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

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).

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.

Best,
Yutani

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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]]
>
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