Merge pull request marshmallow-code#1685 from marshmallow-code/dict_c…

…ast_mapping_type

Cast to mapping type in Mapping.serialize/deserialize

CHANGELOG.rst

@@ -1,6 +1,16 @@
 Changelog
 ---------
 
+3.9.1 (unreleased)
+******************
+
+Bug fixes:
+
+- Cast to mapping type in ``Mapping.serialize`` and ``Mapping.deserialize``
+  (:pr:`1685`).
+- Fix bug letting ``Dict`` pass invalid dict on deserialization when no key or
+  value ``Field`` is specified (:pr:`1685`).
+
 3.9.0 (2020-10-31)
 ******************
 

src/marshmallow/fields.py

@@ -1505,7 +1505,7 @@ def _serialize(self, value, attr, obj, **kwargs):
         if value is None:
             return None
         if not self.value_field and not self.key_field:
-            return value
+            return self.mapping_type(value)
 
         #  Serialize keys
         if self.key_field is None:
@@ -1532,7 +1532,7 @@ def _deserialize(self, value, attr, data, **kwargs):
         if not isinstance(value, _Mapping):
             raise self.make_error("invalid")
         if not self.value_field and not self.key_field:
-            return value
+            return self.mapping_type(value)
 
         errors = collections.defaultdict(dict)
 

tests/test_deserialization.py

@@ -719,8 +719,13 @@ def test_invalid_date_field_deserialization(self, in_value):
         assert excinfo.value.args[0] == msg
 
     def test_dict_field_deserialization(self):
+        data = {"foo": "bar"}
         field = fields.Dict()
-        assert field.deserialize({"foo": "bar"}) == {"foo": "bar"}
+        load = field.deserialize(data)
+        assert load == {"foo": "bar"}
+        # Check load is a distinct object
+        load["foo"] = "baz"
+        assert data["foo"] == "bar"
         with pytest.raises(ValidationError) as excinfo:
             field.deserialize("baddict")
         assert excinfo.value.args[0] == "Not a valid mapping type."

tests/test_schema.py

@@ -641,11 +641,6 @@ def test_can_serialize_time(user, serialized_user):
     assert serialized_user["time_registered"] == expected
 
 
-def test_invalid_dict_but_okay():
-    u = User("Joe", various_data="baddict")
-    UserSchema().dump(u)
-
-
 def test_json_module_is_deprecated():
     with pytest.deprecated_call():
 

tests/test_serialization.py

@@ -369,16 +369,14 @@ def test_dict_field_serialize_none(self, user):
         field = fields.Dict()
         assert field.serialize("various_data", user) is None
 
-    def test_dict_field_invalid_dict_but_okay(self, user):
-        user.various_data = "okaydict"
-        field = fields.Dict()
-        field.serialize("various_data", user)
-        assert field.serialize("various_data", user) == "okaydict"
-
     def test_dict_field_serialize(self, user):
         user.various_data = {"foo": "bar"}
         field = fields.Dict()
-        assert field.serialize("various_data", user) == {"foo": "bar"}
+        dump = field.serialize("various_data", user)
+        assert dump == {"foo": "bar"}
+        # Check dump is a distinct object
+        dump["foo"] = "baz"
+        assert user.various_data["foo"] == "bar"
 
     def test_dict_field_serialize_ordereddict(self, user):
         user.various_data = OrderedDict([("foo", "bar"), ("bar", "baz")])