Isolate.spawn{Uri} only reports errors asynchronously.

sdk/lib/_internal/pub/lib/src/dart.dart

Index: sdk/lib/_internal/pub/lib/src/dart.dart
diff --git a/sdk/lib/_internal/pub/lib/src/dart.dart b/sdk/lib/_internal/pub/lib/src/dart.dart
index bf6cb2a169b369c20a89b7934aa84c10a212da8a..03bd0451c6dc46b89a47f0bfcaf855cc28d081b8 100644
--- a/sdk/lib/_internal/pub/lib/src/dart.dart
+++ b/sdk/lib/_internal/pub/lib/src/dart.dart
@@ -127,11 +127,9 @@ Future runInIsolate(String code, message) {
 /// Adding an additional isolate in the middle works around this.
 void _isolateBuffer(message) {
   var replyTo = message['replyTo'];
-  // TODO(floitsch): If we do it right we shouldn't need to capture synchronous
-  // errors.
-  new Future.sync(() {
-    return Isolate.spawnUri(Uri.parse(message['uri']), [], message['message']);
-  }).then((_) => replyTo.send({'type': 'success'})).catchError((e, stack) {
+  Isolate.spawnUri(Uri.parse(message['uri']), [], message['message'])

[Lasse Reichstein Nielsen, 2013/12/13 11:16:58]

I still wouldn't guarantee that there are no synchronous errors.
The current code wraps everything in a try/catch, but we could choose to only
wrap the parts that are related to the remote isolate.

If you pass arguments of the wrong type (in checked mode or in unchecked mode),
any statement using the value can fail with a noSuchMethod error. I don't want
to promise that we catch all such errors. This code is an internal hack that
should be invisible to the user, so it should handle all errors, even checked
mode type errors, just as if the remote end had done it.

[floitsch, 2013/12/13 12:13:37]

I think that the pub-team assumes that it doesn't do any Programming Error, so
that all errors should be exceptions that are returned in the future.

[Lasse Reichstein Nielsen, 2013/12/13 12:16:30]

That is reasonable.

+      .then((_) => replyTo.send({'type': 'success'}))
+      .catchError((e, stack) {
     replyTo.send({
       'type': 'error',
       'error': CrossIsolateException.serialize(e, stack)