Injecting metadata into all nodes within one folder

Question

For my school I need to add metadata into the tag of every node/page within the folder /course/

The metadata is the same for every page in this folder:

<meta class="swiftype" name="tags" data-type="string" content="course" />

This will allow me to use weighting for all our course pages in the Swiftype search app.

I've narrowed it down to the html.html.twig file in \core\modules\system\templates - where I believe I need to be adding something along the lines of:

if (preg_match('$^course/', $_SERVER['REQUEST_URI']])) { print_metatag }

But I won't be wanting to use print_metatag. Instead I should be using the fixed metadata referenced above.

Can anyone help me figure out what I need to use, and where, to apply this metadata to all those /course/ nodes/pages.

Many thanks!

Answer 1

You won't be able to use PHP like that in Twig, but your logic isn't far off. One of the reasons Drupal 8 switched to using Twig was to avoid having potentially unsafe PHP in template files – this sort of thing generally belongs in a module rather than in a template, especially as it's not related to the presentation of content.

Drupal doesn't have a concept of folders, but we can look at the path of the content (e.g. /courses/drupal-development or /contact-us or /news/2018/cool-thing-that-happened) and work out if it's 'under' courses or not that way.

Something like this should work, but is untested:

/**
 * Implements hook_page_attachments().
 */
function YOUR_MODULE_NAME_page_attachments(array &$page) {
  $current_path = \Drupal::service('path.current')->getPath();
  $exploded_path = explode('/', $current_path);

  // Add Swiftype metatag, see https://swiftype.com/documentation/site-search/crawler-configuration/meta-tags.
  if ($exploded_path[1] === 'courses') {
    $metatag = [
      '#tag' => 'meta',
      '#attributes' => [
        'name' => 'tags',
        'data-type' => 'course',
        'class' => 'swiftype',
        'content' => 'course',
      ],
    ];

    $page['#attached']['html_head'][] = [$metatag, 'swiftype_course'];
  }
}

Or to do it by content type:

/**
 * Implements hook_page_attachments().
 */
function YOUR_MODULE_NAME_page_attachments(array &$page) {
  $node = \Drupal::routeMatch()->getParameter('node');

  if ($node instanceof \Drupal\node\NodeInterface) {
    if ($node->getType() === 'instance') {
      $metatag = [
        '#tag' => 'meta',
        '#attributes' => [
          'name' => 'tags',
          'data-type' => 'course',
          'class' => 'swiftype',
          'content' => 'course',
        ],
      ];

      $page['#attached']['html_head'][] = [$metatag, 'swiftype_course'];
    }
  }
}

If you need help setting up a module then take a look at https://befused.com/drupal/first-drupal8-module - but you can stop once you've created a your_module_name.module file – this is the file that the code above will go into.

Answer 2

The answer linked in the comments is for a render array you build yourself. If you want to attach something to an existing render array you would need to look for a render element (#theme, #type, #markup) you can attach it to. You could look for such a render element in $variables, but a preprocess hook is an exception to this rule. Here the (only) officially supported method of attaching bubbleable metadata (#cache, #attached) is the top level of $variables, even if there is no render element. Drupal looks for such metadata and bubbles it up.

Example:

/**
 * Implements hook_preprocess_HOOK() for node.html.twig.
 */
function mytheme_preprocess_node(&$variables) {

  if ($variables['node']->getType() == 'article' && $variables['view_mode'] == 'full') {

    $metatag = [
      '#tag' => 'meta',
      '#attributes' => [
        'name' => 'tags',
        'data-type' => 'course',
        'class' => 'swiftype',
        'content' => 'course',
      ],
    ];

    $variables['#attached']['html_head'][] = [$metatag, 'swiftype_course'];

  }
}

Answer 3

So there are three methods really.

1. I won't go over, since it is what Phil said

2. Create a custom module extending metatag. This is in many way ideal, but is the most complicated method. Given your stated experience level, this is likely a challenge, and probably not worth it for such a static option.

3. Use the html template you identified. For this just copy core/themes/classy/templates/layout/html.html.twig to %your_theme/templates/layout/ as html--node--instance.html.twig. Or if you you already have an html.html.twig in yuor theme, copy that to the new name. Then add your metatag directly into the new template.

Do note that any of those three options will require you to clear caches or they won't take effect.