DDC async* bug - another flavor with more awaits

[mrmax99]

I'm hitting another variant of this bug:
#39994

It only reproduces for me on web / DDC.

Expected output (just running in dart on the console works correctly):

Hello, World 1!
Hello, World 2!
[hello, hello]

Output when running a flutter web debug app on chrome:

Hello, World 1!

Relevant code portion:

  Stream<String> testStream(String test) async* {
    yield test;
    try {
      await testFunction1();
      yield test;
    } catch (e) {
      print('Hello, World 1!');
      await testFunction2();
      print('Hello, World 2!');
      yield test;
    }
  }

  Future<String> testFunction1() async {
    throw Exception("test");
  }

  Future<String> testFunction2() async {
    return "foo";
  }


void main() async {
  var stream = testStream("hello");
  print(await stream.toList());
}

My version info:

> dart --version
Dart VM version: 2.9.0-14.1.beta (beta) (Tue Jun 9 10:52:57 2020 +0200) on "windows_x64"
> flutter --version
Flutter 1.19.0-4.3.pre • channel beta • https://github.com/flutter/flutter.git
Framework • revision 8fe7655ed2 (3 weeks ago) • 2020-07-01 14:31:18 -0700
Engine • revision 9a28c3bcf4
Tools • Dart 2.9.0 (build 2.9.0-14.1.beta)

[mrmax99]

Tagging @vsmenon @Markzipan since they seemed involved in the related bug, in case they weren't aware of this one. It's pretty frustrating to hit this and it makes debugging flutter web code a huge pain.

[Markzipan]

Thanks for finding this - checking this out now. Making the web's async semantics consistent is on our roadmap, so this is another data point to escalate its priority.

[vsmenon]

fyi - @sigmundch

[mrmax99]

any update on this?

[Markzipan]

Sorry about the delay, Max. These discrepancies with DDC's async generator are on our radar, but we've been prioritizing other items at the moment. I'll resume fiddling here soon.