I recently wrote a plugin to provide missing GTIN, GTIN-8, GTIN-12 (UPC), GTIN-13 (EAN), GTIN-14, ISBN, MPN, Depth, and Volume values for WooCommerce Products and Variations. As part of that plugin, I extended the WordPress search feature to search metadata from WooCommerce products (and their variations). The standard way to extend the WordPress search feature is to hook the “pre_get_posts” action and modify the WP_Query to include additional posts / products in search results. There are some serious drawbacks to doing this – with or without WooCommerce – but especially with WooCommerce.