CancelableOperation value is not propagating errors, so they cannot be catched and app is crashing

[busslina]

This problem began with Dio library on this issue.

Basically the thing is that be have a CancelableOperation being constructed from a Future value.

A) If we manage this future possible errors before constructing the CancelableOperation , it works fine: errors can be catched.

final operation = CancelableOperation.fromFuture(_fetch(
      options,
      requestStream,
      cancelFuture,
    ).catchError((error) {
      print('IOHttpClientAdapter.fetch() -- Future.catchError() -- $error');
    }));
    if (cancelFuture != null) {
      cancelFuture.whenComplete(() => operation.cancel());
    }
    return operation.value;

B) Then the trouble, if we manage the future possible errors after CancelableOperation being constructed, via its value property, errors are not catched and app is crashing.

final operation = CancelableOperation.fromFuture(_fetch(
      options,
      requestStream,
      cancelFuture,
    ));
    if (cancelFuture != null) {
      cancelFuture.whenComplete(() => operation.cancel());
    }
    return operation.value.catchError((error) {
      print('IOHttpClientAdapter.fetch() -- Future.catchError() -- $error');
    });

Is it the normal behaviour?
It would not be preferable to propagate also the future's error?

[busslina]

UPDATE I

In order to illustrate the issue with a test:

import 'package:async/async.dart';

void main(List<String> arguments) async {
  // _test1();
  // _test2();
  // await _test3();
}

void _test1() {
  final op = CancelableOperation.fromFuture(_getFutureError());

  op.value.then(
    (value) {
      print('Future value: $value');
    },
  ).catchError(
    (error) {
      print('Future catched error: $error');
      return null;
    },
  );
}

void _test2() {
  final op = CancelableOperation.fromFuture(
    _getFutureError().catchError(
      (error) {
        print('Future catched error: $error');
        return null;
      },
    ),
  );

  op.value.then((value) {
    print('Future value: $value');
  });
}

Future<void> _test3() async {
  final op = CancelableOperation.fromFuture(_getFutureError());

  try {
    final value = await op.value;
    print('Future value: $value');
  } catch (e) {
    print('Future catched error: $e');
  }
}

Future<String?> _getFutureError() async {
  // 5 seconds delay
  await Future.delayed(const Duration(seconds: 5));

  // Throwing error
  throw ('Manual triggered test error');
}

_test1() result:

_test2() result:

_test3() result:

[busslina]

UPDATE II

Also not working using CancelableOperation.then method with onError argument. Giving same result: unhandled exception

[busslina]

I'm closing due to this issue is related to VSCode and not the plugin:

dart-lang/sdk#47692
dart-lang/sdk#47985
https://docs.flutter.dev/testing/errors#errors-not-caught-by-flutter