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}
  ''