pkg/scheduled_test: handle null currentSchedule due to timeout

pkg/scheduled_test/lib/scheduled_test.dart

 // Copyright (c) 2013, 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.
 
 // TODO(nweiz): Add support for calling [schedule] while the schedule is already
 // running.
 // TODO(nweiz): Port the non-Pub-specific scheduled test libraries from Pub.
 /// A package for writing readable tests of asynchronous behavior.
 ///
 /// ## Installing ##
@@ skipping 227 matching lines @@
 void _test(String description, body(), Function testFn) {
   maybeWrapFuture(future, description) {
     if (future != null) wrapFuture(future, description);
   }
 
   unittest.ensureInitialized();
   _ensureSetUpForTopLevel();
   testFn(description, () {
     var completer = new Completer();
 
+    // Capture this in a local variable in case we capture an out-of-band error
+    // after the schedule completes.
+    var errorHandler;
+
     Chain.capture(() {
       _currentSchedule = new Schedule();
+      errorHandler = _currentSchedule.signalError;
       return currentSchedule.run(() {
         if (_setUpFn != null) maybeWrapFuture(_setUpFn(), "set up");
         maybeWrapFuture(body(), "test body");
       }).catchError((error, stackTrace) {
         if (error is ScheduleError) {
           assert(error.schedule.errors.contains(error));
           assert(error.schedule == currentSchedule);
           unittest.registerException(error.schedule.errorString());
         } else {
           unittest.registerException(error, new Chain.forTrace(stackTrace));
         }
       }).then(completer.complete);
-    }, onError: (error, chain) => currentSchedule.signalError(error, chain));
+    }, onError: (error, stackTrace) => errorHandler(error, stackTrace));
 
     return completer.future;
   });
 }
 
 /// Whether or not the tests currently being defined are in a group. This is
 /// only true when defining tests, not when executing them.
 bool _inGroup = false;
 
 /// Creates a new named group of tests. This has the same semantics as
@@ skipping 106 matching lines @@
 /// [description] provides an optional description of the future, which is
 /// used when generating error messages.
 Future wrapFuture(Future future, [String description]) {
   if (currentSchedule == null) {
     throw new StateError("Unexpected call to wrapFuture with no current "
         "schedule.");
   }
 
   return currentSchedule.wrapFuture(future, description);
 }