Limit search results to WooCommerce Products only in frontend

functions.php

/**
 * Only allow the product CPT to be search on the golbal search page
 *
 *  @param WP_Query $query The WP_Query instance (passed by reference).
 */
function tometal_filter_search_only_products( $query ) {

	if ( ! is_admin() && $query->is_main_query() && $query->is_search() ) {
		$query->set( 'post_type', 'product' );
	}
}
add_action( 'pre_get_posts', 'tometal_filter_search_only_products' );