R/setup_cachix.R

In rix: Reproducible Data Science Environments with 'Nix'

#' setup_cachix Setup up the rstats-on-nix binary repository
#' @param nix_conf_path Character, path to folder containing 'nix.conf' file.
#'   Defaults to "~/.config/nix".
#' @details This function edits `~/.config/nix/nix.conf` to add the
#'   `rstats-on-nix` public cache as a substituter. The `rstats-on-nix` public
#'   cache, hosted on Cachix, contains many prebuild binaries of R and R
#'   packages for x86_64 Linux and macOS (Intel architectures for packages
#'   released before 2021 and Apple Silicon from 2021 onwards). This function
#'   automatically performs a backup of `~/.config/nix/nix.conf`, or creates one
#'   if there is no `nix.conf` file. If you installed Nix by following the
#'   instructions provided in the "Getting started" vignette and also followed
#'   the instructions to install Cachix and configure the cache, you don't need
#'   to run this. This function is useful in mainly two cases: if you somehow
#'   mess up `~/.config/nix/nix.conf` and need to generate a new one from
#'   scratch, or if you're using Nix inside Docker, write a `RUN Rscript -e
#'   'rix::setup_cachix()'` statement to configure the cache there. Because
#'   Docker runs using `root` by default no need to install the `cachix` client
#'   to configure the cache, running `setup_cachix()` is enough. See the
#'   'z - Advanced topic: Using Nix inside Docker' vignette for more details.
#' @return Nothing; changes a file in the user's home directory.
#' @export
#' @examples
#' \dontrun{
#' setup_cachix()
#' }
setup_cachix <- function(nix_conf_path = "~/.config/nix") {
  nix_conf_file <- file.path(nix_conf_path, "nix.conf")

  if (!nix_build_installed()) {
    stop(
      "Nix is not installed in this system,
there is no need to configure the cache.
Install Nix first."
    )
  }

  if (nix_conf_exists(nix_conf_file)) {
    add_to_existing_nix_conf_file(nix_conf_path)
  } else {
    add_new_nix_conf_file(nix_conf_path)
  }
}

#' @noRd
#' @param nix_conf_path Character, path to folder containing 'nix.conf' file.
#'   Defaults to "~/.config/nix".
add_new_nix_conf_file <- function(nix_conf_path) {
  if (!dir.exists(nix_conf_path)) {
    dir.create(nix_conf_path, recursive = TRUE)
  }

  source <- system.file(
    file.path("extdata", "nix.conf"),
    package = "rix",
    mustWork = TRUE
  )

  file.copy(source, nix_conf_path)

  if (identical(Sys.getenv("TESTTHAT"), "true")) {
    message("New Nix user config file saved to: ", nix_conf_path)
  }
}

#' @noRd
#' @param nix_conf_path Character, path to folder containing 'nix.conf' file.
#'   Defaults to "~/.config/nix".
add_to_existing_nix_conf_file <- function(nix_conf_path) {
  nix_conf_file <- file.path(nix_conf_path, "nix.conf")

  nix_conf_content <- readLines(con = nix_conf_file)

  if (is_cachix_configured(nix_conf_content)) {
    stop("rstats-on-nix cache already configured!")
  } else {
    if (identical(Sys.getenv("TESTTHAT"), "true")) {
      NULL
    } else {
      timestamp <- format(Sys.time(), "%Y-%m-%dT%H:%M:%S%z")
      nix_conf_backup <- paste0(nix_conf_file, "_backup_", timestamp)
      file.copy(from = nix_conf_file, to = nix_conf_backup)
    }

    substituter_line <- grep("substituters", nix_conf_content)
    nix_conf_content[substituter_line] <- paste0(
      append(
        nix_conf_content[substituter_line],
        "https://rstats-on-nix.cachix.org"
      ),
      collapse = " "
    )

    key_line <- grep("trusted-public-keys", nix_conf_content)
    nix_conf_content[key_line] <- paste0(
      append(
        nix_conf_content[key_line],
        "rstats-on-nix.cachix.org-1:vdiiVgocg6WeJrODIqdprZRUrhi1JzhBnXv7aWI6+F0="
      ),
      collapse = " "
    )

    writeLines(
      enc2utf8(c(nix_conf_content, "")),
      nix_conf_file,
      useBytes = TRUE
    )
    if (identical(Sys.getenv("TESTTHAT"), "false")) {
      message("Added rstats-on-nix as a substituter to ", nix_conf_file)
    }
    invisible(nix_conf_file)
  }
}


#' @noRd
#' @param nix_conf_path Connection to nix_conf_file
nix_conf_exists <- function(nix_conf_file) {
  # Test for existence and size instead of only existence,
  # as an active file connection makes the file exist, but is empty
  file.exists(nix_conf_file) &&
    `!=`(file.size(nix_conf_file), 0L)
}

#' @noRd
#' @param nix_conf_path Content of 'nix.conf' file
is_cachix_configured <- function(nix_conf_content) {
  substituter_line <- grep("substituters", nix_conf_content)
  any((grepl("rstats-on-nix", nix_conf_content[substituter_line])))
}