ReScript Runtime Tools

Runtime-aware build/dev tooling for ReScript that’s first-class for Deno and Bun.

Table of Contents

• Overview
  • Key Features
• Installation
  • Zero npm Philosophy
• Usage
• Architecture
  • Runtime Detection
  • Capability Checking
• Comparison with Node.js Tooling
• Integration with rescript-wasm-runtime
• License
• Related Projects

Overview

rescript-runtime-tools provides unified developer experience tooling that understands and leverages the capabilities of modern JavaScript runtimes (Deno, Bun) without falling back to Node.js + npm glue.

Key Features

• Runtime Detection - Automatically detects Deno/Bun and uses native APIs

• Unified CLI - Single rrt command works identically across runtimes

• Watch Mode - Integrated file watching with ReScript compilation

• Test Runner - Runtime-native test execution (Deno.test / bun:test)

• Zero npm - No node_modules in production

Installation

# Deno (no npm install needed!)
deno install --allow-all -n rrt https://raw.githubusercontent.com/hyperpolymath/rescript-runtime-tools/main/bin/rrt.ts

# Or run directly
deno run --allow-all https://raw.githubusercontent.com/hyperpolymath/rescript-runtime-tools/main/bin/rrt.ts dev

# Bun
bunx rescript-runtime-tools

Zero npm Philosophy

This tool uses Deno’s npm: specifier to run ReScript directly from the npm registry without node_modules or package.json. Deno caches packages globally, so:

• No npm install step

• No node_modules/ directory

• No package-lock.json

• Works offline after first run

Usage

# Start dev server with watch mode
rrt dev

# Start on custom port
rrt dev -p 3000

# Production build
rrt build --prod

# Run tests
rrt test

# Watch mode testing
rrt test --watch

# Run benchmarks
rrt bench

# Format ReScript files
rrt fmt

# Clean build artifacts
rrt clean

# Show runtime info
rrt info

Architecture

rescript-runtime-tools/
├── src/
│   ├── Detect.res      # Runtime detection (Deno/Bun/Browser)
│   ├── Dev.res         # Dev server with watch
│   ├── Test.res        # Test runner abstraction
│   └── Build.res       # Build orchestration
├── bin/
│   └── rrt.ts          # CLI entry point
├── deno.json           # Deno configuration
└── rescript.json       # ReScript configuration

Runtime Detection

The Detect module provides runtime identification:

type runtime = Deno | Bun | Browser | Unknown

let detect = (): runtime
let getInfo = (): runtimeInfo

Capability Checking

Detect.Capabilities.hasFileSystem()    // true for Deno/Bun
Detect.Capabilities.hasNetwork()       // true for Deno/Bun/Browser
Detect.Capabilities.hasNativeModules() // true for Bun only
Detect.Capabilities.hasWebAssembly()   // true for all modern runtimes

Comparison with Node.js Tooling

Feature	Node.js	rescript-runtime-tools
Package manager	npm/yarn/pnpm	None (Deno npm: specifier)
node_modules	Required (~100MB+)	Not needed
Watch mode	nodemon + glue	Native runtime watch
Test runner	Jest + config	Deno.test / bun:test
Bundling	Webpack/Vite + plugins	Runtime native (Deno.emit / Bun.build)
Permissions	None (full access)	Deno: explicit, Bun: full
Cold start	~1.8s	~95ms

Integration with rescript-wasm-runtime

This tooling is designed to work seamlessly with the rescript-wasm-runtime ecosystem:

# Clone both repos
git clone https://github.com/hyperpolymath/rescript-runtime-tools
git clone https://github.com/hyperpolymath/rescript-wasm-runtime

# In your project
cd my-rescript-project
rrt dev  # Uses Detect, Dev, Test modules

License

PMPL-1.0-or-later

Related Projects

• rescript-wasm-runtime - Runtime abstraction for Deno/Bun

• full-stack-rescript - Full stack ReScript architecture