Wrong stub for `fileinput.input()` #7922

Molkree · 2022-05-22T22:01:48Z

the stubs appear to be wrong here:

typeshed/stdlib/fileinput.pyi

Line 32 in 6e18441

openhook: Callable[[StrOrBytesPath, str], IO[AnyStr]] = ...,

Only the openhook argument constrains the TypeVar, but it has a default, and if the argument is not given there's nothing for the type checker to use to decide on the value of the TypeVar. The typeshed stub should be changed to add a separate overload where openhook is not given.

microsoft/pyright#3494 (comment)

The text was updated successfully, but these errors were encountered:

AlexWaygood · 2022-05-22T22:48:39Z

The stubs at the moment look quite buggy indeed! From my reading of the source code, I don't think it's actually the openhook parameter at all that determines whether the object returned is of type FileInput[str] or FileInput[bytes]. Instead, it's the value passed into the mode parameter. (You can see this by looking at the FileInput._readline method, which is called from FileInput.__next__.)

IO modes can be tricky to type in stub files, but it should be possible.

Fixes python#7922, part of python#7928. Also discovered an apparent CPython bug in the process: python/cpython#93157

* fileinput: Fix TypeVar usage Fixes #7922, part of #7928.

This was referenced May 23, 2022

TypeVars in some generic functions can go unsolved, resulting in an Any in the evaluated type #7928

Closed

fileinput: Fix TypeVar usage #7934

Merged

JelleZijlstra added a commit to JelleZijlstra/typeshed that referenced this issue May 24, 2022

fileinput: Fix TypeVar usage

860cd4a

Fixes python#7922, part of python#7928. Also discovered an apparent CPython bug in the process: python/cpython#93157

AlexWaygood closed this as completed in #7934 May 24, 2022

AlexWaygood pushed a commit that referenced this issue May 24, 2022

fileinput: Fix TypeVar usage (#7934)

d950ec3

* fileinput: Fix TypeVar usage Fixes #7922, part of #7928.

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