == 'batch') {

    if ($this->getOption('export_method') == 'batch') {

      $route->setOption('no_cache', TRUE);

      // Additionally if the path is an admin path we need to set the

      // _admin_route option to TRUE so the batch process is executed in the

      // same theme as we'd normally expect for the path even though this is

      // not an HTML route.

      if (str_starts_with($this->getOption('path') ?? '', 'admin/')) {

        $route->setOption('_admin_route', TRUE);

      }

    }

    return $route;

  }