Code-Snippets-Functions/Execute a function on a child site/WooCommerce/automatic-sales-category.txt

add_action( 'woocommerce_product_query', 'wc_sale_category' );
 
function wc_sale_category( $q ) {
   if ( "sale" !== $q->get( 'product_cat' ) ) return; // "sale" = slug
   $q->set( 'post_type', 'product' );
   $q->set( 'product_cat', null );
   $product_ids_on_sale = wc_get_product_ids_on_sale() ? wc_get_product_ids_on_sale() : array();
   $q->set( 'post__in', $product_ids_on_sale );
}