class ViewsExposedFilterBlock

class ViewsExposedFilterBlock implements ContainerDeriverInterface {
  use StringTranslationTrait;
  
  /**
   * List of derivative definitions.
   *
   * @var array
   */
  protected $derivatives = [];
  
  /**
   * The view storage.
   *
   * @var \Drupal\Core\Entity\EntityStorageInterface
   */
  protected $viewStorage;
  
  /**
   * The base plugin ID that the derivative is for.
   *
   * @var string
   */
  protected $basePluginId;
  
  /**
   * Constructs a ViewsExposedFilterBlock object.
   *
   * @param string $base_plugin_id
   *   The base plugin ID.
   * @param \Drupal\Core\Entity\EntityStorageInterface $view_storage
   *   The entity storage to load views.
   */
  public function __construct($base_plugin_id, EntityStorageInterface $view_storage) {
    $this->basePluginId = $base_plugin_id;
    $this->viewStorage = $view_storage;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, $base_plugin_id) {
    return new static($base_plugin_id, $container->get('entity_type.manager')
      ->getStorage('view'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function getDerivativeDefinition($derivative_id, $base_plugin_definition) {
    if (!empty($this->derivatives) && !empty($this->derivatives[$derivative_id])) {
      return $this->derivatives[$derivative_id];
    }
    $this->getDerivativeDefinitions($base_plugin_definition);
    return $this->derivatives[$derivative_id];
  }
  
  /**
   * {@inheritdoc}
   */
  public function getDerivativeDefinitions($base_plugin_definition) {
    // Check all Views for displays with an exposed filter block.
    foreach ($this->viewStorage
      ->loadMultiple() as $view) {
      // Do not return results for disabled views.
      if (!$view->status()) {
        continue;
      }
      $executable = $view->getExecutable();
      $executable->initDisplay();
      foreach ($executable->displayHandlers as $display) {
        if (isset($display) && $display->getOption('exposed_block')) {
          // Add a block definition for the block.
          if ($display->usesExposedFormInBlock()) {
            $delta = $view->id() . '-' . $display->display['id'];
            $desc = $this->t('Exposed form: @view-@display_id', [
              '@view' => $view->id(),
              '@display_id' => $display->display['id'],
            ]);
            $this->derivatives[$delta] = [
              'admin_label' => $desc,
              'config_dependencies' => [
                'config' => [
                  $view->getConfigDependencyName(),
                ],
              ],
            ];
            $this->derivatives[$delta] += $base_plugin_definition;
          }
        }
      }
    }
    return $this->derivatives;
  }

}