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typing.get_type_hints fails when passed a class with PEP 695 type parameters and PEP 563 is enabled #114053

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mjog opened this issue Jan 14, 2024 · 5 comments
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typing.get_type_hints fails when passed a class with PEP 695 type parameters and PEP 563 is enabled #114053

mjog opened this issue Jan 14, 2024 · 5 comments
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3.12 bugs and security fixes 3.13 new features, bugs and security fixes stdlib Python modules in the Lib dir topic-typing type-bug An unexpected behavior, bug, or error

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@mjog
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mjog commented Jan 14, 2024 •
edited by bedevere-app bot

Bug report

Bug description:

from __future__ import annotations

import typing

class Test[M]:
    attr: M

print(typing.get_type_hints(Test))

This fails with a NameError:

$ poetry run python3 pep_695_get_type_hints.py
Traceback (most recent call last):
  File "/home/mjog/pep_695_get_type_hints.py", line 8, in <module>
    print(typing.get_type_hints(Test))
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/typing.py", line 2197, in get_type_hints
    value = _eval_type(value, base_globals, base_locals)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/typing.py", line 393, in _eval_type
    return t._evaluate(globalns, localns, recursive_guard)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/typing.py", line 900, in _evaluate
    eval(self.__forward_code__, globalns, localns),
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<string>", line 1, in <module>
NameError: name 'M' is not defined

Although get_type_hints does not work with imported imported type aliases, this is not imported, so I would expect it to work. Further, the documentation for the function indicates using PEP 563 should /help/, but in this case it actually causes an error.

FWIW, removing the PEP 563 import works fine, giving:

{'attr': M}

Python version:

$ poetry run python3 --version
Python 3.12.0

CPython versions tested on:

3.12

Operating systems tested on:

Linux

Linked PRs
@mjog mjog added the type-bug An unexpected behavior, bug, or error label Jan 14, 2024
@Eclips4 Eclips4 added topic-typing 3.12 bugs and security fixes 3.13 new features, bugs and security fixes labels Jan 14, 2024
@mjog

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@mjog mjog changed the title typing.get_type_hints fails when passed a class with PEP 695 type parameters and PEP 563 is enabled typing.get_type_hints fails when passed a generic class and PEP 563 is enabled Jan 14, 2024
@mjog mjog changed the title typing.get_type_hints fails when passed a generic class and PEP 563 is enabled typing.get_type_hints fails when passed a class with PEP 695 type parameters and PEP 563 is enabled Jan 15, 2024
@mjog
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mjog commented Jan 15, 2024 •
edited

Sorry, my now-hidden comment above is incorrect - it does work fine with pre-695 generic classes, I just had a typo in the code.

This is only an issue with PEP 695 type parameters in conjunction with PEP 563.

@treykeown
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+1, just ran into this as well.

@aspizu aspizu mentioned this issue Apr 17, 2024
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@AlexWaygood
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I suppose the problem is probably that get_type_hints looks things up in the global scope but doesn't look things up in the new annotation scopes introduced by PEP-695. The old way of defining TypeVars doesn't suffer from this because TypeVars were defined in the global scope; now they aren't.

AlexWaygood added a commit to AlexWaygood/cpython that referenced this issue Apr 17, 2024
@AlexWaygood
pythongh-114053: Fix bad interaction of PEP-695, PEP-563 and ``get_ty…
c76bfc0 
…pe_hints``
@bedevere-app bedevere-app bot mentioned this issue Apr 17, 2024
Merged
AlexWaygood added a commit that referenced this issue Apr 19, 2024
@AlexWaygood @JelleZijlstra
gh-114053: Fix bad interaction of PEP-695, PEP-563 and ``get_type_hin…
1e3e7ce 
…ts`` (#118009)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
@bedevere-app bedevere-app bot mentioned this issue Apr 19, 2024
Merged
AlexWaygood added a commit to AlexWaygood/cpython that referenced this issue Apr 19, 2024
@AlexWaygood @JelleZijlstra
[3.12] pythongh-114053: Fix bad interaction of PEP-695, PEP-563 and `…
58a86e5 
…`get_type_hints`` (python#118009)

(cherry-picked from commit 1e3e7ce)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
AlexWaygood added a commit that referenced this issue Apr 19, 2024
@AlexWaygood @JelleZijlstra
[3.12] gh-114053: Fix bad interaction of PEP-695, PEP-563 and ``get_t…
5430f61 
…ype_hints`` (#118009) (#118104)

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
@AlexWaygood AlexWaygood added the stdlib Python modules in the Lib dir label Apr 19, 2024
@treykeown
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I created a temporary workaround based off the fix by @AlexWaygood if anyone needs a hack around this in the meantime: https://gist.github.com/treykeown/65c45b3da330d2293c7fb9d2a46520ed

@AlexWaygood AlexWaygood mentioned this issue Apr 30, 2024
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@treykeown @mjog @AlexWaygood @Eclips4