Errors in rejected promises not handled

Hi I’m not sure if this is expected or not but we have errors happening inside a try/catch in a promise where the catch rejects the promise with the caught error. Chrome shows these as errors in the dev console, but Bugsnag doesn’t seem to get them.

I put together a JS fiddle with bugsnag loaded in to demonstrate the error: https://jsfiddle.net/zz050pg4/2/ . If you just put in your bugsnag api key on the first line, you can see that it notifies correctly for errors outside the promise. The promise code below is in a library and is basically:

var errPromise = new Promise(function (resolve, reject) {
    try {
        // call some of our source code to cause error
    } catch (err) {
        reject(err);
    }
})

Any thoughts?

[jmshal]

IMO, this is a bit inconvenient. I’d prefer if the uncaught exception thing would trigger when there’s no explicit catch

I agree. There is no reason why the notifier cannot hook into the unhandledrejection event.

I will submit a PR this evening soon, unless anybody wants to beat me to it - or has any other ideas.

Shout out to @jacobmarshall for the good explanation and suggestion, though.

You’re most welcome 😃

[jmshal]

This is because you are catching the errors yourself. Promises automatically reject if a thrown error is uncaught. If you need the caught error to be passed to Bugsnag, I would recommend doing something along the lines of…

new Promise(function (resolve, reject) {
    try {
        // throw an error
    } catch (err) {
        reject(err);
        Bugsnag.notifyException(err);
    }
});

or, better yet…

new Promise(function (resolve, reject) {
    throw new Error('Whoops, I threw a bad error!');
})
.then(function () { /* Won't ever get here... */ })
.catch(Bugsnag.notifyException);

It turns out that Bugsnag.notifyException is compatible with promises, because the first argument accepts an Error, and promises only pass one argument to then and catch.