rbxts-transform-boost

rbxts-transform-boost

A roblox-ts / rotor TypeScript transformer that improves compiled Luau performance by hoisting repeated expressions and caching property chains.

What it does

GetService hoisting

game:GetService("X") calls used two or more times in a file are hoisted to a top-level local so the lookup only happens once.

// Input
function a() { return game.GetService("RunService").Heartbeat }
function b() { return game.GetService("RunService").IsRunning }

-- Output
const _RunService = game:GetService("RunService")

local function a() return _RunService.Heartbeat end
local function b() return _RunService.IsRunning end

Property chain caching

Repeated property accesses (e.g. workspace.CurrentCamera.CFrame) inside loops or hot functions are cached into a local so the engine only walks the chain once.

// Input
for (let i = 0; i < n; i++) {
    const pos = workspace.CurrentCamera.CFrame.Position
}

-- Output
const _CFrame = workspace.CurrentCamera.CFrame
for i = 0, n - 1 do
    const pos = _CFrame.Position
end

Loop bounds hoisting

Upper bounds that are non-trivial expressions are extracted to a local so they are not re-evaluated on every iteration.

-- Before
for i = 0, someTable:size() - 1 do

-- After
const _size = someTable:size()
for i = 0, _size - 1 do

Benchmarks

Measured on a live Roblox server (published baseplate), 100,000 iterations per benchmark (10,000 for CFrame constructors). Both suites use //!native. Compiled with roblox-ts.

With transformer = GetService hoisting + property chain caching + --!strict + --!optimize 2 + type annotations (via rbxts-transform-luau) Without transformer = raw roblox-ts output (//!native only)

You can run the benchmark yourself: Boost Transformer Bench

GetService hoisting

Benchmark	With	Without	Speedup
svc ×1 (baseline)	0.112 µs	0.320 µs	2.9×
svc ×2 (same service)	0.198 µs	0.614 µs	3.1×
svc ×3 (diff services)	0.301 µs	0.878 µs	2.9×

Property chain caching

Benchmark	With	Without	Speedup
cam.CFrame ×3	0.454 µs	0.494 µs	1.1×
cam.CFrame.Position ×3	0.443 µs	0.885 µs	2.0×

Vector3 field hoisting

Benchmark	With	Without	Speedup
dot (×1 each field)	0.062 µs	0.099 µs	1.6×
cross (×2 each field)	0.057 µs	0.151 µs	2.6×
lerp (×2 each field)	0.054 µs	0.126 µs	2.3×
integrate (method calls)	0.056 µs	0.075 µs	1.3×

Loop bounds hoisting

Benchmark	With	Without	Speedup
sumArray (size ×1)	0.120 µs	0.106 µs	—
weightedSum (size ×1)	0.135 µs	0.116 µs	—

CFrame

Benchmark	With	Without	Speedup
cfLookAt (ctor)	0.146 µs	0.142 µs	—
cfChain (mul+angles)	0.158 µs	0.160 µs	—

Installation

npm install --save-dev rbxts-transform-boost

Setup

{
  "compilerOptions": {
    "plugins": [
      {
        "transform": "rbxts-transform-boost",
        "hoist": true
      }
    ]
  }
}

Options

Option	Type	Default	Description
hoist	boolean	true	Enable GetService hoisting, property chain caching, and loop bounds hoisting
verbose	boolean	false	Log per-file stats to the console