educate people on how to add custom exceptions

[kevinburkeshyp]

So, borrowed from somewhere on the Internet, we were doing custom exceptions that looked something like this:

var ValueError;

ValueError = (function() {
  function ValueError() {}
  ValueError.prototype = Object.create(Error.prototype);
  return ValueError;
})();

module.exports = ValueError;

Unfortunately if you call sentry.client.captureError(new ValueError("foobar")), Sentry doesn't have the stack trace.

Instead you want something like this

var ValueError;

ValueError = (function() {
  function ValueError(message) {
    this.message = message;
    this.stack = new Error(this.message).stack;
  }
  ValueError.prototype = Object.create(Error.prototype);
  return ValueError;
})();

module.exports = ValueError;

It's pretty hacky (well, subclassing exceptions in general is a shit show), but creating a fake error and copying the stack will set the stack trace properly.

Was thinking raven could take the lead here and actually document the right way to create/subclass exceptions so this kind of data doesn't get lost / your Sentry data is more useful.

[mattrobenolt]

The best way I've seen is the way I do it inside raven.js: https://github.com/getsentry/raven-js/blob/master/src/raven.js#L381-L386

Not sure the pros/cons though. :)

[mattrobenolt]

fwiw, I think doing this.stack = new Error(this.message).stack is not the best. You're also not carrying over the name. Also, the stack attribute is typically lazily evaluated. So by initializing it here, you're forcing it to be evaluated. And lastly, this will add an extra frame to your stack trace.

[askaliuk]

Useful. +1

[kamilogorek]

There's a great post on how to achieve it: https://coderwall.com/p/m3-cqw/subclassing-error-in-javascript-is-harder-than-it-seems

I don't think we will add this to our docs anytime soon, so closing it for now.