Add an error listener on isolates.

tests/isolate/handle_error2_test.dart

+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library handle_error_test;
+
+import "dart:isolate";
+import "dart:async";
+import "package:async_helper/async_helper.dart";
+import "package:expect/expect.dart";
+
+isomain1(replyPort) {
+  RawReceivePort port = new RawReceivePort();
+  port.handler = (v) {
+    switch (v) {
+      case 0:
+        replyPort.send(42);
+        break;
+      case 1:
+        throw new ArgumentError("whoops");
+      case 2:
+        throw new RangeError.value(37);
+      case 3:
+        port.close();
+    }
+  };
+  replyPort.send(port.sendPort);
+}
+
+/// Do Isolate.spawn(entry) and get a sendPort from the isolate that it
+/// expects commands on.
+/// The isolate has errors set to non-fatal.
+/// Returns a list of `[isolate, commandPort]` in a future.
+Future spawn(entry) {
+  ReceivePort reply = new ReceivePort();
+  Future isolate = Isolate.spawn(entry, reply.sendPort, paused: true);
+  return isolate.then((Isolate isolate) {
+    isolate.setErrorsFatal(false);
+    isolate.resume(isolate.pauseCapability);
+    Future result = reply.first.then((sendPort) {
+      return [isolate, sendPort];
+    });
+    return result;
+  });
+}
+
+main(){
+  asyncStart();
+  RawReceivePort reply = new RawReceivePort(null);
+  RawReceivePort reply2 = new RawReceivePort(null);
+  // Create two isolates waiting for commands, with errors non-fatal.
+  Future iso1 = spawn(isomain1);
+  Future iso2 = spawn(isomain1);
+  Future.wait([iso1, iso2]).then((l) {
+    var isolate1 = l[0][0];
+    var sendPort1 = l[0][1];
+    var isolate2 = l[1][0];
+    var sendPort2 = l[1][1];
+    Stream errors = isolate1.errors;  // Broadcast stream, never a done message.
+    int state = 1;
+    var subscription;
+    subscription = errors.listen(null, onError: (error, stack) {
+      switch (state) {
+        case 1:
+          Expect.equals(new ArgumentError("whoops").toString(), "$error");
+          state++;
+          break;
+        case 2:
+          Expect.equals(new RangeError.value(37).toString(), "$error");
+          state++;
+          reply.close();
+          subscription.cancel();
+          asyncEnd();
+          break;
+        default:
+          throw "Bad state for error: $state: $error";
+      }
+    });
+    sendPort1.send(0);
+    sendPort2.send(0);
+    sendPort1.send(1);
+    sendPort2.send(1);
+    sendPort1.send(2);
+    sendPort2.send(2);
+    sendPort1.send(3);
+    sendPort2.send(3);
+  });
+}
+