ParagraphsSummaryFormatter.php

<?php

namespace Drupal\paragraphs\Plugin\Field\FieldFormatter;

use Drupal\Core\Field\FieldDefinitionInterface;
use Drupal\Core\Field\FieldItemListInterface;
use Drupal\Core\Field\Plugin\Field\FieldFormatter\EntityReferenceFormatterBase;
use Drupal\paragraphs\ParagraphInterface;

/**
 * Plugin implementation of the 'paragraph_summary' formatter.
 *
 * @FieldFormatter(
 *   id = "paragraph_summary",
 *   label = @Translation("Paragraph summary"),
 *   field_types = {
 *     "entity_reference_revisions"
 *   }
 * )
 */
class ParagraphsSummaryFormatter extends EntityReferenceFormatterBase {

  /**
   * {@inheritdoc}
   */
  public function viewElements(FieldItemListInterface $items, $langcode) {
    $elements = [];
    foreach ($this
      ->getEntitiesToView($items, $langcode) as $delta => $entity) {
      if ($entity
        ->id()) {
        $elements[$delta] = [
          '#type' => 'container',
          '#attributes' => [
            'class' => [
              'paragraph-formatter',
            ],
          ],
        ];
        $elements[$delta]['info'] = [
          '#type' => 'container',
          '#attributes' => [
            'class' => [
              'paragraph-info',
            ],
          ],
        ];
        $elements[$delta]['info'] += $entity
          ->getIcons();
        $elements[$delta]['summary'] = [
          '#type' => 'container',
          '#attributes' => [
            'class' => [
              'paragraph-summary',
            ],
          ],
        ];
        $elements[$delta]['summary']['description'] = [
          '#theme' => 'paragraphs_summary',
          '#summary' => $entity
            ->getSummaryItems(),
        ];
      }
    }
    if ($elements) {
      $elements['#attached']['library'][] = 'paragraphs/drupal.paragraphs.formatter';
    }
    return $elements;
  }

  /**
   * {@inheritdoc}
   */
  public static function isApplicable(FieldDefinitionInterface $field_definition) {
    $target_type = $field_definition
      ->getSetting('target_type');
    $paragraph_type = \Drupal::entityTypeManager()
      ->getDefinition($target_type);
    if ($paragraph_type) {
      return $paragraph_type
        ->entityClassImplements(ParagraphInterface::class);
    }
    return FALSE;
  }

}