trait WebformTermReferenceTrait in Webform 8.5

trait WebformTermReferenceTrait {

  /**
   * Set referencable term entities as options for an element.
   *
   * @param array $element
   *   An element.
   */
  public static function setOptions(array &$element) {
    $language = \Drupal::languageManager()
      ->getCurrentLanguage()
      ->getId();
    if (!empty($element['#options'])) {
      return;
    }
    if (!\Drupal::moduleHandler()
      ->moduleExists('taxonomy') || empty($element['#vocabulary'])) {
      $element['#options'] = [];
      return;
    }
    if (!empty($element['#breadcrumb'])) {
      $element['#options'] = static::getOptionsBreadcrumb($element, $language);
    }
    else {
      $element['#options'] = static::getOptionsTree($element, $language);
    }

    // Add the vocabulary to the cache tags.
    // Issue #2920913: The taxonomy_term_list cache should be invalidated
    // on a vocabulary-by-vocabulary basis.
    // @see https://www.drupal.org/project/drupal/issues/2920913
    $element['#cache']['tags'][] = 'taxonomy_term_list';
  }

  /**
   * Get options to term breadcrumb.
   *
   * @param array $element
   *   The term reference element.
   * @param string $language
   *   The language to be displayed.
   *
   * @return array
   *   An associative array of term options formatted as a breadcrumbs.
   */
  protected static function getOptionsBreadcrumb(array $element, $language) {
    $element += [
      '#breadcrumb_delimiter' => ' › ',
    ];

    /** @var \Drupal\Core\Entity\EntityRepositoryInterface $entity_repository */
    $entity_repository = \Drupal::service('entity.repository');
    $tree = static::loadTree($element['#vocabulary']);
    $options = [];
    $breadcrumb = [];
    foreach ($tree as $item) {

      // Set the item in the correct language for display.
      $item = $entity_repository
        ->getTranslationFromContext($item);
      if (!$item
        ->access('view')) {
        continue;
      }

      // Check depth.
      if (!empty($element['#depth']) && $item->depth >= $element['#depth']) {
        continue;
      }
      $breadcrumb[$item->depth] = $item
        ->getName();
      $breadcrumb = array_slice($breadcrumb, 0, $item->depth + 1);
      $options[$item
        ->id()] = implode($element['#breadcrumb_delimiter'], $breadcrumb);
    }
    return $options;
  }

  /**
   * Get options to term tree.
   *
   * @param array $element
   *   The term reference element.
   * @param string $language
   *   The language to be displayed.
   *
   * @return array
   *   An associative array of term options formatted as a tree.
   */
  protected static function getOptionsTree(array $element, $language) {
    $element += [
      '#tree_delimiter' => '-',
    ];

    /** @var \Drupal\Core\Entity\EntityRepositoryInterface $entity_repository */
    $entity_repository = \Drupal::service('entity.repository');
    $tree = static::loadTree($element['#vocabulary']);
    $options = [];
    foreach ($tree as $item) {

      // Set the item in the correct language for display.
      $item = $entity_repository
        ->getTranslationFromContext($item);
      if (!$item
        ->access('view')) {
        continue;
      }

      // Check depth.
      if (!empty($element['#depth']) && $item->depth >= $element['#depth']) {
        continue;
      }
      $options[$item
        ->id()] = str_repeat($element['#tree_delimiter'], $item->depth) . $item
        ->getName();
    }
    return $options;
  }

  /**
   * Finds all terms in a given vocabulary ID.
   *
   * @param string $vid
   *   Vocabulary ID to retrieve terms for.
   *
   * @return object[]|\Drupal\taxonomy\TermInterface[]
   *   An array of term objects that are the children of the vocabulary $vid.
   */
  protected static function loadTree($vid) {

    /** @var \Drupal\taxonomy\TermStorageInterface $taxonomy_storage */
    $taxonomy_storage = \Drupal::entityTypeManager()
      ->getStorage('taxonomy_term');
    return $taxonomy_storage
      ->loadTree($vid, 0, NULL, TRUE);
  }

}