class ViewsHandlerManager

class ViewsHandlerManager extends DefaultPluginManager implements FallbackPluginManagerInterface {
    
    /**
     * The views data cache.
     *
     * @var \Drupal\views\ViewsData
     */
    protected $viewsData;
    
    /**
     * The handler type.
     *
     * @var string
     *
     * @see \Drupal\views\ViewExecutable::getHandlerTypes().
     */
    protected $handlerType;
    
    /**
     * Constructs a ViewsHandlerManager object.
     *
     * @param string $handler_type
     *   The plugin type, for example filter.
     * @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\views\ViewsData $views_data
     *   The views data cache.
     * @param \Drupal\Core\Cache\CacheBackendInterface $cache_backend
     *   Cache backend instance to use.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler to invoke the alter hook with.
     */
    public function __construct($handler_type, \Traversable $namespaces, ViewsData $views_data, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
        $plugin_definition_annotation_name = 'Drupal\\views\\Annotation\\Views' . Container::camelize($handler_type);
        // Special handling until all views plugins have attribute classes.
        $attribute_name_candidate = 'Drupal\\views\\Attribute\\Views' . Container::camelize($handler_type);
        $plugin_definition_attribute_name = class_exists($attribute_name_candidate) ? $attribute_name_candidate : Plugin::class;
        $plugin_interface = 'Drupal\\views\\Plugin\\views\\ViewsHandlerInterface';
        if ($handler_type == 'join') {
            $plugin_interface = 'Drupal\\views\\Plugin\\views\\join\\JoinPluginInterface';
        }
        parent::__construct("Plugin/views/{$handler_type}", $namespaces, $module_handler, $plugin_interface, $plugin_definition_attribute_name, $plugin_definition_annotation_name);
        $this->setCacheBackend($cache_backend, "views:{$handler_type}");
        $this->alterInfo('views_plugins_' . $handler_type);
        $this->viewsData = $views_data;
        $this->handlerType = $handler_type;
        $this->defaults = [
            'plugin_type' => $handler_type,
        ];
    }
    
    /**
     * Fetches a handler from the data cache.
     *
     * @param array $item
     *   An associative array representing the handler to be retrieved:
     *   - table: The name of the table containing the handler.
     *   - field: The name of the field the handler represents.
     * @param string|null $override
     *   (optional) Override the actual handler object with this plugin ID. Used for
     *   aggregation when the handler is redirected to the aggregation handler.
     *
     * @return \Drupal\views\Plugin\views\ViewsHandlerInterface
     *   An instance of a handler object. May be a broken handler instance.
     */
    public function getHandler($item, $override = NULL) {
        $table = $item['table'];
        $field = $item['field'];
        // Get the plugin manager for this type.
        $data = $table ? $this->viewsData
            ->get($table) : $this->viewsData
            ->getAll();
        if (isset($data[$field][$this->handlerType])) {
            $definition = $data[$field][$this->handlerType];
            foreach ([
                'group',
                'title',
                'title short',
                'label',
                'help',
                'real field',
                'real table',
                'entity type',
                'entity field',
            ] as $key) {
                if (!isset($definition[$key])) {
                    // First check the field level.
                    if (!empty($data[$field][$key])) {
                        $definition[$key] = $data[$field][$key];
                    }
                    elseif (!empty($data['table'][$key])) {
                        $definition_key = $key === 'entity type' ? 'entity_type' : $key;
                        $definition[$definition_key] = $data['table'][$key];
                    }
                }
            }
            // @todo This is crazy. Find a way to remove the override functionality.
            $plugin_id = $override ?: $definition['id'];
            // Try to use the overridden handler.
            $handler = $this->createInstance($plugin_id, $definition);
            if ($override && method_exists($handler, 'broken') && $handler->broken()) {
                $handler = $this->createInstance($definition['id'], $definition);
            }
            return $handler;
        }
        // Finally, use the 'broken' handler.
        return $this->createInstance('broken', [
            'original_configuration' => $item,
        ]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function createInstance($plugin_id, array $configuration = []) {
        $instance = parent::createInstance($plugin_id, $configuration);
        if ($instance instanceof HandlerBase) {
            $instance->setModuleHandler($this->moduleHandler);
            $instance->setViewsData($this->viewsData);
        }
        return $instance;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFallbackPluginId($plugin_id, array $configuration = []) {
        return 'broken';
    }

}