Fix: use validate_set_permissions' normalized dict, dedupe action list

BulkEditObjectsSerializer._validate_permissions discarded the
id-checked/None-normalized dict validate_set_permissions returns, so a
literal null for users/groups reached set_permissions_for_objects raw
and blew up with an uncaught TypeError, masked by the view's broad
except into a vague "check logs" 400. Now stores the returned dict back
onto attrs["permissions"].

Also replaced the two independently hardcoded ("view", "change") lists
in SetPermissionsSerializer.to_internal_value and
validate_set_permissions with one PERMISSION_ACTIONS constant, so
adding a new action can't update one and silently miss the other.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/documents/serialisers.py

@@ -210,6 +210,9 @@ class MatchingModelSerializer(serializers.ModelSerializer[Any]):
         return match
 
 
+PERMISSION_ACTIONS = ("view", "change")
+
+
 class SetPermissionsMixin:
     def _validate_user_ids(self, user_ids):
         users = User.objects.none()
@@ -232,12 +235,9 @@ class SetPermissionsMixin:
         return groups
 
     def validate_set_permissions(self, set_permissions=None):
-        permissions_dict = {
-            "view": {},
-            "change": {},
-        }
+        permissions_dict = {action: {} for action in PERMISSION_ACTIONS}
         if set_permissions is not None:
-            for action in ["view", "change"]:
+            for action in PERMISSION_ACTIONS:
                 if action in set_permissions:
                     if "users" in set_permissions[action]:
                         users = set_permissions[action]["users"]
@@ -284,7 +284,7 @@ class SetPermissionsSerializer(serializers.Serializer[dict[str, Any]]):
 
     def to_internal_value(self, data):
         if isinstance(data, dict):
-            unknown_keys = set(data) - {"view", "change"}
+            unknown_keys = set(data) - set(PERMISSION_ACTIONS)
             if unknown_keys:
                 raise serializers.ValidationError(
                     {key: "Unknown permission action." for key in sorted(unknown_keys)},
@@ -3032,8 +3032,8 @@ class BulkEditObjectsSerializer(SerializerWithPerms, SetPermissionsMixin):
             )
         return objects
 
-    def _validate_permissions(self, permissions) -> None:
-        self.validate_set_permissions(
+    def _validate_permissions(self, permissions) -> dict:
+        return self.validate_set_permissions(
             permissions,
         )
 
@@ -3061,7 +3061,7 @@ class BulkEditObjectsSerializer(SerializerWithPerms, SetPermissionsMixin):
                     raise serializers.ValidationError(
                         "permissions must not be empty",
                     )
-                self._validate_permissions(permissions)
+                attrs["permissions"] = self._validate_permissions(permissions)
 
         return attrs
 

src/documents/tests/test_api_permissions.py

@@ -1574,6 +1574,34 @@ class TestBulkEditObjectPermissions(APITestCase):
 
         self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
 
+    def test_bulk_object_set_permissions_null_users_is_a_noop(self) -> None:
+        """
+        GIVEN:
+            - Existing objects
+        WHEN:
+            - bulk_edit_objects API endpoint is called with set_permissions
+              operation and an explicit null for users/groups on an action
+        THEN:
+            - Request succeeds and is treated as "no users/groups for this
+              action", not a crash -- the normalized (id-checked) dict
+              returned by validate_set_permissions must actually be used,
+              not discarded in favor of the raw un-normalized input.
+        """
+        response = self.client.post(
+            "/api/bulk_edit_objects/",
+            json.dumps(
+                {
+                    "objects": [self.t1.id],
+                    "object_type": "tags",
+                    "operation": "set_permissions",
+                    "permissions": {"view": {"users": None}},
+                },
+            ),
+            content_type="application/json",
+        )
+
+        self.assertEqual(response.status_code, status.HTTP_200_OK)
+
     def test_bulk_edit_object_permissions_validation(self) -> None:
         """
         GIVEN: