interrupting in a zone

interrupt.dart

import 'dart:async';

void main(List<String> arguments) {
  var stop = false;
  final checkShouldStop = () {
    if (stop) {
      throw StopException();
    }
  };
  runZoned(
    run,
    zoneSpecification: ZoneSpecification(
      registerCallback: <R>(self, parent, zone, f) {
        checkShouldStop();
        return f;
      },
      registerUnaryCallback: <R, T>(self, parent, zone, f) {
        checkShouldStop();
        return f;
      },
      registerBinaryCallback: <R, T, U>(self, parent, zone, f) {
        checkShouldStop();
        return f;
      },
    ),
  );

  // Cause an interrupt after some time
  Future.delayed(Duration(milliseconds: 750), () {
    stop = true;
  });

}

Future<void> run() async {
  print('run');
  await something(1, 2, 3, 4);
  print('done something');
  final output = await slowlyMakeString(['foo', 'bar', 'baz']);
  print(output);
}

Future<String> slowlyMakeString(List<String> args) async {
  final needToCleanUp = <String>[];
  try {
    print('slowlyMakeString');
    final output = StringBuffer();
    for (final arg in args) {
      print('awaiting delay');
      await Future.delayed(Duration(milliseconds: 500));
      output.write(arg);
      needToCleanUp.add(arg);
    }
    return output.toString();
  } on StopException {
    print('cleaning up: $needToCleanUp');
    rethrow;
  }
}

Future<void> something(int a, int b, int c, int d) async {
  print('doing something');
  return;
}

class StopException implements Exception {}