multilingual_menu_urls.module

<?php

/**
 * @file
 * Contains multilingual_menu_urls.module.
 */

use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Entity\EntityTypeInterface;
use Drupal\Core\Field\BaseFieldDefinition;
use Drupal\Core\URL;

/**
 * Implements hook_help().
 */
function multilingual_menu_urls_help($route_name, RouteMatchInterface $route_match)
{
  switch ($route_name) {
    // Main module help for the multilingual_menu_urls module.
    case 'help.page.multilingual_menu_urls':
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('Provides the options to add different external URLs to a menu item translation') . '</p>';
      return $output;

    default:
  }
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function multilingual_menu_urls_form_menu_link_content_menu_link_content_form_alter(&$form, FormStateInterface $form_state) {

  $menu_config = $form_state->getFormObject()->getEntity();
  $form['#attached']['library'][] = 'multilingual_menu_urls/multilingual_menu_urls';
  if ($menu_config->isDefaultTranslation()) {
    // Mltilingual external URL options unavailable to default translations.
    $form['translated_link_on']['#access'] = FALSE;
    $form['translated_link_url']['#access'] = FALSE;
  }
  else {
    // Move enabled field for better UX.
    $form['enabled']['#weight'] = 4;

    // Translated link options only visible if "Enable Translated Link"
    // is true.
    $form['translated_link_url']['#states'] = [
      'visible' => [
        ':input[name="translated_link_on[value]"]'  => [
          'checked' => TRUE,
        ],
      ],
    ];
    // If "Enable Translated Link", hide default link and title fields.
    $form['link']['#states'] = $form['title']['#states'] = [
      'visible' => [
        ':input[name="translated_link_on[value]"]'  => [
          'checked' => FALSE,
        ],
      ],
    ];
    $form['translated_link_url']['widget'][0]['title']['#weight'] = 5;
    $form['translated_link_url']['widget'][0]['uri']['#weight'] = 10;
    // If translated links are enabled, then the link and URL are required.
    $form['translated_link_url']['widget'][0]['title']['#states'] = $form['translated_link_url']['widget'][0]['uri']['#states'] = [
      'required' => [
        ':input[name="translated_link_on[value]"]'  => [
          'checked' => TRUE,
        ],
      ],
    ];
  }
}

/**
 * Implements hook_entity_base_field_info().
 */
function multilingual_menu_urls_entity_base_field_info(EntityTypeInterface $entityType)
{
  if ($entityType->id() == 'menu_link_content') {

    $fields = [];
    $fields['translated_link_on'] = BaseFieldDefinition::create('boolean')
      ->setLabel(t('Provide Translated External Link'))
      ->setDescription(t('Not necessary for internall links. Allows you to provide a language-specific link for this menu item.'))
      ->setTranslatable(TRUE)
      ->setDisplayOptions('form', [
        'type' => 'boolean_checkbox',
        'settings' => [
          'display_label' => TRUE,
        ],
        'weight' => -8,
      ])
      ->setDisplayConfigurable('form', TRUE);

    $fields['translated_link_url'] = BaseFieldDefinition::create('link')
      ->setLabel(t('Translated Link'))
      ->setDescription(t('Overrides the menu link field - use only if this is an external link that differs from the URL used in the default language'))
      ->setTranslatable(TRUE)
      ->setDisplayOptions('form', [
        'type' => 'link_default',
        'settings' => [
          'display_label' => TRUE,
        ],
        'weight' => -7,
      ])
      ->setDisplayConfigurable('form', TRUE);
    return $fields;


  }
}

/**
 * Implements template_preprocess_menu().
 * TODO: Find a way to do this earlier than a preprocessor
 */
function multilingual_menu_urls_preprocess_menu(&$variables) {
  $default_language = \Drupal::languageManager()->getDefaultLanguage()->getId();
  $current_language = \Drupal::languageManager()->getCurrentLanguage()->getId();
  // There is no need to continue if we are on a page in the default language.
  if ($default_language == $current_language) {
    return;
  }
  /*
   * Loop through each menu link. If multilingual URL is enabled and
   * the multilingual link field is available, use those values
   * in the rendered menu link.
   */
  foreach ($variables['items'] as $k => $item) {
    $menu_link = $item['original_link'];
    $uuid = $menu_link->getDerivativeId();
    if (!empty($uuid)) {
      $entity = \Drupal::entityManager()->loadEntityByUuid('menu_link_content', $menu_link->getDerivativeId());
      if ($entity->hasTranslation($current_language)) {
        $translated_entity = $entity->getTranslation($current_language);
        if ($translated_entity->hasField('translated_link_on') && $translated_entity->translated_link_on->value) {
          $translated_url = $translated_entity->translated_link_url->uri;
          $translated_title = $translated_entity->translated_link_url->title;
          if (!empty($translated_title)) {
            $variables['items'][$k]['title'] = $translated_title;
          }
          if (!empty($translated_url)) {
            $options = $item['url']->getOptions();
            $new_url = Url::fromUri($translated_url);
            $new_url->setOptions($options);
            $variables['items'][$k]['url'] = $new_url;
          }
        }
      }
    }
  }
}