PluginManagerCacheClearer.php

<?php

namespace Drupal\module_test;

use Drupal\Core\Plugin\DefaultPluginManager;
use Drupal\Core\State\StateInterface;

/**
 * Helps test module uninstall.
 */
class PluginManagerCacheClearer extends DefaultPluginManager {
    
    /**
     * @var \Drupal\Core\State\StateInterface
     */
    protected $state;
    
    /**
     * An optional service dependency.
     *
     * @var object|null
     */
    protected $optionalService;
    
    /**
     * PluginManagerCacheClearer constructor.
     *
     * @param \Drupal\Core\State\StateInterface $state
     *   The state service for recording what happens.
     * @param null $optional_service
     *   An optional service for testing.
     */
    public function __construct(StateInterface $state, $optional_service = NULL) {
        $this->state = $state;
        $this->optionalService = $optional_service;
    }
    
    /**
     * Tests call to CachedDiscoveryInterface::clearCachedDefinitions().
     *
     * @see \Drupal\Component\Plugin\Discovery\CachedDiscoveryInterface::clearCachedDefinitions()
     */
    public function clearCachedDefinitions() {
        $this->state
            ->set(self::class, isset($this->optionalService));
    }

}