Move `contextlib.chdir` to `shutil.chdir_context` contingent on gh-128432

[jb2170]

Feature or enhancement

Proposal:

Summary

• We relocate contextlib.chdir to shutil.chdir_context.
• We silently change the contextlib.chdir member to be a compatibility import, which can be removed when Python <=3.13 is no longer supported, for a gentle deprecation path.

Rationale

This is really part (2/2) of #128432 which is resolved by the pending #128433. The naming convention chdir_context follows umask_context. Documentation re-organising, and code style introduced in #128433 allows this one to slot right in.

contextlib shouldn't have been the location that chdir was added to in the first place, and now is the opportune time to correct this mis-step.

PR Preview

Git (re)based on #128433, the PR draft branch is on my fork

Discussions

On discuss.python.org.

Has this already been discussed elsewhere?

I have already discussed this feature proposal on Discourse

Links to previous discussion of this feature:

https://discuss.python.org/t/move-contextlib-chdir-to-become-shutil-chdir/76007/

[JelleZijlstra]

I believe we should not change anything here (some people expressed the same sentiment in the Discourse thread, though it got a little buried around the naming discussion). Deprecations have a cost in terms of making Python upgrades harder, and this change isn't worth that cost.

[picnixz]

which can be removed when Python <=3.13 is no longer supported, for a gentle deprecation path.

This essentially means that we're removing it in 2029, when it's no more accepting security patches but many distributions are still patching very old releases (e.g., openSUSE with 3.6 patches) so, if we can alleviate the work on their side (even if this targets an EOL branch), why not doing it. So I'm rather a -0.5 on this one even though it's for the sake of consistency (if we really want to change it, I would prefer that contextlib.chdir stays indefinitely as an alias to shutil.chdir_context).

[jb2170]

We're continuing with this issue / PR.

We'll see in 2029 whether the contextlib.chdir compatibility import should be removed as planned, or kept indefinitely. 🙂

Really though for distros who choose to use dead versions of Python it's up to them to write compatibility code, eg

import sys
if sys.version_info >= (3,18):
    from shutil import chdir_context as chdir
else:
    from contextlib import chdir

beyond the lifespan of chdir inside contextlib

[erlend-aasland]

We're continuing with this issue / PR.

Hold on; there is no consensus for making this change. Several core devs seem to want to reject this. Please wait with a PR until there is consensus.

[ncoghlan]

With the umask proposal in #128432 closed, the motivation to move away from the status quo with regards to contextlib.chdir goes away. Accordingly, closing this proposal as well.

However, we'll continue with the contextlib.ModificationContext pattern extraction proposal in #128574

[jb2170]

Closed due to cancellation of #128432