only validate db_field if it's a string type

mongoengine/base/fields.py

@@ -41,7 +41,7 @@ class BaseField(object):
         """
         :param db_field: The database field to store this field in
             (defaults to the name of the field)
-        :param name: Depreciated - use db_field
+        :param name: Deprecated - use db_field
         :param required: If the field is required. Whether it has to have a
             value or not. Defaults to False.
         :param default: (optional) The default value for this field if no value
@@ -81,6 +81,17 @@ class BaseField(object):
         self.sparse = sparse
         self._owner_document = None
 
+        # Validate the db_field
+        if isinstance(self.db_field, six.string_types) and (
+            '.' in self.db_field or
+            '\0' in self.db_field or
+            self.db_field.startswith('$')
+        ):
+            raise ValueError(
+                'field names cannot contain dots (".") or null characters '
+                '("\\0"), and they must not start with a dollar sign ("$").'
+            )
+
         # Detect and report conflicts between metadata and base properties.
         conflicts = set(dir(self)) & set(kwargs)
         if conflicts:

mongoengine/document.py

@@ -313,9 +313,6 @@ class Document(BaseDocument):
         .. versionchanged:: 0.10.7
             Add signal_kwargs argument
         """
-        if self._meta.get('abstract'):
-            raise InvalidDocumentError('Cannot save an abstract document.')
-
         signal_kwargs = signal_kwargs or {}
         signals.pre_save.send(self.__class__, document=self, **signal_kwargs)
 
@@ -831,6 +828,7 @@ class Document(BaseDocument):
         """ Lists all of the indexes that should be created for given
         collection. It includes all the indexes from super- and sub-classes.
         """
+
         if cls._meta.get('abstract'):
             return []
 

mongoengine/queryset/transform.py

@@ -233,7 +233,8 @@ def update(_doc_cls=None, **update):
                 # Support decrement by flipping a positive value's sign
                 # and using 'inc'
                 op = 'inc'
-                value = -value
+                if value > 0:
+                    value = -value
             elif op == 'add_to_set':
                 op = 'addToSet'
             elif op == 'set_on_insert':

tests/document/instance.py

@@ -435,15 +435,6 @@ class InstanceTest(unittest.TestCase):
 
         person.to_dbref()
 
-    def test_save_abstract_document(self):
-        """Saving an abstract document should fail."""
-        class Doc(Document):
-            name = StringField()
-            meta = {'abstract': True}
-
-        with self.assertRaises(InvalidDocumentError):
-            Doc(name='aaa').save()
-
     def test_reload(self):
         """Ensure that attributes may be reloaded.
         """

tests/fields/fields.py

@@ -306,6 +306,24 @@ class FieldTest(unittest.TestCase):
         person.id = '497ce96f395f2f052a494fd4'
         person.validate()
 
+    def test_db_field_validation(self):
+        """Ensure that db_field doesn't accept invalid values."""
+
+        # dot in the name
+        with self.assertRaises(ValueError):
+            class User(Document):
+                name = StringField(db_field='user.name')
+
+        # name starting with $
+        with self.assertRaises(ValueError):
+            class User(Document):
+                name = StringField(db_field='$name')
+
+        # name containing a null character
+        with self.assertRaises(ValueError):
+            class User(Document):
+                name = StringField(db_field='name\0')
+
     def test_string_validation(self):
         """Ensure that invalid values cannot be assigned to string fields.
         """
@@ -3973,30 +3991,25 @@ class FieldTest(unittest.TestCase):
         """Tests if a `FieldDoesNotExist` exception is raised when trying to
         instanciate a document with a field that's not defined.
         """
-
         class Doc(Document):
-            foo = StringField(db_field='f')
+            foo = StringField()
 
-        def test():
+        with self.assertRaises(FieldDoesNotExist):
             Doc(bar='test')
 
-        self.assertRaises(FieldDoesNotExist, test)
 
     def test_undefined_field_exception_with_strict(self):
         """Tests if a `FieldDoesNotExist` exception is raised when trying to
         instanciate a document with a field that's not defined,
         even when strict is set to False.
         """
-
         class Doc(Document):
-            foo = StringField(db_field='f')
+            foo = StringField()
             meta = {'strict': False}
 
-        def test():
+        with self.assertRaises(FieldDoesNotExist):
             Doc(bar='test')
 
-        self.assertRaises(FieldDoesNotExist, test)
-
     def test_long_field_is_considered_as_int64(self):
         """
         Tests that long fields are stored as long in mongo, even if long value

tests/queryset/queryset.py

@@ -1826,11 +1826,6 @@ class QuerySetTest(unittest.TestCase):
         post.reload()
         self.assertEqual(post.hits, 10)
 
-        # Negative dec operator is equal to a positive inc operator
-        BlogPost.objects.update_one(dec__hits=-1)
-        post.reload()
-        self.assertEqual(post.hits, 11)
-
         BlogPost.objects.update(push__tags='mongo')
         post.reload()
         self.assertTrue('mongo' in post.tags)