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Inspection errors on valid union syntax for Python < 3.10 #737
Description
Description
The following code:
from __future__ import annotations
from msgspec import Struct, inspect
class Bug(Struct):
field: str | int = 0
inspect.type_info(Bug)produces the following:
Traceback (most recent call last):
File "C:\Users\ofek\Desktop\rf\m.py", line 7, in <module>
inspect.type_info(Bug)
File "C:\Users\ofek\AppData\Local\Programs\Python\Python39\lib\site-packages\msgspec\inspect.py", line 629, in type_info
return multi_type_info([type])[0]
File "C:\Users\ofek\AppData\Local\Programs\Python\Python39\lib\site-packages\msgspec\inspect.py", line 598, in multi_type_info
return _Translator(types).run()
File "C:\Users\ofek\AppData\Local\Programs\Python\Python39\lib\site-packages\msgspec\inspect.py", line 744, in run
MsgpackDecoder(Tuple[self.types])
File "C:\Users\ofek\AppData\Local\Programs\Python\Python39\lib\site-packages\msgspec\_utils.py", line 130, in get_class_annotations
value = typing._eval_type(value, cls_locals, cls_globals)
File "C:\Users\ofek\AppData\Local\Programs\Python\Python39\lib\typing.py", line 292, in _eval_type
return t._evaluate(globalns, localns, recursive_guard)
File "C:\Users\ofek\AppData\Local\Programs\Python\Python39\lib\typing.py", line 554, in _evaluate
eval(self.__forward_code__, globalns, localns),
File "<string>", line 1, in <module>
TypeError: unsupported operand type(s) for |: 'type' and 'type'
The following code is a workaround but limits what users are allowed to do when providing a library that extends msgspec:
from __future__ import annotations
from typing import Union
from msgspec import Struct, inspect
class Bug(Struct):
field: Union[str, int] = 0
inspect.type_info(Bug)
Activity
chuckwondo commentedon Sep 18, 2024
Using a pipe for type unions was introduced in Python 3.10, so anybody running an earlier version of Python shouldn't be surprised by this. If you want to "extend" msgspec and use the pipe syntax, then your extension must require python >= 3.10. If you want to support use of earlier versions of Python, then you must use the
Unionsyntax, not the pipe syntax.ofek commentedon Sep 18, 2024
Doesn't
from __future__ import annotationsallow for that syntax though?ofek commentedon Sep 18, 2024
It looks like the reason the syntax error goes away is only due to the lazy computation. Thanks Chuck!
chuckwondo commentedon Sep 18, 2024
No, that only allows for postponed evaluation of annotations.
ofek commentedon Sep 19, 2024
Yes thanks, I added a note for users earlier today! https://ofek.dev/msgspec-click/usage/#caveats
ashb commentedon Nov 12, 2024
Pydantic handles this via https://github.com/alexmojaki/eval_type_backport -- is there any appetite for doing the same in msgspec? Happy to PR it if that it'd be supported.
@jcrist What would your appetite for it be?
jcrist commentedon Nov 15, 2024
Thanks for the comment - I'd be open to doing something like that. I've opened #771 to track this, lets continue discussion there :).