Display metadata about out-of-band callbacks in scheduled test errors.

pkg/scheduled_test/lib/src/schedule_error.dart

Index: pkg/scheduled_test/lib/src/schedule_error.dart
diff --git a/pkg/scheduled_test/lib/src/schedule_error.dart b/pkg/scheduled_test/lib/src/schedule_error.dart
index 179419b5ae6c4362b7b64308cb3b664e93c1eade..c628bfba5a06b9f68cf316dd4a6945f37a0a8815 100644
--- a/pkg/scheduled_test/lib/src/schedule_error.dart
+++ b/pkg/scheduled_test/lib/src/schedule_error.dart
@@ -23,6 +23,10 @@ class ScheduleError extends AsyncError {
   /// `null` if there was no such queue.
   final TaskQueue queue;
 
+  /// The descriptions of out-of-band callbacks that were pending when this
+  /// error occurred.
+  final Collection<String> pendingCallbacks;
+
   /// The state of the schedule at the time the error was detected.
   final ScheduleState _stateWhenDetected;
 
@@ -52,6 +56,8 @@ class ScheduleError extends AsyncError {
         this.schedule = schedule,

[Bob Nystrom, 2013/03/12 20:08:51]

Are the "this."s needed here?

[nweiz, 2013/03/12 20:56:51]

No, removed.

         this.task = schedule.currentTask,
         this.queue = schedule.currentQueue,
+        this.pendingCallbacks = schedule.currentQueue == null ? <String>[]
+            : new List<String>.from(schedule.currentQueue.pendingCallbacks),

[Bob Nystrom, 2013/03/12 20:08:51]

schedule.currentQueue.pendingCallbacks.toList()

[nweiz, 2013/03/12 20:56:51]

Done.

         this._stateWhenDetected = schedule.state;
 
   bool operator ==(other) => other is ScheduleError && task == other.task &&
@@ -88,6 +94,14 @@ class ScheduleError extends AsyncError {
       result.write('Error detected before the schedule started running.');
     }
 
-    return result.toString();
+    if (!pendingCallbacks.isEmpty) {
+      result.write("\n\n");
+      result.writeln("Pending out-of-band callbacks:");
+      for (var callback in pendingCallbacks) {
+        result.writeln("* $callback");
+      }
+    }
+
+    return result.toString().trim();
   }
 }