ForwardRef is broken on 3.12

[PerchunPak]

3.12 added a new argument, which your wrapper doesn't accept and therefore crashes.

https://github.com/alexmojaki/eval_type_backport/actions/runs/11103634046/job/30846002124#step:5:116
python/cpython@5430f61#diff-ddb987fca5f5df0c9a2f5521ed687919d70bb3d64eaeb8021f98833a2a716887R916

[bswck]

This library is useless in Python versions higher than 3.10.
I recommend using a snippet like

if sys.version_info >= (3, 11):
    from typing import ForwardRef
else:
    from eval_type_backport import ForwardRef

to work around the breaking change.

[PerchunPak]

Well, I am a package maintainer for this library on NixOS and a few packages have tests failures after updating from 0.1.3 to 0.2.0

• immich-machine-learning
• python312Packages.albumentations
• python312Packages.insightface
• unstructured-api

Changing code of those packages is obviously not an option, would it be okay if I will submit a PR fixing this?

[DanCardin]

Seems like these packages likely are depending on this one transitively through e.g. pydantic, and (to me it seems like) this is more of a bug in how pydantic is calling into this library in python versions where it shouldnt (at least at a glance, i dont see that it is making conditional use of this library based on python version).

[PerchunPak]

Here is a dependency tree for those packages

• immich-machine-learning
  • insightface
    • albumentations
      • eval-type-backport

No pydantic involved. In fact, eval-type-backport is installed with pydantic only if Python version is 3.10 or lower.

[alexmojaki]

@DanCardin here's how the import in pydantic depends on Python version:

https://github.com/pydantic/pydantic/blob/5bd3a6507b749fcd4833173fba88b3690ff77170/pydantic/_internal/_typing_extra.py#L635-L640

https://github.com/pydantic/pydantic/blob/5bd3a6507b749fcd4833173fba88b3690ff77170/pydantic/_internal/_typing_extra.py#L672-L680

@PerchunPak I don't see any mentions of eval-type-backport in the code of these libraries, so they're almost certainly just using it via pydantic. I'm curious where tests are failing in those libraries. But I agree that this should be fixed here anyway, and a PR would be appreciated.

[alexmojaki]

BTW in Python 3.13 typing._eval_type also accepts a new type_params argument, so that should be added to the eval_type_backport function.

[DanCardin]

@DanCardin here's how the import in pydantic depends on Python version:

idk if i'm being crazy here but...

def is_backport_fixable_error(e: TypeError) -> bool:
    msg = str(e)

    return (
        sys.version_info < (3, 10)  # in 3.12, false
        and msg.startswith('unsupported operand type(s) for |: ')
        or sys.version_info < (3, 9)  # in 3.12, false
        and "' object is not subscriptable" in msg
    )  # thus this whole thing is false

...
        if (
           not (isinstance(value, typing.ForwardRef)  # presumably can be true or false
           and is_backport_fixable_error(e)  # thus false
       ):
            raise  # thus this isn't hit

       # thus it calls eval_type_backport

to me, this reads as that it will call to this library in 3.12, unless i'm missing something fundamental. And i guess clearly it is being called in 3.12, given the bug report.

While it might be something this library wants to address anyways, it still seems like pydantic should have a much clearer: if the version is > x, dont call it ever, condition.

[alexmojaki]

@DanCardin you're reading the parentheses wrong in the second part

[PerchunPak]

It is

if not (
    isinstance(value, typing.ForwardRef)  # presumably can be true or false
    and is_backport_fixable_error(e)  # false (see above)
):  # thus true

[alexmojaki]

Released the fix now in version 0.2.1