Adding API Support to Your Formatter

1. Explicitly declare support by add the supportsDateAugmenter() method to your date formatter. In a typical use case it only needs to return TRUE, but if your formatter may need more than one set of configuration, you can return a keyed array instead. You can see an example of returning a keyed array in the Smart Date Recurring formatter.
2. In your viewElements method, check for any enabled augmenters before processing the $items, with code like:
   

       // Look for the Date Augmenter plugin manager service.
       $augmenters = [];
       if (!empty(\Drupal::hasService('plugin.manager.dateaugmenter'))) {
         $dateAugmenterManager = \Drupal::service('plugin.manager.dateaugmenter');
         $config = $this->getThirdPartySettings('date_augmenter');
         $augmenters = $dateAugmenterManager->getActivePlugins($config);
         $entity = $items->getEntity();
       }

3. Within your loop to process the $items and generate output, add code to apply any enabled augmenters, such as:
   

         if ($augmenters) {
           foreach ($augmenters as $augmenter_id => $augmenter) {
             // Use the enabled plugin to manipulate the output.
             $augmenter->augmentOutput(
               // The existing render array.
               $elements[$delta],
               // The start and end (optional), as DrupalDateTime objects.
               $item->start_date,
               $item->end_date,
               // An optional array of additional parameters.
               [
                 'entity' => $entity,
                 'settings' => $config['settings'][$augmenter_id],
                 'delta' => $delta,
                 'formatter' => $this,
                 'field_name' => $this->fieldDefinition->getName(),
               ]
             );
           }
         }
   

Note that in the above, the start and end may need to be changed to match the structure of data used by your formatter.

• $entity is the parent entity (node, taxonomy term, etc)
• $delta is numerical key of the value