R/plugin-rmarkdown.R

In hadley/rsmith: rsmith: a static site generator for R.

#' Convert rmarkdown to html
#'
#' Use the \pkg{rmarkdown} package. You can set options that apply to all
#' files in the global metadata field \code{rmarkdown}. The plugin ignores
#' binary files.
#'
#' @param pattern Regular expression used to identify Rmarkdown files.
#' @export
#' @examples
#' rmarkdown_demo <- rsmith_demo("rmarkdown")
#' rmarkdown_demo %>% preview()
#' rmarkdown_demo %>% use(rmarkdown()) %>% preview()
rmarkdown <- function(pattern = "\\.Rmd$") {
  if (!is_installed("rmarkdown")) {
    stop("Please install the rmarkdown package", call. = FALSE)
  }

  global <- NULL
  init <- function(rsmith) {
    global <<- rsmith$metadata$rmarkdown %||% list()

    rsmith
  }

  process <- function(file) {
    if (!grepl(pattern, path(file)) || is_binary(file)) return(file)

    metadata <- modifyList(global, file$metadata)

    # Save file to temporary location
    tmp_in <- tempfile()
    on.exit(unlink(tmp_in), add = TRUE)
    cat("---\n", yaml::as.yaml(metadata), "---\n\n", file = tmp_in, sep = "")
    cat(file$contents, file = tmp_in, append = TRUE)

    # Render with rmarkdown
    out <- rmarkdown::render(tmp_in, NULL, quiet = TRUE,
      output_options = list(self_contained = FALSE))
    on.exit(unlink(out), add = TRUE)

    # Update file object
    file$contents <- read_file(out)
    path <- tools::file_path_sans_ext(file$metadata$.path)
    file$metadata$.path <- paste0(path, ".", tools::file_ext(out))

    file
  }

  plugin_with_init("rmarkdown", init, process)
}