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

[Tomas Kalibera]

On 2/27/23 17:02, Yihui Xie wrote:
> 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!

Thanks a lot for spotting and reporting this, fixed in R-devel. 
Normalization of non-existent paths was broken.

Best
Tomas

>
> 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
>     >>
>     >
>
>             [[alternative HTML version deleted]]
>
>     ______________________________________________
>     R-devel using r-project.org mailing list
>     https://stat.ethz.ch/mailman/listinfo/r-devel
>
	[[alternative HTML version deleted]]