FilterPluginManager.php

<?php

namespace Drupal\filter;

use Drupal\Component\Plugin\FallbackPluginManagerInterface;
use Drupal\Core\Cache\CacheBackendInterface;
use Drupal\Core\Extension\ModuleHandlerInterface;
use Drupal\Core\Plugin\DefaultPluginManager;

/**
 * Manages text processing filters.
 *
 * @see hook_filter_info_alter()
 * @see \Drupal\filter\Annotation\Filter
 * @see \Drupal\filter\Plugin\FilterInterface
 * @see \Drupal\filter\Plugin\FilterBase
 * @see plugin_api
 */
class FilterPluginManager extends DefaultPluginManager implements FallbackPluginManagerInterface {
    
    /**
     * Constructs a FilterPluginManager object.
     *
     * @param \Traversable $namespaces
     *   An object that implements \Traversable which contains the root paths
     *   keyed by the corresponding namespace to look for plugin implementations.
     * @param \Drupal\Core\Cache\CacheBackendInterface $cache_backend
     *   Cache backend instance to use.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler to invoke the alter hook with.
     */
    public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
        parent::__construct('Plugin/Filter', $namespaces, $module_handler, 'Drupal\\filter\\Plugin\\FilterInterface', 'Drupal\\filter\\Annotation\\Filter');
        $this->alterInfo('filter_info');
        $this->setCacheBackend($cache_backend, 'filter_plugins');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFallbackPluginId($plugin_id, array $configuration = []) {
        return 'filter_null';
    }

}