RestConfigSubscriber.php

<?php

namespace Drupal\rest\EventSubscriber;

use Drupal\Core\Config\ConfigCrudEvent;
use Drupal\Core\Config\ConfigEvents;
use Drupal\Core\Routing\RouteBuilderInterface;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

/**
 * A subscriber triggering a route rebuild when certain configuration changes.
 */
class RestConfigSubscriber implements EventSubscriberInterface {
    
    /**
     * The router builder.
     *
     * @var \Drupal\Core\Routing\RouteBuilderInterface
     */
    protected $routerBuilder;
    
    /**
     * Constructs the RestConfigSubscriber.
     *
     * @param \Drupal\Core\Routing\RouteBuilderInterface $router_builder
     *   The router builder service.
     */
    public function __construct(RouteBuilderInterface $router_builder) {
        $this->routerBuilder = $router_builder;
    }
    
    /**
     * Informs the router builder a rebuild is needed when necessary.
     *
     * @param \Drupal\Core\Config\ConfigCrudEvent $event
     *   The Event to process.
     */
    public function onSave(ConfigCrudEvent $event) {
        $saved_config = $event->getConfig();
        // @see \Drupal\rest\Plugin\rest\resource\EntityResource::permissions()
        if ($saved_config->getName() === 'rest.settings' && $event->isChanged('bc_entity_resource_permissions')) {
            $this->routerBuilder
                ->setRebuildNeeded();
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() {
        $events[ConfigEvents::SAVE][] = [
            'onSave',
        ];
        return $events;
    }

}