Open
Description
- cattrs version: 1.10.0
- Python version: 3.10.2
- Operating System: Ubuntu 20.04.3
Description
This is related to #201, but probably worth making a separate issue for, since it affects one of the (previously working) workarounds mentioned in that issue. Feel free to close this if you feel this is redundant with #201 or #94.
I have a converter that registers a ForwardRef. In python 3.6.x through 3.10.1, this has worked as intended. As of python 3.10.2, this is now throwing a TypeError:
TypeError: Invalid first argument to `register()`. ForwardRef('MyClass') is not a class.Strangely, I don't see anything in the python 3.10.2 changelog that would indicate changed behavior with ForwardRef or register().
What I Did
Minimal example:
from attr import define, field
from cattr import Converter # Note: same behavior with GenConverter
from typing import ForwardRef, List
@define()
class MyClass:
history: List['MyClass'] = field(factory=list)
converter = Converter()
converter.register_structure_hook(
ForwardRef('MyClass'), lambda obj, _: converter.structure(obj, MyClass)
)Traceback:
TypeError Traceback (most recent call last)
Input In [17], in <module>
----> 1 converter.register_structure_hook(
2 ForwardRef("MyClass"), (lambda obj, _: converter.structure(obj, MyClass))
3 )
File ~/.virtualenvs/rc-310/lib/python3.10/site-packages/cattr/converters.py:269, in Converter.register_structure_hook(self, cl, func)
267 self._structure_func.clear_cache()
268 else:
--> 269 self._structure_func.register_cls_list([(cl, func)])
File ~/.virtualenvs/rc-310/lib/python3.10/site-packages/cattr/dispatch.py:57, in MultiStrategyDispatch.register_cls_list(self, cls_and_handler, direct)
55 self._direct_dispatch[cls] = handler
56 else:
---> 57 self._single_dispatch.register(cls, handler)
58 self.clear_direct()
59 self.dispatch.cache_clear()
File ~/.pyenv/versions/3.10.2/lib/python3.10/functools.py:856, in singledispatch.<locals>.register(cls, func)
854 else:
855 if func is not None:
--> 856 raise TypeError(
857 f"Invalid first argument to `register()`. "
858 f"{cls!r} is not a class."
859 )
860 ann = getattr(cls, '__annotations__', {})
861 if not ann:
TypeError: Invalid first argument to `register()`. ForwardRef('MyClass') is not a class.