Ability to avoid fork via config options (babel problem)

[nodkz]

I'm using nodemon in a script which started via babel-node in some complex dev environment.

In simplified view it looks like:

$> ./node_modules/.bin/babel-node ./startNodemon.js

import nodemon from 'nodemon';

...

  const opts = {
      execMap: {
        // js: 'node', // use `childProcess.fork` and it's bad, case transpile server.js via babel
        js: process.execPath, // use `childProcess.spawn` for running server.js
      },
      script: serverPath,
      env: {
        NODE_ENV: 'development',
        EXPRESS_PORT: port,
      },
      watch: [serverPath],
    };

    supervisor = nodemon(opts);
    ...

So after several hours of debugging following error:

[21:49:08] Starting 'backendNodemon'...

/app/build/development/webpack:/webpack/bootstrap 5a375fcb339c4e886c1a:271

^
Error: only one instance of @babel/polyfill is allowed
    at Object../node_modules/@babel/polyfill/lib/index.js (/app/build/development/webpack:/webpack/bootstrap 5a375fcb339c4e886c1a:271:1)
    at __webpack_require__ (/app/build/development/webpack:/webpack/bootstrap 5a375fcb339c4e886c1a:40:1)
    at fn (/app/build/development/webpack:/webpack/bootstrap 5a375fcb339c4e886c1a:7:1)

    at Object.0 (/app/build/development/webpack:/lib/rabota-fresh-jobs/WatchJob.js:60:1)
    at __webpack_require__ (/app/build/development/webpack:/webpack/bootstrap 5a375fcb339c4e886c1a:40:1)
    at module.exports.modules../lib/lvovich/city.js.Object.defineProperty.value (/app/build/development/webpack:/webpack/bootstrap 5a375fcb339c4e886c1a:50:1)
    at Object.<anonymous> (/app/build/development/webpack:/webpack/bootstrap 5a375fcb339c4e886c1a:50:1)
    at Module._compile (module.js:624:30)
    at Module._compile (/app/node_modules/pirates/lib/index.js:91:24)
    at Module._extensions..js (module.js:635:10)

I found that you use fork for spinning up a script

nodemon/lib/monitor/run.js

Lines 68 to 84 in 33fa6f4

	if (
	firstArg.indexOf('-') === -1 && // don't fork if there's a node arg
	firstArg !== 'inspect' && // don't fork it's `inspect` debugger
	executable === 'node' && // only fork if node
	utils.version.major > 4 // only fork if node version > 4
	) {
	var forkArgs = cmd.args.slice(1);
	var env = utils.merge(options.execOptions.env, process.env);
	stdio.push('ipc');
	child = fork(options.execOptions.script, forkArgs, {
	env: env,
	stdio: stdio,
	silent: !hasStdio,
	});
	utils.log.detail('forking');
	debug(forkArgs);
	} else {

So i'm using babel-node and it automatically again transpile provided bundled server script (cause use fork). It spends time on this operation, and also break my server script with error.

1. For what purpose do you use childProcess.fork instead of childProcess.spawn?

2. Can we add some option, to not use childProcess.fork?

For now I solved this via following hack:

  const opts = {
      execMap: {
        // js: 'node', // use `childProcess.fork` and it's bad, case transpile server.js via babel
        js: process.execPath, // use `childProcess.spawn` for running server.js
      },
      ...
  };

[remy]

Background reading to why fork exists is here (short version: fixed a lot of bugs).

I'm happy to take a PR that accepts a new argument --spawn, that forces the logic down the spawn pathway. You'll need to the following places (off the top of my head):

• https://github.com/remy/nodemon/blob/master/lib/cli/parse.js
• https://github.com/remy/nodemon/blob/master/doc/cli/options.txt (under Execution - note it's in alphabetical order)

…and then the run logic that you found would use (something like) if (config.spawn).

How does that sound?