LanguageAddForm::validatePredefined

public LanguageAddForm::validatePredefined($form, FormStateInterface $form_state)

public function validatePredefined($form, FormStateInterface $form_state) {
  $langcode = $form_state->getValue('predefined_langcode');
  if ($langcode == 'custom') {
    $form_state->setErrorByName('predefined_langcode', $this->t('Fill in the language details and save the language with <em>Add custom language</em>.'));
  }
  else {
    if ($language = $this->languageManager->getLanguage($langcode)) {
      $form_state->setErrorByName('predefined_langcode', $this->t('The language %language (%langcode) already exists.', array('%language' => $language->getName(), '%langcode' => $langcode)));
    }
  }
}