From hpages at fhcrc.org  Mon Jan 14 22:14:53 2013
From: hpages at fhcrc.org (=?ISO-8859-1?Q?Herv=E9_Pag=E8s?=)
Date: Mon, 14 Jan 2013 13:14:53 -0800
Subject: [Rd] Patch for setwd() to show path in error message
In-Reply-To: <CAFDcVCRCHnyW3=xk6N5z35KtvMcAM9y+iE-geJ9TTRKF+ruf2w@mail.gmail.com>
References: <CAFDcVCSbs3nh_Lnc8xi0RhHpL4WS=QpSakyD+ERyUU7nv-H68Q@mail.gmail.com>
	<50F1056E.4050207@stats.ox.ac.uk>
	<CAFDcVCRCHnyW3=xk6N5z35KtvMcAM9y+iE-geJ9TTRKF+ruf2w@mail.gmail.com>
Message-ID: <50F4754D.6070705@fhcrc.org>

Hi,

Of course we all want better error messages. What's the point of trying
to make a case against that?

Even the cd Unix command (a shell built-in in that case) -- and Unix
commands are known for their lack of verbosity and minimalist error
messages -- manages to report something informative:

   hpages at thinkpad:~$ cd /aaa/bbb
   bash: cd: /aaa/bbb: No such file or directory

There is an important difference between being "minimalist" and
"uninformative". The former is ok, not the latter.

Henrik's request makes a lot of sense.

Thanks,
H.


On 01/12/2013 11:21 AM, Henrik Bengtsson wrote:
> On Fri, Jan 11, 2013 at 10:40 PM, Prof Brian Ripley
> <ripley at stats.ox.ac.uk> wrote:
>> On 11/01/2013 20:22, Henrik Bengtsson wrote:
>>>
>>> Below is a patch for setwd() to show path in error message.  Current
>>> it just gives error messages such as:
>>>
>>> Error in setwd(libdir) : cannot change working directory
>>>
>>> with the patch it should (read untested) give:
>>>
>>> Error in setwd(libdir) : cannot change working directory to
>>> 'path/that/fails/'
>>
>>
>> And why is this needed?  You know it is 'libdir' and could check what that
>> was (or if doing this programatically, check its existence first).
>
> Risking to state the obvious:
>
> To me, the main purpose of error messages is to make troubleshooting
> easier. The more informative the error message is, the easier it is to
> troubleshoot and the faster the origin of the error can be resolved.
> The other extreme is to provide an empty error message (stop("")) and
> leave it to whoever needs to troubleshoot to use traceback() and
> debug() and/or inspect the source code.
>
> Also, a well written error message makes it more likely that the end
> user will be able to resolve the problem without asking others for
> help (read r-help, the maintainer, an R savvy person that the user
> happens to know, ...).  As an example of this, over at
> aroma-project.org I receive fewer support emails after updating the
> format of file-not-found error messages from:
>
>    Pathname not found: R-devel/src/library/base/R/R/utils.R
>
> to:
>
>    Pathname not found: R-devel/src/library/base/R/R/utils.R
> (R-devel/src/library/base/R/ exists, but nothing beyond; current
> directory is 'x:/CRAN')
>
>
> Moreover, it is not always the person who receives/reads the error
> message that is the one who will resolve the problem.  In some cases
> it is not even possible for that person to access the environment
> where the problem occurs.  However, as a good R citizen, the more
> troubleshooting you can at your end before requesting help by the
> person who can take action the better.  This also makes it more likely
> that the error will be resolved sooner.
>
> As my postscript hinted to, this post originates from an error in the
> 'R CMD check' service ran by r-forge.r-project.org).  That particular
> error is likely to occur internally in tools:::.check_packages();
>
>   if (nzchar(libdir)) {
>     setwd(libdir)
>     ...
>   }
>
> where 'libdir' is an internal object, but there is no way for me (and
> all the others who also see this error for their packages) to help out
> with the troubleshooting.
>
> /Henrik
>
>>
>> As you fumbled towards, it would require all the translations to be redone,
>> so we don't do this sort of thing lightly.  (Redone twice if it were done
>> correctly, AFAICS.)  The .pot and .po files are generated automatically, but
>> not filled in automatically.  This is all in the manuals ....
>>
>> In any case, the correct procedure was to file an enhancement request on
>> R-bugs, with a case and after testing on both platforms you are proposing to
>> patch.
>>
>>
>>
>>>
>>>
>>> PATCH:
>>>
>>> % diff -u util.c "util,patch.c"
>>>
>>> --- util.c      2012-12-16 13:13:05.002249900 -0800
>>> +++ util,patch.c        2013-01-11 11:52:16.843236400 -0800
>>> @@ -696,14 +696,14 @@
>>>        {
>>>           const wchar_t *path = filenameToWchar(STRING_ELT(s, 0), TRUE);
>>>           if(_wchdir(path) < 0)
>>> -           error(_("cannot change working directory"));
>>> +         error(_("cannot change working directory to '%s'"), path);
>>
>>
>> That is a wchar_t*, so the format would need to be %ls.
>>
>>
>>>        }
>>>    #else
>>>        {
>>>           const char *path
>>>               = R_ExpandFileName(translateChar(STRING_ELT(s, 0)));
>>>        if(chdir(path) < 0)
>>> -       error(_("cannot change working directory"));
>>> +      error(_("cannot change working directory to '%s'"), path);
>>
>>
>>>        }
>>>    #endif
>>>        return(wd);
>>>
>>>
>>> TRANSLATIONS:
>>> I have zero experience with GNU gettext/*.po files, but I understand
>>> that the above change requires updates to src/library/base/*.po files,
>>> which now looks like (e.g. de.po):
>>>
>>> #: src/main/util.c:699 src/main/util.c:706
>>> msgid "cannot change working directory"
>>> msgstr "kann Arbeitsverzeichnis nicht wechseln"
>>>
>>> A generic/automatic update would be to use the format:
>>>
>>> #: src/main/util.c:699 src/main/util.c:706
>>> msgid "cannot change working directory: '%s'"
>>> msgstr "kann Arbeitsverzeichnis nicht wechseln: '%s'"
>>>
>>> but I don't think that is in line with the current R style.
>>>
>>> /Henrik
>>>
>>> PS. Background for this patch:
>>>
>>> https://r-forge.r-project.org/tracker/index.php?func=detail&aid=2395&group_id=34&atid=194
>>>
>>> ______________________________________________
>>> R-devel at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>
>>
>>
>> --
>> Brian D. Ripley,                  ripley at stats.ox.ac.uk
>> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
>> University of Oxford,             Tel:  +44 1865 272861 (self)
>> 1 South Parks Road,                     +44 1865 272866 (PA)
>> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>>
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>

-- 
Herv? Pag?s

Program in Computational Biology
Division of Public Health Sciences
Fred Hutchinson Cancer Research Center
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[Rd] Patch for setwd() to show path in error message
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