fix(core): Do not double-refund payments when refund total not covered

packages/core/e2e/order-modification.e2e-spec.ts

@@ -19,7 +19,7 @@ import gql from 'graphql-tag';
 import path from 'path';
 
 import { initialData } from '../../../e2e-common/e2e-initial-data';
-import { TEST_SETUP_TIMEOUT_MS, testConfig } from '../../../e2e-common/test-config';
+import { testConfig, TEST_SETUP_TIMEOUT_MS } from '../../../e2e-common/test-config';
 
 import {
     failsToSettlePaymentMethod,
@@ -1929,6 +1929,28 @@ describe('Order modification', () => {
             const variant2 = await getVariant('T_3');
             expect(variant2.stockOnHand).toBe(100);
             expect(variant2.stockAllocated).toBe(1);
+
+            const result = await adminTransitionOrderToState(orderId5, 'ArrangingAdditionalPayment');
+            orderGuard.assertSuccess(result);
+            expect(result!.state).toBe('ArrangingAdditionalPayment');
+            const { addManualPaymentToOrder } = await adminClient.query<
+                AddManualPayment.Mutation,
+                AddManualPayment.Variables
+            >(ADD_MANUAL_PAYMENT, {
+                input: {
+                    orderId: orderId5,
+                    method: 'test',
+                    transactionId: 'manual-extra-payment',
+                    metadata: {
+                        foo: 'bar',
+                    },
+                },
+            });
+            orderGuard.assertSuccess(addManualPaymentToOrder);
+            const result2 = await adminTransitionOrderToState(orderId5, 'PaymentSettled');
+            orderGuard.assertSuccess(result2);
+            const result3 = await adminTransitionOrderToState(orderId5, 'Modifying');
+            orderGuard.assertSuccess(result3);
         });
 
         it('updates stock when removing item before fulfillment', async () => {

packages/core/src/service/services/payment.service.ts

@@ -287,8 +287,7 @@ export class PaymentService {
             const paymentToRefund =
                 (refundedPaymentIds.length === 0 &&
                     refundablePayments.find(p => idsAreEqual(p.id, selectedPayment.id))) ||
-                refundablePayments.find(p => !refundedPaymentIds.includes(p.id)) ||
-                refundablePayments[0];
+                refundablePayments.find(p => !refundedPaymentIds.includes(p.id));
             if (!paymentToRefund) {
                 throw new InternalServerError(`Could not find a Payment to refund`);
             }