Thanks! I expected to be able to use relative_to() as described in this PR, I'm happy to know it is being worked on.

Python 3.9 included an is_relative_to() method to PurePath(). Should that method gain a strict argument as well?

A what's new entry should go in What's New 3.11.

Hi, I'm sorry but I'm not sure about the what's new entry, should I put it under Improved Modules > pathlib? Something like:

pathlib
-------

:meth:`pathlib.PurePath.relative_to` now allows a path that is not a direct
child of the current if the *strict* keyword-only argument is set to False,
the new behavior is more consistent with :meth:`os.relpath`.
(Contributed by Domenico Ragusa in :issue:`40358`.)

Hi, I'm sorry but I'm not sure about the what's new entry, should I put it under Improved Modules > pathlib? Something like:

pathlib
-------

:meth:`pathlib.PurePath.relative_to` now allows a path that is not a direct
child of the current if the *strict* keyword-only argument is set to False,
the new behavior is more consistent with :meth:`os.relpath`.
(Contributed by Domenico Ragusa in :issue:`40358`.)

This is indeed tricky to phrase! How about:

:meth:`pathlib.PurePath.relative_to` now supports generating relative paths
containing ``..`` entries if its new *strict* keyword-only argument is set to
``False``. The new behavior is more consistent with :func:`os.path.relpath`.
(Contributed by Domenico Ragusa in :issue:`40358`.)

I'm trying to think if there's a better word than 'strict'. In other places, 'strict' usually refers to our behaviour when we get an error from the OS. In this case it's more to do with whether we tolerate the possibility of the path's meaning changing in our pure operation that can't ever raise OSError anyway.

Perhaps something like parents=True to enable the new behaviour, mirroring mkdir()? Or walk_up?

Yeah, strict doesn't give any clue about the actual function. I like walk_up, I'll change it to that tomorrow.

Sorry for the long delay, I just updated the code to follow the suggestion you made about the name of the option.

Aside from a small docs issue, this looks great to me. Really useful feature, nice implementation :)

Others may want to chip in on the naming of walk_up.

Hey @domragusa , there has been further interest in this over on the Python discourse; any chance you could tweak the docs, fix the merge conflicts and retrigger the builds?

I have made the requested changes; please review again

Thanks for making the requested changes!

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

@domragusa: Status check is done, and it's a failure or timed out ❌.

I'm not sure I understand the last comment, what status check has failed? Should I do anything else?

Status check is done, and it's a success ✅.

@domragusa thanks so much for your patience with this!

I'm very happy to see this being merged, thanks to @brettcannon and everyone else who helped along the way :)

Maybe I‘m misunderstanding, but this was an incompatibility to path.relpath which is now fixed. Should it not be considered a bug, and the fix be back-ported to a few versions?

I don't think anybody is currently relying on pathlib for this behaviour, in fact when I looked around for anwsers they were generally saying to use os.path.relpath and also the original developer told me it was the intended behaviour (see #84538), so I'm not convinced we should consider it as a bug.

Anyway, if there are specific arguments for backporting it's fine by me.

Ok, the table at the end of the pathlib doc was augmented, and relpath was listed with a comment.
You are right, it is not a bug. Still, we were trying to convert everything, but this is the only function that has no equivalent at os.path, and it would take quite long until this change makes it through our supported versions from 3.7 on :)

Hi

With respect to the backporting, I took this pull request and created a small package out of it, following the backports package guidelines.

I included some of the tests.

https://pypi.org/project/backports-pathlib-relative-to/0.1.0/

https://github.com/zeehio/backports-pathlib-relative-to

Issues and pull requests are welcome

FYI, I've opened a bug and PR to address one final incompatibility between PurePath.relative_to() and os.path.relpath().