make payment_provider and use_gift_cards exclusive

doc/api/resources/orders.rst

@@ -1104,10 +1104,9 @@ Creating orders
      pay for the order. Processing of the gift cards stops as soon as the order is payed for. All gift card transactions
      are listed under ``payments`` in the response.
      This option can only be used with orders that are in the pending state.
-     In addition to ``use_gift_cards``, you can provide ``payment_info`` and ``payment_provider`` fields. A matching
-     payment record for the ``payment_provider`` will be created once all the gift cards have been processed. This
-     entry's amount is what you'll need to charge your customer. The above-mentioned caveats for ``payment_info`` still
-     apply.
+     The ``use_gift_cards`` attribute can not be combined with ``payment_info`` and ``payment_provider`` fields. If the
+     order isn't completely paid after its creation with ``use_gift_cards``, then a subsequent request to the payment
+     endpoint is needed.
 
    If you want to use add-on products, you need to set the ``positionid`` fields of all positions manually
    to incrementing integers starting with ``1``. Then, you can reference one of these

src/pretix/api/serializers/order.py

@@ -1314,6 +1314,8 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
         simulate = validated_data.pop('simulate', False)
         gift_card_secrets = validated_data.pop('use_gift_cards') if 'use_gift_cards' in validated_data else []
 
+        if (payment_provider is not None or payment_info != '{}') and len(gift_card_secrets) > 0:
+            raise ValidationError({"use_gift_cards": ['The attribute use_gift_cards is not compatible with payment_provider or payment_info']})
         if validated_data.get('status') != Order.STATUS_PENDING and len(gift_card_secrets) > 0:
             raise ValidationError({"use_gift_cards": ['The attribute use_gift_cards is only supported for orders that are created as pending']})
         if len(set(gift_card_secrets)) != len(gift_card_secrets):

src/tests/api/test_order_create.py

@@ -3400,6 +3400,7 @@ def test_order_create_use_gift_cards_only_pending(token_client, organizer, event
     gc.transactions.create(value=Decimal("100.00"), acceptor=organizer).save()
 
     res['status'] = order_status
+    del res['payment_provider']
     res['use_gift_cards'] = [gc.secret]
 
     resp = token_client.post(
@@ -3430,7 +3431,6 @@ def test_order_create_use_gift_card(token_client, organizer, event, item, quota,
     res['positions'][0]['answers'][0]['question'] = question.pk
     with scopes_disabled():
         customer = organizer.customers.create()
-    del res['payment_provider']
 
     res['customer'] = customer.identifier
     res['api_meta'] = {
@@ -3442,7 +3442,7 @@ def test_order_create_use_gift_card(token_client, organizer, event, item, quota,
 
     gc = GiftCard.objects.create(issuer=organizer, currency='EUR')
     gc.transactions.create(value=Decimal("100.00"), acceptor=organizer).save()
-
+    del res['payment_provider']
     res['use_gift_cards'] = [gc.secret]
 
     djmail.outbox = []
@@ -3519,13 +3519,12 @@ def test_order_create_use_multiple_gift_cards(token_client, organizer, event, it
 
 
 @pytest.mark.django_db
-def test_order_create_use_gift_card_and_payment_provider(token_client, organizer, event, item, quota, question):
+def test_order_create_use_gift_card_exclusive_with_payment_provider(token_client, organizer, event, item, quota, question):
     res = copy.deepcopy(ORDER_CREATE_PAYLOAD)
     res['positions'][0]['item'] = item.pk
     res['positions'][0]['answers'][0]['question'] = question.pk
     with scopes_disabled():
         customer = organizer.customers.create()
-
     res['customer'] = customer.identifier
     res['api_meta'] = {
         'test': 1
@@ -3536,21 +3535,25 @@ def test_order_create_use_gift_card_and_payment_provider(token_client, organizer
 
     res['use_gift_cards'] = [gc.secret]
 
+    res_with_payment_provider=copy.deepcopy(res)
     resp = token_client.post(
         '/api/v1/organizers/{}/events/{}/orders/'.format(
             organizer.slug, event.slug
-        ), format='json', data=res
+        ), format='json', data=res_with_payment_provider
     )
-    assert resp.status_code == 201
+    assert resp.status_code == 400
+    assert resp.json() ==  {"use_gift_cards":["The attribute use_gift_cards is not compatible with payment_provider or payment_info"]}
 
-    with scopes_disabled():
-        o = Order.objects.get(code=resp.data['code'])
-        assert o.status == Order.STATUS_PENDING
-
-        open_payment = o.payments.last()
-        assert open_payment.state == OrderPayment.PAYMENT_STATE_CREATED
-        assert open_payment.amount == o.total - gc_value
-        assert open_payment.payment_provider.identifier == res['payment_provider']
+    res_with_payment_info = copy.deepcopy(res)
+    res_with_payment_info['payment_info'] = {"a": "b"}
+    del res_with_payment_info['payment_provider']
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res_with_payment_info
+    )
+    assert resp.status_code == 400
+    assert resp.json() ==  {"use_gift_cards":["The attribute use_gift_cards is not compatible with payment_provider or payment_info"]}
 
 
 @pytest.mark.django_db