WooCommerce Disable Coupons on Sale Items

gistfile1.php

<?php
// Exclude coupons from being applied when products on sale
add_filter( 'woocommerce_coupon_is_valid', 'woocommerce_coupon_check_sale_items', 10, 2 );
function woocommerce_coupon_check_sale_items( $valid, $coupon ) {
  	global $woocommerce;
  	
	$valid_for_cart = $valid;
	if (sizeof($woocommerce->cart->get_cart())>0) : foreach ($woocommerce->cart->get_cart() as $cart_item_key => $cart_item) :
		if ( function_exists( 'get_product') )
			$product = get_product( $cart_item['product_id'] );
		else $product = new WC_Product( $cart_item['product_id'] );

		if ( $product->is_on_sale() )
			$valid_for_cart = false;

	endforeach; endif;

	if ( ! $valid_for_cart ) $valid = false;
	
	return $valid;
}
?>

What does this function do that the "Exclude sale items" check box function does not do?

thanks

What does this function do that the "Exclude sale items" check box function does not do?

@mikakaltoft It does it manually, for all coupons. So useful when you have more number of coupons.