mlua-language-server

Standalone LSP server for the mLua language (MapleStory Worlds scripting).

Wraps the msw.mlua VS Code extension and exposes a standard stdio JSON-RPC interface compatible with any LSP client (Neovim, Zed, Helix, etc.).

Requirements

• Node.js >= 16

Installation

npm install -g mlua-language-server

Or clone and use directly:

git clone https://github.com/...
cd mlua-language-server
node mlua-server.js --stdio

Usage

mlua-language-server --stdio

The extension (msw.mlua) is downloaded automatically from the VS Code Marketplace on first run. Subsequent runs use the cached copy.

To pin a specific install directory:

MLUA_INSTALL_DIR=/path/to/msw.mlua-1.1.5 mlua-language-server --stdio

Editor Setup

Neovim

Use mlua.nvim which bundles this wrapper and handles setup automatically.

For manual setup with nvim-lspconfig:

vim.lsp.config('mlua', {
  cmd = { 'mlua-language-server', '--stdio' },
  filetypes = { 'mlua' },
  root_dir = function(bufnr, on_dir)
    -- point to your project root
    on_dir(vim.fn.getcwd())
  end,
})
vim.lsp.enable('mlua')

Zed

Add to settings.json:

{
  "lsp": {
    "mlua": {
      "binary": {
        "path": "mlua-language-server",
        "args": ["--stdio"]
      }
    }
  }
}

Helix

Add to languages.toml:

[[language]]
name = "mlua"
language-servers = ["mlua-language-server"]

[language-server.mlua-language-server]
command = "mlua-language-server"
args = ["--stdio"]

Project Root Detection

The server indexes the entire project on startup. The project root is determined from the rootUri sent by the editor, with the following logic:

1. If the given directory (or any ancestor) contains both a RootDesk/ and an Environment/ sibling, that ancestor is used as the project root.
2. Otherwise the directory sent by the editor is used as-is.

This ensures Environment/NativeScripts/ (type definitions) is always included in the workspace index regardless of which subdirectory the editor reports as the root.

How It Works

Editor  ──stdio──▶  mlua-server.js  ──▶  proxy.js  ──stdio──▶  languageServer.js
                       (entry)             (LSP bridge)          (msw.mlua engine)

proxy.js intercepts the LSP initialize request, resolves the project root, indexes all .mlua and entry files (.map, .ui, .model, .collisiongroupset), and injects the result into initializationOptions before forwarding to the language server engine.

File watching is set up for the resolved project root so entry file changes (.ent) are forwarded to the server in real time.

Environment Variables

| Variable | Description | |---|---| | MLUA_INSTALL_DIR | Absolute path to the msw.mlua-<version>/ directory. Skips auto-discovery. |