class RestPermissions

class RestPermissions implements ContainerInjectionInterface {
    
    /**
     * The rest resource plugin manager.
     *
     * @var \Drupal\rest\Plugin\Type\ResourcePluginManager
     */
    protected $restPluginManager;
    
    /**
     * The REST resource config storage.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $resourceConfigStorage;
    
    /**
     * Constructs a new RestPermissions instance.
     *
     * @param \Drupal\rest\Plugin\Type\ResourcePluginManager $rest_plugin_manager
     *   The rest resource plugin manager.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     */
    public function __construct(ResourcePluginManager $rest_plugin_manager, EntityTypeManagerInterface $entity_type_manager) {
        $this->restPluginManager = $rest_plugin_manager;
        $this->resourceConfigStorage = $entity_type_manager->getStorage('rest_resource_config');
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('plugin.manager.rest'), $container->get('entity_type.manager'));
    }
    
    /**
     * Returns an array of REST permissions.
     *
     * @return array
     */
    public function permissions() {
        $permissions = [];
        
        /** @var \Drupal\rest\RestResourceConfigInterface[] $resource_configs */
        $resource_configs = $this->resourceConfigStorage
            ->loadMultiple();
        foreach ($resource_configs as $resource_config) {
            $plugin = $resource_config->getResourcePlugin();
            // Add the rest resource configuration entity as a dependency to the
            // permissions.
            $permissions += array_map(function (array $permission_info) use ($resource_config) {
                $merge_info['dependencies'][$resource_config->getConfigDependencyKey()] = [
                    $resource_config->getConfigDependencyName(),
                ];
                return NestedArray::mergeDeep($permission_info, $merge_info);
            }, $plugin->permissions());
        }
        return $permissions;
    }

}