Add ability to set up the .Result of (value) tasks

CHANGELOG.md

@@ -7,6 +7,38 @@ The format is loosely based on [Keep a Changelog](http://keepachangelog.com/en/1
 
 ## Unreleased
 
+#### Added
+
+* Ability to directly set up the `.Result` of tasks and value tasks, which makes setup expressions more uniform by rendering dedicated async verbs like `.ReturnsAsync`, `.ThrowsAsync`, etc. unnecessary:
+
+   ```diff
+   -mock.Setup(x => x.GetFooAsync()).ReturnsAsync(foo)
+   +mock.Setup(x => x.GetFooAsync().Result).Returns(foo)
+   ```
+
+   This is useful in places where there currently aren't any such async verbs at all:
+
+   ```diff
+   -Mock.Of<X>(x => x.GetFooAsync() == Task.FromResult(foo))
+   +Mock.Of<X>(x => x.GetFooAsync().Result == foo)
+   ```
+
+   This also allows recursive setups / method chaining across async calls inside a single setup expression:
+
+   ```diff
+   -mock.Setup(x => x.GetFooAsync()).ReturnsAsync(Mock.Of<IFoo>(f => f.Bar == bar))
+   +mock.Setup(x => x.GetFooAsync().Result.Bar).Returns(bar)
+   ```
+
+   or, with only `Mock.Of`:
+
+   ```diff
+   -Mock.Of<X>(x => x.GetFooAsync() == Task.FromResult(Mock.Of<IFoo>(f => f.Bar == bar)))
+   +Mock.Of<X>(x => x.GetFooAsync().Result.Bar == bar)
+   ```
+
+   This should work in all principal setup methods (`Mock.Of`, `mock.Setup…`, `mock.Verify…`). Support in `mock.Protected()` and for custom awaitable types may be added in the future. (@stakx, #1125)
+
 #### Changed
 
 * Attempts to mark conditionals setup as verifiable are once again allowed; it turns out that forbidding it (as was done in #997 for version 4.14.0) is in fact a regression. (@stakx, #1121)

src/Moq/ActionObserver.cs

@@ -9,6 +9,7 @@
 using System.Linq.Expressions;
 using System.Reflection;
 
+using Moq.Async;
 using Moq.Expressions.Visitors;
 using Moq.Internals;
 using Moq.Properties;
@@ -60,6 +61,19 @@ public override Expression<Action<T>> ReconstructExpression<T>(Action<T> action,
 					var invocation = recorder.Invocation;
 					if (invocation != null)
 					{
+						var resultType = invocation.Method.DeclaringType;
+						if (resultType.IsAssignableFrom(body.Type) == false)
+						{
+							if (AwaitableFactory.TryGet(body.Type) is { } awaitableHandler
+								&& awaitableHandler.ResultType.IsAssignableFrom(resultType))
+							{
+								// We are here because the current invocation cannot be chained onto the previous one,
+								// however it *can* be chained if we assume that there was a `.Result` query on the
+								// former invocation that we don't see because non-virtual members aren't recorded.
+								// In this case, we make things work by adding back the missing `.Result`:
+								body = awaitableHandler.CreateResultExpression(body);
+							}
+						}
 						body = Expression.Call(body, invocation.Method, GetArgumentExpressions(invocation, recorder.Matches.ToArray()));
 					}
 					else
@@ -227,7 +241,7 @@ private sealed class Recorder : IInterceptor
 			private int creationTimestamp;
 			private Invocation invocation;
 			private int invocationTimestamp;
-			private IProxy returnValue;
+			private object returnValue;
 
 			public Recorder(MatcherObserver matcherObserver)
 			{
@@ -248,7 +262,7 @@ public IEnumerable<Match> Matches
 				}
 			}
 
-			public Recorder Next => this.returnValue?.Interceptor as Recorder;
+			public Recorder Next => (Awaitable.TryGetResultRecursive(this.returnValue) as IProxy)?.Interceptor as Recorder;
 
 			public void Intercept(Invocation invocation)
 			{
@@ -277,6 +291,11 @@ public void Intercept(Invocation invocation)
 					{
 						this.returnValue = null;
 					}
+					else if (AwaitableFactory.TryGet(returnType) is { } awaitableFactory)
+					{
+						var result = CreateProxy(awaitableFactory.ResultType, null, this.matcherObserver, out _);
+						this.returnValue = awaitableFactory.CreateCompleted(result);
+					}
 					else if (returnType.IsMockable())
 					{
 						this.returnValue = CreateProxy(returnType, null, this.matcherObserver, out _);

