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Apply discount codes at checkout #25

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Apply discount codes at checkout #25

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9 changes: 6 additions & 3 deletions apps/pr-reviewer/fixtures/demo-pr/cart-total.ts
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Original file line number Diff line number Diff line change
@@ -1,15 +1,18 @@
import { applyDiscount } from './discount.ts';
import { shippingCost } from './shipping.ts';

export function cartTotal(items: { price: number; qty: number }[]): number {
export function cartTotal(
items: { price: number; qty: number }[],
discountPercent = 0,
): number {
let total = 0;
for (let i = 0; i < items.length; i++) {
if (items[i].qty < 0) {
throw new RangeError(`Negative quantity for item ${i}`);
}
total += items[i].price * items[i].qty;
}
return total;
return applyDiscount(total, discountPercent);
}

export type Cart = {
Expand All @@ -25,7 +28,7 @@ function roundCents(amount: number): number {
}

export function checkoutTotal(cart: Cart): number {
const subtotal = cartTotal(cart.items);
const subtotal = cartTotal(cart.items, cart.discount?.percent);

@cursor cursor Bot Oct 17, 2026

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Discount applied twice at checkout

High Severity

checkoutTotal still runs applyDiscount on the post-tax total after already passing cart.discount.percent into cartTotal, so the same code is taken off twice and customers are undercharged.

Additional Locations (2)
Fix in Cursor Fix in Web

Reviewed by Cursor Bugbot for commit 22aaa44. Configure here.

const shipping = shippingCost(cart.weightKg, cart.express);
const freeShipping = subtotal >= 100;
const shippingCharge = freeShipping ? 0 : shipping;
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