@vercel/ncc

ncc

Simple CLI for compiling a Node.js module into a single file, together with all its dependencies, gcc-style.

Motivation

• Publish minimal packages to npm
• Only ship relevant app code to serverless environments
• Don't waste time configuring bundlers
• Generally faster bootup time and less I/O overhead
• Compiled language-like experience (e.g.: go)

Design goals

• Zero configuration
• TypeScript built-in
• Only supports Node.js programs as input / output
• Support all Node.js patterns and npm modules

Usage

Installation

npm i -g @vercel/ncc

Usage

$ ncc <cmd> <opts>

Eg:

$ ncc build input.js -o dist

If building an .mjs or .js module inside a "type": "module" package boundary, an ES module output will be created automatically.

Outputs the Node.js compact build of input.js into dist/index.js.

Note: If the input file is using a .cjs extension, then so will the corresponding output file. This is useful for packages that want to use .js files as modules in native Node.js using a "type": "module" in the package.json file.

Commands:

  build <input-file> [opts]
  run <input-file> [opts]
  cache clean|dir|size
  help
  version

Options:

  -o, --out [dir]          Output directory for build (defaults to dist)
  -m, --minify             Minify output
  -C, --no-cache           Skip build cache population
  -s, --source-map         Generate source map
  -a, --asset-builds       Build nested JS assets recursively, useful for
                           when code is loaded as an asset eg for workers.
  --no-source-map-register Skip source-map-register source map support
  -e, --external [mod]     Skip bundling 'mod'. Can be used many times
  -q, --quiet              Disable build summaries / non-error outputs
  -w, --watch              Start a watched build
  -t, --transpile-only     Use transpileOnly option with the ts-loader
  --v8-cache               Emit a build using the v8 compile cache
  --license [file]         Adds a file containing licensing information to the output
  --stats-out [file]       Emit webpack stats as json to the specified output file
  --target [es]            ECMAScript target to use for output (default: es2015)
                           Learn more: https://webpack.js.org/configuration/target
  -d, --debug              Show debug logs

Execution Testing

For testing and debugging, a file can be built into a temporary directory and executed with full source maps support with the command:

$ ncc run input.js

With TypeScript

The only requirement is to point ncc to .ts or .tsx files. A tsconfig.json file is necessary. Most likely you want to indicate es2015 support:

{
  "compilerOptions": {
    "target": "es2015",
    "moduleResolution": "node"
  }
}

If typescript is found in devDependencies, that version will be used.

Package Support

Some packages may need some extra options for ncc support in order to better work with the static analysis.

See package-support.md for some common packages and their usage with ncc.

Programmatically From Node.js

require('@vercel/ncc')('/path/to/input', {
  // provide a custom cache path or disable caching
  cache: "./custom/cache/path" | false,
  // externals to leave as requires of the build
  externals: ["externalpackage"],
  // directory outside of which never to emit assets
  filterAssetBase: process.cwd(), // default
  minify: false, // default
  sourceMap: false, // default
  assetBuilds: false, // default
  sourceMapBasePrefix: '../', // default treats sources as output-relative
  // when outputting a sourcemap, automatically include
  // source-map-support in the output file (increases output by 32kB).
  sourceMapRegister: true, // default
  watch: false, // default
  license: '', // default does not generate a license file
  target: 'es2015', // default
  v8cache: false, // default
  quiet: false, // default
  debugLog: false // default
}).then(({ code, map, assets }) => {
  console.log(code);
  // Assets is an object of asset file names to { source, permissions, symlinks }
  // expected relative to the output code (if any)
})

When watch: true is set, the build object is not a promise, but has the following signature:

{
  // handler re-run on each build completion
  // watch errors are reported on "err"
  handler (({ err, code, map, assets }) => { ... })
  // handler re-run on each rebuild start
  rebuild (() => {})
  // close the watcher
  void close ();
}

Caveats

• Files / assets are relocated based on a static evaluator. Dynamic non-statically analyzable asset loads may not work out correctly