Metatag: How to programmaticaly set a node's canonical URL

Question

I am using the metatag module for defining several meta tags. As a default value, canonical tags use '[current-page:url:absolute]'. Now I want to create a module that sets the value of the canonical tag to some other url.

Setting $node['metatags']['und']['canonical']['value'] to another string doesn't seem to work. Unfortunately, I also can't use an entity_wrapper, since metatag doesn't define information for its custom fields, which is needed by entity_wrapper.

Is there something else I could do?

Answer 1

look into the hook: metatag_metatags_view_alter().

/**
 * Implements metatag_metatags_view_alter()
 */
function mymodule_metatag_metatags_view_alter(&$output, $instance) {
  // Add Custom logic to overwrite the canonical tag here.
  $canonical = 'http://www.mysourceurl.com';

  // Alter canonical tag.
  $output['canonical']['#attached']['drupal_add_html_head'][0][0]['#value'] = $canonical;
}

Answer 2

The metatag module provides server hooks. You can find them in the metatag.api.php file inside the module.

The one you need is hook_metatag_metatags_view_alter.

/**
 * Alter metatags before being cached.
 *
 * This hook is invoked prior to the meta tags for a given page are cached.
 *
 * @param array $output
 *   All of the meta tags to be output for this page in their raw format. This
 *   is a heavily nested array.
 * @param string $instance
 *   An identifier for the current page's page type, typically a combination
 *   of the entity name and bundle name, e.g. "node:story".
 * @param array $options
 *   All of the options used to generate the meta tags.
 */
function hook_metatag_metatags_view_alter(&$output, $instance, $options) {
  if (isset($output['description']['#attached']['drupal_add_html_head'][0][0]['#value'])) {
    $output['description']['#attached']['drupal_add_html_head'][0][0]['#value'] = 'O rly?';
  }
}