core/pkgs/build-support/build-fhsenv-chroot/default.nix

{ lib, callPackage, runCommandLocal, writeScript, stdenv, coreutils }:

let buildFHSEnv = callPackage ./env.nix { };

in args@{ name, version ? null, runScript ? "bash", extraInstallCommands ? ""
, meta ? { }, passthru ? { }, ... }:

let
  env = buildFHSEnv (removeAttrs args [
    "version"
    "runScript"
    "extraInstallCommands"
    "meta"
    "passthru"
  ]);

  chrootenv = callPackage ./chrootenv { };

  init = run:
    writeScript "${name}-init" ''
      #! ${stdenv.shell}
      for i in ${env}/* /host/*; do
        path="/''${i##*/}"
        [ -e "$path" ] || ${coreutils}/bin/ln -s "$i" "$path"
      done

      [ -d "$1" ] && [ -r "$1" ] && cd "$1"
      shift

      source /etc/profile
      exec ${run} "$@"
    '';

  versionStr = lib.optionalString (version != null) ("-" + version);

  nameAndVersion = name + versionStr;

in runCommandLocal nameAndVersion {
  inherit meta;

  passthru = passthru // {
    env = runCommandLocal "${name}-shell-env" {
      shellHook = ''
        exec ${chrootenv}/bin/chrootenv ${init runScript} "$(pwd)"
      '';
    } ''
      echo >&2 ""
      echo >&2 "*** User chroot 'env' attributes are intended for interactive nix-shell sessions, not for building! ***"
      echo >&2 ""
      exit 1
    '';
  };
} ''
  mkdir -p $out/bin
  cat <<EOF >$out/bin/${name}
  #! ${stdenv.shell}
  exec ${chrootenv}/bin/chrootenv ${init runScript} "\$(pwd)" "\$@"
  EOF
  chmod +x $out/bin/${name}
  ${extraInstallCommands}
''