[Python-ideas] Re: Add mechanism to check if a path is a junction (for Windows)

[Paul Moore]

On Tue, 8 Nov 2022 at 23:34, Steven D'Aprano  wrote:

>
> Most Python coders are using Windows. Surely it is time to do better
> for them than "just roll your own"?


While I frequently advocate on the side of "not every 3-line function needs
to be in the stdlib", there are a lot of convenience functions for Unix in
the stdlib (reflecting the fact that Python was initially developed on
Unix) and having them for Windows as well seems only fair. Given the
existence of pathlib.Path.is_fifo(), I think it's reasonable to include
is_junction() too. (There's no isfifo() in os.path, though, so the argument
for os.path.isjunction() is correspondingly weaker).

Paul
___
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-le...@python.org
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at 
https://mail.python.org/archives/list/python-ideas@python.org/message/AY6PMBU7DWFO3CB3WXOGF5Y7XEVKQXNU/
Code of Conduct: http://python.org/psf/codeofconduct/

[Python-ideas] Re: Add mechanism to check if a path is a junction (for Windows)

[Steven D'Aprano]

On Tue, Nov 08, 2022 at 09:55:04PM +, Barry wrote:

> But anyone that is suitably motivated can implement this.

This is true for every function in a Turing Complete language. Perhaps 
we should start using iota or jot? :-)

https://en.wikipedia.org/wiki/Iota_and_Jot

A "suitably motivated" person could implement ismount, islink, the 
entire os and Pathlib modules, and more. But they probably won't do as 
good a job of it as what we have.

On systems that support junction points, they are as much a fundamental 
file system object as symlinks, directories and mount points. 
Non-experts will probably have to google for hints how to implement 
this, and the internet is full of bad advice. On Stackoverflow, I find 
this question:

https://stackoverflow.com/questions/17174703/symlinks-on-windows

which starts off by giving the false information (or at least obsolete) 
that Windows doesn't support symlinks only shortcuts (NTFS has supported 
symlinks since at least Windows Vista, in 2006), and then later gives a 
solution for detecting junction points which requires ctypes.

Most Python coders are using Windows. Surely it is time to do better 
for them than "just roll your own"? 


-- 
Steve
___
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-le...@python.org
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at 
https://mail.python.org/archives/list/python-ideas@python.org/message/VLUZSVAS6TJVRTQNRGHZJ7AQIVFEMGIS/
Code of Conduct: http://python.org/psf/codeofconduct/

[Python-ideas] Re: Add mechanism to check if a path is a junction (for Windows)

[Barry]

On 8 Nov 2022, at 17:56, Charles Machalow  wrote:I would argue that just because it was easy for one to implement doesn't mean it's easy for others. That is true of so many things in life!I would have had no idea how to implement this without extra Googling and confusion.Having the abstraction makes it easier for others.But anyone that is suitably motivated can implement this.Barry- Charlie Scott Machalow
On Tue, Nov 8, 2022 at 1:12 AM Eryk Sun  wrote:On 11/8/22, Charles Machalow  wrote:
>
> Funny enough in PowerShell, for prints an "l" for both symlinks and
> junctions.. so it kind of thinks of it as a link of some sort too I guess.

As does Python already in many cases. For example, os.lstat() doesn't
traverse a mount point (junction). On Windows, symlinks and mount
points are in a general category of name-surrogate reparse points.
os.lstat() doesn't traverse them.

If Python supported copying a mount point via
os.symlink(os.readlink(src), dst), I'd be reluctantly in favor of just
letting ntpath.islink() return true for a mount point, as a practical
measure for seamless cross-platform implementations of functions like
rmtree() and copytree(). In terms of POSIX that's nonsense, but not
really on Windows.

> Is it that much of a waste to just return False on posix? I mean it's a
> couple lines and just maintains api.. and in theory can be more clear to
> some.

I'm just thinking this through in terms of conceptual cost and
usefulness in the standard library relative to how easy it is to
implement one's own isjunction() or is_name_surrogate() test. Of
course, a lot of the os.path tests have simple implementations, such
as exists(), isdir() and isfile(). They're in the standard library
because they're commonly needed. The question is whether isjunction()
is needed enough generally to justify adding it.

___Python-ideas mailing list -- python-ideas@python.orgTo unsubscribe send an email to python-ideas-le...@python.orghttps://mail.python.org/mailman3/lists/python-ideas.python.org/Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/MOY5NNFQK5PMD5GQBADZE3COVT7ONA62/Code of Conduct: http://python.org/psf/codeofconduct/___
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-le...@python.org
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at 
https://mail.python.org/archives/list/python-ideas@python.org/message/WKA3ZPPLHTY3K3CCADUYC3KZI76NYTTA/
Code of Conduct: http://python.org/psf/codeofconduct/

[Python-ideas] Re: Add mechanism to check if a path is a junction (for Windows)

[Charles Machalow]

I would argue that just because it was easy for one to implement doesn't
mean it's easy for others.
I would have had no idea how to implement this without extra Googling and
confusion.
Having the abstraction makes it easier for others.

