R function for reading a subset of front-matter keys for one or more Qmd documents into a table

read_qmd_params.R

#' Use lightparser::split_to_tbl to read YAML keys from one or more Quarto
#' document
#'
#' Created 2024-08-29 to reconcile the file names and schedule of the slides,
#' week overview pages, and exercises.
read_qmd_params <- function(path,
                            ...,
                            recurse = FALSE,
                            keys = c("order",
                                     "title",
                                     "subtitle",
                                     "date",
                                     "date-due",
                                     "date-modified",
                                     "image"),
                            regex = "qmd$",
                            perl = TRUE) {
  files <- path

  if (fs::is_dir(path)) {
    files <- fs::dir_ls(
      path,
      regexp = paste0("^", path ,"/_"),
      invert = TRUE,
      type = "file"
    )

    files <- stringr::str_subset(
      files,
      pattern = "^_",
      negate = TRUE
    )
  }

  files <- rlang::set_names(files, files)

  file_tbl <- purrr::map(
    files,
    \(x) {
      tbl <- withCallingHandlers(
        lightparser::split_to_tbl(x),
        error = NULL
      )

      if (is.null(tbl)) {
        return(NULL)
      }

      params <- tbl |>
        dplyr::filter(type == "yaml") |>
        dplyr::pull(params)

      # Select the frontmatter
      params <- params[[1]][keys]

      as.data.frame(vctrs::list_drop_empty(params))
    }
  )

  file_tbl |>
    purrr::list_rbind(
      names_to = "path"
    ) |>
    dplyr::mutate(
      filename = fs::path_ext(path),
      .after = dplyr::all_of("path")
    )
}