filter unknown keys from choices due to django-formsets

src/pretix/api/serializers/organizer.py

@@ -643,7 +643,40 @@ class OrganizerSettingsSerializer(SettingsSerializer):
         return 'pub/' + fname
 
 
+class KeyLabelObjectListField(serializers.Field):
+
+    def to_representation(self, value):
+        # django added unneccessary keys DELETE, ORDER through formsets, filter them here for backwards compat
+        def strip_unknown_keys(v):
+            return {k: v[k] for k in v.keys() if k in ("key", "label")}
+        return [strip_unknown_keys(v) for v in value]
+
+    def to_internal_value(self, data):
+        if data is None:
+            return data
+        if not isinstance(data, list):
+            raise ValidationError("Choices need to be a list or null.")
+        if not data:
+            # empty list
+            return None
+
+        if any([not isinstance(choice, dict) for choice in data]):
+            raise ValidationError("Choices need to contain only objects.")
+
+        required_keys = {"key"}
+        allowed_keys = {"key", "label"}
+        if not all([required_keys <= set(choice.keys()) <= allowed_keys for choice in data]):
+            raise ValidationError("Each choice must contain a key and optionally a label.")
+
+        choice_keys = [choice.get("key") for choice in data]
+        if len(set(choice_keys)) < len(choice_keys):
+            raise ValidationError("Each choice must have a unique key.")
+        return data
+
+
 class EventMetaPropertiesSerializer(I18nAwareModelSerializer):
+    choices = KeyLabelObjectListField(allow_null=True)
+
     class Meta:
         model = EventMetaProperty
         fields = (
@@ -657,26 +690,13 @@ class EventMetaPropertiesSerializer(I18nAwareModelSerializer):
         full_data.update(data)
 
         choices = full_data.get("choices")
-        if "choices" in data and data["choices"] is not None:
-            if not isinstance(choices, list):
-                raise ValidationError("Choices need to be a list or null.")
-            if any([not isinstance(c, dict) for c in choices]):
-                raise ValidationError("Choices need to contain only objects.")
-            required_keys = {"key"}
-            allowed_keys = {"key", "label"}
-            if not all([required_keys <= set(c.keys()) <= allowed_keys for c in choices]):
-                raise ValidationError("Each choice must contain a key and optionally a label.")
-
-        if choices:
+        default = full_data.get("default")
+        if choices and default:
             choice_keys = [c.get("key") for c in choices]
-            if len(set(choice_keys)) < len(choice_keys):
-                raise ValidationError("Each choice must have a unique key.")
-
-            default = full_data.get("default")
-            if default and default not in choice_keys:
+            if default not in choice_keys:
                 raise ValidationError("You cannot set a default value that is not a valid value.")
 
         if not choices and "choices" in data:
-            # normalize empty dict to None 
+            # normalize empty dict to None
             data["choices"] = None
         return data

src/tests/api/test_event_meta_properties.py

@@ -29,7 +29,14 @@ def event_meta_property(organizer):
         name="Color",
         default="Red",
         required=False,
-        choices=None,
+        choices=[
+            {
+                "key": "Red",
+                "label": "Rot",
+                "DELETE": False,
+                "ORDER": 1,
+            }
+        ],
     )
 
 
@@ -37,7 +44,7 @@ TEST_TYPE_RES = {
     "name": "Color",
     "default": "Red",
     "required": False,
-    "choices": None,
+    "choices": [{"key": "Red", "label": "Rot"}],
     'filter_allowed': True,
     'filter_public': False,
     'protected': False,
@@ -141,6 +148,18 @@ def test_meta_property_patch(token_client, organizer, event_meta_property):
         }
     )
     assert resp.status_code == 400
+    resp = token_client.patch(
+        '/api/v1/organizers/{}/event_meta_properties/{}/'
+        .format(organizer.slug, event_meta_property.pk),
+        format='json',
+        data={
+            "choices": [],
+        }
+    )
+    assert resp.status_code == 200
+    event_meta_property.refresh_from_db()
+    assert event_meta_property.choices is None
+
     resp = token_client.patch(
         '/api/v1/organizers/{}/event_meta_properties/{}/'
         .format(organizer.slug, event_meta_property.pk),
@@ -156,8 +175,6 @@ def test_meta_property_patch(token_client, organizer, event_meta_property):
     assert event_meta_property.choices is None
 
 
-
-
 @pytest.mark.django_db
 def test_meta_property_delete(token_client, organizer, event_meta_property):
     resp = token_client.delete(