Errors are ignored in broadcast StreamController without listeners

[alsemenov]

The description for constructor StreamController.broadcast() reads:

StreamController.broadcast({
void onListen(),
void onCancel(),
bool sync: false
})
A controller where stream can be listened to more than once.
...
The controller does not have any internal queue of events, and if there are no listeners at the time the event is added, it will just be dropped, or, if it is an error, be reported as uncaught.

The following sample code shows that errors are just ignored:

import "dart:async";

main() {
  StreamController controller = new StreamController.broadcast();
  try {
    controller.addError("lost error");
    print("'lost error' is ignored");
  } catch (e) {
    print("caught $e");
  }
}

Output:

'lost error' is ignored

Expected output:

caught 'lost error'

Dart VM version: 1.22.1 (Tue Feb 21 14:29:45 2017) on "windows_x64"

[anders-sandholm]

Unclear to me if this is a VM or async issue. Re-label as you see fit.

[lrhn]

Still appears to be the case. Not sure if we really want to make the error into an async uncaught error now, but we should document that it isn't.

The code above doesn't check for uncaught async errors, but it's also not reported by:

import "dart:async";

main() {
  runZoned(() {
    StreamController controller = StreamController.broadcast();
    controller.addError("lost error");
    Future.error("found error");
  }, onError: print);
}

[sgrekhov]

https://dart-review.googlesource.com/c/sdk/+/340860 updates the documentation

[sgrekhov]

Documentation has been updated. The current behavior is according to the spec now. Closing this issue