Fix behavior when patch removes null uneditable fields

scim2_server/operators.py

@@ -258,16 +258,17 @@ class RemoveOperator(Operator):
     @classmethod
     def operation(cls, model: BaseModel, attribute: str, value: Any):
         alias = get_by_alias(type(model), attribute)
-        existing_value = getattr(model, alias)
-        if not existing_value:
-            return
 
         if model.get_field_annotation(alias, Mutability) in (
             Mutability.read_only,
             Mutability.immutable,
         ):
             raise SCIMException(Error.make_mutability_error())
 
+        existing_value = getattr(model, alias)
+        if not existing_value:
+            return
+
         if model.get_field_annotation(alias, Required) == Required.true:
             raise SCIMException(Error.make_invalid_value_error())
 

tests/test_operators.py

@@ -451,6 +451,16 @@ def test_simple_remove_operator_immutable(self):
         with pytest.raises(SCIMException, match="immutable"):
             RemoveOperator.operation(u, "groups", None)
 
+    def test_remove_operator_mutability_validation_on_empty_fields(self):
+        """Test that mutability constraints are enforced even on empty/unset fields."""
+        u = User(id="123")  # groups field is None/empty by default
+        with pytest.raises(SCIMException, match="mutability"):
+            RemoveOperator.operation(u, "groups", None)
+
+        u2 = User()  # id field is None/empty by default
+        with pytest.raises(SCIMException, match="mutability"):
+            RemoveOperator.operation(u2, "id", None)
+
     def test_remove_operator_root_object(self):
         u = User()
         with pytest.raises(SCIMException, match="noTarget"):