Merge pull request #1640 from erdenezul/fix_changed_field_reload

add fix for reload(fields) affect changed fields #1371

docs/changelog.rst

@@ -13,6 +13,7 @@ dev
 -  Use insert_one, insert_many in Document.insert #1491
 -  Use new update_one, update_many on document/queryset update #1491
 -  Use insert_one, insert_many in Document.insert #1491
+-  Fix reload(fields) affect changed fields #1371
 
 Changes in 0.15.0
 =================

mongoengine/document.py

@@ -705,7 +705,6 @@ class Document(BaseDocument):
             obj = obj[0]
         else:
             raise self.DoesNotExist('Document does not exist')
-
         for field in obj._data:
             if not fields or field in fields:
                 try:
@@ -721,7 +720,9 @@ class Document(BaseDocument):
                         # i.e. obj.update(unset__field=1) followed by obj.reload()
                         delattr(self, field)
 
-        self._changed_fields = obj._changed_fields
+        self._changed_fields = list(
+            set(self._changed_fields) - set(fields)
+        ) if fields else obj._changed_fields
         self._created = False
         return self
 

tests/document/instance.py

@@ -476,6 +476,24 @@ class InstanceTest(unittest.TestCase):
         doc.save()
         doc.reload()
 
+    def test_reload_with_changed_fields(self):
+        """Ensures reloading will not affect changed fields"""
+        class User(Document):
+            name = StringField()
+            number = IntField()
+        User.drop_collection()
+
+        user = User(name="Bob", number=1).save()
+        user.name = "John"
+        user.number = 2
+
+        self.assertEqual(user._get_changed_fields(), ['name', 'number'])
+        user.reload('number')
+        self.assertEqual(user._get_changed_fields(), ['name'])
+        user.save()
+        user.reload()
+        self.assertEqual(user.name, "John")
+
     def test_reload_referencing(self):
         """Ensures reloading updates weakrefs correctly."""
         class Embedded(EmbeddedDocument):
@@ -521,7 +539,7 @@ class InstanceTest(unittest.TestCase):
         doc.save()
         doc.dict_field['extra'] = 1
         doc = doc.reload(10, 'list_field')
-        self.assertEqual(doc._get_changed_fields(), [])
+        self.assertEqual(doc._get_changed_fields(), ['dict_field.extra'])
         self.assertEqual(len(doc.list_field), 5)
         self.assertEqual(len(doc.dict_field), 3)
         self.assertEqual(len(doc.embedded_field.list_field), 4)