gh-85984: Remove legacy Lib/pty.py code.

[8vasu]

This follows #29658. This is one in a series of PRs aimed at cleaning-up, fixing bugs in, introducing new features in, and updating the code in "Lib/pty.py".

Signed-off-by: Soumendra Ganguly soumendraganguly@gmail.com

• Issue: Lib/pty.py major revision #85984

[8vasu]

@gpshead Please take a look at this when you have time.

Two changes are being made.

1. Remove code for pty.openpty() that uses the "old SGI method or the manual BSD open-a-pty code" that was marked as deprecated way back in year 2000 by Thomas Wouters; this includes pty.master_open(), pty._open_terminal(), and pty.slave_open(); these are not even in the test_pty.py anymore.

2. Make the fallback code in pty.fork() use os.login_tty(). Please note that the replacement code in pty.fork() is different from the removed code in the following way.

• The removed code is using the legacy System V method of open()-ing a tty device to make it a controlling terminal;
• The replacement code is using os.login_tty(), which uses login_tty(3) if available, or else uses the TIOCSCTTY ioctl(), which even System V derivatives support now: https://marc.info/?l=glibc-help&m=164436296715753&w=3

@asvetlov @ethanfurman @aeros please take a look if you have time as well.

[8vasu]

@gpshead thank you for the review.

@kumaraditya303 thank you for the review request.

I have many other improvements planned (and to a large extent ready) for this module for which I will make pull requests once this is merged (after December since I am busy applying for postdocs now).

[smontanaro]

(I'm working my way through some PRs which have been approved and are labeled "awaiting merge", hence my seemingly bolt from the blue comment. Why? Read here.)

Maybe this didn't get addressed in the sprint? Is it ready to merge or does it need more work? If it needs more work, maybe the DO-NOT-MERGE label should be added.

[8vasu]

@smontanaro Thank you for the review. This does not need more work unless @gpshead has any suggestions. This is a part of a series of PRs aimed at improving the pty library. A few have been merged before, and if this one gets merged, then I have more to follow, which I will work on right after December (I am still applying for postdocs).

[8vasu]

@gpshead If/when you have time, please let me know if you need me to make any changes to this.

[gpshead]

While master_open() and slave_open() are ancient and undocumented, even way back in 2.7, with "Deprecated" in the docstrings... they do appear in real code:

https://cs.github.com/?scopeName=All+repos&scope=&q=%2F%28pty.slave_open%7Cpty.master_open%29%2F+language%3Apython

So lets not delete those two in 3.12. Instead have them use warnings.warn(DeprecationWarning, "use os.openpty() instead").
We can remove their implementations in 3.14+.

[bedevere-bot]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[8vasu]

I have made the requested changes; please review again.

[bedevere-bot]

Thanks for making the requested changes!

@gpshead: please review the changes made to this pull request.

[8vasu]

@gpshead Just realized that I had forgotten to add the deprecation warnings.
Thank you for adding them.

[gpshead]

Refactored the implementation of pty.fork to use os.login_tty.

A DeprecationWarning is now raised by pty.master_open() and pty.slave_open(). They were
undocumented and deprecated long long ago in the docstring in favor of pty.openpty.