API: Correctly set default position IDs for orders

src/pretix/api/serializers/order.py

@@ -312,7 +312,6 @@ class OrderSerializer(I18nAwareModelSerializer):
         # Even though all fields that shouldn't be edited are marked as read_only in the serializer
         # (hopefully), we'll be extra careful here and be explicit about the model fields we update.
         update_fields = ['comment', 'checkin_attention', 'email', 'locale']
-        print(validated_data)
 
         if 'invoice_address' in validated_data:
             iadata = validated_data.pop('invoice_address')
@@ -598,6 +597,9 @@ class OrderCreateSerializer(I18nAwareModelSerializer):
                 {'positionid': ["If you set addon_to on any position, you need to specify position IDs manually."]}
                 for p in data
             ]
+        else:
+            for i, p in enumerate(data):
+                p['positionid'] = i + 1
 
         if any(errs):
             raise ValidationError(errs)

src/tests/api/test_orders.py

@@ -2064,6 +2064,37 @@ def test_order_create_positionid_validation(token_client, organizer, event, item
         ]
     }
 
+    res['positions'] = [
+        {
+            "item": item.pk,
+            "variation": None,
+            "price": "23.00",
+            "attendee_name_parts": {"full_name": "Peter"},
+            "attendee_email": None,
+            "answers": [],
+            "subevent": None
+        },
+        {
+            "item": item.pk,
+            "variation": None,
+            "price": "23.00",
+            "attendee_name_parts": {"full_name": "Peter"},
+            "attendee_email": None,
+            "answers": [],
+            "subevent": None
+        }
+    ]
+    resp = token_client.post(
+        '/api/v1/organizers/{}/events/{}/orders/'.format(
+            organizer.slug, event.slug
+        ), format='json', data=res
+    )
+    assert resp.status_code == 201
+    with scopes_disabled():
+        o = Order.objects.get(code=resp.data['code'])
+        assert o.positions.first().positionid == 1
+        assert o.positions.last().positionid == 2
+
 
 @pytest.mark.django_db
 def test_order_create_answer_validation(token_client, organizer, event, item, quota, question, question2):