[R] Seemingly bizarre behavior in R CMD check

[Prof Brian D Ripley]

On Fri, 27 Jul 2001, Bartz, Kevin wrote:

> Maybe someone can help shed some light on an odd and repeatedly irritating
> error I noticed when running the check Perl script on my R 1.3 project. In
> following it line by line, I traced my problem down to the
> code/documentation matching within check, the most recent version of which
> seems to verify proper .Rd formatting by means of R's codoc and undoc
> functions. Under R --vanilla, those two then unpack and repack my project,
> with each assembling a kind of test tempfile to ensure various structural
> requirements within my project. At first, I got bogged down in a mysterious
> "parse" problem, R's not-too-revealing result of a simple eval, but after
> discovering the keep.tempfiles flag I was able to trace the obvious errors
> without running codoc line by line interactively. Apparently, R keeps very
> stringent requirements on its documentation's usage field. If it's anything
> other than myFunc(arg1, arg2...), codoc won't parse it correctly in its
> tempfiles. And the particular S code I was translating used chiefly example
> calls in its documentation's usage fields. Is this formatting an intended
> necessity? I know it ensures consistency but it's too often the source of
> cryptic errors.
>
> Anyway, fixing these usage fields worked for the time being but without fail
> another similar problem soon emerged, this time with the check for
> undocumented objects. This leg of the script uses undoc, and after
> examination I found that undoc's concatenation of the R code in the
> project/R directory fails to insert a newline at the end of each .R file's
> contribution to the appended tempfile. Now I'm a clean kind of guy and I
> like to keep my code immaculate, so it was more than disturbing when my R
> functions, each stored in a single .R file, bombed out because each did not
> have a newline proceeding its closing bracket. Without that, undoc's file

Do you mean a newline *after* the closing brace (to be precise)?  That
would explain the rest of the sentence.  A well-formed .R file *does* have
a final newline, so `immaculate' code should have one.  (BTW, the
tidying-up procedure mentioned in `Writing R Extensions' does ensure a
final newline.)

> appending sticks the next function right up against the last's final
> bracket, triggering an obvious syntax error, albeit one hidden underneath
> tempfiles and a parse/eval combo. Now I can understand somewhat the benefits
> of establishing consistency in the usage fields, but for the life of me I
> can't figure out the reasoning behind this seemingly superfluous stringency.
> Is this R's intended behavior, and if so, forgive me for asking, but why?

(Assuming I have decoded your explanation correctly.)  Because Unix text
files do have a final newline.  It's a very widespread convention, and the
most widespread editor, vi, enforces it.  Now undoc could be asked to
insert a newline (and given your experience it is probably a good idea) for
files which lack one, but this has not arisen in the hundreds of packages
which have been tested to date.

> Thanks in advance for any light you can cast on the issue.
>
> Kevin
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-- 
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 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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