FacetWP - automatically index all child terms when a parent taxonomy term is checked

facetwp-autoindex-child-terms.php

/**
* Filter to customize FacetWP, should be pasted in FacetWP's "Custom Hooks" plugin
* 
* Made for a "location" FacetWP autocomplete filter that uses a taxonomy "location" 
* consisting of parent county terms and child city terms
*
* When indexing, for every post, for the location taxonomy filter, 
* Check to see if it has any location taxonomy set
* Check to see if selected location taxonomy has children (i.e. selected county has cities)
* Create a new index row for each child city
* 
* So that Admin Panel editors can check only county for content
* But front-end users will be able to type city into autocomplete and find parent county content
*/
add_filter( 'facetwp_indexer_row_data', function( $rows, $params ) {
	if ( 'location_filter' == $params['facet']['name'] ) {
   			
        $post_id = (int) $params['defaults']['post_id'];

        $locations = get_the_terms( $post_id, 'location' );
        if ( !empty( $locations ) ) {
			foreach ( $locations as $location ) { 

				$child_term_ids = get_term_children( $location->term_id, 'location' );
				if ( !empty( $child_term_ids ) ){
				
					foreach ($child_term_ids as $child_term_id){
						$term = get_term_by('id', $child_term_id, 'location'); 

						$new_row = $params['defaults'];
	        			$new_row['facet_value'] = $term->slug;
	        			$new_row['facet_display_value'] = $term->name;
	        			$new_row['term_id'] = $term->term_id; 
	        			$new_row['parent_id'] = $term->parent;
	        			$new_row['depth'] = '1';
	        			$rows[] = $new_row;

					}
				}	
			}//foreach location term
		}//if location taxonomy assigned
	
	}
	return $rows;
}, 10, 2 );