Capturing common IDB errors before sending to sentry

[poltak]

Feature freeze task. Need somewhere to write what I found out

Sentry gets spammed with the same IDB/Dexie errors, like QuotaExceededError, every time we publish a new version. Most of these seem to be completely out of our control and the sheer volume of them really makes it difficult to see the actual important errors that we have accidentally introduced in new changes in the codebase.

All of these errors should be going to the DOM's unhandledrejection event (http://dexie.org/docs/Promise/unhandledrejection-event) in the background script, so we should be able to tap into that to handle them. The main issue is raven-js/sentry also uses that same event to track errors by default (https://docs.sentry.io/clients/javascript/usage/#promises). So we would need to disable sentry's default behaviour, write our own unhandledrejection event handler, and explicitly forward them onto sentry if the errors are unknown (although only in the background script).

Unknowns

• need an easy-to-reproduce method to test solution to see if IDB/Dexie errors are actually being caught and excluded from sentry (it would be very inconvenient if the only way we can test is by publishing an update)

Future ideas

• notify users if they encounter errors such as quota exceeded and offer explanation of how ext experience may change and advice

[poltak]

Sadly this unhandledrejection seems to be unsupported in FF although it's in progress: https://bugzilla.mozilla.org/show_bug.cgi?id=1362272 I haven't found any alternative to this, so I will probably have to catch these specific errors wherever we are interacting with Dexie. Less work for the newer code that uses StorageManager, but the non-StorageManager search is still a very large interface.