Order create API: Fix addon_to in simulated mode

PRETIXEU-275

src/pretix/api/serializers/order.py

@@ -416,6 +416,14 @@ class OrderSerializer(I18nAwareModelSerializer):
         return instance
 
 
+class SimulatedOrderPositionSerializer(OrderPositionSerializer):
+    addon_to = serializers.SlugRelatedField(read_only=True, slug_field='positionid')
+
+
+class SimulatedOrderSerializer(OrderSerializer):
+    positions = SimulatedOrderPositionSerializer(many=True, read_only=True)
+
+
 class PriceCalcSerializer(serializers.Serializer):
     item = serializers.PrimaryKeyRelatedField(queryset=Item.objects.none(), required=False, allow_null=True)
     variation = serializers.PrimaryKeyRelatedField(queryset=ItemVariation.objects.none(), required=False, allow_null=True)
@@ -963,7 +971,10 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
                 else:
                     pos.order = order
                 if addon_to:
-                    pos.addon_to = pos_map[addon_to]
+                    if simulate:
+                        pos.addon_to = pos_map[addon_to]._wrapped
+                    else:
+                        pos.addon_to = pos_map[addon_to]
 
                 if pos.price is None:
                     price = get_price(

src/pretix/api/views/order.py

@@ -26,7 +26,7 @@ from pretix.api.serializers.order import (
     InvoiceSerializer, OrderCreateSerializer, OrderPaymentCreateSerializer,
     OrderPaymentSerializer, OrderPositionSerializer,
     OrderRefundCreateSerializer, OrderRefundSerializer, OrderSerializer,
-    PriceCalcSerializer,
+    PriceCalcSerializer, SimulatedOrderSerializer,
 )
 from pretix.base.i18n import language
 from pretix.base.models import (
@@ -488,10 +488,12 @@ class OrderViewSet(viewsets.ModelViewSet):
             self.perform_create(serializer)
             send_mail = serializer._send_mail
             order = serializer.instance
-            serializer = OrderSerializer(order, context=serializer.context)
             if not order.pk:
                 # Simulation
+                serializer = SimulatedOrderSerializer(order, context=serializer.context)
                 return Response(serializer.data, status=status.HTTP_201_CREATED)
+            else:
+                serializer = OrderSerializer(order, context=serializer.context)
 
             order.log_action(
                 'pretix.event.order.placed',