Adds Unit Tests and reverts IDisposable pattern

Author: pedrolamas

Microsoft.Toolkit/Deferred/DeferredEventArgs.cs

@@ -4,14 +4,15 @@
 
 using System;
 using System.ComponentModel;
-using System.Runtime.CompilerServices;
+
+#pragma warning disable CA1001
 
 namespace Microsoft.Toolkit.Deferred
 {
     /// <summary>
     /// <see cref="EventArgs"/> which can retrieve a <see cref="EventDeferral"/> in order to process data asynchronously before an <see cref="EventHandler"/> completes and returns to the calling control.
     /// </summary>
-    public class DeferredEventArgs : EventArgs, IDisposable
+    public class DeferredEventArgs : EventArgs
     {
         /// <summary>
         /// Gets a new <see cref="DeferredEventArgs"/> to use in cases where no <see cref="EventArgs"/> wish to be provided.
@@ -21,12 +22,6 @@ public class DeferredEventArgs : EventArgs, IDisposable
         private readonly object _eventDeferralLock = new object();
 
         private EventDeferral? _eventDeferral;
-        private bool _disposed;
-
-        /// <summary>
-        /// Finalizes an instance of the <see cref="DeferredEventArgs"/> class.
-        /// </summary>
-        ~DeferredEventArgs() => Dispose(false);
 
         /// <summary>
         /// Returns an <see cref="EventDeferral"/> which can be completed when deferred event is ready to continue.
@@ -36,7 +31,7 @@ public EventDeferral GetDeferral()
         {
             lock (_eventDeferralLock)
             {
-                return _eventDeferral ?? (_eventDeferral = new EventDeferral());
+                return _eventDeferral ??= new EventDeferral();
             }
         }
 
@@ -61,31 +56,5 @@ public EventDeferral GetDeferral()
                 return eventDeferral;
             }
         }
-
-        /// <summary>
-        /// Recommended helper method pattern for <see cref="IDisposable"/>.
-        /// </summary>
-        /// <param name="disposing">Source of dispose request.</param>
-        protected virtual void Dispose(bool disposing)
-        {
-            if (_disposed)
-            {
-                return;
-            }
-
-            _eventDeferral?.Dispose();
-
-            _disposed = true;
-        }
-
-        /// <inheritdoc/>
-        public void Dispose()
-        {
-            // Dispose of unmanaged resources.
-            Dispose(true);
-
-            // Suppress finalization.
-            GC.SuppressFinalize(this);
-        }
     }
 }

Microsoft.Toolkit/Deferred/EventDeferral.cs

@@ -7,6 +7,8 @@
 using System.Threading;
 using System.Threading.Tasks;
 
+#pragma warning disable CA1063
+
 namespace Microsoft.Toolkit.Deferred
 {
     /// <summary>
@@ -16,17 +18,11 @@ public class EventDeferral : IDisposable
     {
         //// TODO: If/when .NET 5 is base, we can upgrade to non-generic version
         private readonly TaskCompletionSource<object?> _taskCompletionSource = new TaskCompletionSource<object?>();
-        private bool _disposed = false;
 
         internal EventDeferral()
         {
         }
 
-        /// <summary>
-        /// Finalizes an instance of the <see cref="EventDeferral"/> class.
-        /// </summary>
-        ~EventDeferral() => Dispose(false);
-
         /// <summary>
         /// Call when finished with the Deferral.
         /// </summary>
@@ -50,30 +46,10 @@ public async Task WaitForCompletion(CancellationToken cancellationToken)
             }
         }
 
-        /// <summary>
-        /// Recommended helper method pattern for <see cref="IDisposable"/>.
-        /// </summary>
-        /// <param name="disposing">Source of dispose request.</param>
-        protected virtual void Dispose(bool disposing)
-        {
-            if (_disposed)
-            {
-                return;
-            }
-
-            Complete();
-
-            _disposed = true;
-        }
-
         /// <inheritdoc/>
         public void Dispose()
         {
-            // Dispose of unmanaged resources.
-            Dispose(true);
-
-            // Suppress finalization.
-            GC.SuppressFinalize(this);
+            Complete();
         }
     }
 }

