Fix type errors when deriving from a MapAttribute and another type (#904)

Author: ikonst

docs/release_notes.rst

@@ -1,6 +1,14 @@
 Release Notes
 =============
 
+v5.0.1
+----------
+
+:date: 2021-02-10
+
+* Fix type errors when deriving from a MapAttribute and another type (#904)
+
+
 v5.0.0
 ----------
 

mypy.ini

@@ -8,6 +8,7 @@ warn_unused_configs = True
 warn_redundant_casts = True
 warn_incomplete_stub = True
 follow_imports = normal
+show_error_codes = True
 
 # TODO: burn these down
 [mypy-tests.*]

pynamodb/__init__.py

@@ -7,4 +7,4 @@
 """
 __author__ = 'Jharrod LaFon'
 __license__ = 'MIT'
-__version__ = '5.0.0'
+__version__ = '5.0.1'

pynamodb/attributes.py

@@ -339,7 +339,7 @@ def _set_attributes(self, **attributes: Attribute) -> None:
                 raise ValueError("Attribute {} specified does not exist".format(attr_name))
             setattr(self, attr_name, attr_value)
 
-    def serialize(self, null_check=True) -> Dict[str, Dict[str, Any]]:
+    def _container_serialize(self, null_check: bool = True) -> Dict[str, Dict[str, Any]]:
         """
         Serialize attribute values for DynamoDB
         """
@@ -357,7 +357,7 @@ def serialize(self, null_check=True) -> Dict[str, Dict[str, Any]]:
                 attribute_values[attr.attr_name] = {attr.attr_type: attr_value}
         return attribute_values
 
-    def deserialize(self, attribute_values: Dict[str, Dict[str, Any]]) -> None:
+    def _container_deserialize(self, attribute_values: Dict[str, Dict[str, Any]]) -> None:
         """
         Sets attributes sent back from DynamoDB on this object
         """
@@ -387,17 +387,9 @@ def _instantiate(cls: Type[_ACT], attribute_values: Dict[str, Dict[str, Any]]) -
             raise ValueError("Cannot instantiate a {} from the returned class: {}".format(
                 cls.__name__, stored_cls.__name__))
         instance = (stored_cls or cls)(_user_instantiated=False)
-        AttributeContainer.deserialize(instance, attribute_values)
+        AttributeContainer._container_deserialize(instance, attribute_values)
         return instance
 
-    def __eq__(self, other: Any) -> bool:
-        # This is required so that MapAttribute can call this method.
-        return self is other
-
-    def __ne__(self, other: Any) -> bool:
-        # This is required so that MapAttribute can call this method.
-        return self is not other
-
 
 class DiscriminatorAttribute(Attribute[type]):
     attr_type = STRING
@@ -835,14 +827,14 @@ def _update_attribute_paths(self, path_segment):
             if isinstance(local_attr, MapAttribute):
                 local_attr._update_attribute_paths(path_segment)
 
-    def __eq__(self, other):
+    def __eq__(self, other: Any) -> 'Comparison':  # type: ignore[override]
         if self._is_attribute_container():
-            return AttributeContainer.__eq__(self, other)
+            return self is other  # type: ignore
         return Attribute.__eq__(self, other)
 
-    def __ne__(self, other):
+    def __ne__(self, other: Any) -> 'Comparison':  # type: ignore[override]
         if self._is_attribute_container():
-            return AttributeContainer.__ne__(self, other)
+            return self is not other  # type: ignore
         return Attribute.__ne__(self, other)
 
     def __iter__(self):
@@ -940,7 +932,7 @@ def serialize(self, values):
                         setattr(instance, name, values[name])
                 values = instance
 
-            return AttributeContainer.serialize(values)
+            return AttributeContainer._container_serialize(values)
 
         # Continue to serialize NULL values in "raw" map attributes for backwards compatibility.
         # This special case behavior for "raw" attributes should be removed in the future.

pynamodb/models.py

@@ -1120,6 +1120,18 @@ def _serialize_keys(cls, hash_key, range_key=None) -> Tuple[_KeyType, _KeyType]:
             range_key = cls._range_key_attribute().serialize(range_key)
         return hash_key, range_key
 
+    def serialize(self, null_check: bool = True) -> Dict[str, Dict[str, Any]]:
+        """
+        Serialize attribute values for DynamoDB
+        """
+        return self._container_serialize(null_check=null_check)
+
+    def deserialize(self, attribute_values: Dict[str, Dict[str, Any]]) -> None:
+        """
+        Sets attributes sent back from DynamoDB on this object
+        """
+        return self._container_deserialize(attribute_values=attribute_values)
+
 
 class _ModelFuture(Generic[_T]):
     """

tests/test_mypy.py

@@ -160,6 +160,7 @@ class MyModel(Model):
     reveal_type(MyModel.my_list[0] == MyModel())  # N: Revealed type is 'pynamodb.expressions.condition.Comparison'
     # the following string indexing is not type checked - not by mypy nor in runtime
     reveal_type(MyModel.my_list[0]['my_sub_attr'] == 'foobar')  # N: Revealed type is 'pynamodb.expressions.condition.Comparison'
+    reveal_type(MyModel.my_map == 'foobar')  # N: Revealed type is 'pynamodb.expressions.condition.Comparison'
     """)
 
 
@@ -203,3 +204,12 @@ class MyModel(Model):
     model = next(typed_result)
     not_model = next(typed_result)  # E: Incompatible types in assignment (expression has type "MyModel", variable has type "int")  [assignment]
     """)
+
+
+def test_map_attribute_derivation(assert_mypy_output):
+    assert_mypy_output("""
+    from pynamodb.attributes import MapAttribute
+
+    class MyMap(MapAttribute, object):
+        pass
+    """)