Catch a rejected promise and log custom error message + reason

1

What’s the recommended approach to catching a browser’s Promise rejection and logging it with a custom message?

e.g.

.catch(function(err) {
  Raven.captureException('Error in user creation code', err);
}

However I’m not sure that captureException supports two parameters, or how much useful information that err will have. e.g. I’ve seen references to err.reason, err.stack, etc.

2

What you’re looking for is captureMessage here, as you dont have an actual Error object (which is what the captureException call requires).

Raven.captureMessage('foo bar', {extra: {reason: err.reason}})
3

Thanks for the quick advice. For cases where I don’t have my own catch, what would be the best way to configure Raven?

e.g.

  window.addEventListener('unhandledrejection', function(err) {
    Raven.captureMessage(err.reason);
 });

or would you recommend perhaps Raven.captureMessage('unhandled rejection', err.reason)? I thought that might result in every uncaught promise being grouped together mistakenly as the same problem.

4

There is some new fancy stacktrace generation for messages (thought I dont know much about it), and when that’s present we’d use it for grouping.

If thats not present however, you may want to add fingerprints:

Raven.capturemessage('Unhandled Rejection', {fingerprint: [err.reason, '{{ default }}']})

Alternatively, just add err.reason to the message string, which likely will increase usability.

5

I like your idea to add the err.reason string to 'Unhandled Rejection' - I think that would work best in the web UI. thanks