NancyEngine: try-catch around the CheckStatusCodeHandler and flatten

exception in the nancy engine extensions NancyFx#1458

Author: damianh

src/Nancy/NancyEngine.cs

@@ -101,9 +101,17 @@ public Task<NancyContext> HandleRequest(Request request, Func<NancyContext, Nanc
             task.WhenCompleted(
                 completeTask =>
                 {
-                    this.CheckStatusCodeHandler(completeTask.Result);
+                    try
+                    {
+                        this.CheckStatusCodeHandler(completeTask.Result);
 
-                    this.SaveTraceInformation(completeTask.Result);
+                        this.SaveTraceInformation(completeTask.Result);
+                    }
+                    catch (Exception ex)
+                    {
+                        tcs.SetException(ex);
+                        return;
+                    }
 
                     tcs.SetResult(completeTask.Result);
                 },
@@ -280,7 +288,7 @@ private static void InvokeOnErrorHook(NancyContext context, ErrorPipeline pipeli
             }
         }
 
-        private static Exception FlattenException(Exception exception)
+        internal static Exception FlattenException(Exception exception)
         {
             if (exception is AggregateException)
             {

src/Nancy/NancyEngineExtensions.cs

@@ -28,10 +28,14 @@ public static NancyContext HandleRequest(this INancyEngine nancyEngine, Request
         public static NancyContext HandleRequest(this INancyEngine nancyEngine, Request request, Func<NancyContext, NancyContext> preRequest)
         {
             var task = nancyEngine.HandleRequest(request, preRequest, CancellationToken.None);
-            task.Wait();
-            if (task.IsFaulted)
+            try
             {
-                throw task.Exception ?? new Exception("Request task faulted");
+                task.Wait();
+            }
+            catch (Exception ex)
+            {
+                var flattenedException = NancyEngine.FlattenException(ex);
+                throw flattenedException;
             }
             return task.Result;
         }