Unhandled exceptions in isolates does not terminate the VM

[sgjesse]

The tests

  isolate/isolate2_negative_test.dart
  isolate/isolate3_negative_test.dart

expect the VM to terminate when there is an unhandled exception in an isolate.

Might be releatd to issue #3734.

[iposva-google]

I don't think this is the expected behaviour any longer:

// Dart test program for testing that exceptions in other isolates bring down
// the program.

We specifically added code that will be notified if a spawned isolate had an unhandled exception.

---

cc @floitschG.
cc @a-siva.
Removed Area-VM label.
Added Area-Library, Library-Isolate labels.

[floitschG]

With the isolate refactoring the error should be propagated back to the spawner. But somehow this is not working.
This issue is hence relevant again. (Not sure if it already was before).

[mkustermann]

Any updates on this?

Looking at tests/isolate/isolate2_negative_test.dart:
 - test is marked as SKIP on "$compiler == none"!
 - Isolate.spawn() takes 2 parameters, the test gives only 1.
 - when changing the test to call Isolate.spawn() with two arguments, the VM will stay alive (should it?)
   => this makes it timeout instead of fail

@floitsch/iposva: Could you take a look?
Please also assign a priority -- this could impact users if they rely on correct error propagation.

[floitschG]

This seems to be related to issue #8.
After fixing isolate2_negative_test (as suggested by Martin) both tests print an error message, coming from ShutdownIsolate, and then keep running:

Assigning to VM for further investigation. (Ping me, if we misuse the API and should be able to handle these errors in Dart code).
===
$ out/ReleaseIA32/dart --package-root=$PWD/out/ReleaseIA32/packages tests/isolate/isolate3_negative_test.dart
unittest-suite-wait-for-done
in ShutdownIsolate: 'file:///mnt/ssd/floitsch/code/dart/dart/tests/isolate/isolate3_negative_test.dart': error: line 13 pos 41: illegal implicit access to receiver 'this'
  TestClass.named(num this.fld1) : fld2=fld1 {
                                        ^

===
$ out/ReleaseIA32/dart --package-root=$PWD/out/ReleaseIA32/packages tests/isolate/isolate2_negative_test.dart
unittest-suite-wait-for-done
in ShutdownIsolate: Unhandled exception:
foo
#­0 entry (file:///mnt/ssd/floitsch/code/dart/dart/tests/isolate/isolate2_negative_test.dart:13:3)
#­1 _startIsolate.isolateStartHandler (dart:isolate-patch/isolate_patch.dart:226)
#­2 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:120)

---

Removed Area-Library label.
Added Area-VM label.

[lrhn]

Should an uncaught error in the original isolate terminate the program?
I think it does now, but I don't see why that isolate should be special.

[zanderso]

This looks stale. The tests named above don't appear to exist anymore.

[floitschG]

This is still an issue.
The problem is pretty much, that errors in other isolates are completely ignored.

See for example:

import 'dart:isolate';
import 'dart:async';

foo(x) {
  print("throwing");
  throw "in other isolate";
}

main() {
  Isolate.spawn(foo, null);
  new Timer.periodic(const Duration(seconds: 1), (_) { print("tick"); });
}

Silently ignoring is the worst of all options. We should come up with a better way to deal with it.
@zanderso, @a-siva : I suggest working together with us (mostly with @lrhn and me, since we designed most of the isolate library), to improve the situation.

[zanderso]

@floitschG Could you give this issue a better title? As stated, I think the VM is working as intended. Thanks.

[floitschG]

Fair enough. I will close this one.
Let's meet for my example anyway (probably there is already a bug for that one too).