"Non-Error promise rejection captured with value:"

[adilanchian]

Hi all!

I didn't want to create a bug as I don't believe there is a bug here considering this error has been talked about a few times here. TL:DR - We are receiving a copious amount i these errors with no values provided. I can't see anything that sticks out in our code for why this is happening, but I don't want to dismiss this as an external factor. Some information about our Sentry Setup:

"@sentry/browser": "^6.2.5",
"@sentry/integrations": "^6.2.5", 
"@sentry/react": "^6.2.5",
"@sentry/tracing": "^6.2.5"
...
integrations: [new Integrations.BrowserTracing(), new ExtraErrorData()],

Was curious if anyone has any advice/thoughts on how to to begin debugging this further? Thanks in advance for your time!

[kamilogorek]

Unfortunately, there's nothing we can extract from promise rejections that were thrown with an empty string. Even trying to "fake" an error doesn't provide a valid stack trace, as global error handlers are not keeping track of the callers.

e.g.

This event is produced in one of three ways:

async function foo() {
  throw '';
}

// or

new Promise((resolve, reject) => {
  throw '';
});

// or

new Promise((resolve, reject) => {
  reject('');
});

In order for us to extract the stack trace, rejections/throws inside async functions have to be done through an Error instance.

[wynnw]

This started happening to us on April 16th, on a day where we didn't change any code at all. Since them we've had 98k of these errors. We've added some code to filter this out in our js as we can't figure out a way to silence these at all. I'm guessing it's related to some password manager like lastpass as it only happens on our login page, with chrome, on windows 10. We've added code like:

            beforeSend: function(event, hint) {
                // filter out UnhandledRejection errors that have no information
                if (event !== undefined && event.exception !== undefined && event.exception.values !== undefined
                    && event.exception.values.length == 1) {
                    var e = event.exception.values[0];
                    if (e.type === 'UnhandledRejection' && e.value === 'Non-Error promise rejection captured with value: ') {
                        return null;
                    }
                }
           }

If there's a better way to deal with this, I'd love to know about it. On one hand, I can see how you don't want to editorialize here and prevent these errors, but when there's no info at all there's nothing actionable and we can't do anything about it other than be annoyed.

[adilanchian]

@wynnw

Thanks for the insight here! Really helpful. We are having the same affected browser and device, but really can't tell where this is coming from.

@kamilogorek said it great where it is just returning an empty error object so not much Sentry can do here. Would be cool to know the origin of the error maybe? Not sure how this works with extensions.

Either way appreciate the insight!

[wynnw]

Adding an update for anyone else, this problem has evolved to be a "Non-Error promise rejection captured with value: Object Not Found Matching Id:5" error, so we had to update our hack to deal with that. We decided to just put the hack on the login page, as it appears this is from some password manager browser extension.

[m-bp]

We are also getting this error, both empty and now with the "Object Not Found Matching Id:" message. I want to point out that while we do not have a login page we do have forms all over the site and there's two characteristics that stick out:

• Some of the URLs do not exist. Part of the path would be valid but the last part is just gibberish. ie: /blog/fashion/AWBM2HW instead of a real post's title. The random part repeats itself on different clients, it's not like every error has a different slug. This 404 page has no form in it.
• Most other URLs are links sent through email to our clients. Too many of them for it to be a random coincidence. In fact the gibberish links from before are related to links we've sent through email.

It may be a completely different issue from yours @wynnw but who knows.

[abhishek1234321]

This is most likely happening due to the safe links being scanned by Outlook

If you have an Office 365 subscription and your emails contain links to your site and these links use Safe Links feature then it is bound to happen

We were able to reproduce this and get the error in Sentry

For details see this thread https://forum.sentry.io/t/unhandledrejection-non-error-promise-rejection-captured-with-value/14062

[kamilogorek]

In the next version - 6.9.0 (releasing as we speak), Dedupe integration is turned on by default, which should lower the impact of this issue tremendously.

[michaelschufi]

Is there any way to disable sending those events to sentry? We are on 6.13.3 (Next.js package) and are seeing a very high number of such errors.

[kamilogorek]

Sentry.init({
  ignoreErrors: ['Non-Error promise rejection captured']
});

or through beforeSend callback.