RouteSubscriber.php

<?php

namespace Drupal\media_library\Routing;

use Drupal\Core\Routing\RouteSubscriberBase;
use Symfony\Component\Routing\RouteCollection;

/**
 * Subscriber for media library routes.
 *
 * @internal
 *   Tagged services are internal.
 */
class RouteSubscriber extends RouteSubscriberBase {
    
    /**
     * {@inheritdoc}
     */
    protected function alterRoutes(RouteCollection $collection) {
        // Add the media library UI access checks to the widget displays of the
        // media library view.
        if ($route = $collection->get('view.media_library.widget')) {
            $route->addRequirements([
                '_custom_access' => 'media_library.ui_builder:checkAccess',
            ]);
        }
        if ($route = $collection->get('view.media_library.widget_table')) {
            $route->addRequirements([
                '_custom_access' => 'media_library.ui_builder:checkAccess',
            ]);
        }
    }

}