Enable SKU search in woocommerce

functions.php

<?php
/**
 * Join posts and postmeta tables
 *
 * @param string   $join
 * @param WP_Query $query
 *
 * @see https://iconicwp.com/blog/add-product-sku-woocommerce-search/
 *
 * @return string
 */
function iconic_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} iconic_post_meta ON {$wpdb->posts}.ID = iconic_post_meta.post_id ";

	return $join;
}

add_filter( 'posts_join', 'iconic_product_search_join', 10, 2 );

/**
 * Modify the search query with posts_where.
 *
 * @param string   $where
 * @param WP_Query $query
 *
 * @see https://iconicwp.com/blog/add-product-sku-woocommerce-search/
 *
 * @return string
 */
function iconic_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 (iconic_post_meta.meta_key = '_sku' AND iconic_post_meta.meta_value LIKE $1)", $where );

	return $where;
}

add_filter( 'posts_where', 'iconic_product_search_where', 10, 2 );