R/line_insert.R

In frite: Functions Writing Functions

#' Inserts code into function
#'
#' Inserts code wrapped in the quote function into a function after the specified line.
#'
#' @param .f Any non-primitive function
#' @param after_line An integer that specifies where to insert quoted_code
#' @param quoted_code An expression wrapped in quote()
#'
#' @return function
#'
#' @seealso \code{\link{list_body}} \code{\link{line_insert}} \code{\link{line_remove}}
#'
#' @export
#'
#' @examples
#'
#' lapply_hello <- line_insert(lapply, 1, quote(print('Hello!')))
#'

line_insert <- function(.f, after_line, quoted_code){

  # Error checking
  assert_not_primitive(.f)
  assert_that(is.function(.f), is.number(after_line), is.call(quoted_code))
  assert_that(after_line %% 1 == 0, after_line >= 0,
              msg = "after_line must be a positive integer")

  # Appends the body list with quoted_code, converts to call, assigns it as body
  int_f <- .f
  body(int_f) <- list_body(int_f) %>%
    append(quoted_code, after = after_line) %>%
    as.call()

  return(int_f)
}