Where to put the unhandled error event hook? Looking for ideas/thoughts

For version 6, we need to remove the error rethrowing behavior for Observables. Basically this means that if an error propagates to the end of an Observable chain, it will no longer be rethrown, rather, it will be reported to a global error handler. There are a variety of reasons for this that have already been discussed, so I don’t want to discuss those here, but the thing we need to know is, where should we put this error handler?

Prior Art: Promises

Promises allow handling unhandled rejections via window.addEventListener('unhandledrejection', handler) in a browser or process.on('unhandledRejection', handler) in Node.

Caveats

• It’s entirely likely that this solution might change with whatever the spec does.
• initially, we might just have it log until we can figure out where the eventing should exist.

[domenic]

I think for observables, which don’t have the “can be handled later” problem that promises have, you just want to deliver it to the global scope. That basically means setTimeout(() => { throw err; }, 0). In browsers that will fire an error event on the appropriate window (which window is pretty complicated…) and in Node it will cause crashes.

That’s what HostReportErrors means in the spec, as well.

[acutmore]

More of an FYI than a serious suggestion:

let err;
const btn = document.createElement(‘button’);
btn.onClick = () => { throw err; };

export function reportError(e) {
  err = e;
  btn.click();
}

Gets reported just like if throwing inside a setTimeout but syncronous. So appears in log at the correct place.