class BlockManager

class BlockManager extends DefaultPluginManager implements BlockManagerInterface, FallbackPluginManagerInterface {
    use CategorizingPluginManagerTrait {
        getSortedDefinitions as traitGetSortedDefinitions;
    }
    use FilteredPluginManagerTrait;
    
    /**
     * The logger.
     *
     * @var \Psr\Log\LoggerInterface
     */
    protected $logger;
    
    /**
     * Constructs a new \Drupal\Core\Block\BlockManager 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.
     * @param \Psr\Log\LoggerInterface $logger
     *   The logger.
     */
    public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler, LoggerInterface $logger) {
        parent::__construct('Plugin/Block', $namespaces, $module_handler, 'Drupal\\Core\\Block\\BlockPluginInterface', 'Drupal\\Core\\Block\\Annotation\\Block');
        $this->alterInfo($this->getType());
        $this->setCacheBackend($cache_backend, 'block_plugins');
        $this->logger = $logger;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getType() {
        return 'block';
    }
    
    /**
     * {@inheritdoc}
     */
    public function processDefinition(&$definition, $plugin_id) {
        parent::processDefinition($definition, $plugin_id);
        $this->processDefinitionCategory($definition);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getSortedDefinitions(array $definitions = NULL) {
        // Sort the plugins first by category, then by admin label.
        $definitions = $this->traitGetSortedDefinitions($definitions, 'admin_label');
        // Do not display the 'broken' plugin in the UI.
        unset($definitions['broken']);
        return $definitions;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFallbackPluginId($plugin_id, array $configuration = []) {
        return 'broken';
    }
    
    /**
     * {@inheritdoc}
     */
    protected function handlePluginNotFound($plugin_id, array $configuration) {
        $this->logger
            ->warning('The "%plugin_id" was not found', [
            '%plugin_id' => $plugin_id,
        ]);
        return parent::handlePluginNotFound($plugin_id, $configuration);
    }

}