Isolate.spawn{Uri} only reports errors asynchronously.

runtime/lib/isolate_patch.dart

Index: runtime/lib/isolate_patch.dart
diff --git a/runtime/lib/isolate_patch.dart b/runtime/lib/isolate_patch.dart
index 46e4f4039fb0280e74acec775d4b2dd9a71c2e31..eede93c6a1e1edabdac9d1c7895bff7e2055b008 100644
--- a/runtime/lib/isolate_patch.dart
+++ b/runtime/lib/isolate_patch.dart
@@ -57,6 +57,28 @@ class _ReceivePortImpl extends Stream implements ReceivePort {
   StreamController _controller;
 }
 
+typedef void ImmediateCallback();
+
+/// The callback that has been registered through `scheduleImmediate`.
+ImmediateCallback _pendingImmediateCallback;
+
+/// The closure that should be used as scheduleImmediateClosure, when the VM
+/// is responsible for the event loop.
+void _isolateScheduleImmediate(void callback()) {
+  assert(_pendingImmediateCallback == null);
+  _pendingImmediateCallback = callback;
+}
+
+/// Provide closurized access to _isolateScheduleImmediate.
+/// This makes it easier for embedders to set the scheduleImmediate closure.
+Function get _isolateScheduleImmediateClosure => _isolateScheduleImmediate;
+
+/// The embedder can execute this function to get hold of
+/// [_isolateScheduleImmediate] above.
+Function _getIsolateScheduleImmediateClosure() {
+  return _isolateScheduleImmediate;
+}
+
 class _RawReceivePortImpl implements RawReceivePort {
   factory _RawReceivePortImpl() native "RawReceivePortImpl_factory";
 
@@ -92,7 +114,15 @@ class _RawReceivePortImpl implements RawReceivePort {
   static void _handleMessage(
       _RawReceivePortImpl port, int replyId, var message) {
     assert(port != null);
+    // TODO(floitsch): this relies on the fact that any exception aborts the

[Lasse Reichstein Nielsen, 2013/11/27 11:41:28]

Bugnumber for catching uncaught exceptions?

[floitsch, 2013/11/27 13:57:06]

I have added 8875.

+    // VM. Once we have non-fatal global exceptions we need to catch errors
+    // so that we can run the immediate callbacks.
     port._handler(message);
+    if (_pendingImmediateCallback != null) {
+      var callback = _pendingImmediateCallback;
+      _pendingImmediateCallback = null;
+      callback();
+    }
   }
 
   // Call into the VM to close the VM maintained mappings.
@@ -215,8 +245,11 @@ patch class Isolate {
         completer.complete(new Isolate._fromControlPort(controlPort));
       };
     } catch(e, st) {
-      // TODO(14718): we want errors to go into the returned future.
-      rethrow;
+      // Don't complete immediately with an error, since the caller didn't
+      // yet have the time to install an error handler.
+      scheduleMicrotask(() {
+        completer.completeError(e, st);

[Lasse Reichstein Nielsen, 2013/11/27 11:41:28]

Could we add this to the head of the queue instead of at the end?

[floitsch, 2013/11/27 13:57:06]

The current implementation is consistent with a non-sync completer.

+      });
     };
     return completer.future;
   }
@@ -235,8 +268,11 @@ patch class Isolate {
         completer.complete(new Isolate._fromControlPort(controlPort));
       };
     } catch(e, st) {
-      // TODO(14718): we want errors to go into the returned future.
-      rethrow;
+      // Don't complete immediately with an error, since the caller didn't
+      // yet have the time to install an error handler.
+      scheduleMicrotask(() {
+        completer.completeError(e, st);
+      });
     };
     return completer.future;
   }