src/Moq/Async/AwaitExpression.cs

@@ -0,0 +1,40 @@
+// Copyright (c) 2007, Clarius Consulting, Manas Technology Solutions, InSTEDD, and Contributors.
+// All rights reserved. Licensed under the BSD 3-Clause License; see License.txt.
+
+using System;
+using System.Diagnostics;
+using System.Linq.Expressions;
+
+namespace Moq.Async
+{
+	internal sealed class AwaitExpression : Expression
+	{
+		private readonly IAwaitableFactory awaitableFactory;
+		private readonly Expression operand;
+
+		public AwaitExpression(Expression operand, IAwaitableFactory awaitableFactory)
+		{
+			Debug.Assert(awaitableFactory != null);
+			Debug.Assert(operand != null);
+
+			this.awaitableFactory = awaitableFactory;
+			this.operand = operand;
+		}
+
+		public override bool CanReduce => false;
+
+		public override ExpressionType NodeType => ExpressionType.Extension;
+
+		public Expression Operand => this.operand;
+
+		public override Type Type => this.awaitableFactory.ResultType;
+
+		public override string ToString()
+		{
+			return this.awaitableFactory.ResultType == typeof(void) ? $"await {this.operand}"
+			                                                        : $"(await {this.operand})";
+		}
+
+		protected override Expression VisitChildren(ExpressionVisitor visitor) => this;
+	}
+}

src/Moq/Async/AwaitableFactory`1.cs

@@ -2,7 +2,10 @@
 // All rights reserved. Licensed under the BSD 3-Clause License; see License.txt.
 
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
+using System.Linq;
+using System.Linq.Expressions;
 
 namespace Moq.Async
 {
@@ -23,6 +26,30 @@ object IAwaitableFactory.CreateCompleted(object result)
 			return this.CreateCompleted();
 		}
 
+		public abstract TAwaitable CreateFaulted(Exception exception);
+
+		object IAwaitableFactory.CreateFaulted(Exception exception)
+		{
+			Debug.Assert(exception != null);
+
+			return this.CreateFaulted(exception);
+		}
+
+		public abstract TAwaitable CreateFaulted(IEnumerable<Exception> exceptions);
+
+		object IAwaitableFactory.CreateFaulted(IEnumerable<Exception> exceptions)
+		{
+			Debug.Assert(exceptions != null);
+			Debug.Assert(exceptions.Any());
+
+			return this.CreateFaulted(exceptions);
+		}
+
+		Expression IAwaitableFactory.CreateResultExpression(Expression awaitableExpression)
+		{
+			return new AwaitExpression(awaitableExpression, this);
+		}
+
 		bool IAwaitableFactory.TryGetResult(object awaitable, out object result)
 		{
 			Debug.Assert(awaitable is TAwaitable);

src/Moq/Async/AwaitableFactory`2.cs

@@ -2,7 +2,10 @@
 // All rights reserved. Licensed under the BSD 3-Clause License; see License.txt.
 
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
+using System.Linq;
+using System.Linq.Expressions;
 
 namespace Moq.Async
 {
@@ -23,8 +26,29 @@ object IAwaitableFactory.CreateCompleted(object result)
 			return this.CreateCompleted((TResult)result);
 		}
 
+		public abstract TAwaitable CreateFaulted(Exception exception);
+
+		object IAwaitableFactory.CreateFaulted(Exception exception)
+		{
+			Debug.Assert(exception != null);
+
+			return this.CreateFaulted(exception);
+		}
+
+		public abstract TAwaitable CreateFaulted(IEnumerable<Exception> exceptions);
+
+		object IAwaitableFactory.CreateFaulted(IEnumerable<Exception> exceptions)
+		{
+			Debug.Assert(exceptions != null);
+			Debug.Assert(exceptions.Any());
+
+			return this.CreateFaulted(exceptions);
+		}
+
 		public abstract bool TryGetResult(TAwaitable awaitable, out TResult result);
 
+		public abstract Expression CreateResultExpression(Expression awaitableExpression);
+
 		bool IAwaitableFactory.TryGetResult(object awaitable, out object result)
 		{
 			Debug.Assert(awaitable is TAwaitable);

src/Moq/Async/IAwaitableFactory.cs

@@ -2,6 +2,8 @@
 // All rights reserved. Licensed under the BSD 3-Clause License; see License.txt.
 
 using System;
+using System.Collections.Generic;
+using System.Linq.Expressions;
 
 namespace Moq.Async
 {
@@ -11,6 +13,12 @@ internal interface IAwaitableFactory
 
 		object CreateCompleted(object result = null);
 
+		object CreateFaulted(Exception exception);
+
+		object CreateFaulted(IEnumerable<Exception> exceptions);
+
+		Expression CreateResultExpression(Expression awaitableExpression);
+
 		bool TryGetResult(object awaitable, out object result);
 	}
 }

src/Moq/Async/TaskFactory.cs

@@ -1,6 +1,10 @@
 // Copyright (c) 2007, Clarius Consulting, Manas Technology Solutions, InSTEDD, and Contributors.
 // All rights reserved. Licensed under the BSD 3-Clause License; see License.txt.
 
