woocommerce_product_is_on_sale filter-hook . WC 1.0

Usage

add_filter( 'woocommerce_product_is_on_sale', 'filter_function_name_5112', 10, 2 );
function filter_function_name_5112( $on_sale, $that ){
	// filter...

	return $on_sale;
}

$on_sale

-

$that

-

Where the hook is called

return 'view' === $context ? apply_filters( 'woocommerce_product_is_on_sale', $on_sale, $this ) : $on_sale;

return 'view' === $context ? apply_filters( 'woocommerce_product_is_on_sale', $on_sale, $this ) : $on_sale;

return 'view' === $context ? apply_filters( 'woocommerce_product_is_on_sale', $on_sale, $this ) : $on_sale;

Where in WP core the hook is used WooCommerce