Package Exports

flagged-respawn

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Readme

flagged-respawn

A tool for respawning node binaries when special flags are present.

What is it?

Say you wrote a command line tool that runs arbitrary javascript (e.g. task runner, test framework, etc). Now, say you want to support running it with v8 flags enabled (--harmony, for example).

For example, let's run an imaginary testing tool with the following command: test --harmony spec tests.js. This would produce a process.argv of:

['node', '/usr/local/bin/test', '--harmony', 'spec', 'tests.js']

The --harmony flag is in the wrong place! It needs to be a part of the node command. What we actually wanted was:

['node', '--harmony', '/usr/local/bin/test', 'spec', 'tests.js']

Good news, flaggedRespawn does exactly this. All it takes it a simple conditional in your cli code:

Example

#!/usr/bin/env node

const flaggedRespawn = require('flagged-respawn');

// get a list of all possible v8 flags to intercept
const v8flags = require('v8flags').fetch();

// if necessary, respawn to apply node flags
if (!flaggedRespawn.needed(v8flags)) {
  // If we are here, no respawn was needed a.k.a no special flags
  // were seen, or this is the child process that was spawned by
  // the first run.
  console.log('Running!');
} else {
  // respawn so the above branch is entered
  console.log('Respawning...');
  flaggedRespawn.execute(v8flags);
}

To see it in action, clone this repository and run npm install / npm run respawn / npm run nospawn.

Release History

2014-09-04 - v0.1.0 - initial release