R/str_collapse.R

In mlr-org/mlr3misc: Helper Functions for 'mlr3'

#' @title Collapse Strings
#'
#' @description
#' Collapse multiple strings into a single string.
#'
#' @param str (`character()`)\cr
#'   Vector of strings.
#' @param sep (`character(1)`)\cr
#'   String used to collapse the elements of `x`.
#' @param quote (`character()`)\cr
#'   Quotes to use around each element of `x`.
#'
#'   Will be replicated to lenght 2.
#' @param n (`integer(1)`)\cr
#'   Number of elements to keep from `x`. See [utils::head()].
#' @param ellipsis (`character(1)`)\cr
#'   If the string has to be shortened, this is signaled by appending `ellipsis` to `str`. Default is `" [...]"`.
#'
#' @return (`character(1)`).
#'
#' @export
#' @examples
#' str_collapse(letters, quote = "'", n = 5)
str_collapse = function(str, sep = ", ", quote = character(), n = Inf, ellipsis = "[...]") {
  formatted = head(str, n)

  if (length(quote)) {
    assert_character(quote, min.len = 1L, max.len = 2L, any.missing = FALSE)
    formatted = if (length(quote) == 1L) {
      paste0(quote, formatted, quote)
    } else {
      formatted = paste0(quote[1L], formatted, quote[2L])
    }
  }

  if (length(str) > n) {
    formatted = c(formatted, ellipsis)
  }
  paste0(formatted, collapse = sep)
}