fcntl nicer polyfill

[Lewiscowles1986]

Feature or enhancement

Proposal:

The following line errors on Windows

import fcntl

It's error is not helpful at all, but powers library code sysadmins use, such as sh:

• https://sh.readthedocs.io/en/latest/sections/sudo.html#etc-sudoers-nopasswd
• https://pypi.org/project/sh/

To provide the minimum amount of confusion, I've written a polyfill:

https://github.com/Lewiscowles1986/python-fcntl

It writes to stderr and exits with non-zero error code, so that CI systems can know it doesn't work.

I've also tested it using sh on both mac and windows. Essentially it just gives a nicer error, which signposts the user to maybe use Docker (if they insist on using non linux or darwin systems).

All I'm shooting for here is a better error message, than an import error, for something folks have come to expect as part of the standard library (probably their fault, but I came across this with a user of mastodon complaining about Python, not sh and not fcntl)

https://mastodon.social/@mistersql/113314636889503344

I have asked PyPi to release the fcntl name to me, so that folks can pip install fcntl which I tested using a virtual environment using poetry, within the sh project itself to check it works.

But a nicer error for others without the shenanigans I went through might be better for all.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

[ZeroIntensity]

Hi @Lewiscowles1986!

Unfortunately, I don't think this is a minor feature--please discuss it on Discourse first. A fair warning: you'll certainly get pushback there. In which case, that doesn't mean the idea is bad! In my experience, people very rarely shift opinions on discourse, I wouldn't bother with trying to get in arguments with them :)

A few notes about your polyfill implementation:

• Printing to stderr and then calling exit is a bad idea for the standard library. Users don't really have a good way of preventing that message from coming up, other than disabling stderr entirely. Instead of printing, just raise an error.
• I do like the idea of nicer import errors for OS-dependent libraries, but this should apply to all of those modules, not just fcntl--for example, curses and msvcrt have this problem as well. I would focus your proposal on discourse around that.

I'm going to close this for the time being. Let me know if you have any other questions, thanks!

[Lewiscowles1986]

Thank you. I knew this would be the long and slow fix route internally. I'll now begin trying to search for similar issues on Discourse... If nobody hears from me again, I gave up 😆