Merge pull request #1259 from stakx/async-null-results

Allow async `.Result` setups to return `null`

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to this project will be documented in this file.
 The format is loosely based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 
+## Unreleased
+
+#### Fixed
+
+* Difference in behavior when mocking async method using `.Result` vs without (@cyungmann, #1253)
+
+
 ## 4.18.0 (2022-05-12)
 
 New major version of DynamicProxy (you may get better performance!), so please update with care.

src/Moq/Invocation.cs

@@ -97,7 +97,7 @@ public void ConvertResultToAwaitable(IAwaitableFactory awaitableFactory)
 			{
 				this.result = awaitableFactory.CreateFaulted(r.Exception);
 			}
-			else if (this.result != null && !this.method.ReturnType.IsAssignableFrom(this.result.GetType()))
+			else if (!this.method.ReturnType.IsAssignableFrom(this.result?.GetType()))
 			{
 				this.result = awaitableFactory.CreateCompleted(this.result);
 			}

tests/Moq.Tests/Regressions/IssueReportsFixture.cs

@@ -3802,6 +3802,29 @@ public void No_ArgumentException_due_to_parameter_refness()
 
 		#endregion
 
+		#region 1253
+
+		public class Issue1253
+		{
+			public interface IFoo
+			{
+				Task<string> Bar();
+			}
+
+			[Fact]
+			public async Task Test()
+			{
+				var mock = new Mock<IFoo>();
+				mock.Setup(x => x.Bar().Result).Returns((string)null);
+
+				var result = await mock.Object.Bar();
+
+				Assert.Null(result);
+			}
+		}
+
+		#endregion
+
 		// Old @ Google Code
 
 		#region #47