Fix: DictField are always marked as changed

mongoengine/base/datastructures.py

@@ -31,9 +31,9 @@ def mark_key_as_changed_wrapper(parent_method):
 
     def wrapper(self, key, *args, **kwargs):
         # Can't use super() in the decorator.
-        result = parent_method(self, key, *args, **kwargs)
-        self._mark_as_changed(key)
-        return result
+        if not args or not key or key not in self or self[key] != args[0]:
+            self._mark_as_changed(key)
+        return parent_method(self, key, *args, **kwargs)
 
     return wrapper
 

tests/document/test_delta.py

@@ -952,6 +952,31 @@ class Doc(Document):
         assert "oops" == delta[0]["users.007.rolist"][0]["type"]
         assert uinfo.id == delta[0]["users.007.info"]
 
+    def test_delta_on_dict(self):
+        class MyDoc(Document):
+            dico = DictField()
+
+        MyDoc.drop_collection()
+
+        MyDoc(dico={"a": {"b": 0}}).save()
+
+        mydoc = MyDoc.objects.first()
+        assert mydoc._get_changed_fields() == []
+        mydoc.dico["a"]["b"] = 0
+        assert mydoc._get_changed_fields() == []
+        mydoc.dico["a"] = {"b": 0}
+        assert mydoc._get_changed_fields() == []
+        mydoc.dico = {"a": {"b": 0}}
+        assert mydoc._get_changed_fields() == []
+        mydoc.dico["a"]["c"] = 1
+        assert mydoc._get_changed_fields() == ["dico.a.c"]
+        mydoc.dico["a"]["b"] = 2
+        mydoc.dico["d"] = 3
+        assert mydoc._get_changed_fields() == ["dico.a.c", "dico.a.b", "dico.d"]
+
+        mydoc._clear_changed_fields()
+        assert mydoc._get_changed_fields() == []
+
 
 if __name__ == "__main__":
     unittest.main()