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pathlib.Path.absolute() mishandles drive-relative Windows paths #100809

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barneygale opened this issue Jan 6, 2023 · 1 comment
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pathlib.Path.absolute() mishandles drive-relative Windows paths #100809

barneygale opened this issue Jan 6, 2023 · 1 comment
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3.10 only security fixes 3.11 only security fixes 3.12 bugs and security fixes topic-pathlib type-bug An unexpected behavior, bug, or error

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@barneygale
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barneygale commented Jan 6, 2023 •
edited by bedevere-bot
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Windows has one current directory per drive, and supports drive-relative paths like 'X:' and 'X:foo.txt'. This makes a conversion from relative to absolute paths more complicated than simply prepending a (single) current directory.

It's correctly handled in ntpath.abspath() by calling NT's GetFullPathNameW() function. But in pathlib we simply prepend os.getcwd(), leading to incorrect results:

>>> import os, nt, pathlib
>>> os.chdir('Z:/build')
>>> os.chdir('C:/')
>>> os.path.abspath('Z:')
'Z:\\build'
>>> nt._getfullpathname('Z:')
'Z:\\build'
>>> pathlib.Path('Z:').absolute()
WindowsPath('Z:')

This bug is present in all versions of CPython pathlib. We can't fix it by calling abspath() because it will also normalize the path, eliding '..' parts.

Linked PRs
@barneygale barneygale added type-bug An unexpected behavior, bug, or error topic-pathlib 3.11 only security fixes 3.10 only security fixes 3.12 bugs and security fixes labels Jan 6, 2023
barneygale added a commit to barneygale/cpython that referenced this issue Jan 6, 2023
@barneygale
pythongh-100809: Fix handling of drive-relative paths in pathlib.Path…
28e7831 
….absolute()

If it's available, use `nt._getfullpathname()` to retrieve an absolute
path. This allows paths such as 'X:' to be made absolute even when
`os.getcwd()` returns a path on another drive. It follows the behaviour of
`os.path.abspath()`, except that no path normalisation is performed.
@bedevere-bot bedevere-bot mentioned this issue Jan 6, 2023
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@barneygale barneygale mentioned this issue Jan 8, 2023
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barneygale added a commit to barneygale/cpython that referenced this issue Feb 16, 2023
@barneygale
Merge branch 'main' into pythongh-100809-path-absolute-nt
ce26d13
zooba pushed a commit that referenced this issue Feb 17, 2023
@barneygale
gh-100809: Fix handling of drive-relative paths in pathlib.Path.absol…
072011b 
…ute() (GH-100812)

Resolving the drive independently uses the OS API, which ensures it starts from the current directory on that drive.
@bedevere-bot bedevere-bot mentioned this issue Feb 17, 2023
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barneygale added a commit to barneygale/cpython that referenced this issue Feb 17, 2023
@barneygale
[3.11] pythongh-100809: Fix handling of drive-relative paths in pathl…
09ecea7 
…ib.Path.absolute() (pythonGH-100812)

Resolving the drive independently uses the OS API, which ensures it starts from the current directory on that drive..
(cherry picked from commit 072011b)

Co-authored-by: Barney Gale <barney.gale@gmail.com>
@barneygale
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Fixed in #100812 (3.12), not backported due to interactions with other recent pathlib work.

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