smart-restart

CommonJS module load hook that restarts or does Webpack-style hot module replacement when a file is changed

nodemon and piping are great, but each has their limitations:

nodemon sometimes restarts when you change files the server isn't using, which is a hassle when you're working on isomorphic apps and just want a webpack hot update on the client.

piping is difficult to use with node-inspector because it runs a cluster; the supervisor process gets debug port 5858, and your app process gets something else. It's even more of a pain to use with --debug-brk because the supervisor process starts with a breakpoint as well, so you have to open node-inspector for it, resume it, then open node-inspector for your actual app.

On top of that, neither supports any hot module replacement, which is the only way to react to changes quickly in a large project.

smart-restart combines both approaches: it uses piping's require hook to only watch files that have been required, but it spawns your app instead of running a cluster, so that you can pass --debug or --debug-brk to your app. And it provides a basic version of Webpack's hot module replacement API for Node CommonJS, without using Webpack or doing any bundling.

Usage

To run ./src/index.js in a child process and watch files it requires:

var launch = require('smart-restart')

launch({
  main: './src/index.js',         // path to your script
  command: 'node',                // optional, the command to `spawn` (default: `process.argv[0]`)
  commandOptions: ['--inspect'],  // optional, arguments that come before `main`
  args: [...],                    // optional, arguments that come after `main`
  spawnOptions: {...},            // optional, options for `spawn`
  onChildSpawned: child => {},    // optional, callback to receive ChildProcess instance
  ignore: /(\/\.|~$)/,            // optional, ignore pattern for `chokidar` (default: /(\/\.|~$)/)
  usePolling: false,              // optional, whether to use polling in `chokidar` (default: false)
  interval: 100,                  // optional, polling interval for `chokidar` (default: 100)
  binaryInterval: 300,            // optional, binary polling interval for `chokidar` (default: 300)
  includeModules: false,          // optional, whether to include `node_modules` (default: false)
  killSignal: 'SIGTERM',          // optional, signal to kill process with when restarting
  killTimeout: 5000,              // optional, max amount of milliseconds to wait for process to get killed (default: 10000)
  deleteRequireCache: [           // optional, when any files in this array (or files they require)
                                  //    are changed, all of these files will be deleted from `require.cache`
                                  //    instead of restarting the process.
    'src/server/ssr/serverSideRender.js',
  ],
  restartOnError: true,           // optional, restart when child process has an uncaught error/promise rejection (default: true)
  restartOnExit: true,            // optional, restart when child process exits (default: true)
})

You can launch as many other processes as you want in the same supervisor process.

Hot Module Replacement

smart-restart supports the following subset of Webpack's hot module replacement API:

if (module.hot) {
  module.hot.accept('./myModule', () => {
    const newVersion = require('./myModule')
    // do something with newVersion
  })
}

Webpack's other overloads for module.hot.accept aren't supported.

If not all ancestors of a changed module have module.hot.accept hooks, then smart-restart will relaunch the whole process.

Exiting for good

You can process.send({exit: <code>}) to tell smart-restart to exit immediately instead of waiting to relaunch your process.