[R-pkg-devel] pandoc missing on r-release-macos-x86_64, r-oldrel-macos-x86_64

Two (related) questions:

1. Could pandoc be installed on the macoOS machines CRAN uses? If not, could
    R Core devise a way to have a registered vignette builder fail gracefully?

Can't help with the first request, but the second is really something 
that's up to the vignette writer and builder.  For example, in rgl, the 
vignettes use knitr, and they all execute this at the start:

if (!requireNamespace("rmarkdown", quietly = TRUE) ||
     !rmarkdown::pandoc_available("1.14")) {
   warning(call. = FALSE, "These vignettes assume rmarkdown and pandoc 
version 1.14.  These were not found. Older versions will not work.")
   knitr::knit_exit()
}

The warning message doesn't cause a check failure, and the knit_exit() 
call just stops processing at that point.

When I wrote this, knitr would fall back to an earlier version of 
rmarkdown that didn't need Pandoc.  I had to quit the vignette because 
that earlier version couldn't handle rgl output.

I'm not sure knitr does fail gracefully nowadays, but the point is that 
it could make a graceful exit if it wanted to.  This doesn't require R 
Core to make changes.

Duncan Murdoch

2. Could CRAN define and publish a minimal set of external applications
    available on each build + test machine?

Happy to help with patches or tests if there is interest.

Thanks, as always, for everything CRAN does.

Dirk