- Charlie Scott Machalow


On Tue, Nov 8, 2022 at 1:12 AM Eryk Sun  wrote:

> On 11/8/22, Charles Machalow  wrote:
> >
> > Funny enough in PowerShell, for prints an "l" for both symlinks and
> > junctions.. so it kind of thinks of it as a link of some sort too I
> guess.
>
> As does Python already in many cases. For example, os.lstat() doesn't
> traverse a mount point (junction). On Windows, symlinks and mount
> points are in a general category of name-surrogate reparse points.
> os.lstat() doesn't traverse them.
>
> If Python supported copying a mount point via
> os.symlink(os.readlink(src), dst), I'd be reluctantly in favor of just
> letting ntpath.islink() return true for a mount point, as a practical
> measure for seamless cross-platform implementations of functions like
> rmtree() and copytree(). In terms of POSIX that's nonsense, but not
> really on Windows.
>
> > Is it that much of a waste to just return False on posix? I mean it's a
> > couple lines and just maintains api.. and in theory can be more clear to
> > some.
>
> I'm just thinking this through in terms of conceptual cost and
> usefulness in the standard library relative to how easy it is to
> implement one's own isjunction() or is_name_surrogate() test. Of
> course, a lot of the os.path tests have simple implementations, such
> as exists(), isdir() and isfile(). They're in the standard library
> because they're commonly needed. The question is whether isjunction()
> is needed enough generally to justify adding it.
>
___
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-le...@python.org
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at 
https://mail.python.org/archives/list/python-ideas@python.org/message/MOY5NNFQK5PMD5GQBADZE3COVT7ONA62/
Code of Conduct: http://python.org/psf/codeofconduct/

[Python-ideas] Re: Add mechanism to check if a path is a junction (for Windows)

[Eryk Sun]

On 11/8/22, Charles Machalow  wrote:
>
> Funny enough in PowerShell, for prints an "l" for both symlinks and
> junctions.. so it kind of thinks of it as a link of some sort too I guess.

As does Python already in many cases. For example, os.lstat() doesn't
traverse a mount point (junction). On Windows, symlinks and mount
points are in a general category of name-surrogate reparse points.
os.lstat() doesn't traverse them.

If Python supported copying a mount point via
os.symlink(os.readlink(src), dst), I'd be reluctantly in favor of just
letting ntpath.islink() return true for a mount point, as a practical
measure for seamless cross-platform implementations of functions like
rmtree() and copytree(). In terms of POSIX that's nonsense, but not
really on Windows.

> Is it that much of a waste to just return False on posix? I mean it's a
> couple lines and just maintains api.. and in theory can be more clear to
> some.

I'm just thinking this through in terms of conceptual cost and
usefulness in the standard library relative to how easy it is to
implement one's own isjunction() or is_name_surrogate() test. Of
course, a lot of the os.path tests have simple implementations, such
as exists(), isdir() and isfile(). They're in the standard library
because they're commonly needed. The question is whether isjunction()
is needed enough generally to justify adding it.
___
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-le...@python.org
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at 
https://mail.python.org/archives/list/python-ideas@python.org/message/G4YQTXFPDN5YQLNYUUKCP2NV4DLGWSTN/
Code of Conduct: http://python.org/psf/codeofconduct/

[Python-ideas] Re: Add mechanism to check if a path is a junction (for Windows)

[Steven D'Aprano]

On Mon, Nov 07, 2022 at 07:31:36PM -, Charles Machalow wrote:

> I propose adding a mechanism to both pathlib.Path and os.path to check 
> if a given path is a junction or not. Currently is_symlink/islink 
> return False for junctions.

+1 on a function is_junction.

I am neutral on the question of whether that function should:

1. only exist on Windows,
2. or exist on other platforms but always return False.

Prior art suggests the second is probably better: when Python doesn't 
support symbolic links, `os.islink` exists but always returns False.

https://docs.python.org/3/library/os.path.html#os.path.islink

I am also neutral on whether ismount() on Windows should always return 
True for junctions, as well as mount points. I leave that to Windows 
experts to decide.

-1 on adding a flag parameter to existing functions.


-- 
Steve
___
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-le...@python.org
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at 
https://mail.python.org/archives/list/python-ideas@python.org/message/M36XXF4QZ6VJJSTEDPOTAGEODC35NVLM/
Code of Conduct: http://python.org/psf/codeofconduct/