R/path.R

In jimhester/withr: Run Code 'With' Temporarily Modified Global State

# path -----------------------------------------------------------------------

get_path <- function(...) {
  strsplit(Sys.getenv("PATH"), .Platform$path.sep)[[1]]
}

set_path <- function(path, action = c("prefix", "suffix", "replace")) {
  action <- match.arg(action)

  path <- as_character(path)
  path <- normalizePath(path, mustWork = FALSE)

  old <- get_path()
  path <- merge_new(old, path, action)

  path <- paste(path, collapse = .Platform$path.sep)
  Sys.setenv(PATH = path)
  invisible(old)
}

#' PATH environment variable
#'
#' Temporarily change the system search path.
#'
#' @template with
#' @param new `[character]`\cr New `PATH` entries
#' @param action `[character(1)]`\cr Should new values `"replace"`, `"prefix"`
#'   (the default) or `"suffix"` existing paths
#' @inheritParams with_collate
#' @seealso [Sys.setenv()]
#' @examples
#' # temporarily modify the system PATH, *prefixing* the current path
#' with_path(getwd(), Sys.getenv("PATH"))

#' # temporarily modify the system PATH, *appending* to the current path
#' with_path(getwd(), Sys.getenv("PATH"), "suffix")
#' @export
with_path <- with_(
  set_path,
  reset = function(old) set_path(old, "replace"),
  get = get_path
)

#' @rdname with_path
#' @export
local_path <- local_(
  set_path,
  reset = function(old) set_path(old, "replace"),
  get = get_path
)