StateError deep ind stack_trace code: Future already completed.

[escamoteur]

I currently get these here on a regular basis in Sentry:

StateError: Bad state: Future already completed
  File "future_impl.dart", line 18, in _Completer.completeError
  File "zone.dart", line 1666, in _RootZone.runBinary
  File "stack_zone_specification.dart", line 158, in StackZoneSpecification._handleUncaughtError
  File "zone.dart", line 1081, in _Zone._processUncaughtError
  File "zone.dart", line 1285, in _CustomZone.handleUncaughtError
  File "future_impl.dart", line 754, in Future._propagateToListeners
  File "future_impl.dart", line 649, in Future._completeError
  File "stack_zone_specification.dart", line 135, in StackZoneSpecification._registerBinaryCallback.<fn>.<fn>
  File "stack_zone_specification.dart", line 204, in StackZoneSpecification._run
  File "stack_zone_specification.dart", line 135, in StackZoneSpecification._registerBinaryCallback.<fn>
  File "zone.dart", line 1423, in _rootRunBinary
  File "zone.dart", line 1315, in _CustomZone.runBinary
  File "future_impl.dart", line 171, in _FutureListener.handleError
  File "future_impl.dart", line 852, in Future._propagateToListeners.handleError
  File "future_impl.dart", line 873, in Future._propagateToListeners
  File "future_impl.dart", line 649, in Future._completeError
  File "stack_zone_specification.dart", line 135, in StackZoneSpecification._registerBinaryCallback.<fn>.<fn>
  File "stack_zone_specification.dart", line 204, in StackZoneSpecification._run
  File "stack_zone_specification.dart", line 135, in StackZoneSpecification._registerBinaryCallback.<fn>
  File "zone.dart", line 1423, in _rootRunBinary
  File "zone.dart", line 1315, in _CustomZone.runBinary
  File "future_impl.dart", line 171, in _FutureListener.handleError
  File "future_impl.dart", line 852, in Future._propagateToListeners.handleError
  File "future_impl.dart", line 873, in Future._propagateToListeners
  File "future_impl.dart", line 649, in Future._completeError
  File "future_impl.dart", line 550, in Future._chainForeignFuture.<fn>
  File "stack_zone_specification.dart", line 204, in StackZoneSpecification._run
  File "stack_zone_specification.dart", line 114, in StackZoneSpecification._registerCallback.<fn>
  File "zone.dart", line 1399, in _rootRun
  File "zone.dart", line 1301, in _CustomZone.run
  File "zone.dart", line 1209, in _CustomZone.runGuarded
  File "zone.dart", line 1249, in _CustomZone.bindCallbackGuarded.<fn>
  File "schedule_microtask.dart", line 40, in _microtaskLoop
  File "schedule_microtask.dart", line 49, in _startMicrotaskLoop

This is how I use Chain.capture to get better stacktraces when en exception happens in the wrapped async function of a flutter_command:

        final completer = Completer<TResult>();
        Chain.capture(
          () => _func!(param as TParam).then(completer.complete),
          onError: completer.completeError,
        );
        result = await completer.future;

The use of the completer this way was the only way I could get back a meaningful stack_trace from Chain.capture

[escamoteur]

@mraleph any help would be awesome to improve my package

[mraleph]

I can take a look next week

[escamoteur]

That would be awesome Am 19. Sept. 2023, 19:40 +0200 schrieb Slava Egorov @.***>:

I can take a look next week — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you authored the thread.Message ID: @.***>

[escamoteur]

hi @mraleph would be great if you could look into this

[mraleph]

Do you have some specific issue for me to look at? e.g. do you have an example code I could run which prints meaningless stack-trace? I am just unsure what I am supposed to help with.

[escamoteur]

When I use the Chain.capture like in the above I get the exception Future already completed. Is it at all the right approach that I do above to call a passed function inside a Capture to get better stacktraces?

[mraleph]

@escamoteur The documentation for Chain.capture says:

Note that if callback produces multiple unhandled errors, onError may be called more than once.

That's what you are seeing here.

TBH, I am not sure why you need package:stack_trace for this to begin with. Native VM stacks should be good enough for asynchronous code.

[escamoteur]

How can the wrapped call back produce more than one unhandled error? Is the way I try to use capture the right way at all? Am 26. Okt. 2023, 12:53 +0200 schrieb Slava Egorov @.***>:

@escamoteur The documentation for Chain.capture says:

Note that if callback produces multiple unhandled errors, onError may be called more than once. That's what you are seeing here. — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you were mentioned.Message ID: @.***>

[mraleph]

It can spawn multiple asynchronous operations in parallel and not listen to either, e.g.

void foo() {
  Future.delayed(const Duration(milliseconds: 10), () => throw 'One');
  Future.delayed(const Duration(milliseconds: 10), () => throw 'Two');
}

This function will produce two unhandled errors. It's up to you to decide how to handle it, e.g. you can just ignore all errors after the first one.