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 |