Correcly cancel payments when starting a new one

src/pretix/base/services/orders.py

@@ -1470,7 +1470,7 @@ def cancel_order(self, order: int, user: int=None, send_mail: bool=True, api_tok
         raise OrderError(error_messages['busy'])
 
 
-def change_payment_provider(order: Order, payment_provider, amount=None):
+def change_payment_provider(order: Order, payment_provider, amount=None, new_payment=None):
     e = OrderPayment.objects.filter(fee=OuterRef('pk'), state__in=(OrderPayment.PAYMENT_STATE_CONFIRMED,
                                                                    OrderPayment.PAYMENT_STATE_REFUNDED))
     open_fees = list(
@@ -1502,7 +1502,10 @@ def change_payment_provider(order: Order, payment_provider, amount=None):
             fee = None
 
     open_payment = None
-    lp = order.payments.exclude(provider=payment_provider.identifier).last()
+    if new_payment:
+        lp = order.payments.exclude(pk=new_payment.pk).last()
+    else:
+        lp = order.payments.last()
     if lp and lp.state not in (OrderPayment.PAYMENT_STATE_CONFIRMED, OrderPayment.PAYMENT_STATE_REFUNDED):
         open_payment = lp
 

src/pretix/plugins/banktransfer/tasks.py

@@ -109,7 +109,7 @@ def _handle_transaction(trans: BankTransaction, code: str, event: Event=None, or
 
         if created:
             # We're perform a payment method switchign on-demand here
-            old_fee, new_fee, fee = change_payment_provider(trans.order, p.payment_provider, p.amount)  # noqa
+            old_fee, new_fee, fee = change_payment_provider(trans.order, p.payment_provider, p.amount, new_payment=p)  # noqa
             if fee:
                 p.fee = fee
                 p.save(update_fields=['fee'])

src/tests/presale/test_orders.py

@@ -681,6 +681,47 @@ class OrdersTest(TestCase):
         p.refresh_from_db()
         assert p.state == OrderPayment.PAYMENT_STATE_CREATED
 
+    def test_change_paymentmethod_to_same(self):
+        p_old = self.order.payments.create(
+            provider='banktransfer',
+            state=OrderPayment.PAYMENT_STATE_CREATED,
+            amount=Decimal('10.00'),
+        )
+        self.client.post(
+            '/%s/%s/order/%s/%s/pay/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret),
+            {
+                'payment': 'banktransfer'
+            }
+        )
+        self.order.refresh_from_db()
+        p_new = self.order.payments.last()
+        assert p_new.provider == 'banktransfer'
+        assert p_new.id != p_old.id
+        assert p_new.state == OrderPayment.PAYMENT_STATE_CREATED
+        p_old.refresh_from_db()
+        assert p_old.state == OrderPayment.PAYMENT_STATE_CANCELED
+
+    def test_change_paymentmethod_cancel_old(self):
+        self.event.settings.set('payment_banktransfer__enabled', True)
+        p_old = self.order.payments.create(
+            provider='testdummy',
+            state=OrderPayment.PAYMENT_STATE_CREATED,
+            amount=Decimal('10.00'),
+        )
+        self.client.post(
+            '/%s/%s/order/%s/%s/pay/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret),
+            {
+                'payment': 'banktransfer'
+            }
+        )
+        self.order.refresh_from_db()
+        p_new = self.order.payments.last()
+        assert p_new.provider == 'banktransfer'
+        assert p_new.id != p_old.id
+        assert p_new.state == OrderPayment.PAYMENT_STATE_CREATED
+        p_old.refresh_from_db()
+        assert p_old.state == OrderPayment.PAYMENT_STATE_CANCELED
+
     def test_change_paymentmethod_delete_fee(self):
         self.event.settings.set('payment_banktransfer__enabled', True)
         self.event.settings.set('payment_testdummy__enabled', True)