get_type_hints() always raises on forward references

ericvsmith/dataclasses#92 (comment) raised an important question (this existing problem is also mentioned in PEP 563). Currently, get_type_hints will raise a NameError in situations where it might not be the desired behaviour (e.g. if used by a class decorator). For example:

def modify(cls):
    types = get_type_hints(cls)
    # do something with 'cls' and 'types'
    return cls

@modify
class C:
    linked: 'C'

It looks like it will be useful to have an option to keep forward references that are currently undefined. For example:

class C:
    x: 'ClassVar[B]'

assert get_type_hints(C, allow_forward=True) == {'x': ClassVar['B']}

class B:
    ...

assert get_type_hints(C, allow_forward=True) == {'x': ClassVar[B]}

If it's easy to fix, go ahead!

I take it this was not easy to fix? I, for one, would be very glad to see this fixed, but I gather that's unlikely to happen soon...

This is not easy, but not too hard either. I just didn't have time for this, sorry.

Oh, no need to apologise! I commented only in the hope of bumping this slightly higher the priority list, but I'll survive, and life is short.

A somewhat related Python bug I've opened about this a couple of weeks ago (before finding this issue): Issue 43463: typing.get_type_hints with TYPE_CHECKING imports / getting hints for single argument - Python tracker

Please report this bug to bugs.python.org if it still exists.

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get_type_hints() always raises on forward references #508

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get_type_hints() always raises on forward references #508

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gvanrossum commented on Dec 4, 2017

djrochford commented on Apr 17, 2019

ilevkivskyi commented on Apr 17, 2019

djrochford commented on Apr 17, 2019

The-Compiler commented on Apr 16, 2021

srittau commented on Nov 4, 2021

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