[Rd] optional package dependency

[Jari Oksanen]

On Fri, 2010-01-15 at 00:12 -0600, Jeff Ryan wrote:
> Hi Ross,
> 
> The quantmod package makes available routines from a variety of
> contributed packages, but gets around your issues with a bit of, um,
> trickery.
> 
> Take a look here (unless your name is Kurt ;-) ):
> 
> http://r-forge.r-project.org/plugins/scmsvn/viewcvs.php/pkg/R/buildModel.methods.R?rev=367&root=quantmod&view=markup
> 
> It would be nice to have Suggests really mean suggests to check, but I
> am sure there is a good reason it doesn't.
> 
I agree: it would be nice to have "Suggests" really mean "suggests", and
I 'suggested' so in an R-devel message of 20/9/05 with subject "Shy
Suggestion" (but this seems not exist in the R-devel archive?). I got
some support, but not from the right people, and so the R suggestion
remains the one you can't refuse or you'll wake up with a horse head in
your bed. I can live with this forced suggestion, although it is
sometimes painful, in particular in Mac or after re-installing
everything from scratch in Linux. 

The main argument was that building may fail later if you don't check
"suggests" early so that you must (de facto) depend on packages you
suggest. I'm sure many packages would fail now if the interpretation of
"suggests" was changed because the behaviour of "suggests" and "depends"
has been near identical for a long time and people have adapted. The
window of opportunity for another interpretation was when the checks for
undefined request() was added to the R CMD check routines in 2005, but
then it was decided that "suggests" should be near equivalent to
"depends", and this will stick.

Cheers, Jari Oksanen

-- 
Jari Oksanen, Department of Biology, Univ Oulu, FI-90014 Oulu, Finland
http://www.oulu.fi/~jarioksa http://vegan.r-forge.r-project.org