R/pandoc_template.R

In muuankarski/kazdoc: document templates for Rmarkdown for rstatscon

#' Render a pandoc template.
#'
#' This is a hacky way to access the pandoc templating engine.
#'
#' @param metadata A named list containing metadata to pass to template.
#' @param template Path to a pandoc template.
#' @param output Path to save output.
#' @return (Invisibly) The path of the generate file.
#' @examples
#' x <- rticles:::template_pandoc(
#'   list(preamble = "%abc", filename = "wickham"),
#'   rticles:::find_resource("rjournal_article", "RJwrapper.tex"),
#'   tempfile()
#' )
#' if (interactive()) file.show(x)
template_pandoc <- function(metadata, template, output, verbose = FALSE) {
  tmp <- tempfile(fileext = ".md")
  on.exit(unlink(tmp))

  cat("---\n", file = tmp)
  cat(yaml::as.yaml(metadata), file = tmp, append = TRUE)
  cat("---\n", file = tmp, append = TRUE)
  cat("\n", file = tmp, append = TRUE)

  rmarkdown::pandoc_convert(tmp, "markdown", output = output,
                            options = paste0("--template=", template), verbose = verbose)

  invisible(output)
}