LuaLS Setup

Manually

If you use lua-language-server, download schema.lua from the repo and create a .luarc.json like this to benefit from autocompletion. Unfortunately there is no easier solution since luals doesn't support loading libraries from URLs.

.luarc.json

{
  "$schema": "https://raw.githubusercontent.com/LuaLS/vscode-lua/master/setting/schema.json",
  "workspace": {
    "library": [
      "/path/to/schema.lua"
    ]
  }
}

Using Soonix

Alternatively, if you use Soonix, you can do the following to automatically get the correct schema.lua added to your .luarc.json:

soonix.hooks.luarc = {
  output = ".luarc.json";
  data = {
    "$schema" = "https://raw.githubusercontent.com/LuaLS/vscode-lua/master/setting/schema.json";
    workspace.library = [
      "${kenchiku.packages.default}/share/kenchiku/schema.lua"
    ];
  };
  hook.mode = "copy";
  opts.format = "json";
};

Now when running Soonix (manually or using the devshell integration), it will generate a local .luarc.json, which is gitignored (since the Nix store path might not be the same across platforms).