Hugh,
You may be looking at this from the wrong angle. "Imports" is really an
updated variant of "Depends". Both of them declaure _unconditional_ use of
another package. (How they are used is the fine distinction between loading
and attaching which we'll skip here). The key point is that a package named
by either of these _must_ be present.
"Suggests" is different as it declares _optional_ use for which you should
then test. To take a simple example, Rcpp offers Rcpp.package.skeleton() by
extending / wrapping around package.skeleton(). If and when the _optional_
package pkgKitten (which is a Suggests: of Rcpp) is present, we use it:
havePkgKitten <- requireNamespace("pkgKitten", quietly=TRUE)
# ... stuff omitted
## update the package description help page
if (havePkgKitten) { # if pkgKitten is available, use it
pkgKitten::playWithPerPackageHelpPage(name, path, maintainer, email)
} else {
### other fallback code ....
}
See https://github.com/RcppCore/Rcpp/blob/master/R/Rcpp.package.skeleton.R
Hth, Dirk
--
http://dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org
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