R devel - Feb 2023 - Undocumented change of dirname("C:/") on R-devel on Windows

Thanks for the prompt response, I'll confirm it after the new R-devel
binary is available.
Also, thanks for the detailed explanation. I agree with you in general.
> "/" in "C:/" is a path separator or not, and whether it
is trailing or not
It seems a Windows' path basically consists of two components; a drive
specification (e.g., C:) and the directory structure within the drive. What
I learned today is that both "C:/" and "C:" are valid path
specifications,
but refer to different locations; "C:" is not the root directory of
the
drive, but just a relative path [1]. So, I agree with you that the basename
of "C:/" should be "C:/". However, at the same time, I
don't feel this is
worth a breaking change, so I think we can preserve the current (R 4.2.2)
behavior.

[1]:
https://learn.microsoft.com/en-us/dotnet/standard/io/file-path-formats#apply-the-current-directory

Best,
Yutani

2023?2?23?(?) 17:15 Tomas Kalibera <tomas.kalibera at gmail.com>:
>
> On 2/23/23 03:27, Hiroaki Yutani wrote:
> > Hi,
> >
> > I found dirname() behaves differently on R-devel on Windows. Since
I'm
> not
> > sure which behavior is right, let me ask here before filing this to
R's
> > Bigzilla.
> >
> > On R 4.2.2., we get
> >
> >      > dirname("C:/")
> >      [1] "C:/"
> >
> > However, on R-devel (r83888), we get
> >
> >      > dirname("C:/")
> >      [1] "."
> >
> > ?dirname says 'dirname returns the part of the path up to but
excluding
> the
> > last path separator, or "." if there is no path
separator,' but I don't
> see
> > how the root path is supposed to be treated based on this rule (,
whether
> > it's WIndows or UNIX-alike).
> Thanks for spotting the difference, I've reverted to the previous
> behavior, the change was unintentional. If you spot any other suspicious
> changes in behavior in file-system operations, please report.
> > What should we expect as the return value of dirname("C:/")?
I feel the
> > current behavior on R 4.2.2 is right, but I'd like to confirm.
>
> I also think the old behavior is better, even though it could be argued
> whether the "/" in "C:/" is a path separator or not,
and whether it is
> trailing or not. But the behavior is in line with Unix where dirname of
> "/" is also "/". Msys2 would return "C:".
>
> If  "/" in "C:/" is a path separator but not a trailing
path separator,
> then basename("C:/") should probably be "" and not
"C:", and this would
> be in line with what R does on Unix. However, to be in line with Unix, I
> think the basename of "C:/" should be "C:/". Yet, Msys2
returns "C:"
> which is what R does now.
>
> So what these functions should do on Windows is definitely tricky. In
> either case the behavior is now again as in R 4.2.2.
>
> Best
> Tomas
>
> >
> > Best,
> > Yutani
> >
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-devel at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
>
	[[alternative HTML version deleted]]

I confirmed the revert fixed my failing test. Thanks!

2023?2?23?(?) 20:12 Hiroaki Yutani <yutani.ini at gmail.com>:
> Thanks for the prompt response, I'll confirm it after the new R-devel
> binary is available.
> Also, thanks for the detailed explanation. I agree with you in general.
>
> > "/" in "C:/" is a path separator or not, and
whether it is trailing or
> not
>
> It seems a Windows' path basically consists of two components; a drive
> specification (e.g., C:) and the directory structure within the drive. What
> I learned today is that both "C:/" and "C:" are valid
path specifications,
> but refer to different locations; "C:" is not the root directory
of the
> drive, but just a relative path [1]. So, I agree with you that the basename
> of "C:/" should be "C:/". However, at the same time, I
don't feel this is
> worth a breaking change, so I think we can preserve the current (R 4.2.2)
> behavior.
>
> [1]:
>
https://learn.microsoft.com/en-us/dotnet/standard/io/file-path-formats#apply-the-current-directory
>
> Best,
> Yutani
>
> 2023?2?23?(?) 17:15 Tomas Kalibera <tomas.kalibera at gmail.com>:
>
>>
>> On 2/23/23 03:27, Hiroaki Yutani wrote:
>> > Hi,
>> >
>> > I found dirname() behaves differently on R-devel on Windows. Since
I'm
>> not
>> > sure which behavior is right, let me ask here before filing this
to R's
>> > Bigzilla.
>> >
>> > On R 4.2.2., we get
>> >
>> >      > dirname("C:/")
>> >      [1] "C:/"
>> >
>> > However, on R-devel (r83888), we get
>> >
>> >      > dirname("C:/")
>> >      [1] "."
>> >
>> > ?dirname says 'dirname returns the part of the path up to but
excluding
>> the
>> > last path separator, or "." if there is no path
separator,' but I don't
>> see
>> > how the root path is supposed to be treated based on this rule (,
>> whether
>> > it's WIndows or UNIX-alike).
>> Thanks for spotting the difference, I've reverted to the previous
>> behavior, the change was unintentional. If you spot any other
suspicious
>> changes in behavior in file-system operations, please report.
>> > What should we expect as the return value of
dirname("C:/")? I feel the
>> > current behavior on R 4.2.2 is right, but I'd like to confirm.
>>
>> I also think the old behavior is better, even though it could be argued
>> whether the "/" in "C:/" is a path separator or
not, and whether it is
>> trailing or not. But the behavior is in line with Unix where dirname of
>> "/" is also "/". Msys2 would return "C:".
>>
>> If  "/" in "C:/" is a path separator but not a
trailing path separator,
>> then basename("C:/") should probably be "" and not
"C:", and this would
>> be in line with what R does on Unix. However, to be in line with Unix,
I
>> think the basename of "C:/" should be "C:/". Yet,
Msys2 returns "C:"
>> which is what R does now.
>>
>> So what these functions should do on Windows is definitely tricky. In
>> either case the behavior is now again as in R 4.2.2.
>>
>> Best
>> Tomas
>>
>> >
>> > Best,
>> > Yutani
>> >
>> >       [[alternative HTML version deleted]]
>> >
>> > ______________________________________________
>> > R-devel at r-project.org mailing list
>> > https://stat.ethz.ch/mailman/listinfo/r-devel
>>
>
	[[alternative HTML version deleted]]