Put RStudio's Pandoc on the path during a check

[dpprdan]

At least on Windows Pandoc (as installed by RStudio) is unlikely to be on the system PATH, which means that URLs in Rmds and READMEs are not checked. (I have had a package submission rejected due to this.)

RStudio users do have Pandoc installed and the path can be found out with Sys.getenv("RSTUDIO_PANDOC"). So this could be put on the path with withr::local_path(Sys.getenv("RSTUDIO_PANDOC")). This would add a dependency on {withr}, however. (Cf. https://github.com/r-lib/rcmdcheck/issues/109, https://github.com/r-lib/rcmdcheck/pull/132).

Please consider putting RStudio's Pandoc on the path. I could draft a PR if it helps.

Possible workaround: Run withr::with_path(Sys.getenv("RSTUDIO_PANDOC"), url_check()).

[jimhester]

I think probably it would be best to use rmarkdown::find_pandoc() for this and only do it conditional on the presence of the rmarkdown and withr packages.

[dpprdan]

I've used Sys.getenv("RSTUDIO_PANDOC") over rmarkdown::find_pandoc() in https://github.com/r-lib/rcmdcheck/pull/132, because rmarkdown::find_pandoc() effectively only adds ~/opt/pandoc/ as a search location for pandoc at the cost of its dependency:

this function searches for pandoc from the environment variable RSTUDIO_PANDOC (the RStudio IDE will set this variable to the directory of Pandoc bundled with the IDE), the environment variable PATH, and the directory ~/opt/pandoc/ https://rmarkdown.rstudio.com/docs/reference/find_pandoc.html

But maybe ~/opt/pandoc/ is more relevant than I realise. (I.e. this is just a note, either approach is fine).

I am a bit worried that it is easy to miss that certain docs are not checked, if you don't have the right packages installed (re: your suggestion to make this conditional). CRAN will check those docs either way. To put it more bluntly: what's the use of an incomplete URL check? So should there generally be messages/warnings about which docs were (not) checked?

[jimhester]

Ok, you could use something like this to also avoid the withr dependency, which I would prefer.

with_pandoc_path <- function(code) {
  pandoc_path <- Sys.getenv("RSTUDIO_PANDOC")
  if (nzchar(pandoc_path)) {
    old_path <- Sys.getenv("PATH")
    Sys.setenv("PATH", file.path(pandoc_path, old, sep = .Platform$path.sep))
    on.exit(Sys.setenv("PATH", old_path))
  }
  pandoc_location <- Sys.which("pandoc")
  if (!nzchar(pandoc_location)) {
    stop("pandoc not found!")
  }
  force(code)
}