/**
 * Implements hook_page_attachments().
 */
function {{ machine_name }}_page_attachments(array &$attachments) {
  // Unconditionally attach an asset to the page.
  $attachments['#attached']['library'][] = 'core/domready';

  // Conditionally attach an asset to the page.
  if (!\Drupal::currentUser()->hasPermission('may pet kittens')) {
    $attachments['#attached']['library'][] = 'core/jquery';
  }
}
