2 discount bug fixes (multiple discounts + shipping discounts) #1039

kdaviduik · 2025-06-20T21:08:29Z

Nicer diffs if you review commit by commit (and without whitespace diffs!) :)

Fix bug with adding multiple discount codes when not all codes are applicable
- A discount code can be added to a cart but might not be applicable. In that case, the code will appear in the discountCodes array, but there won't be any discount allocations.
- Since we were using discount allocations to determine which discount codes existed, we would end up inadvertently removing discount codes that were added but not applicable.
Fix bug where a shipping discount could appear as a line item discount (ie: fixes Discount allocation mapping "graceful abort" causing frontend to incorrectly show discounts (from #1032) #1040)
- Our previous discount mapping logic did not properly map shipping discounts - they were treated the same as order-level discounts, but behave differently.
- Unlike order-level discounts (which must get mapped onto line items), shipping discounts should ONLY appear in the checkout.discountApplications array.
- Importantly, if a shipping discount has been added but there is no shipping address known, the Cart APIs behave differently than the Checkout APIs and we therefore have no way of knowing the value, target type, etc. This information was returned by the Checkout APIs in the checkout.discountApplications array, but now we cannot return shipping discounts in that array if we don't have a shipping address.

src/utilities/cart-discount-mapping.js

…plicable A discount code can be added to a cart but might not be `applicable`. In that case, the code will appear in the `discountCodes` array, but there won't be any discount allocations. Since we were using discount allocations to determine which discount codes existed, we would end up inadvertently removing discount codes that were added but not `applicable`.

We're going to use this in the next commit. Separating out this change makes the diffs much easier to read

test/client-checkout-discounts-integration-test.js

src/checkout-resource.js

Our previous discount mapping logic did not properly map shipping discounts - they were treated the same as order-level discounts, but behave differently. Unlike order-level discounts (which must get mapped onto line items), shipping discounts should ONLY appear in the `checkout.discountApplications` array. Importantly, if a shipping discount has been added but there is no shipping address known, the Cart APIs behave differently than the Checkout APIs and we therefore have no way of knowing the value, target type, etc. This information was returned by the Checkout APIs in the `checkout.discountApplications` array, but now we cannot return shipping discounts in that array if we don't have a shipping address.

juanpprieto

Amazing, thanks LGTM

kdaviduik self-assigned this Jun 20, 2025

kdaviduik requested a review from juanpprieto June 20, 2025 21:08

kdaviduik force-pushed the kd-shipping-discount-fix branch from 878bc8c to f4b3f4b Compare June 20, 2025 21:09

kdaviduik marked this pull request as draft June 20, 2025 21:11

kdaviduik force-pushed the kd-shipping-discount-fix branch 3 times, most recently from 21fc47a to ee368bb Compare June 20, 2025 21:18