dartmouth

function dartmouth_server_entity_load(array $entities, $entity_type_id) {
  if ($entity_type_id == "node") {
    $request = \Drupal::request();
    $controller = $request->get("_controller");
    $staging = $request->query->get("staging");
    if ($staging == "TRUE" && strpos($controller, "jsonapi") !== false) {

      // If we are previewing…
      foreach ($entities as $entity) {
        // Get the nid of the current entity
        $nid = $entity->get('nid')->getValue()[0]['value'];

        // Get the latest revision of the current entity
        $result = \Drupal::entityTypeManager()->getStorage('node')->getQuery()
          ->latestRevision()
          ->condition('nid', $nid, '=')
          ->execute();

        // Extract its ID
        $revision_id = key($result);

        // And load that revision to be passed on for serialization
        $entity = \Drupal::entityTypeManager()->getStorage('node')->loadRevision($revision_id);
      }
    }
  }
}