graphene/graphene/pyutils/init_subclass.py
2017-08-07 20:48:26 -07:00

20 lines
903 B
Python

is_init_subclass_available = hasattr(object, '__init_subclass__')
if not is_init_subclass_available:
class InitSubclassMeta(type):
"""Metaclass that implements PEP 487 protocol"""
def __new__(cls, name, bases, ns, **kwargs):
__init_subclass__ = ns.pop('__init_subclass__', None)
if __init_subclass__:
__init_subclass__ = classmethod(__init_subclass__)
ns['__init_subclass__'] = __init_subclass__
return super(InitSubclassMeta, cls).__new__(cls, name, bases, ns, **kwargs)
def __init__(cls, name, bases, ns, **kwargs):
super(InitSubclassMeta, cls).__init__(name, bases, ns)
super_class = super(cls, cls)
if hasattr(super_class, '__init_subclass__'):
super_class.__init_subclass__.__func__(cls, **kwargs)
else:
InitSubclassMeta = type # type: ignore