@gwigz/tstl-bundle-flatten

A TypeScriptToLua plugin that flattens luaBundle output, eliminating the module system entirely.

TSTL's bundler wraps each module in a closure with a require() runtime. This plugin rewrites the bundle to emit all module code in dependency order as top-level locals, removing the ____modules table, ____moduleCache, require() function, module closures, and import/export boilerplate.

When is this useful?

Some Lua runtimes don't support or benefit from a module system, or are have tight limitations. If you're targeting an environment like this and using luaBundle, the generated runtime adds unnecessary overhead. This plugin strips it out and gives you clean, top-level code.

Install

bun add -D @gwigz/tstl-bundle-flatten
# or
npm install -D @gwigz/tstl-bundle-flatten

Setup

Add the plugin to your tsconfig.json:

{
  "tstl": {
    "luaBundle": "bundle.lua",
    "luaBundleEntry": "src/index.ts",
    "luaPlugins": [
+     { "name": "@gwigz/tstl-bundle-flatten" }
    ]
  }
}

Options

Options are passed inline in the plugin entry:

{
  "name": "@gwigz/tstl-bundle-flatten",
  // Modules to exclude from flattening (kept in the bundle runtime)
  "skipModules": ["constants"],
  // Insert blank lines at code boundaries for readability (default: true)
  "format": true,
  // Remove unused code after flattening, requires darklua-wasm (default: false)
  "shake": false,
}

Option	Type	Default	Description
skipModules	string[]	[]	Module names to leave untouched by the flattener
format	boolean	true	Add whitespace between logical code blocks in the output
shake	boolean	false	Remove unused top-level code after flattening

Tree shaking

Flattening turns every module export into a top-level local, which makes dead code elimination simple: anything nothing references can be removed. With "shake": true, the plugin runs darklua's remove_unused_variable and remove_empty_do rules over the flattened output.

This requires the optional darklua-wasm peer dependency:

bun add -D darklua-wasm
# or
npm install -D darklua-wasm

What it does:

• Removes unused local function definitions and unused locals, including functions only referenced by other removed functions
• Keeps side effects: an unused local x = call() becomes a bare call()
• Shakes inlined lualib functions too, since they flatten into locals like everything else

Unlike TypeScript-level tree shaking, this happens after bundling, so it also catches unused exports pulled in through re-export chains (barrel files).

Source maps

With "sourceMap": true in your compilerOptions, the plugin rewrites the emitted .map alongside the code, so generated lines still resolve back to the original TypeScript after flattening, shaking and formatting.

Mapping is line accurate, not column accurate: the transforms rewrite line contents, so only the line a statement ended up on is meaningful. That is enough to turn a runtime or compiler error in the flattened output back into a file and line you recognise.

TSTL writes the map before plugins run, so without this the .map on disk would describe the unflattened bundle and point at the wrong lines.

inlineSourceMap is not supported: TSTL appends its comment after the bundle's entry call, which flattening drops along with the rest of the module runtime.

Example

Given a bundle with two modules:

src/
├── greet.ts → export function greet(name: string) { ... }
└── index.ts → import { greet } from "./greet"

TSTL's default luaBundle output wraps everything in a module runtime. After tstl-bundle-flatten, you get:

local function greet(name)
  print("Hello, " .. name)
end

greet("world")

No ____modules, no require, no closures, just flat Lua.