10up/ElasticPress — pull request #88 by ivanlopez (2014-09-04 15:36:34+00:00)
Title: Adding ep_search_fields filter for adding custom search fields

Currently you can add custom fields with the ep_post_sync_args filter before a post is synced but there is no way to add those fields to the array that is returned from the format_args method. This filter allows you to add any custom fields you might need to the $search_fields array.