Shouldn't FileIO indicate None as possible return of read/write?

[dcolascione]

Typeshed currently has these declarations in io.pyi for FileIO.

    def write(self, b: ReadableBuffer, /) -> int: ...
    def read(self, size: int = -1, /) -> bytes: ...

Shouldn't these return int | None and bytes | None? A FileIO is non-blocking mode can return None from these methods, yes?

[tomasr8]

Looking at the code, both read and write return None when EAGAIN is raised so technically the return annotation should include None as well.

[srittau]

For reference, this is similar to what has been discussed in https://discuss.python.org/t/handling-sys-stdin-read-in-non-blocking-mode/59633.

[srittau]

Also related to #12414. PR: #12686