lua.lib: lift toLua to top in generateLuarocksConfig

      externalDepsDirs = map

        (x: builtins.toString x)

        (lib.filter (lib.isDerivation) externalDeps);

  in ''

    local_cache = ""

    -- To prevent collisions when creating environments, we install the rock

    -- files into per-package subdirectories

    rocks_subdir = ${toLua {} rocksSubdir}

    -- first tree is the default target where new rocks are installed,

    -- any other trees in the list are treated as additional sources of installed rocks for matching dependencies.

    rocks_trees = ${toLua {} (

  in toLua { asBindings = true; } ({

    local_cache = "";

    # To prevent collisions when creating environments, we install the rock

    # files into per-package subdirectories

    rocks_subdir = rocksSubdir;

    # first tree is the default target where new rocks are installed,

    # any other trees in the list are treated as additional sources of installed rocks for matching dependencies.

    rocks_trees = (

      [{name = "current"; root = "${placeholder "out"}"; rocks_dir = "current"; }] ++

      rocksTrees

    )}

  '' + lib.optionalString lua.pkgs.isLuaJIT ''

    -- Luajit provides some additional functionality built-in; this exposes

    -- that to luarock's dependency system

    rocks_provided = ${toLua {} {

    );

  } // lib.optionalAttrs lua.pkgs.isLuaJIT {

    # Luajit provides some additional functionality built-in; this exposes

    # that to luarock's dependency system

    rocks_provided = {

      jit = "${lua.luaversion}-1";

      ffi = "${lua.luaversion}-1";

      luaffi = "${lua.luaversion}-1";

      bit = "${lua.luaversion}-1";

    }}

  '' + ''

    -- For single-output external dependencies

    external_deps_dirs = ${toLua {} externalDepsDirs}

    -- Some needed machinery to handle multiple-output external dependencies,

    -- as per https://github.com/luarocks/luarocks/issues/766

    variables = ${toLua {} (depVariables // extraVariables)}

  '';

    };

  } // {

    # For single-output external dependencies

    external_deps_dirs = externalDepsDirs;

    # Some needed machinery to handle multiple-output external dependencies,

    # as per https://github.com/luarocks/luarocks/issues/766

    variables = (depVariables // extraVariables);

  });

}