How to add fields to menu items

Question

I need to build a main menu that is a subset of the regular menu. The design team thinks it would be better for user to have only the most important links in the main menu and not have everything. Some links are top level menu and some are sub menus. For this I was hoping to be able to add a field to the menu link item form as a drop down. When creating a link the user could use this dropdown to "promoteToMainMenuAsBigLink" or "promoteToMainMenuAsSmallLink" or leave none to not show the item on the main menu.

I'm looking for a similar solution as this Drupal 7 solution but for Drupal 8.

I was hoping to be able to add a column in the table menu_link_content_data beside 'expanded'. I was hoping not to have to record this information in an other table like shown in the d7 solution.

I was able to add a field to the link form in a custom module I build, just for test purpose I only added a text field to start with:

custom_menu.module:

function custom_menu_form_alter(&$form, FormStateInterface $form_state, $form_id) {
  if($form_id == 'menu_link_content_menu_link_content_form') {
    $form['promoteToMainMenu'] = array(
      '#type' => 'textfield',
      '#title' => t('Promote to main menu'),
      '#description' => t('Promote link menu to main menu.'),
      '#default_value' => '',
      '#weight' => -9
    );
  }
}

The field is indeed shown in the link form but it is never recorded.

Can someone help me with this?

Answer 1

Check the Menu Item Extras module.

Answer 2

You can use hook_entity_base_field_info to add an additional field to the menu_link_content entity with the following code:

/**
 * Implements hook_entity_base_field_info().
 */
function MYMODULE_entity_base_field_info(\Drupal\Core\Entity\EntityTypeInterface $entity_type) {
  $fields = [];

  if ($entity_type->id() == 'menu_link_content') {
    $fields['FIELD_NAME'] = \Drupal\Core\Field\BaseFieldDefinition::create('FIELD_TYPE')
      ->setLabel(t('FIELD_LABEL'))
      ->setDescription(t('FIELD_DESCRIPTION '))
      ->setDisplayOptions('form', ['type' => 'FIELD_TYPE', 'weight' => 0]);
  }

  return $fields;
}

See https://www.drupal.org/docs/8/api/entity-api/defining-and-using-content-entity-field-definitions for more details on BaseFieldDefinition.

After which, you'll need hook_form_menu_link_content_menu_link_content_form_alter() to add a field to the form.

Answer 3

Unfortunately there is indeed no fields UI for menu links by default in Drupal 8 as @MatthieuScarset said. But menu_link_content is a content entity in Drupal 8, so it is possible to add fields to it.

Option #1 Of course you can do it programmatically as @Decipher suggested.

Option #2 But there is another workaround to enable fields UI for menu links temporary:

1. Open Drupal\menu_link_content\Entity\MenuLinkContent
2. Add field_ui_base_route = "entity.menu.add_link_form" to the annotation
3. Rebuild cache
4. Visit /admin/structure/menu/manage/main/add/fields
5. Manage all your fields, displays
6. Export your site configuration (drush cex -y).
7. Remove field_ui_base_route = "entity.menu.add_link_form" from the annotation at Drupal\menu_link_content\Entity\MenuLinkContent
8. Rebuild cache.

Answer 4

You could use Colossal Menu to add the field instead of the core Menu module.

Answer 5

"Menu item extras" is one way to achieve this, as @Mykhailo Gurei suggested.

But in my case I had to add extra fields and to use Mega menu module. I was using "We mega menu" and with it "Menu item extras" is not working. Simply menu is not shown on front-end (some templates override issue).

So other option that works with "We mega menu" is "Menu item content fields":

https://www.drupal.org/project/menu_item_fields

Has the same functionality and doesn't have conflict with We mega menu module.

Answer 6

A newer solution could be menu item content fields

According to the project description its features are:

• Add fields to menu items and sort their display.
• Show fielded menu items with a block chosing the view mode.
• Configure additional options on the formatter like the rel and target attributes.
• Add more attributes with the Link attributes module.
• Optionally have a field on the menu link entity that overrides the display mode.
  • Is up to the site builder to create it.
  • This field needs to store the string value of the display mode, for example: 'mega'.

Answer 7

Unfortunately, Drupal 8 core developers have not made Menu links fieldable. So it is not possible to add fields to menu links for now.

The site builder "work around" is to create a custom vocabulary which can have custom fields.