zip() throws (swallowed) error when closed synchronously in next() handler

[chrisguttandin]

Describe the bug

After enabling logging for notifications on stopped observables with config.onStoppedNotification I noticed that zip() sometimes throws an error which can't be delivered anymore in case the observable gets closed from within the next handler.

Firefox: TypeError: buffers is null
Chrome: TypeError: Cannot read properties of null (reading 'some')

The error originates from here:

rxjs/src/internal/observable/zip.ts

Line 91 in 081ca2b

if (buffers.some((buffer, i) => !buffer.length && completed[i])) {

Expected behavior

I would not expect this to happen. I think this case should be handled internally.

Reproduction code

import { NEVER, concat, config, first, of, zip } from 'rxjs';

config.onStoppedNotification = (notification) => {
  if (notification.kind === 'E') {
    throw notification.error;
  }
};

const source$ = concat(of(1), NEVER);

zip(source$).pipe(first()).subscribe();

Reproduction URL

https://stackblitz.com/edit/rxjs-qxrbts?devtoolsheight=60&file=index.ts

Version

7.4.0

Environment

I discovered this in an Angular App (v13.1) which also uses NgRx (v13) but I guess it's not relevant for this issue.

Additional context

I think adding a simple check if buffers is already null before calling buffers.some() should fix the issue. I would be happy to provide a PR with this fix.

[truebden]

I just faced this issue in my code too and it would be great to have the PR merged 😉

[benlesh]

Hi @chrisguttandin — thank you for taking the time to open this issue and for sharing your thoughtful feedback with the RxJS project. I’m sorry it took us so long to respond. Given how much time has passed and the lack of recent activity, I’m going to close this for now so the tracker reflects the work we’re likely to act on. If this is still relevant on a current RxJS release, please feel welcome to open a new issue with updated context and a reproduction. Thank you again for your contribution and patience.

— Ben