Using meta query (‘meta_query’) with a search query (‘s’)

I have been searching for hours for a solution to this problem. Array merging is not the way to go, especially when the queries are complex and you must be able to add to meta queries in the future. The solution which is simplistically beautiful is to change ‘s’ to one which allows both searching titles and meta fields.

add_action( 'pre_get_posts', function( $q )
{
    if( $title = $q->get( '_meta_or_title' ) )
    {
        add_filter( 'get_meta_sql', function( $sql ) use ( $title )
        {
            global $wpdb;

            // Only run once:
            static $nr = 0; 
            if( 0 != $nr++ ) return $sql;

            // Modified WHERE
            $sql['where'] = sprintf(
                " AND ( %s OR %s ) ",
                $wpdb->prepare( "{$wpdb->posts}.post_title like '%%%s%%'", $title),
                mb_substr( $sql['where'], 5, mb_strlen( $sql['where'] ) )
            );

            return $sql;
        });
    }
});

Usage:

$meta_query = array();
$args = array();
$search_string = "test";

$meta_query[] = array(
    'key' => 'staff_name',
    'value' => $search_string,
    'compare' => 'LIKE'
);
$meta_query[] = array(
    'key' => 'staff_email',
    'value' => $search_string,
    'compare' => 'LIKE'
);

//if there is more than one meta query 'or' them
if(count($meta_query) > 1) {
    $meta_query['relation'] = 'OR';
}

// The Query
$args['post_type'] = "staff";
$args['_meta_or_title'] = $search_string; //not using 's' anymore
$args['meta_query'] = $meta_query;



$the_query = new WP_Query($args)