bun-patterns

name	bun-patterns
description	Bun runtime: HTTP server, file I/O, SQLite, test runner, package manager, bundler — all-in-one JS toolchain.
triggers	{"extensions":[".ts",".tsx"],"filenames":["bun.lockb","bunfig.toml"],"keywords":["bun","Bun.serve","Bun.file","bun:sqlite","bun test","bun build"]}
auto_load_when	Using Bun as runtime, package manager, or test runner
agent	architect
tools	["Read","Write","Bash"]

Bun Patterns

Version: Bun v1.2+ | Focus: HTTP server, SQLite, test runner, bundler, APIs

---

1. HTTP Server

// server.ts
const server = Bun.serve({
  port: 3000,
  fetch(req) {
    const url = new URL(req.url);

    if (url.pathname === '/') return new Response('Hello Bun!');
    if (url.pathname === '/health') return Response.json({ ok: true });

    return new Response('Not found', { status: 404 });
  },
  error(err) {
    return new Response(`Error: ${err.message}`, { status: 500 });
  },
});

console.log(`Listening on http://localhost:${server.port}`);

---

2. File I/O (Faster Than Node.js)

// Read file
const file = Bun.file('./data.json');
const data = await file.json<MyType>();
const text = await file.text();
const buffer = await file.arrayBuffer();

// Write file
await Bun.write('./output.txt', 'Hello World');
await Bun.write('./output.json', JSON.stringify(data));

// Stream large file
const input = Bun.file('./large.csv');
const output = Bun.file('./output.csv');
await Bun.write(output, input); // efficient piping

// Check exists
const exists = await Bun.file('./data.json').exists();

---

3. SQLite (Built-in, No Dependencies)

import { Database } from 'bun:sqlite';

const db = new Database('./mydb.sqlite');

// Create table
db.run(`CREATE TABLE IF NOT EXISTS users (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  email TEXT UNIQUE NOT NULL,
  name TEXT
)`);

// Prepared statements (fast, safe from injection)
const insert = db.prepare('INSERT INTO users (email, name) VALUES ($email, $name)');
insert.run({ $email: '[e-mail]', $name: 'Alice' });

// Query
const getUser = db.prepare('SELECT * FROM users WHERE email = $email');
const user = getUser.get({ $email: '[e-mail]' });

// Transaction
const insertMany = db.transaction((users) => {
  for (const user of users) insert.run(user);
});
insertMany([{ $email: '[e-mail]', $name: 'A' }, { $email: '[e-mail]', $name: 'C' }]);

---

4. Test Runner

// mytest.test.ts
import { describe, test, expect, beforeAll, mock } from 'bun:test';

describe('User service', () => {
  beforeAll(() => { /* setup */ });

  test('creates a user', () => {
    const user = createUser('[e-mail]');
    expect(user.email).toBe('[e-mail]');
  });

  test('throws on duplicate email', () => {
    expect(() => createUser('[e-mail]')).toThrow();
  });

  test('mocks fetch', async () => {
    const mockFetch = mock(() => Promise.resolve(new Response('{"ok":true}')));
    globalThis.fetch = mockFetch;
    const result = await fetchUser('123');
    expect(mockFetch).toHaveBeenCalledTimes(1);
  });
});

bun test                    # run all tests
bun test --watch            # watch mode
bun test --coverage         # with coverage
bun test src/user.test.ts   # specific file

---

5. Bundler

// bundle.ts
const result = await Bun.build({
  entrypoints: ['./src/index.ts'],
  outdir: './dist',
  target: 'browser',        // 'node' | 'bun' | 'browser'
  format: 'esm',
  minify: true,
  splitting: true,           // code splitting
  sourcemap: 'external',
});

if (!result.success) {
  console.error(result.logs);
}

---

6. Environment & Package Manager

# Install dependencies (much faster than npm/pnpm)
bun install
bun add express
bun add -d @types/express

# Run scripts
bun run dev
bun run build

# Execute TypeScript directly (no tsc needed)
bun run src/server.ts

# Workspace support
bun install --filter './apps/*'

---

Quick Reference

Feature	Bun API
HTTP server	Bun.serve({ fetch(req) {} })
Read file	await Bun.file(path).text()
Write file	await Bun.write(path, data)
SQLite	import { Database } from 'bun:sqlite'
Test	import { test, expect } from 'bun:test'
Hash	Bun.password.hash(pwd) / verify()
Env vars	Bun.env.MY_VAR (auto-loads .env)

Anti-Patterns

❌ Using Node.js fs module in Bun
✅ Use Bun.file() / Bun.write() — much faster

❌ Installing sqlite3 npm package
✅ Use built-in bun:sqlite — no native compilation needed

❌ ts-node or tsx for TypeScript
✅ Bun natively runs TypeScript — just bun run file.ts

❌ Separate jest/vitest setup
✅ bun test is built-in — no config needed for basic use

🌍 Universal Language Support

• Turkish Native: This skill natively supports Turkish. If the user prompt is in Turkish, all analysis, formatting, and output MUST be entirely in Turkish.