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###########################################################################/**
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# @RdocDefault findPandoc
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#
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# @title "Locates the pandoc executable"
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#
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# \description{
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# @get "title" on the current system.
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# }
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#
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# @synopsis
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#
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# \arguments{
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# \item{mustExist}{If @TRUE, an exception is thrown if the executable
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# could not be located.}
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# \item{...}{Not used.}
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# \item{verbose}{See @see "R.utils::Verbose".}
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# }
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#
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# \value{
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# Returns the pathname to the executable, or @NULL if not found.
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# }
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#
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# \details{
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# The executable is searched for as follows:
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# \enumerate{
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# \item \code{Sys.which("pandoc")}
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# }
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# }
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#
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# @author
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#
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# @keyword file
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# @keyword IO
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# @keyword internal
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#*/###########################################################################
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setMethodS3("findPandoc", "default", function(mustExist=TRUE, ..., verbose=FALSE) {
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# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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# Validate arguments
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# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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# Argument 'mustExist':
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mustExist <- Arguments$getLogical(mustExist)
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# Argument 'verbose':
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verbose <- Arguments$getVerbose(verbose)
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if (verbose) {
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pushState(verbose)
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on.exit(popState(verbose))
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}
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command <- "pandoc"
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verbose && enter(verbose, "Locating external software")
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verbose && cat(verbose, "Command: ", command)
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bin <- Sys.getenv("R_PANDOC")
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if (identical(bin, "")) bin <- Sys.getenv("RSTUDIO_PANDOC")
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if (identical(bin, "")) bin <- Sys.which(command)
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if (identical(bin, "")) bin <- NULL
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if (!isFile(bin)) bin <- NULL
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verbose && cat(verbose, "Located pathname: ", bin)
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if (mustExist && !isFile(bin)) {
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throw(sprintf("Failed to located external executable: '%s'", command))
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}
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# Validate by retrieving version information
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if (isFile(bin)) {
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output <- tryCatch({
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system2(bin, args="--version", stdout=TRUE)
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}, error = function(ex) {
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NULL
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})
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if (!is.null(output)) {
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name <- "pandoc"
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pattern <- "pandoc.* ([0-9.-]+).*"
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ver <- grep(pattern, output, value=TRUE)
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ver <- gsub(pattern, "\\1", ver)
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## No matching output?
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if (length(ver) == 0) {
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stop(sprintf("Failed to infer version of %s based on captured output: ", sQuote(name), paste(dQuote(output), collapse=", ")))
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}
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## Try to coerce to version objects
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ver <- numeric_version(ver, strict = FALSE)
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ver <- ver[!is.na(ver)]
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## Failed to coerce?
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if (length(ver) == 0) {
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stop("Failed to parse version of %s based on captured output: ", sQuote(name), paste(dQuote(output), collapse=", "))
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}
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## If more than one match, use the first one
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ver <- ver[[1]]
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attr(bin, "version") <- ver
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}
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}
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verbose && exit(verbose)
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bin
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}) # findPandoc()
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