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functools.update_wrapper does not work with type #119011

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functools.update_wrapper does not work with type#119011
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JelleZijlstra
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3.12only security fixes3.13only security fixes3.14bugs and security fixesstdlibStandard Library Python modules in the Lib/ directorytopic-typingtype-bugAn unexpected behavior, bug, or error

Description

@nikola-benes
nikola-benes
opened on May 13, 2024

Bug report

Bug description:

from functools import update_wrapper

def my_type(*args): pass

t = update_wrapper(my_type, type)

This works on Python ≤ 3.11, and I think this is expected because the docs for update_wrapper claim that it may be used with callables other than functions.

However, with 3.12, I get

TypeError: __type_params__ must be set to a tuple

(Similarly for functools.wraps.)

The problem is that update_wrapper includes __type_params__ by default (which is undocumented, see related issue) and type.__type_params__ is a descriptor.

CPython versions tested on:

3.12

Operating systems tested on:

Linux

Linked PRs

Activity

  1. nikola-benes
    added
    type-bugAn unexpected behavior, bug, or error
    on May 13, 2024
  2. AlexWaygood
    added
    topic-typing
    stdlibStandard Library Python modules in the Lib/ directory
    on May 13, 2024
  3. JelleZijlstra
    self-assigned this
    on May 13, 2024

  4. sobolevn commented on May 13, 2024

    @sobolevn
    sobolevn
    on May 13, 2024
    Member

    3.11:

    Python 3.11.5 (main, Sep  5 2023, 10:34:31) [Clang 14.0.3 (clang-1403.0.22.14.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from functools import update_wrapper
>>> 
>>> def my_type(*args): pass
... 
>>> t = update_wrapper(my_type, type)
>>> 
>>> t
<function type at 0x104963060>

    3.12+:

    >>> from functools import update_wrapper
... 
... def my_type(*args): pass
... 
... t = update_wrapper(my_type, type)
Traceback (most recent call last):
  File "<python-input-8>", line 5, in <module>
    t = update_wrapper(my_type, type)
  File "/Users/sobolev/Desktop/cpython2/Lib/functools.py", line 57, in update_wrapper
    setattr(wrapper, attr, value)
    ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
TypeError: __type_params__ must be set to a tuple
  5. AlexWaygood
    added
    3.12only security fixes
    3.13only security fixes
    3.14bugs and security fixes
    on May 13, 2024

  6. dwt commented on May 16, 2024

    @dwt
    dwt
    on May 16, 2024

    This was reported to me at dwt/fluent#14

    I'm seeing this when wrapping type() to make it useable in a fluent way.

    Is there something I need to do differently for python 3.12, or is this a bug in the python stdlib?

  7. AlexWaygood commented on May 16, 2024

    @AlexWaygood
    AlexWaygood
    on May 16, 2024
    Member

    Is there something I need to do differently for python 3.12, or is this a bug in the python stdlib?

    This is a CPython bug

  8. mdkcore0 commented on May 20, 2024

    @mdkcore0
    mdkcore0
    on May 20, 2024
    Contributor

    hi @AlexWaygood, I'm trying to figure out what is happening here; what CPython should do with __type_params__? Should it be skipped?

    @encukou is also helping me to understand it :)

  9. JelleZijlstra commented on May 20, 2024

    @JelleZijlstra
    JelleZijlstra
    on May 20, 2024
    Member

    Some notes from in-person conversation:

    The problem is this:

    >>> type.__type_params__
<attribute '__type_params__' of 'type' objects>

    We would instead want this to be an empty tuple, because that's the normal behavior for classes that are not PEP 695 generics.

    The way to achieve this would be to use a special case for &PyType_Type in the type_get_type_params getter. There is a similar check in the __abstractmethods__ getter.

  10. sobolevn
    added a commit that references this issue on May 21, 2024

    pythongh-119011: `type.__type_params__` now return an empty tuple

    22b0241
  11. mdkcore0
    added 3 commits that reference this issue on May 21, 2024

    pythongh-119011: Return an empty tuple on type_get_type_params as spe…

    cb8d85d

    pythongh-119011: Return an empty tuple on type_get_type_params as spe…

    65ae07b

    pythongh-119011: Return an empty tuple on type_get_type_params as spe…

    a493713
  12. JelleZijlstra
    added a commit that references this issue on May 28, 2024

    gh-119011: `type.__type_params__` now return an empty tuple (#119296)

    6b240c2
  13. miss-islington
    added a commit that references this issue on May 28, 2024

    pythongh-119011: `type.__type_params__` now return an empty tuple (py…

    7910e84
  14. JelleZijlstra
    added 3 commits that reference this issue on May 28, 2024

    [3.12] pythongh-119011: `type.__type_params__` now return an empty tu…

    b37f71a

    [3.13] gh-119011: `type.__type_params__` now return an empty tuple (G…

    c0e9961

    [3.12] gh-119011: `type.__type_params__` now return an empty tuple (G…

    7f06cd3

  15. encukou commented on May 30, 2024

    @encukou
    encukou
    on May 30, 2024
    Member

    Is there more to do here?

  16. JelleZijlstra
    closed this as completedon May 30, 2024

  17. dwt commented on Jun 5, 2024

    @dwt
    dwt
    on Jun 5, 2024

    Sorry if this is daft, but could someone help me understand how I can find out what python release this fix will be part of?

  18. AlexWaygood commented on Jun 5, 2024

    @AlexWaygood
    AlexWaygood
    on Jun 5, 2024
    Member

    The fix will be included in 3.13.0b2 and 3.12.4. I think both should be coming pretty soon.

  19. noahbkim
    added a commit that references this issue on Jul 11, 2024

    pythongh-119011: `type.__type_params__` now return an empty tuple (py…

    04e5479
  20. estyxx
    added a commit that references this issue on Jul 17, 2024

    pythongh-119011: `type.__type_params__` now return an empty tuple (py…

    cdbe7bb
  21. chinmaydk99
    added a commit that references this issue on Oct 7, 2026

    [Dynamo] Require Python 3.12.4+ for the type.__type_params__ check

    2165be0
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3.12only security fixes3.13only security fixes3.14bugs and security fixesstdlibStandard Library Python modules in the Lib/ directorytopic-typingtype-bugAn unexpected behavior, bug, or error

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