List format and extensions from Pandoc in R

list_extensions.R

pandoc_list_extension <- function(format = "markdown") {
  res <- processx::run(rmarkdown::pandoc_exec(), c("--list-extension", format))
  tmp_file <- tempfile()
  on.exit(unlink(tmp_file))
  brio::write_file(res$stdout, tmp_file)
  ext <- brio::read_lines(tmp_file)
  tibble::tibble(
    format = format,
    extensions = gsub("^[-+]", "", extensions),
    default = ifelse(gsub("^([-+]{1}).*", "\\1", ext) == "+", TRUE, FALSE)
  )
}

pandoc_list_format <- function(type = c("input", "output")) {
  rlang::arg_match(type)
  flag <- sprintf("--list-%s-formats", type)
  res <- processx::run(rmarkdown::pandoc_exec(), flag)
  tmp_file <- tempfile()
  on.exit(unlink(tmp_file))
  brio::write_file(res$stdout, tmp_file)
  formats <- brio::read_lines(tmp_file)
  tibble::tibble(
    type = type,
    formats = formats
  )
}

gfm <- pandoc_list_extension("gfm")
markdown <- pandoc_list_extension("markdown")

# all formats
input_formats <- pandoc_list_format("input")
all_extensions <- purrr::map_df(input_formats$formats, pandoc_list_extension)

all_extensions %>%
  filter(default)