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asottile-sentry opened this issue Apr 17, 2025 · 3 comments · May be fixed by #19072
Open

dmypy gives up on trivial decorator #18940

asottile-sentry opened this issue Apr 17, 2025 · 3 comments · May be fixed by #19072
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feature topic-daemon dmypy

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@asottile-sentry
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Bug Report

seems dmypy is unable to suggest an annotation when a function is decorated even with a trivial decorator (likely as the implementation predates widespread ParamSpec usage)

I believe the fix is deleting this line?

mypy/mypy/suggestions.py

Line 656 in 454989f

and isinstance(ct.arg_types[0], TypeVarType)

To Reproduce

from typing import Callable

def dec[R, **P](f: Callable[P, R]) -> Callable[P, R]:
    return f

@dec
def f():
    print('hello world')
[mypy]
check_untyped_defs = true

Expected Behavior

$ dmypy check .
...
$ dmypy suggest t.f
() -> None

Actual Behavior

$ dmypy check .
...
$ dmypy suggest t.f
Object t.f is a decorator we can't handle

Your Environment

  • Mypy version used: 1.15.0
  • Mypy command-line flags: (see above)
  • Mypy configuration options from mypy.ini (and other config files): (see above)
  • Python version used: 3.13.1
@asottile-sentry asottile-sentry added the bug mypy got something wrong label Apr 17, 2025
@brianschubert brianschubert added feature topic-daemon dmypy and removed bug mypy got something wrong labels Apr 18, 2025
@Jdwashin9
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I can check it out.

@Jdwashin9 Jdwashin9 mentioned this issue Apr 18, 2025
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@A5rocks
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A5rocks commented Apr 18, 2025

Note that the line you commented about is a special case for this decorator seemingly (I have not tested):

def f(x: T) -> T:
  return x

So as a workaround you could use that, especially if you're not using the paramspec to transform parameters!

@asottile-sentry
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I could but I have no control over the particular decorator -- and the real one uses the ParamSpec

also would like to use @contextlib.contextmanager-based decorators as well but it looks like those might be more complicated 🤔

@asottile-sentry asottile-sentry mentioned this issue Apr 21, 2025
Merged
asottile-sentry added a commit to getsentry/sentry that referenced this issue Apr 22, 2025
@asottile-sentry
ref: run auto-type-annotate on **/issues/**.py (#90000)
1b74829 
first commit automated via
https://github.com/getsentry/auto-type-annotate

- I used these patches to mypy:
    - python/mypy#18948
- (the line mentioned in the issue commented out):
python/mypy#18940 (comment)
- and with this unreverted (coming soon!):
#89854

<!-- Describe your PR here. -->
andrewshie-sentry pushed a commit to getsentry/sentry that referenced this issue Apr 22, 2025
@asottile-sentry @andrewshie-sentry
ref: run auto-type-annotate on **/issues/**.py (#90000)
7942d8a 
first commit automated via
https://github.com/getsentry/auto-type-annotate

- I used these patches to mypy:
    - python/mypy#18948
- (the line mentioned in the issue commented out):
python/mypy#18940 (comment)
- and with this unreverted (coming soon!):
#89854

<!-- Describe your PR here. -->
@asottile asottile linked a pull request May 10, 2025 that will close this issue
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@brianschubert @A5rocks @asottile-sentry @Jdwashin9