fix SerializerMutation regression for 2.x

72529b7 seems to break SerializerMutation by commenting out support for
input fields. As a result input only ever had a clientMutationId field.

graphene_django/rest_framework/mutation.py

@@ -55,6 +55,7 @@ class SerializerMutation(ClientIDMutation):
         output_fields = fields_for_serializer(serializer, only_fields, exclude_fields, is_input=False)
 
         _meta = SerializerMutationOptions(cls)
+        _meta.serializer_class = serializer_class
         _meta.fields = yank_fields_from_attrs(
             output_fields,
             _as=Field,

graphene_django/rest_framework/serializer_converter.py

@@ -42,8 +42,7 @@ def convert_serializer_field(field, is_input=True):
 
     if isinstance(field, serializers.ModelSerializer):
         if is_input:
-            return Dynamic(lambda: None)
-            # graphql_type = convert_serializer_to_input_type(field.__class__)
+            graphql_type = convert_serializer_to_input_type(field.__class__)
         else:
             global_registry = get_global_registry()
             field_model = field.Meta.model
@@ -52,6 +51,21 @@ def convert_serializer_field(field, is_input=True):
     return graphql_type(*args, **kwargs)
 
 
+def convert_serializer_to_input_type(serializer_class):
+    serializer = serializer_class()
+
+    items = {
+        name: convert_serializer_field(field)
+        for name, field in serializer.fields.items()
+    }
+
+    return type(
+        '{}Input'.format(serializer.__class__.__name__),
+        (graphene.InputObjectType,),
+        items
+    )
+
+
 @get_graphene_type_from_serializer_field.register(serializers.Field)
 def convert_serializer_field_to_string(field):
     return graphene.String

graphene_django/rest_framework/tests/test_mutation.py

@@ -65,7 +65,6 @@ def test_nested_model():
     assert model_field.type == MyFakeModelGrapheneType
 
     model_input = MyMutation.Input._meta.fields['model']
-    model_input_type = model_input.get_type()
-    assert not model_input_type
-    # assert issubclass(model_input_type, InputObjectType)
-    # assert 'cool_name' in model_input_type._meta.fields
+    model_input_type = model_input._type.of_type
+    assert issubclass(model_input_type, InputObjectType)
+    assert 'cool_name' in model_input_type._meta.fields