Developer forum

We have a customer voucher discount, which in our code loops though the orderlines and adds those to determine the maximum discount to give without resulting in a negative order price.

Example
discount: 120 euro
product 1: 20 euro
product 2: 30 euro
shipping :  5 euro

Our discount providers calculates the discount price as 55 euro.
So the order looks like:

product 1: 20 euro
product 2: 30 euro
shipping : 5 euro
discount : 55 euro 
total order: 0 euro

Now if we active an additional discount, like 10 euro discount on product 1 we get:

product 1: 20 euro
product 2: 30 euro
shipping : 5 euro
discount : 55 euro
discount : 10 euro
total order: -10 euro

In the discount provider we already loop though the orderlines, however the discount order lines are not available.
Probably because discounts are handled after the providers have triggered to ensure correct behavior.

However it seems necessary to be able to retrieve the discounts that apply on the order in the discount provider so we can make sure the discount we give is never more then the total order amount.