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
        '';
      };