+using System;
+using System.Collections.Generic;
+using System.Linq.Expressions;
+using System.Reflection;
 using System.Threading.Tasks;
 
 namespace Moq.Async
@@ -17,5 +21,19 @@ public override Task CreateCompleted()
 		{
 			return Task.FromResult<object>(default);
 		}
+
+		public override Task CreateFaulted(Exception exception)
+		{
+			var tcs = new TaskCompletionSource<object>();
+			tcs.SetException(exception);
+			return tcs.Task;
+		}
+
+		public override Task CreateFaulted(IEnumerable<Exception> exceptions)
+		{
+			var tcs = new TaskCompletionSource<object>();
+			tcs.SetException(exceptions);
+			return tcs.Task;
+		}
 	}
 }

src/Moq/Async/TaskFactory`1.cs

@@ -1,6 +1,9 @@
 // Copyright (c) 2007, Clarius Consulting, Manas Technology Solutions, InSTEDD, and Contributors.
 // All rights reserved. Licensed under the BSD 3-Clause License; see License.txt.
 
+using System;
+using System.Collections.Generic;
+using System.Linq.Expressions;
 using System.Threading.Tasks;
 
 namespace Moq.Async
@@ -12,6 +15,27 @@ public override Task<TResult> CreateCompleted(TResult result)
 			return Task.FromResult(result);
 		}
 
+		public override Task<TResult> CreateFaulted(Exception exception)
+		{
+			var tcs = new TaskCompletionSource<TResult>();
+			tcs.SetException(exception);
+			return tcs.Task;
+		}
+
+		public override Task<TResult> CreateFaulted(IEnumerable<Exception> exceptions)
+		{
+			var tcs = new TaskCompletionSource<TResult>();
+			tcs.SetException(exceptions);
+			return tcs.Task;
+		}
+
+		public override Expression CreateResultExpression(Expression awaitableExpression)
+		{
+			return Expression.MakeMemberAccess(
+				awaitableExpression,
+				typeof(Task<TResult>).GetProperty(nameof(Task<TResult>.Result)));
+		}
+
 		public override bool TryGetResult(Task<TResult> task, out TResult result)
 		{
 			if (task.Status == TaskStatus.RanToCompletion)

src/Moq/Async/ValueTaskFactory.cs

@@ -1,6 +1,8 @@
 // Copyright (c) 2007, Clarius Consulting, Manas Technology Solutions, InSTEDD, and Contributors.
 // All rights reserved. Licensed under the BSD 3-Clause License; see License.txt.
 
+using System;
+using System.Collections.Generic;
 using System.Threading.Tasks;
 
 namespace Moq.Async
@@ -17,5 +19,19 @@ public override ValueTask CreateCompleted()
 		{
 			return default;
 		}
+
+		public override ValueTask CreateFaulted(Exception exception)
+		{
+			var tcs = new TaskCompletionSource<object>();
+			tcs.SetException(exception);
+			return new ValueTask(tcs.Task);
+		}
+
+		public override ValueTask CreateFaulted(IEnumerable<Exception> exceptions)
+		{
+			var tcs = new TaskCompletionSource<object>();
+			tcs.SetException(exceptions);
+			return new ValueTask(tcs.Task);
+		}
 	}
 }

src/Moq/Async/ValueTaskFactory`1.cs

@@ -1,6 +1,9 @@
 // Copyright (c) 2007, Clarius Consulting, Manas Technology Solutions, InSTEDD, and Contributors.
 // All rights reserved. Licensed under the BSD 3-Clause License; see License.txt.
 
+using System;
+using System.Collections.Generic;
+using System.Linq.Expressions;
 using System.Threading.Tasks;
 
 namespace Moq.Async
@@ -12,6 +15,27 @@ public override ValueTask<TResult> CreateCompleted(TResult result)
 			return new ValueTask<TResult>(result);
 		}
 
+		public override ValueTask<TResult> CreateFaulted(Exception exception)
+		{
+			var tcs = new TaskCompletionSource<TResult>();
+			tcs.SetException(exception);
+			return new ValueTask<TResult>(tcs.Task);
+		}
+
+		public override ValueTask<TResult> CreateFaulted(IEnumerable<Exception> exceptions)
+		{
+			var tcs = new TaskCompletionSource<TResult>();
+			tcs.SetException(exceptions);
+			return new ValueTask<TResult>(tcs.Task);
+		}
+
+		public override Expression CreateResultExpression(Expression awaitableExpression)
+		{
+			return Expression.MakeMemberAccess(
+				awaitableExpression,
+				typeof(ValueTask<TResult>).GetProperty(nameof(ValueTask<TResult>.Result)));
+		}
+
 		public override bool TryGetResult(ValueTask<TResult> valueTask, out TResult result)
 		{
 			if (valueTask.IsCompletedSuccessfully)