Merge pull request #73 from alextercete/bug/reference-type-tasks-throwing-exception

Fix error when returning Task of a reference type

Author: kzu

Source/EmptyDefaultValueProvider.cs

@@ -93,7 +93,7 @@ private static object GetReferenceTypeDefault(Type valueType)
 			else if (valueType == typeof(Task))
 			{
 				// Task<T> inherits from Task, so just return Task<bool>
-				return GetCompletedTaskWithResult(false);
+				return GetCompletedTaskForType(typeof (bool));
 			}
 #endif
 			else if (valueType.IsGenericType && valueType.GetGenericTypeDefinition() == typeof(IEnumerable<>))
@@ -115,9 +115,7 @@ private static object GetReferenceTypeDefault(Type valueType)
 			else if (valueType.IsGenericType && valueType.GetGenericTypeDefinition() == typeof(Task<>))
 			{
 				var genericType = valueType.GetGenericArguments()[0];
-
-				return GetCompletedTaskWithResult(
-					genericType.IsValueType ? GetValueTypeDefault(genericType) : GetReferenceTypeDefault(genericType));
+				return GetCompletedTaskForType(genericType);
 			}
 #endif
 
@@ -136,14 +134,15 @@ private static object GetValueTypeDefault(Type valueType)
 		}
 
 #if !NET3x && !SILVERLIGHT
-		private static Task GetCompletedTaskWithResult(object result)
+		private static Task GetCompletedTaskForType(Type type)
 		{
-			var type = result.GetType();
 			var tcs = Activator.CreateInstance(typeof (TaskCompletionSource<>).MakeGenericType(type));
 
 			var setResultMethod = tcs.GetType().GetMethod("SetResult");
 			var taskProperty = tcs.GetType().GetProperty("Task");
 
+			var result = type.IsValueType ? GetValueTypeDefault(type) : GetReferenceTypeDefault(type);
+
 			setResultMethod.Invoke(tcs, new[] {result});
 			return (Task) taskProperty.GetValue(tcs, null);
 		}

UnitTests/EmptyDefaultValueProviderFixture.cs

@@ -123,23 +123,35 @@ public void ProvidesDefaultTask()
 		}
 
 		[Fact]
-		public void ProvidesDefaultGenericTask()
+		public void ProvidesDefaultGenericTaskOfValueType()
 		{
 			var provider = new EmptyDefaultValueProvider();
 
-			var value = provider.ProvideDefault(typeof(IFoo).GetProperty("GenericTaskValue").GetGetMethod());
+			var value = provider.ProvideDefault(typeof(IFoo).GetProperty("GenericTaskOfValueType").GetGetMethod());
 
 			Assert.NotNull(value);
 			Assert.True(((Task)value).IsCompleted);
 			Assert.Equal(default(int), ((Task<int>)value).Result);
 		}
 
+		[Fact]
+		public void ProvidesDefaultGenericTaskOfReferenceType()
+		{
+			var provider = new EmptyDefaultValueProvider();
+
+			var value = provider.ProvideDefault(typeof(IFoo).GetProperty("GenericTaskOfReferenceType").GetGetMethod());
+
+			Assert.NotNull(value);
+			Assert.True(((Task)value).IsCompleted);
+			Assert.Equal(default(string), ((Task<string>)value).Result);
+		}
+
 		[Fact]
 		public void ProvidesDefaultTaskOfGenericTask()
 		{
 			var provider = new EmptyDefaultValueProvider();
 
-			var value = provider.ProvideDefault(typeof(IFoo).GetProperty("TaskOfGenericTaskValue").GetGetMethod());
+			var value = provider.ProvideDefault(typeof(IFoo).GetProperty("TaskOfGenericTaskOfValueType").GetGetMethod());
 
 			Assert.NotNull(value);
 			Assert.True(((Task)value).IsCompleted);
@@ -162,8 +174,9 @@ public interface IFoo
 			IQueryable QueryableObjects { get; }
 #if !NET3x && !SILVERLIGHT
 			Task TaskValue { get; set; }
-			Task<int> GenericTaskValue { get; set; }
-			Task<Task<int>> TaskOfGenericTaskValue { get; set; }
+			Task<int> GenericTaskOfValueType { get; set; }
+			Task<string> GenericTaskOfReferenceType { get; set; }
+			Task<Task<int>> TaskOfGenericTaskOfValueType { get; set; }
 #endif
 		}