R/hook_number_lines.R

In chunkhooks: Chunk Hooks for 'R Markdown'

#' Number lines on code blocks
#'
#' Number lines on code blocks created by chunks, i.e. source, output,
#' message, warning, and/or error.
#'
#' @param targets A character vector specifying what kind of code blocks
#'  automatically number lines (default: `"source"`). Choices are
#'  `"source"`, `"output"`, `"message"`, `"warning"`, and/or `"error"`.`
#'  `NULL` disables the automation.
#' @param .set `TRUE` or `FALSE` to set the hook.
#'
#' @return invisible hook function
#'
#' @examples
#' hook_numberLines("source")
#'
#' @export
hook_numberLines <- function(targets = "source", .set = TRUE) {
  targets <- if (!is.null(targets)) {
    match.arg(
      targets,
      c("source", "output", "message", "warning", "error"),
      several.ok = TRUE
    )
  }

  hook <- function(options) {
    targets <- paste0("class.", knitr::opts_current$get("numberLines"))
    options[targets] <- lapply(options[targets], append, "numberLines")
    return(options)
  }

  if (.set) {
    knitr::opts_chunk$set(numberLines = targets)
    knitr::opts_hooks$set(numberLines = hook)
  }

  return(invisible(hook))
}