pkgs.requireFile

The following is the current implementation of this function.

requireFile =
    {
      name ? null,
      sha256 ? null,
      sha1 ? null,
      hash ? null,
      url ? null,
      message ? null,
      hashMode ? "flat",
    }:
    assert (message != null) || (url != null);
    assert (sha256 != null) || (sha1 != null) || (hash != null);
    assert (name != null) || (url != null);
    let
      msg =
        if message != null then
          message
        else
          ''
            Unfortunately, we cannot download file ${name_} automatically.
            Please go to ${url} to download it yourself, and add it to the Nix store
            using either
              nix-store --add-fixed ${hashAlgo} ${name_}
            or
              nix-prefetch-url --type ${hashAlgo} file:///path/to/${name_}
          '';
      hashAlgo =
        if hash != null then
          (builtins.head (lib.strings.splitString "-" hash))
        else if sha256 != null then
          "sha256"
        else
          "sha1";
      hashAlgo_ = if hash != null then "" else hashAlgo;
      hash_ =
        if hash != null then
          hash
        else if sha256 != null then
          sha256
        else
          sha1;
      name_ = if name == null then baseNameOf (toString url) else name;
    in
    stdenvNoCC.mkDerivation {
      name = name_;
      outputHashMode = hashMode;
      outputHashAlgo = hashAlgo_;
      outputHash = hash_;
      preferLocalBuild = true;
      allowSubstitutes = false;
      builder = writeScript "restrict-message" ''
        source ${stdenvNoCC}/setup
        cat <<_EOF_

        ***
        ${msg}
        ***

        _EOF_
        exit 1
      '';
    };