gh-134210: handle signals in _curses.window.getch

[picnixz]

• Issue: _curses.window.getch does not check for interruption signals as _curses.window.{getkey,get_wch} do #134210

[vstinner]

I tried this change with the script:

from curses import wrapper
import ctypes

def main(window):
    window.nodelay(True)
    return window.getch()

print(wrapper(main))

Before (without this change), it displays -1.

After (with this change), it fails with the exception: _curses.error: wgetch() (called by getch()): no input.

So this change is backward incompatible. Is it deliberate?

[picnixz]

Hum. No it's not meant to be broken!

Only the signals should be handled, but otherwise we shouldn't raise an exception.

[picnixz]

Now I am bit conflicted. Ideally, we should return -1 for everything or raise an exception as in the other functions. I don't know why it was historically chosen to return -1 for getch but not for get_wch in no-delay mode.

However, since I don't want to break stuff, I don't know how we can make a smooth transition, except by raising a warning before returning -1.

[picnixz]

For now, let's keep the same behavior (namely, -1 for getch, and exception for get_wch and getkey). The functions have been there at least since Python 3.4 and I prefer not to change anything unless a more pressing issue exists. At least, signal handlers will be properly called.

[picnixz]

I could backport this as it's half a bugfix and half a feature. I'll only backport this to 3.14 as the layout of 3.13 is very different for curses (there was a conversion from static types to heap types and I don't think it made it to 3.13)

[vstinner]

LGTM

[vstinner]

You might backport the change to 3.13 and 3.14 bugfix branches.

[miss-islington-app]

Thanks @picnixz for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

[bedevere-app]

GH-134783 is a backport of this pull request to the 3.14 branch.

[bedevere-app]

GH-134784 is a backport of this pull request to the 3.13 branch.