6

In Drupal 7 I used this to unset unneeded elements and total overwrite meta tags:

function MYTHEME_html_head_alter(&$head_elements) {
  // Unset all.
  $remove_array = array(
    'system_meta_content_type', 
    'system_meta_generator', 
    'system_shortcut_icon', 
    'metatag_canonical',
  );
  foreach ($remove_array as $key) {
    if ($head_elements[$key]) {
      unset($head_elements[$key]);
    }
  }
  // Optimize the mobile viewport.
  $head_elements['mobile_viewport'] = array(
    '#type' => 'html_tag',
    '#tag' => 'meta',
    '#weight' => -10,
    '#attributes' => array(
        'name' => 'viewport',
        'content' => 'initial-scale=1.0, maximum-scale=1.0, user-scalable=no, width=device-width',
    ),
  );
  // ...
  // Many other my META tags
  // ...
}

But in Drupal 8 this doesn't work anymore. New elements such as $head_elements['mobile_viewport'] don't get added.

And old meta tags, such as

  • <meta name="Generator" content="Drupal 8 (https://www.drupal.org)">
  • <meta name="MobileOptimized" content="width">
  • <meta name="HandheldFriendly" content="true">
  • <link rel="shortcut icon" href="http://example.com/core/misc/favicon.ico" type="image/vnd.microsoft.icon">

are still in <head>. How can I remove them and add others instead in Drupal 8?

14

Drupal 8 doesn't use hook_html_head_alter(). Its usage has been removed in Remove invocation of hook_html_head_alter(). As described in drupal_add_*() deprecated in favour of #attached, in Drupal 8 is possible to use hook_page_attachments() and hook_page_attachments_alter(), for example using code similar to the following one, suggested in one of the comments for the change record.

function MYTHEME_page_attachments_alter(array &$page) {
  $viewport = [
    '#type' => 'html_tag',
    '#tag' => 'meta',
    '#attributes' => [
      'name' => 'viewport',
      'content' => 'width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no',
    ],
  ];
  
  $page['#attached']['html_head'][] = [$viewport, 'viewport'];
}
1
2

Just to alter this code is useful:

/**
 * Implements hook_page_attachments_alter().
 */
function MY_THEME_page_attachments_alter(array &$variables) {
  if ($variables['#attached']['html_head']) {
    foreach ($variables['#attached']['html_head'] as $delta => $tag) {
      if (isset($tag[0]['#tag']) && $tag[0]['#tag'] == '__THE_DESIRED_TAG__' && $tag[0]['#attributes']['rel'] == '__THE_REL_ATTR__') {
        $variables['#attached']['html_head'][$delta][0]['#attributes']['__THE_DESIRED_ATTR__'] = '__THE_DESIRED_VALUE__';
      }
    }
  }
}
1

override meta from page generate in routing/controller

/**
 * Implements hook_metatags_alter().
 */
function mymod_metatags_alter(array &$metatags, array $context) {
  $route_name = \Drupal::service('current_route_match')->getRouteName();

  if ($route_name == "mymod.default_controller_content") {
    ...
  }  
}

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