Issue #3268614 by mkalkbrenner: Add configuration whether parents should be...

        type: boolean

        label: 'Should the condition be negated'

plugin.plugin_configuration.facets_processor.show_siblings_processor:

  type: mapping

  label: 'Show siblings processor'

  mapping:

    show_parent_siblings:

      type: boolean

      label: 'Show parents'

plugin.plugin_configuration.facets_processor.date_item:

  type: mapping

  label: 'Date item processor'

namespace Drupal\facets\Plugin\facets\processor;

use Drupal\Core\Form\FormStateInterface;

use Drupal\facets\FacetInterface;

use Drupal\facets\Processor\BuildProcessorInterface;

use Drupal\facets\Processor\ProcessorPluginBase;

use Drupal\facets\Result\Result;

/**

 * Provides a processor that only shows deepest level items.

 * Provides a processor that adds all siblings of the active item to the result.

 *

 * @FacetsProcessor(

 *   id = "show_siblings_processor",

 *   label = @Translation("Show siblings"),

 *   description = @Translation("Show all siblings of a hierarchical facet item. In 'Advanced settings' this processor should be executed early in the processor chain, for example before ids get converted into titles. It is recommended to enable 'Use hierarchy' and 'Ensure that only one result can be displayed', too."),

 *   description = @Translation("Show all siblings of a hierarchical facet item. In 'Advanced settings' this processor should be executed early in the processor chain, for example before the URL handler and before ids get converted into titles. It is recommended to enable 'Use hierarchy' and 'Ensure that only one result can be displayed', too."),

 *   stages = {

 *     "build" = 40

 *     "build" = 11

 *   }

 * )

 */

      $rawValues = array_map(function ($result) {

        return $result->getRawValue();

      }, $results);

      foreach ($facet->getHierarchyInstance()->getSiblingIds($rawValues, $facet->getActiveItems()) as $siblingId) {

      foreach ($facet->getHierarchyInstance()->getSiblingIds($rawValues, $facet->getActiveItems(), $this->getConfiguration()['show_parent_siblings']) as $siblingId) {

        $results[] = new Result($facet, $siblingId, $siblingId, 0);

      }

    }

    return $results;

  }

  /**

   * {@inheritdoc}

   */

  public function defaultConfiguration() {

    return [

      'show_parent_siblings' => TRUE,

    ] + parent::defaultConfiguration();

  }

  /**

   * {@inheritdoc}

   */

  public function buildConfigurationForm(array $form, FormStateInterface $form_state, FacetInterface $facet) {

    $configuration = $this->getConfiguration();

    $build['show_parent_siblings'] = [

      '#type' => 'checkbox',

      '#title' => $this->t('Show parent siblings'),

      '#description' => $this->t('If selected the siblings of all (inactive) parents of an active item will be added be shown. Otherwise only the siblings of active items will be shown. (See "Keep hierarchy parents active".)'),

      '#default_value' => $configuration['show_parent_siblings'],

    ];

    return $build;

  }

}