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 3792a5b4d2ddbdee1d72446d80c67cae5cd82062..e0e7693b4eeac17d1750b546980b59a234954c40 100644
--- a/runtime/lib/isolate_patch.dart
+++ b/runtime/lib/isolate_patch.dart
@@ -241,8 +241,11 @@ 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 opportunity to install an error handler.
+      scheduleMicrotask(() {
+        completer.completeError(e, st);
+      });

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

How about doing the same as in the JS patch:
 try { 
    ...
    Completer completer = new ...
    readyPort.handler = ...
    return completer.future;
 } catch (e, st) {
    return new Future<Isolate>.error(e, st);
 }

Add space after "catch" here and below.

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

Done.

     };
     return completer.future;
   }
@@ -261,8 +264,11 @@ 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 opportunity to install an error handler.
+      scheduleMicrotask(() {
+        completer.completeError(e, st);
+      });
     };
     return completer.future;
   }