WC - Add SKU In WooCommerce Product Search

functions.php

/**
 * Join posts and postmeta tables
 *
 * @param string   $join
 * @param WP_Query $query
 * @return string
 */
if( ! function_exists( 'wc_custom_product_search_join' ) ) {
    function wc_custom_product_search_join( $join, $query ) {
        if ( ! $query->is_main_query() || is_admin() || ! is_search() || ! is_woocommerce() ) {
            return $join;
        }

        global $wpdb;

        $join .= " LEFT JOIN {$wpdb->postmeta} postmeta ON {$wpdb->posts}.ID = postmeta.post_id ";

        return $join;
    }
}
add_filter( 'posts_join', 'wc_custom_product_search_join', 10, 2 );

/**
 * Modify the search query with posts_where.
 *
 * @param string   $where
 * @param WP_Query $query
 * @return string
 */
if( ! function_exists( 'wc_custom_product_search_where' ) ) {
    function wc_custom_product_search_where( $where, $query ) {
        if ( ! $query->is_main_query() || is_admin() || ! is_search() || ! is_woocommerce() ) {
            return $where;
        }

        global $wpdb;

        $where = preg_replace(
            "/\(\s*{$wpdb->posts}.post_title\s+LIKE\s*(\'[^\']+\')\s*\)/",
            "({$wpdb->posts}.post_title LIKE $1) OR (postmeta.meta_key = '_sku' AND postmeta.meta_value LIKE $1)", $where );

        return $where;
    }
}
add_filter( 'posts_where', 'wc_custom_product_search_where', 10, 2 );