DiscountRewardProvider not assigning discount

[TresBlue]

Which component is this issue related to?

Umbraco Commerce (Core)

Which Umbraco Commerce version are you using? (Please write the exact version, example: 10.1.0)

13.2.3

Bug summary

We’ve built our own DiscountRewardProvider following the documentation:
https://docs.umbraco.com/umbraco-commerce/13.latest/key-concepts/discount-rules-and-rewards

Our goal is to calculate discounts based on order lines. If an order line is a bundle, the discount should only apply to the unit/base price of the product.

However, when we implement this, no discount is applied.

What we observed while debugging

• Our code is triggered three times.
• On the first and third runs, ctx.Order.OrderLines do not have a UnitPrice, so no discount is applied.
• On the second run, the order lines contain the expected information, and a price adjustment is added.

Despite this, once the process finishes, no discount appears on the order.

Additional check

If we hardcode a discount, it is applied successfully.

Specifics

Our code:

[DiscountRewardProvider("myDiscountReward", "My Discount Reward")]
public class MyDiscountRewardProvider(Lazy<IMemberService> _memberService,
	IUmbracoHelperAccessor helperAccessor) : DiscountRewardProviderBase<MyDiscountRewardProviderSettings>
{
	public override DiscountRewardCalculation CalculateReward(DiscountRewardContext ctx, MyDiscountRewardProviderSettings settings)
	{
		var result = new DiscountRewardCalculation();

		if (ctx.Order.OrderLines.All(x => x.UnitPrice?.Value == null))
		{
			// No usable prices yet, skip this evaluation
			return result;
		}

		if (!helperAccessor.TryGetUmbracoHelper(out var umbracoHelper))
		{
			return result;
		}

		if (string.IsNullOrWhiteSpace(ctx.Order.CustomerInfo.CustomerReference))
		{
			return result;
		}

		IMember member = null;
		int result2;
		if (Guid.TryParse(ctx.Order.CustomerInfo.CustomerReference, out var memberResult))
		{
			member = _memberService.Value.GetByKey(memberResult);
		}
		else if (int.TryParse(ctx.Order.CustomerInfo.CustomerReference, out result2))
		{
			member = _memberService.Value.GetById(result2);
		}

		if (member != null && member.GetValue<int>("hasSeasonTicket") == 1)
		{
			decimal price = 0;
			decimal priceTax = 0;

			foreach (var orderLine in ctx.Order.OrderLines)
			{
				var content = umbracoHelper.Content(Guid.Parse(orderLine.ProductReference));
				var product = content as IProduct;

				if (!product?.NoDiscountAllowed ?? true)
				{
					price += (orderLine.UnitPrice?.Value?.WithoutTax / settings.DiscountAmount) ?? 0;
					priceTax += (orderLine.UnitPrice?.Value?.Tax / settings.DiscountAmount) ?? 0;
				}
			}

			var discountPrice = new Price(-price, -priceTax, ctx.Currency);

			result.SubtotalPriceAdjustments.Add(new DiscountAdjustment(ctx.Discount, discountPrice));
		}


		return result;
	}
}

public class MyDiscountRewardProviderSettings
{
	[DiscountRewardProviderSetting(Key = "discountAmount",
		Name = "Discount Amount",
		Description = "The percentage discount given")]

	public decimal DiscountAmount { get; set; }

}

If we change var discountPrice = new Price(-price, -priceTax, ctx.Currency); to var discountPrice = new Price((decimal)-7.9, (decimal)-2.1, ctx.Currency);
the discount does get added.

Steps to reproduce

Use above code, add a product to your cart. Remove the member logic in above code.

Expected result / actual result

No response

Dependencies

No response

[mattbrailsford]

During calculation you shouldn't read the prices from the order. These are effectively a snapshot of the prices before calculation began. You should instead read from the order calculation state https://docs.umbraco.com/umbraco-commerce/key-concepts/order-calculation-state

[TresBlue]

This was indeed the probleem. Thank you for your fast reply.