Improved scalar implementation thinking immutable

graphene/types/scalars.py

@@ -6,45 +6,7 @@ from .proxy import TypeProxy
 
 
 class GrapheneScalarType(GrapheneGraphQLType, GraphQLScalarType):
-
+    pass
-    def __init__(self, *args, **kwargs):
-        GrapheneGraphQLType.__init__(self, *args, **kwargs)
-
-    @staticmethod
-    def default_parse(value):
-        return None
-
-    def setup(self):
-        serialize = getattr(self.graphene_type, 'serialize', None)
-        parse_value = getattr(self.graphene_type, 'parse_value', None)
-        parse_literal = getattr(self.graphene_type, 'parse_literal', None)
-
-        assert callable(serialize), (
-            '{} must provide "serialize" function. If this custom Scalar is '
-            'also used as an input type, ensure "parse_value" and "parse_literal" '
-            'functions are also provided.'
-        ).format(self)
-
-        if parse_value is not None or parse_literal is not None:
-            assert callable(parse_value) and callable(parse_literal), (
-                '{} must provide both "parse_value" and "parse_literal" functions.'.format(self)
-            )
-
-        self._serialize = serialize
-        self._parse_value = parse_value
-        self._parse_literal = parse_literal
-
-    @property
-    def serialize(self):
-        return self.graphene_type.serialize
-
-    @property
-    def parse_value(self):
-        return getattr(self.graphene_type, 'parse_value', self.default_parse)
-
-    @property
-    def parse_literal(self):
-        return getattr(self.graphene_type, 'parse_literal', self.default_parse)
 
 
 class ScalarTypeMeta(ClassTypeMeta):
@@ -59,19 +21,21 @@ class ScalarTypeMeta(ClassTypeMeta):
         )
 
     def construct_graphql_type(cls, bases):
+        pass
+
+    def construct(cls, *args, **kwargs):
+        constructed = super(ScalarTypeMeta, cls).construct(*args, **kwargs)
         if not cls._meta.graphql_type and not cls._meta.abstract:
             cls._meta.graphql_type = GrapheneScalarType(
                 graphene_type=cls,
                 name=cls._meta.name or cls.__name__,
                 description=cls._meta.description,
-                # For passing the assertion in GraphQLScalarType
+
-                serialize=lambda: None
+                serialize=getattr(cls, 'serialize', None),
+                parse_value=getattr(cls, 'parse_value', None),
+                parse_literal=getattr(cls, 'parse_literal', None),
             )
 
-    def construct(cls, *args, **kwargs):
-        constructed = super(ScalarTypeMeta, cls).construct(*args, **kwargs)
-        if isinstance(cls._meta.graphql_type, GrapheneScalarType):
-            cls._meta.graphql_type.setup()
         return constructed
 
 

graphene/types/tests/test_scalars.py

@@ -48,8 +48,3 @@ def test_custom_scalar_empty():
             pass
 
     assert """DatetimeScalar must provide "serialize" function.""" in str(excinfo.value)
-
-
-def test_custom_scalar():
-    graphql_type = DatetimeScalar._meta.graphql_type
-    assert graphql_type.serialize == DatetimeScalar.serialize