Fix #864: ComplexDateTimeField should fall back to None when null=True

AUTHORS

@@ -216,3 +216,4 @@ that much better:
  * Mikhail Moshnogorsky (https://github.com/mikhailmoshnogorsky)
  * Diego Berrocal (https://github.com/cestdiego)
  * Matthew Ellison (https://github.com/seglberg)
+ * Jimmy Shen (https://github.com/jimmyshen)

docs/changelog.rst

@@ -5,6 +5,7 @@ Changelog
 
 Changes in 0.9.X - DEV
 ======================
+- ComplexDateTimeField should fall back to None when null=True #864
 - Request Support for $min, $max Field update operators #863
 - `BaseDict` does not follow `setdefault` #866
 - Add support for $type operator # 766
@@ -76,7 +77,6 @@ Changes in 0.9.X - DEV
 - Make `in_bulk()` respect `no_dereference()` #775
 - Handle None from model __str__; Fixes #753 #754
 
-
 Changes in 0.8.7
 ================
 - Calling reload on deleted / nonexistent documents raises DoesNotExist (#538)

mongoengine/fields.py

@@ -510,7 +510,7 @@ class ComplexDateTimeField(StringField):
     def __get__(self, instance, owner):
         data = super(ComplexDateTimeField, self).__get__(instance, owner)
         if data is None:
-            return datetime.datetime.now()
+            return None if self.null else datetime.datetime.now()
         if isinstance(data, datetime.datetime):
             return data
         return self._convert_from_string(data)

tests/document/instance.py

@@ -2760,6 +2760,12 @@ class InstanceTest(unittest.TestCase):
         class User(Document):
             name = StringField()
             height = IntField(default=184, null=True)
+            str_fld = StringField(null=True)
+            int_fld = IntField(null=True)
+            flt_fld = FloatField(null=True)
+            dt_fld = DateTimeField(null=True)
+            cdt_fld = ComplexDateTimeField(null=True)
+
         User.objects.delete()
         u = User(name='user')
         u.save()
@@ -2767,6 +2773,12 @@ class InstanceTest(unittest.TestCase):
         u_from_db.height = None
         u_from_db.save()
         self.assertEquals(u_from_db.height, None)
+        # 864
+        self.assertEqual(u_from_db.str_fld, None)
+        self.assertEqual(u_from_db.int_fld, None)
+        self.assertEqual(u_from_db.flt_fld, None)
+        self.assertEqual(u_from_db.dt_fld, None)
+        self.assertEqual(u_from_db.cdt_fld, None)
 
         # 735
         User.objects.delete()