[Rd] Undocumented change of dirname("C:/") on R-devel on Windows

[Yihui Xie]

Hi Tomas,

There has been an R CMD check error with xfun and r-devel on Windows for a
while:
https://www.r-project.org/nosvn/R.check/r-devel-windows-x86_64/xfun-00check.html
Basically it means that the following would return TRUE before:

  normalizePath('a/b', mustWork = FALSE) == normalizePath('./a/b', mustWork
= FALSE)

but it became FALSE at some point in r-devel. I think 'a/b' and './a/b`
should be treated as the same path. Does that make sense? Thanks!

Regards,
Yihui
--
https://yihui.org


On Thu, Feb 23, 2023 at 11:44 PM Hiroaki Yutani <yutani.ini using gmail.com>
wrote:

> I confirmed the revert fixed my failing test. Thanks!
>
> 2023年2月23日(木) 20:12 Hiroaki Yutani <yutani.ini using 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年2月23日(木) 17:15 Tomas Kalibera <tomas.kalibera using 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 using r-project.org mailing list
> >> > https://stat.ethz.ch/mailman/listinfo/r-devel
> >>
> >
>
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>
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