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gh-138432: zoneinfo: improve error message for PathLike relative paths #138433

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Merged
merged 8 commits into from
Sep 11, 2025
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gh-138432: zoneinfo: improve error message for PathLike relative paths #138433

merged 8 commits into from
Sep 11, 2025
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tungol
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@tungol tungol commented Sep 3, 2025 •
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This corrects a small inconsistency with the error handling of zoneinfo.reset_tzpath. A sequence of os.PathLike instances is documented as valid input, but the error pathway for relative paths doesn't handle these correctly. This pull request corrects this, and adds a relevant test case.

@bedevere-app bedevere-app bot mentioned this pull request Sep 3, 2025
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StanFromIreland
StanFromIreland reviewed Sep 3, 2025
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Please add a news entry.

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tungol commented Sep 3, 2025

Done.

uranusjr
uranusjr reviewed Sep 5, 2025
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@serhiy-storchaka
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I suggest to call os.fspath() for all items before assigning them to TZPATH (and before checking that they are absolute paths). We can also add a check that they all are now strings (bytes object will cause error later in find_tzfile() and available_timezones()).

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tungol commented Sep 5, 2025 •
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I suggest to call os.fspath() for all items before assigning them to TZPATH (and before checking that they are absolute paths).

We can do that, but I don't think it's really necessary. Checking for absolute status is done with os.path.isabs, which already handles os.PathLike objects correctly. Within our code, TZPATH is consumed by find_tzfile, which uses os.path.join to produce a string, so it's again automatically handled.

I found this issue while working on a program to apply typeshed stubs to the stdlib and then analyze with mypy, so I'm relatively confident that this is the only place in (python-source) stdlib where os.Pathlike values for TZPATH were overlooked. (Typeshed correctly annotates TZPATH as tuple[str | PathLike[str], ...])

This leaves the possibility of third-party consumers of TZPATH being surprised by encountering an os.PathLike object instead of a string. If we want to change TZPATH to be restricted to str only on that basis, that's probably reasonable, but I think that's probably best left for a different MR.

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It will help to check that if it is a path-like object, it is PathLike[str], not PathLike[Any]. bytes and PathLike[bytes] in TZPATH will cause runtime error in os.path.join().

Anyway, if os.fspath() is already implicitly called in os.path.isabs() and os.path.join(), why not call it explicitly and save the result?

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tungol commented Sep 10, 2025

@serhiy-storchaka Is this about what you were thinking?

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Thank you for your response @tungol. Yes, this is what I suggested.

Few more nitpicks.

serhiy-storchaka
serhiy-storchaka approved these changes Sep 11, 2025
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LGTM. 👍

Thank you for your contribution.

@serhiy-storchaka serhiy-storchaka merged commit 859aecc into python:main Sep 11, 2025
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@serhiy-storchaka serhiy-storchaka added needs backport to 3.13 bugs and security fixes needs backport to 3.14 bugs and security fixes labels Sep 11, 2025
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Thanks @tungol for the PR, and @serhiy-storchaka for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

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Thanks @tungol for the PR, and @serhiy-storchaka for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

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Sorry, @tungol and @serhiy-storchaka, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 859aecc33b82f45e5b7ae30138d28f2a2f33a575 3.13

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Sep 11, 2025
@tungol @miss-islington
pythongh-138432: Improved invalid path checking in zoneinfo.reset_tzp…
b296541 
…ath() (pythonGH-138433)

* Improve error messages for path-like relative paths and path-like bytes paths.
* TZPATH is now always a tuple of strings.
(cherry picked from commit 859aecc)

Co-authored-by: Stephen Morton <git@tungol.org>
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bedevere-app bot commented Sep 11, 2025

GH-138777 is a backport of this pull request to the 3.14 branch.

@bedevere-app bedevere-app bot removed the needs backport to 3.14 bugs and security fixes label Sep 11, 2025
serhiy-storchaka pushed a commit to serhiy-storchaka/cpython that referenced this pull request Sep 11, 2025
@tungol @serhiy-storchaka
[3.13] pythongh-138432: Improved invalid path checking in zoneinfo.re…
5d3e413 
…set_tzpath() (pythonGH-138433)

* Improve error messages for path-like relative paths and path-like bytes paths.
* TZPATH is now always a tuple of strings.
(cherry picked from commit 859aecc)

Co-authored-by: Stephen Morton <git@tungol.org>
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bedevere-app bot commented Sep 11, 2025

GH-138778 is a backport of this pull request to the 3.13 branch.

@bedevere-app bedevere-app bot removed the needs backport to 3.13 bugs and security fixes label Sep 11, 2025
@tungol tungol deleted the zoneinfo branch September 11, 2025 07:17
serhiy-storchaka added a commit that referenced this pull request Sep 11, 2025
@serhiy-storchaka @tungol
[3.13] gh-138432: Improved invalid path checking in zoneinfo.reset_tz…
72b28ca 
…path() (GH-138433) (GH-138778)

* Improve error messages for path-like relative paths and path-like bytes paths.
* TZPATH is now always a tuple of strings.
(cherry picked from commit 859aecc)

Co-authored-by: Stephen Morton <git@tungol.org>
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