How to detect debug mode

[IonicaBizau]

In 7.0.0, looks like the typeof v8debug always returns undefined. How to detect if the process is running in the debug mode?

[cjihrig]

Check out the discussion in #7102.

[IonicaBizau]

@cjihrig That's useful to know, but I'd like to have a solution without that flag: just another way to know if the process is in the debug mode (maybe some environment variable which is set by the debugger or something like that)?

Thanks!

[bnoordhuis]

Why would you care whether the process is being debugged or not? To answer your question, there is no real way to determine if the debugger is active (that is future proof.)

[IonicaBizau]

@bnoordhuis There are some features I want to disable in the debug mode to make the debugging easier. That's pretty much it.

[bnoordhuis]

You can only divine it indirectly. For example, vm.runInDebugContext('Debug').scripts() throws an 'illegal access' exception unless the debugger is active. It only works with some node.js versions and will likely stop working altogether in the future.

[mscdex]

Another possible way to check for debug mode (asynchronously) is to simply try to bind to the debug port:

function isDebugging(cb) {
  require('net').createServer().on('error', function(err) {
    if (err.code === 'EADDRINUSE')
      cb(null, true);
    else
      cb(err);
  }).listen(process.debugPort, function() {
    this.close();
    cb(null, false);
  });
}

[IonicaBizau]

@mscdex Thanks! I'd prefer a sync version, tho. Actually, isn't possible just to set an environment variable or a global (like before) when debugging?

[mscdex]

@IonicaBizau Well, if you are adventurous and don't mind relying on a "private" API, here is a synchronous version of my above solution....

function isDebugging() {
  var TCP = process.binding('tcp_wrap').TCP;
  var tcp = new TCP();
  var r;
  function doBind() {
    var err = tcp.bind6('::', process.debugPort);
    if (err)
      err = tcp.bind('0.0.0.0', process.debugPort);
    return err;
  }
  doBind();
  r = doBind();
  if (r) {
    tcp.close();
    return false;
  }
  return true;
}

[bnoordhuis]

I think this has been answered. Closing.

[IonicaBizau]

@mscdex Thanks for that! 👍

[IonicaBizau]

@mscdex That code returns true even another process is being debugged. Is there any way to tell if the current process is debugged?

[zurgul]

It seems more simple way is to check execArgv. In DEBUG mode there should be 'debug' or 'inspect' word in argument's list.

const argv = process.execArgv.join();
const isDebug = argv.includes('inspect') || argv.includes('debug'));