Pandoc version report: clarify how to check for {rmarkdown} availability

[xx02al]

Hi

While searching for other information in this package, I came across the function that reports the pandoc version. I’d like to clarify why we are using isNamespaceLoaded() and whether it might be preferable to check instead if {rmarkdown} is installed.

Here is an example that illustrates the reason for my question. Start in a fresh R session and run:

get_pandoc_version <- function() {
  if (isNamespaceLoaded("rmarkdown")) {
    ver <- rmarkdown::find_pandoc()
    if (is.null(ver$dir)) {
      "NA (via rmarkdown)"
    } else {
      paste0(ver$version, " @ ", ver$dir, "/ (via rmarkdown)")
    }
  } else {
    path <- Sys.which("pandoc")
    if (path == "") {
      "NA"
    } else {
      ver <- parse_pandoc_version(path)
      paste0(ver, " @ ", path)
    }
  }
}

parse_pandoc_version <- function(path) {
  tryCatch(
    {
      out <- system2(path, "--version", stdout = TRUE)[1]
      last(strsplit(out, " ", fixed = TRUE)[[1]])
    },
    error = function(e) "NA"
  )
}

Now, i.e., in a session where {rmarkdown} has not been loaded/attached:

> get_pandoc_version()
[1] "NA"

With and after calling rmarkdown::find_pandoc():

> rmarkdown::find_pandoc()
$version
[1] ‘3.6.3’

$dir
[1] "c:\\Program Files\\Positron\\resources\\app\\quarto\\bin\\tools"
> get_pandoc_version()
[1] "3.6.3 @ c:\\Program Files\\Positron\\resources\\app\\quarto\\bin\\tools/ (via rmarkdown)"