UnitTests/UnitTests.Shared/Extensions/Test_EventHandlerExtensions.cs

@@ -0,0 +1,138 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading.Tasks;
+using Microsoft.Toolkit.Deferred;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace UnitTests.Extensions
+{
+    [TestClass]
+    public class Test_EventHandlerExtensions
+    {
+        [TestCategory("Deferred")]
+        [TestMethod]
+        public void Test_EventHandlerExtensions_GettingDeferralCausesAwait()
+        {
+            var tsc = new TaskCompletionSource<bool>();
+
+            var testClass = new TestClass();
+
+            testClass.TestEvent += async (s, e) =>
+            {
+                var deferral = e.GetDeferral();
+
+                await tsc.Task;
+
+                deferral.Complete();
+            };
+
+            var handlersTask = testClass.RaiseTestEvent();
+
+            Assert.IsFalse(handlersTask.IsCompleted);
+
+            tsc.SetResult(true);
+
+            Assert.IsTrue(handlersTask.IsCompleted);
+        }
+
+        [TestCategory("Deferred")]
+        [TestMethod]
+        public void Test_EventHandlerExtensions_NotGettingDeferralCausesNoAwait()
+        {
+            var tsc = new TaskCompletionSource<bool>();
+
+            var testClass = new TestClass();
+
+            testClass.TestEvent += async (s, e) =>
+            {
+                await tsc.Task;
+            };
+
+            var handlersTask = testClass.RaiseTestEvent();
+
+            Assert.IsTrue(handlersTask.IsCompleted);
+
+            tsc.SetResult(true);
+        }
+
+        [TestCategory("Deferred")]
+        [TestMethod]
+        public void Test_EventHandlerExtensions_UsingDeferralCausesAwait()
+        {
+            var tsc = new TaskCompletionSource<bool>();
+
+            var testClass = new TestClass();
+
+            testClass.TestEvent += async (s, e) =>
+            {
+                using (e.GetDeferral())
+                {
+                    await tsc.Task;
+                }
+            };
+
+            var handlersTask = testClass.RaiseTestEvent();
+
+            Assert.IsFalse(handlersTask.IsCompleted);
+
+            tsc.SetResult(true);
+
+            Assert.IsTrue(handlersTask.IsCompleted);
+        }
+
+        [TestCategory("Deferred")]
+        [DataTestMethod]
+        [DataRow(0, 1)]
+        [DataRow(1, 0)]
+        public void Test_EventHandlerExtensions_MultipleHandlersCauseAwait(int firstToReleaseDeferral, int lastToReleaseDeferral)
+        {
+            var tsc = new[]
+            {
+                new TaskCompletionSource<bool>(),
+                new TaskCompletionSource<bool>()
+            };
+
+            var testClass = new TestClass();
+
+            testClass.TestEvent += async (s, e) =>
+            {
+                var deferral = e.GetDeferral();
+
+                await tsc[0].Task;
+
+                deferral.Complete();
+            };
+
+            testClass.TestEvent += async (s, e) =>
+            {
+                var deferral = e.GetDeferral();
+
+                await tsc[1].Task;
+
+                deferral.Complete();
+            };
+
+            var handlersTask = testClass.RaiseTestEvent();
+
+            Assert.IsFalse(handlersTask.IsCompleted);
+
+            tsc[firstToReleaseDeferral].SetResult(true);
+
+            Assert.IsFalse(handlersTask.IsCompleted);
+
+            tsc[lastToReleaseDeferral].SetResult(true);
+
+            Assert.IsTrue(handlersTask.IsCompleted);
+        }
+
+        private class TestClass
+        {
+            public event EventHandler<DeferredEventArgs> TestEvent;
+
+            public Task RaiseTestEvent() => TestEvent.InvokeAsync(this, new DeferredEventArgs());
+        }
+    }
+}

UnitTests/UnitTests.Shared/UnitTests.Shared.projitems

@@ -19,6 +19,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Test_Guard.Array.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Test_Guard.Comparable.Numeric.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Test_Guard.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Extensions\Test_EventHandlerExtensions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Extensions\Test_TaskExtensions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Extensions\Test_ArrayExtensions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Extensions\Test_TypeExtensions.cs" />