In tidymodels/recipes: Preprocessing and Feature Engineering Steps for Modeling

get_dials <- function(x) {
  if (any(names(x) == "range")) {
    cl <- rlang::call2(x$fun, .ns = x$pkg, range = x$range)
  } else {
    cl <- rlang::call2(x$fun, .ns = x$pkg)
  }
  rlang::eval_tidy(cl)
}

get_param_list <- function(x) {
  args <- formals(x)
  params <- getS3method("tunable", x)(list()) %>%
    dplyr::mutate(
      default = args[name],
      dials = purrr::map(call_info, get_dials),
      label = purrr::map_chr(dials, ~ .x$label),
      type = purrr::map_chr(dials, ~ .x$type),
      item = glue::glue("- `{name}`: {label} (type: {type}, default: {default})\n\n")
    )

  params$item
}