Fix ReturnValue for InterceptSynchronous

src/Castle.Core.AsyncInterceptor/AsyncInterceptorBase.cs

@@ -127,6 +127,7 @@ private static void InterceptSynchronousResult<TResult>(AsyncInterceptorBase me,
         }
 
         task.RethrowIfFaulted();
+        invocation.ReturnValue = task.Result;
     }
 
     private static Task ProceedSynchronous(IInvocation invocation, IInvocationProceedInfo proceedInfo)

test/Castle.Core.AsyncInterceptor.Tests/InterfaceProxies/TestProcessingReturnValueWithoutInvokingAsyncInterceptor.cs

@@ -0,0 +1,98 @@
+// Copyright (c) 2016-2023 James Skimming. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See LICENSE in the project root for license information.
+
+namespace Castle.DynamicProxy.InterfaceProxies;
+
+using System.Reflection;
+
+public class TestProcessingReturnValueWithoutInvokingAsyncInterceptor : AsyncInterceptorBase
+{
+    private static readonly MethodInfo TaskFromResultMethod = typeof(Task)
+        .GetMethod(nameof(Task.FromResult), BindingFlags.Static | BindingFlags.Public)!;
+
+    private readonly ListLogger _log;
+
+    public TestProcessingReturnValueWithoutInvokingAsyncInterceptor(ListLogger log)
+    {
+        _log = log ?? throw new ArgumentNullException(nameof(log));
+    }
+
+    protected override Task InterceptAsync(
+        IInvocation invocation,
+        IInvocationProceedInfo proceedInfo,
+        Func<IInvocation, IInvocationProceedInfo, Task> proceed)
+    {
+        try
+        {
+            _log.Add($"{invocation.Method.Name}:StartingVoidInvocation");
+
+            /* Without invoking original method
+            await proceed(invocation, proceedInfo).ConfigureAwait(false);
+            */
+
+            _log.Add($"{invocation.Method.Name}:CompletedVoidInvocation");
+
+            // There is no async call in this example so we just return a completed task without async.
+            return Task.CompletedTask;
+        }
+        catch (Exception e)
+        {
+            _log.Add($"{invocation.Method.Name}:VoidExceptionThrown:{e.Message}");
+            throw;
+        }
+    }
+
+    protected override Task<TResult> InterceptAsync<TResult>(
+        IInvocation invocation,
+        IInvocationProceedInfo proceedInfo,
+        Func<IInvocation, IInvocationProceedInfo, Task<TResult>> proceed)
+    {
+        try
+        {
+            _log.Add($"{invocation.Method.Name}:StartingResultInvocation");
+
+            /* Without invoking original method
+            TResult result = await proceed(invocation, proceedInfo).ConfigureAwait(false);
+            */
+
+            // But we need a default result
+            TResult? result = GetDefaultValue<TResult>();
+
+            _log.Add($"{invocation.Method.Name}:CompletedResultInvocation:{result}");
+
+            // Add ! here because the return value type in the base definition is supposed to be a nullable reference
+            // but it isn't
+            return Task.FromResult(result!);
+        }
+        catch (Exception e)
+        {
+            _log.Add($"{invocation.Method.Name}:VoidExceptionThrown:{e.Message}");
+            throw;
+        }
+    }
+
+    private TResult? GetDefaultValue<TResult>()
+    {
+        return (TResult?)GetDefaultValue(typeof(TResult));
+    }
+
+    private object? GetDefaultValue(Type type)
+    {
+        if (type.IsAssignableFrom(typeof(Task)))
+        {
+            if (type.IsGenericType)
+            {
+                Type innerType = type.GetGenericArguments().Single();
+                object? innerResult = GetDefaultValue(innerType);
+                MethodInfo fromResult = TaskFromResultMethod.MakeGenericMethod(innerType);
+                return fromResult.Invoke(null, new[] { innerResult });
+            }
+
+            return Task.CompletedTask;
+        }
+
+        if (type.IsValueType) return Activator.CreateInstance(type);
+
+        return null;
+    }
+}

test/Castle.Core.AsyncInterceptor.Tests/ProcessingAsyncInterceptorWithoutInvokingShould.cs

@@ -0,0 +1,102 @@
+// Copyright (c) 2016-2023 James Skimming. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See LICENSE in the project root for license information.
+
+namespace Castle.DynamicProxy;
+
+using Castle.DynamicProxy.InterfaceProxies;
+using Xunit;
+using Xunit.Abstractions;
+
+public class WhenProcessingSynchronousVoidMethodsWithoutInvoking
+{
+    private readonly ListLogger _log;
+    private readonly IInterfaceToProxy _proxy;
+
+    public WhenProcessingSynchronousVoidMethodsWithoutInvoking(ITestOutputHelper output)
+    {
+        _log = new ListLogger(output);
+        var interceptor = new TestProcessingReturnValueWithoutInvokingAsyncInterceptor(_log);
+        _proxy = ProxyGen.CreateProxy(_log, interceptor);
+    }
+
+    [Fact]
+    public void ShouldLog4Entries()
+    {
+        // Act
+        _proxy.SynchronousVoidMethod();
+
+        // Assert
+        Assert.Equal(2, _log.Count);
+    }
+}
+
+public class WhenProcessingSynchronousResultMethodsWithoutInvoking
+{
+    private readonly ListLogger _log;
+    private readonly IInterfaceToProxy _proxy;
+
+    public WhenProcessingSynchronousResultMethodsWithoutInvoking(ITestOutputHelper output)
+    {
+        _log = new ListLogger(output);
+        var interceptor = new TestProcessingReturnValueWithoutInvokingAsyncInterceptor(_log);
+        _proxy = ProxyGen.CreateProxy(_log, interceptor);
+    }
+
+    [Fact]
+    public void ShouldLog4Entries()
+    {
+        // Act
+        Guid result = _proxy.SynchronousResultMethod();
+
+        // Assert
+        Assert.Equal(Guid.Empty, result);
+        Assert.Equal(2, _log.Count);
+    }
+}
+
+public class WhenProcessingAsynchronousVoidMethodsWithoutInvoking
+{
+    private readonly ListLogger _log;
+    private readonly IInterfaceToProxy _proxy;
+
+    public WhenProcessingAsynchronousVoidMethodsWithoutInvoking(ITestOutputHelper output)
+    {
+        _log = new ListLogger(output);
+        var interceptor = new TestProcessingReturnValueWithoutInvokingAsyncInterceptor(_log);
+        _proxy = ProxyGen.CreateProxy(_log, interceptor);
+    }
+
+    [Fact]
+    public async Task ShouldLog4Entries()
+    {
+        // Act
+        await _proxy.AsynchronousVoidMethod().ConfigureAwait(false);
+
+        // Assert
+        Assert.Equal(2, _log.Count);
+    }
+}
+
+public class WhenProcessingAsynchronousResultMethodsWithoutInvoking
+{
+    private readonly ListLogger _log;
+    private readonly IInterfaceToProxy _proxy;
+
+    public WhenProcessingAsynchronousResultMethodsWithoutInvoking(ITestOutputHelper output)
+    {
+        _log = new ListLogger(output);
+        var interceptor = new TestProcessingReturnValueWithoutInvokingAsyncInterceptor(_log);
+        _proxy = ProxyGen.CreateProxy(_log, interceptor);
+    }
+
+    [Fact]
+    public async Task ShouldLog4Entries()
+    {
+        // Act
+        Guid result = await _proxy.AsynchronousResultMethod().ConfigureAwait(false);
+
+        // Assert
+        Assert.Equal(Guid.Empty, result);
+        Assert.Equal(2, _log.Count);
+    }
+}