graphene-django: Unable to subclass or emulate DjangoObjectType

Subclassing DjangoObjectType so as to customise it for use in derived objects in the schema causes the execution of:

assert is_valid_django_model(model)

which fails the assertion due toclass MyNewClass(DjangoObjectType): not having a meta class, as it meant to be a subclass of DjangoObjectType for reuse later on, not and thus does not have a Meta class of its own.

Its also not possible to emulate DjangoObjectType by copying DjangoObjectType, subclassing the new class from ObjectType, this gets past assert is_valid_django_model(model) but then things run into trouble in graphene_django.registry.Registry which runs:

assert issubclass(cls, DjangoObjectType), 'Only DjangoObjectTypes can be registered, received "{}"'.format(cls.__name__)

Which fails due to the explicit check for DjangoObjectType.

It shouldn’t require a fork of the entirety of graphene-django just to create a subclass of DjangoObjectType, either the Registry should be more flexible, or DjangoObjectType should be more flexible.

One option might be to use of Abstract Base Classes to enable a specific set of checks via https://docs.python.org/3/reference/datamodel.html?highlight=__subclass#class.__subclasscheck__

Another way would be to just drop these assertions and throw appropriate exceptions when we reach the situations they were designed to guard against. If we check that its a Django model to ensure that Meta exists, why not just throw a “Not A Django Model” exception when we try to do something later on that actually needs the Django model Meta information instead of asserting something way up the call stack that gets in the way of other things.