Empty search fields, breaks autocomplete callback

I have "hack" to solve my problem, but I don't understand why.

In search_api_autocomplete.search_api_views.inc, see the // new line

function search_api_autocomplete_views_query(SearchApiAutocompleteSearch $search, $complete, $incomplete) {
  $views_id = substr($search->machine_name, 17);
  $view = views_get_view($views_id);
  // @todo Let users select display
  $view->set_display();
  // @todo Determine arguments
  $view->pre_execute();
  $view->build();
  $query = $view->query->getSearchApiQuery();
  $query->keys($complete);
  // @morningtime: new line here
  $query->fields(array('search_api_aggregation_1'));
  return $query;
}

(see new line, I have 1 aggregated fulltext field called search_api_aggregation_1)
If I try $query->fields(array('search_api_views_fulltext')); it says it's not an indexed fulltext field.

What I don't understand is why my aggregated & index field is not added to autocomplete's fields?

Yes it's in the Master view, I tried both "search_api_views_fulltext" and my aggregated field. It didn't work, for some reason the field is not added to $query in search_api_autocomplete_views_query().

Maybe it is related to how I show the search textfield. I use the code from example_form_example_search_form_alter() and attach it to a textfield (shown on the search View page, replacing the exposed form.)

It used to work fine, until recently, don't know what changed.

function search_api_widgets_form_search_api_widgets_views_search_form_alter(&$form, &$form_state) {

  // use this search id for autocomplete
  $search_id = 'search_api_views_shopcircuit_search';
  $search = search_api_autocomplete_search_load($search_id);
  if (!empty($search->enabled)) {
    $search->alterElement($form['query']);
  }
}

The search id exists of course.

It seems that SearchApiQuery::fields() is not even called and [fields:protected] exists, but is null (not an array).

Wow, genius. Those patches work for me.