bug: vim: nightfox/lib/vim/compiler.lua:22: nesting of [[...]] is deprecated

Neovim version (nvim -v)

vim 9.0.1894

Operating system/version

debian testing/unstable

Describe the bug

Nightfox no longer works on vim/gvim since it got upgraded on debian to vim 9.0.1894. It worked before that on an older version of vim.

From the debian/vim changelog, this is probably the culprit:

Build against Lua 5.1 instead of Lua 5.2 (Closes: #1050637)

The error I'm getting is as follows:

Error detected while processing nightfox.vim:

nightfox/lib/vim/compiler.lua:22: nesting of [[...]] is deprecated

Steps To Reproduce

1) Try to use nightfox on the latest vim/gvim on debian

Expected Behavior

Nightfox used to work on the previous vim release (compiled with lua 5.2) but the newer version is compiled with lua 5.1 and there nightfox no longer works.

Repro

-- DO NOT change the paths and don't remove the colorscheme
local root = vim.fn.fnamemodify("./.repro", ":p")

-- set stdpaths to use .repro
for _, name in ipairs({ "config", "data", "state", "cache" }) do
  vim.env[("XDG_%s_HOME"):format(name:upper())] = root .. "/" .. name
end

-- bootstrap lazy
local lazypath = root .. "/plugins/lazy.nvim"
if not vim.loop.fs_stat(lazypath) then
  vim.fn.system({ "git", "clone", "--filter=blob:none", "https://github.com/folke/lazy.nvim.git", lazypath })
end
vim.opt.runtimepath:prepend(lazypath)

-- install plugins
local plugins = {
  {
    "EdenEast/nightfox.nvim",
    config = function()
      require("nightfox").setup({
        -- setup here ...
      })
    end,
  },
  -- add any other plugins here
}
require("lazy").setup(plugins, {
  root = root .. "/plugins",
})

vim.cmd.colorscheme("nightfox")

EdenEast / nightfox.nvim