[issue42957] os.readlink produces wrong result on windows

[simon mackenzie]

simon mackenzie <simonm3 at gmail.com> added the comment:

I note os.path.realpath("v1") does produce the right path in windows. Maybe
that is what you meant. Will that work cross-platform?

On Tue, 19 Jan 2021 at 18:48, simon mackenzie <simonm3 at gmail.com> wrote:

> For most people the expectation would be that it returns a path in the
> same format as any other path. Furthermore it seems odd to change the
> default behaviour after years when it worked as expected. I never heard of
> this substitute path before and it does not work in some circumstances e.g.
> docker does not recognise it.
>
> Note also that os.path.realpath(os.path.readlink("v1")) still returns
> \\\\?\\d:\\v1. There needs to be some way of getting to the path that
> everyone actually uses.
>
> On Mon, 18 Jan 2021 at 21:25, Eryk Sun <report at bugs.python.org> wrote:
>
>>
>> Eryk Sun <eryksun at gmail.com> added the comment:
>>
>> Symlinks and mountpoints (aka junctions) contain two forms of the target
>> path. There's a path that's intended for display in the shell, and there's
>> the actual substitute path to which the link resolves. os.readlink() was
>> changed to return the substitute path because the display form is not
>> mandated by filesystem protocols (it's sometimes missing, especially for
>> junctions) and not reliable (e.g. the display path may be a long path or
>> contain reserved names such that it's not valid without the \\?\ prefix).
>> It was decided to keep the C implementation of os.readlink() simple.
>> Whether to retain the \\?\ prefix was shifted to high-level functions that
>> consume the result of os.readlink(), such as os.path.realpath().
>>
>> There was a previous issue related to this, in that the shutil module
>> copies symlinks via os.readlink() and os.symlink(), which thus copies only
>> the substitute path now. The issue was closed as not a bug, but had it been
>> resolved with new functionality, I would have preferred to do so with a
>> low-level function to copy a reparse point, not by reverting the behavior
>> of os.readlink(). I also see no reason against adding an option to
>> readlink() to return the display path instead of the substitute path, or to
>> just remove the prefix. But I'd vote against making it the default behavior.
>>
>> ----------
>> components: +Library (Lib)
>> nosy: +eryksun
>> versions: +Python 3.10
>>
>> _______________________________________
>> Python tracker <report at bugs.python.org>
>> <https://bugs.python.org/issue42957>
>> _______________________________________
>>
>

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue42957>
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