bun-development

# Bun Development ## When to Use This Skill | Scenario | Use this skill | Alternative | |----------|---------------|-------------| | Running scripts with Bun runtime | Yes | `nodejs-development` for Node.js-specific runtime | | Running Bun tests with `bun test` | Yes | `bun-test` for quick invocable test runs | | Bundling/building with Bun | Yes | `bun-build` for quick invocable builds | | Initializing a new Bun project | Yes | `nodejs-development` for Vite/Vue scaffolding | | Compiling to standalone executable | Yes | N/A | | Installing or managing dependencies | No - use `bun-package-manager` | `bun-add` for quick package additions | | Publishing packages to npm | No - use `bun-publishing` | N/A | | Debugging TypeScript/JS code | No - use `typescript-debugging` | N/A | ## Core Expertise Bun is an all-in-one JavaScript runtime: - ~6ms startup vs npm's ~170ms - Native TypeScript execution - Built-in test runner - Fast bundler with compile-to-exe ## Running Scripts ### Basic Execution ```bash # Run package.json script bun run <script> # Run file directly bun <file.ts> # Silent mode (no script echo) bun run --silent <script> ``` ### Watch Mode ```bash # Auto-restart on changes bun --watch run dev # Hot reload (preserve state) bun --hot run dev ``` ### Workspace Scripts ```bash # Run in matching workspaces bun run --filter 'package-*' build # Run in all workspaces bun run --workspaces test # Limit output per workspace bun run --filter '*' --elide-lines=5 build ``` ### Execute Packages (bunx) ```bash # Execute package binary (like npx) bunx <package> # Specific version bunx typescript@5.0 --help # When binary differs from package bunx -p @angular/cli ng new app # Force Bun runtime bunx --bun vite dev ``` ## Testing ### Basic Test Execution ```bash # Run all tests bun test # Run specific file bun test tests/auth.test.ts # Filter by name bun test -t "login" ``` ### Compact Output (Agentic) ```bash # Minimal dots reporter bun test --dots # Fail fast bun test --bail bun test --bail=3 # Stop after 3 failures # Combine for quick feedback bun test --dots --bail=1 ``` ### CI/CD Output ```bash # JUnit XML (most CI systems) bun test --reporter=junit --reporter-outfile=junit.xml # GitHub Actions (auto-detected in CI) # Produces annotations automatically bun test ``` ### Coverage ```bash # Enable coverage bun test --coverage # LCOV format for tools bun test --coverage --coverage-reporter=lcov ``` ### Test Configuration ```bash # Custom timeout bun test --timeout=10000 # Run concurrently bun test --concurrent # Limit concurrency bun test --max-concurrency=5 # Detect flaky tests bun test --rerun-each=3 ``` ## Building ### Bundle JavaScript/TypeScript ```bash # Basic bundle bun build ./src/index.ts --outdir=dist # Production build bun build ./src/index.ts --outdir=dist --minify --sourcemap=external # Watch mode bun build ./src/index.ts --outdir=dist --watch ``` ### Build Targets ```bash # Browser (default) bun build ./src/index.ts --target=browser # Bun runtime bun build ./src/index.ts --target=bun # Node.js bun build ./src/index.ts --target=node ``` ### Compile to Executable ```bash # Standalone binary bun build --compile ./app.ts --outfile myapp # Minified standalone bun build --compile --minify ./app.ts --outfile myapp # Cross-compile bun build --compile --target=bun-linux-x64 ./app.ts ``` ### Code Splitting ```bash # Enable splitting bun build ./src/index.ts --outdir=dist --splitting ``` ## Project Initialization ### Quick Init ```bash # Interactive blank project bun init # With template bun init --react my-app bun init --react=tailwind my-app ``` ### Create from Template ```bash # From npm/GitHub bun create vite my-project bun create hono@latest my-api # From GitHub repo bun create <user>/<repo> destination ``` ## Agentic Optimizations | Context | Command | |---------|---------| | Quick test | `bun test --dots --bail=1` | | CI test | `bun test --reporter=junit --reporter-outfile=junit.xml` | | Coverage | `bun test --coverage --coverage-reporter=lcov` | | Silent run | `bun run --silent <script>` | | Watch dev | `bun --watch run dev` | | Prod build | `bun build --minify --sourcemap=external --outdir=dist` | | Compile | `bun build --compile --minify ./app.ts` | | Memory save | `bun run --smol <script>` | ## Quick Reference ### bun run | Flag | Description | |------|-------------| | `--watch` | Auto-restart on changes | | `--hot` | Hot reload | | `--silent` | Suppress script echo | | `--filter` | Run in matching workspaces | | `--smol` | Reduce memory usage | ### bun test | Flag | Description | |------|-------------| | `--dots` | Compact dot reporter | | `--bail` / `--bail=N` | Stop after N failures | | `--coverage` | Enable coverage | | `--timeout=<ms>` | Per-test timeout | | `--reporter=junit` | JUnit XML output | | `-t <pattern>` | Filter by test name | | `--concurrent` | Parallel async tests | ### bun build | Flag | Description | |------|-------------| | `--outdir` | Output directory | | `--outfile` | Output file (single/compile) | | `--minify` | Minify output | | `--sourcemap` | none/inline/external | | `--target` | browser/bun/node | | `--compile` | Standalone executable | | `--splitting` | Enable code splitting | | `--watch` | Watch mode | ## Environment Variables | Variable | Description | |----------|-------------| | `BUN_OPTIONS` | Global CLI flags | | `NODE_ENV` | Environment (production/development) |