How to use Rules Link to populate Entity References

I need to use the Nodereference URL Widget with Profile2 profiles. Guess what? They aren't nodes. Instead I'm going to use Rules Link.

I used Rules Link instead for Nodereference URL Widget on a job listing content type that needs a button for a user to add a job application to. So I created a Rules Link instance and set the visibility on the entity type, bundle and user role access. The Rule also contains a single action to redirect the user to node/add/application?field_reference_job_listing=[node:nid]. The return path can be included with adding &destination=[node:url:path].

This field needs to be rewritten to emulate the varies fallback behaviors of the Nodereference URL widget. I went with page not found.

Now the form needs to be intercepted and the field's default value needs to be set. This is easier programtically using the Nodereference URL Widget which provides a of useful variables in the form variable to user. However, since the Entity References module is being used it is a bit more tricky. I use hook_field_widget_FIELD_ID_form_alter and it looks something like this.

function MODULE_field_widget_entityreference_autocomplete_form_alter (&$element, &$form_state, $context){
  
  if ($context['field']['field_name'] == 'field_reference_job_listing'){

    extract($context);
    
    $handler = entityreference_get_handler($field);

    // We let the Field API handles multiple values for us, only take
    // care of the one matching our delta.
    if (isset($items[$delta])) {
      $items = array($items[$delta]);
    }
    elseif (isset($_GET['field_reference_job_listing']) && is_numeric($_GET['field_reference_job_listing'])) {
      $items = array(
        array(
          'target_id' => $_GET['field_reference_job_listing'],
        ),
      );
    }  
    else {
      drupal_set_message(t('To create an application, first go to the job listing page of the job you would like to apply to and click the apply button.'));
      drupal_not_found();
      exit();
    }
    
    $entity_ids = array();
    $entity_labels = array();

    // Build an array of entities ID.
    foreach ($items as $item) {
      $entity_ids[] = $item['target_id'];
    }

    // Load those entities and loop through them to extract their labels.
    $entities = entity_load($field['settings']['target_type'], $entity_ids);

    foreach ($entities as $entity_id => $entity) {
      $label = $handler->getLabel($entity);
      $key = "$label ($entity_id)";
      // Labels containing commas or quotes must be wrapped in quotes.
      if (strpos($key, ',') !== FALSE || strpos($key, '"') !== FALSE) {
        $key = '"' . str_replace('"', '""', $key) . '"';
      }
      $entity_labels[] = $key;
    }

    $element['target_id']['#default_value'] = implode(', ', $entity_labels);
    $element['target_id']['#default_label'] = $label;
    $element['target_id']['#default_id'] = $entity_id;
    $element['target_id']['#access'] = FALSE;
  }
      
  return $element;
}

function MODULE_form_application_node_form_alter (&$form, &$form_state, $form_id) {
  $lang = $form['field_reference_job_listing']['#language'];
  if ($label = $form['field_reference_job_listing'][$lang][0]['target_id']['#default_label']){
    $form['company_name'] = array(
     '#markup' => '<label>Submit an application to ' . $label . '</label>',
     '#weight' => 0,
    );
  }
}