FacetWP - index multiple field values for a single autocomplete facet

test.php

<?php

// Add to functions.php
function fwp_combine_sources( $params, $class ) {
    if ( 'MY_FACET_NAME' == $params['facet_name'] ) {

        $value = get_field( 'YOUR_FIELD_1' );
        $params['facet_value'] = sanitize_title( $value );
        $params['facet_display_value'] = $value;
        $class->insert( $params );

        $value = get_field( 'YOUR_FIELD_2' );
        $params['facet_value'] = sanitize_title( $value );
        $params['facet_display_value'] = $value;
        $class->insert( $params );

        return false; // prevent default indexing
    }
    return $params;
}
add_filter( 'facetwp_index_row', 'fwp_combine_sources', 10, 2 );

Thanks so much for this! FYI, I ran into an issue where get_field() was returning a NULL value inside the filter function. Eventually, I realized that I needed to grab the post ID from the params array, like this:

$value = get_field('YOUR_FIELD_1', $params['post_id']);

That solved my issue and it worked great after that. Hope that helps anyone who was experiencing the same issue.

@mgibbs189 I'm coming from this filter example for facetwp_indexer_post_facet and now I wonder, isn't that one better performing for this purpose? At least to avoid querying taxonomies, post types or custom fields values that anyways are not going to be used by this facet.