TermForm::save

public TermForm::save(array $form, FormStateInterface $form_state)

public function save(array $form, FormStateInterface $form_state) {
  $term = $this->entity;

  $result = $term->save();

  $edit_link = $term->link($this->t('Edit'), 'edit-form');
  $view_link = $term->link($term->getName());
  switch ($result) {
    case SAVED_NEW:
      drupal_set_message($this->t('Created new term %term.', array('%term' => $view_link)));
      $this->logger('taxonomy')->notice('Created new term %term.', array('%term' => $term->getName(), 'link' => $edit_link));
      break;
    case SAVED_UPDATED:
      drupal_set_message($this->t('Updated term %term.', array('%term' => $view_link)));
      $this->logger('taxonomy')->notice('Updated term %term.', array('%term' => $term->getName(), 'link' => $edit_link));
      break;
  }

  $current_parent_count = count($form_state->getValue('parent'));
  $previous_parent_count = count($form_state->get(['taxonomy', 'parent']));
  // Root doesn't count if it's the only parent.
  if ($current_parent_count == 1 && $form_state->hasValue(array('parent', 0))) {
    $current_parent_count = 0;
    $form_state->setValue('parent', array());
  }

  // If the number of parents has been reduced to one or none, do a check on the
  // parents of every term in the vocabulary value.
  $vocabulary = $form_state->get(['taxonomy', 'vocabulary']);
  if ($current_parent_count < $previous_parent_count && $current_parent_count < 2) {
    taxonomy_check_vocabulary_hierarchy($vocabulary, $form_state->getValues());
  }
  // If we've increased the number of parents and this is a single or flat
  // hierarchy, update the vocabulary immediately.
  elseif ($current_parent_count > $previous_parent_count && $vocabulary->getHierarchy() != VocabularyInterface::HIERARCHY_MULTIPLE) {
    $vocabulary->setHierarchy($current_parent_count == 1 ? VocabularyInterface::HIERARCHY_SINGLE : VocabularyInterface::HIERARCHY_MULTIPLE);
    $vocabulary->save();
  }

  $form_state->setValue('tid', $term->id());
  $form_state->set('tid', $term->id());
}