Bugfix unset reload issue

docs/changelog.rst

@@ -7,6 +7,7 @@ Changelog
 Development
 ===========
 - (Fill this out as you fix issues and develop your features).
+- Fix partial ``Document.reload()`` leaving custom ``db_field`` values marked as changed.
 
 Changes in 1.0.0
 ================

mongoengine/document.py

@@ -814,14 +814,13 @@ def reload(self, *fields, **kwargs):
                         # i.e. obj.update(unset__field=1) followed by obj.reload()
                         delattr(self, field)
 
-        self._changed_fields = (
-            list(set(self._changed_fields) - set(fields))
-            if fields
-            else obj._changed_fields
-        )
-        self._unset_fields = (
-            list(set(self._unset_fields) - set(fields)) if fields else obj._unset_fields
-        )
+        if fields:
+            reloaded_fields = {self._translate_field_name(field) for field in fields}
+            self._changed_fields = list(set(self._changed_fields) - reloaded_fields)
+            self._unset_fields = list(set(self._unset_fields) - reloaded_fields)
+        else:
+            self._changed_fields = obj._changed_fields
+            self._unset_fields = obj._unset_fields
         self._has_change_tracking_baseline = True
         self._created = False
         return self

tests/document/test_instance.py

@@ -650,6 +650,31 @@ class User(Document):
         assert user.phone == "01234"
         assert user.vital_signs.blood_pressure == 0.99
 
+    def test_reload__field_with_db_field_was_unset__clears_updated_fields(self):
+        class User(Document):
+            display_name = StringField(db_field="displayName")
+
+        User.drop_collection()
+
+        user = User(display_name="Alice").save()
+        del user.display_name
+
+        assert user._get_updated_fields() == ([], ["displayName"])
+
+        user.reload("display_name")
+
+        assert user.display_name == "Alice"
+        assert user._get_updated_fields() == ([], [])
+        assert user._delta() == ({}, {})
+
+        User.objects(id=user.id).update_one(set__display_name="Bob")
+        user.save()
+
+        assert get_as_pymongo(user) == {
+            "_id": user.id,
+            "displayName": "Bob",
+        }
+
     def test_save__reference_and_embedded_fields_are_deleted__unsets_whole_fields(
         self,
     ):