Merge pull request #1140 from bfriesen/lambda_closure_support

Improve error message when verification fails

CHANGELOG.md

@@ -10,6 +10,10 @@ The format is loosely based on [Keep a Changelog](http://keepachangelog.com/en/1
 
 * `CallBase` can now be used with interface methods that have a default interface implementation. It will call [the most specific override](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/proposals/csharp-8.0/default-interface-methods#the-most-specific-override-rule). (@stakx, #1130)
 
+#### Changed
+
+* Improved error message formatting of `It.Is` lambda expressions that capture local variables. (@bfriesen, #1140)
+
 #### Fixed
 
 * `AmbiguousMatchException` raised when interface has property indexer besides property in VB. (@mujdatdinc, #1129)

src/Moq/StringBuilderExtensions.AppendExpression.cs

@@ -6,6 +6,8 @@
 using System.Diagnostics;
 using System.Linq;
 using System.Linq.Expressions;
+using System.Reflection;
+using System.Runtime.CompilerServices;
 using System.Text;
 
 using Moq.Properties;
@@ -68,7 +70,15 @@ public static StringBuilder AppendExpression(this StringBuilder builder, Express
 					return builder.AppendExpression((ConditionalExpression)expression);
 
 				case ExpressionType.Constant:
-					return builder.AppendValueOf(((ConstantExpression)expression).Value);
+					var constantValue = ((ConstantExpression)expression).Value;
+					if (constantValue is LambdaExpression lambda)
+					{
+						return builder.AppendExpression(lambda);
+					}
+					else
+					{
+						return builder.AppendValueOf(constantValue);
+					}
 
 				case ExpressionType.Parameter:
 					return builder.AppendExpression((ParameterExpression)expression);
@@ -251,7 +261,15 @@ private static StringBuilder AppendExpression(this StringBuilder builder, Member
 		{
 			if (expression.Expression != null)
 			{
-				builder.AppendExpression(expression.Expression);
+				if (expression.Expression is ConstantExpression ce
+					&& ce.Type.IsDefined(typeof(CompilerGeneratedAttribute)))
+				{
+					return builder.Append(expression.Member.Name);
+				}
+				else
+				{
+					builder.AppendExpression(expression.Expression);
+				}
 			}
 			else
 			{

tests/Moq.Tests/VerifyFixture.cs

@@ -2,6 +2,7 @@
 // All rights reserved. Licensed under the BSD 3-Clause License; see License.txt.
 
 using System;
+using System.Linq.Expressions;
 using System.Threading.Tasks;
 
 using Moq;
@@ -65,6 +66,40 @@ public void ThrowsWithExpressionIfVerifiableExpectationWithLambdaMatcherNotCalle
 			Assert.Contains(@".Execute(It.Is<string>(s => string.IsNullOrEmpty(s)))", mex.Message);
 		}
 
+		[Fact]
+		public void ThrowsWithExpressionIfVerifiableExpectationWithLambdaMatcherVariableNotCalled()
+		{
+			var mock = new Mock<IFoo>();
+
+			Expression<Func<string, bool>> nullOrEmpty = s => string.IsNullOrEmpty(s);
+
+			mock.Setup(x => x.Execute(It.Is(nullOrEmpty)))
+				.Returns("ack")
+				.Verifiable();
+
+			var mex = Assert.Throws<MockException>(() => mock.Verify());
+			Assert.True(mex.IsVerificationError);
+			Assert.Contains(@".Execute(It.Is<string>(s => string.IsNullOrEmpty(s)))", mex.Message);
+		}
+
+		[Fact]
+		public void ThrowsWithExpressionIfVerifiableExpectationWithLambdaMatcherVariableAndClosureAccessNotCalled()
+		{
+			var mock = new Mock<IFoo>();
+
+			string password = "abc123";
+
+			Expression<Func<string, bool>> matchingPassword = s => s == password;
+
+			mock.Setup(x => x.Execute(It.Is(matchingPassword)))
+				.Returns("ack")
+				.Verifiable();
+
+			var mex = Assert.Throws<MockException>(() => mock.Verify());
+			Assert.True(mex.IsVerificationError);
+			Assert.Contains(@".Execute(It.Is<string>(s => s == password)", mex.Message);
+		}
+
 		[Fact]
 		public void VerifiesNoOpIfNoVerifiableExpectations()
 		{