/**
 * Toolset Support 
 * Filter the Favorites list information to display related Artiste info
 * Currently supports Livres and Oeuvres Sur Papiers post types for Favorites
 * Extendable by adding a case statement for new post type / relationship slug
 * https://toolset.com/forums/topic/find-related-custom-post-type/
 */
 
add_filter( 'favorites/list/listing/html', 'custom_favorites_listing_html', 10, 4 );
function custom_favorites_listing_html($html, $markup_template, $post_id, $list_options)
{
  // relationship slugs per favorite post type
  $post_type = get_post_type( $post_id );
  switch($post_type) {
    case "livre":
      $rel_slug = "livre_artiste";
      break;
 
    case "oeuvre-sur-papier":
      $rel_slug = "oeuvre-sur-papier-artiste";
      break;
 
    default:
      return $html;
  };
   
  // Get related posts with Toolset post relationships API
  $children_args = [
    'query_by_role' => 'parent',
    'role_to_return' => 'child'
  ];
  $children = toolset_get_related_posts( $post_id, $rel_slug, $children_args);
   
  // Build a string of related post titles, separated by a comma, 
  // and concatenate it into response HTML, then return it
  $child_titles = [];
  if( $children && count( $children ) > 0 ) {
    foreach( $children as $child ){
      $child_titles[]= get_the_title($child);
    }
    return $html . implode(',', $child_titles);
  }
   
  // in case no related posts are found, return the default HTML
  return $html;
}