facetwp index parents

custom-hooks.php

<?php

add_filter( 'facetwp_index_row', function ( $params, $class ) {
    if ( 'my_facet' == $params['facet_name'] ) { // change 'my_facet' to facet name
        if ( 0 !== $params['depth'] ) {
            // lookup parent terms
            $ancestors = get_ancestors( $params['facet_name'], 'name_of_taxonomy', 'taxonomy' ); // 'name_of_taxonomy' to name of taxonomy
            $starting_depth = $params['depth'];
            foreach ( $ancestors as $ancestor ) {
                $term = get_term( $ancestor, 'name_of_taxonomy' ); // 'name_of_taxonomy' to name of taxonomy
                $ancester_params = $params;
                $ancester_params['depth'] = --$starting_depth;
                $ancester_params['facet_value'] = $term->slug;
                $ancester_params['facet_display_value'] = $term->name;
                $class->insert( $ancester_params ); // insert each value to the database
            }
        }
    }
    return $params;
}, 10, 2 );