Support interface "inheritance"

src/Directory.Build.props

@@ -29,7 +29,7 @@
 
 		<!-- Make the assembly, file, and NuGet package versions the same. -->
 		<!-- https://docs.microsoft.com/en-us/nuget/concepts/package-versioning#pre-release-versions -->
-		<Version>0.6.0-beta</Version>
+		<Version>0.7.0-beta</Version>
 	</PropertyGroup>
 
 	<PropertyGroup Condition="'$(Configuration)'=='Debug'">

src/Menees.Remoting/RmiServer.cs

@@ -19,8 +19,7 @@ public sealed class RmiServer<TServiceInterface> : RmiNode<TServiceInterface>, I
 {
 	#region Private Data Members
 
-	private static readonly Dictionary<string, MethodInfo> MethodSignatureCache =
-		typeof(TServiceInterface).GetMethods().ToDictionary(method => GetMethodSignature(method));
+	private static readonly Lazy<Dictionary<string, MethodInfo>> MethodSignatureCache = new(CreateMethodSignatureDictionary);
 
 	private readonly PipeServer pipe;
 	private readonly CancellationToken cancellationToken;
@@ -134,6 +133,38 @@ protected override void Dispose(bool disposing)
 
 	#region Private Methods
 
+	private static Dictionary<string, MethodInfo> CreateMethodSignatureDictionary()
+	{
+		List<(string Signature, MethodInfo Method)> items = new();
+
+		void AddMethods(Type interfaceType)
+		{
+			items.AddRange(interfaceType.GetMethods().Select(method => (GetMethodSignature(method), method)));
+
+			foreach (Type implementedType in interfaceType.GetInterfaces())
+			{
+				AddMethods(implementedType);
+			}
+		}
+
+		// Calling GetMethods() on an interface type only gets its declared methods. Even BindingFlags don't help
+		// because a "derived" interface still has "object" as its base and any "inherited" interface is really just an
+		// "implements" relationship and not an "inherits" relationship. So, we have to recursively find all "inherited"
+		// interfaces and flatten them out ourselves.
+		// https://stackoverflow.com/questions/3395174/c-sharp-interface-inheritance/3395327#3395327
+		AddMethods(typeof(TServiceInterface));
+
+		// Take the first MethodInfo instance for each signature because interfaces can have a diamond shaped
+		// "inheritance" pattern. For example, suppose an interface "inherits" from two interfaces that are
+		// both IDisposable like this:
+		//     IStreamReader : IDisposable
+		//     IStreamWriter : IDisposable
+		//     IStreamReaderWriter : IStreamReader, IStreamWriter
+		Dictionary<string, MethodInfo> result = items.GroupBy(pair => pair.Signature)
+			.ToDictionary(pair => pair.Key, pair => pair.First().Method);
+		return result;
+	}
+
 	private async Task ProcessRequestAsync(Stream clientStream)
 	{
 		await ServerUtility.ProcessRequestAsync(
@@ -144,7 +175,7 @@ await ServerUtility.ProcessRequestAsync(
 			{
 				Response response;
 
-				if (!MethodSignatureCache.TryGetValue(request.MethodSignature ?? string.Empty, out MethodInfo? method))
+				if (!MethodSignatureCache.Value.TryGetValue(request.MethodSignature ?? string.Empty, out MethodInfo? method))
 				{
 					response = ServerUtility.CreateResponse(new TargetException(
 						$"A {typeof(TServiceInterface).FullName} method with signature '{request.MethodSignature}' was not found."));

tests/Menees.Remoting.Tests/BaseTests.cs

@@ -122,7 +122,7 @@ protected async Task TestCrossProcessServerAsync(
 		}
 		finally
 		{
-			TimeSpan exitWait = TimeSpan.FromSeconds(5);
+			TimeSpan exitWait = TimeSpan.FromSeconds(10);
 			WaitForExit(hostProcess, exitWait, ExpectedExitCode);
 		}
 	}

tests/Menees.Remoting.Tests/RmiServerTests.cs

@@ -14,6 +14,30 @@
 [TestClass]
 public class RmiServerTests : BaseTests
 {
+	#region Private Interfaces
+
+	private interface IRoot
+	{
+		int GetRoot(int input);
+	}
+
+	private interface ILevel1A : IRoot
+	{
+		int GetLevel1A(int input);
+	}
+
+	private interface ILevel1B : IRoot
+	{
+		int GetLevel1B(int input);
+	}
+
+	private interface IDiamond : ILevel1A, ILevel1B
+	{
+		int GetDiamond(int input);
+	}
+
+	#endregion
+
 	#region Public Methods
 
 	[TestMethod]
@@ -143,6 +167,23 @@ public void SecurityVariations()
 		}
 	}
 
+	[TestMethod]
+	public void InterfaceInheritance()
+	{
+		string serverPath = this.GenerateServerPath();
+		Diamond diamond = new();
+		using RmiServer<IDiamond> server = new(diamond, serverPath, loggerFactory: this.LoggerFactory);
+		server.ReportUnhandledException = WriteUnhandledServerException;
+		server.Start();
+
+		using RmiClient<IDiamond> client = new(serverPath, loggerFactory: this.LoggerFactory);
+		IDiamond proxy = client.CreateProxy();
+		proxy.GetRoot(10).ShouldBe(10);
+		proxy.GetLevel1A(10).ShouldBe(110);
+		proxy.GetLevel1B(10).ShouldBe(210);
+		proxy.GetDiamond(10).ShouldBe(1010);
+	}
+
 	#endregion
 
 	#region Private Methods
@@ -206,4 +247,19 @@ private void TestClient(int clientCount, string serverPath, ClientSecurity? clie
 	}
 
 	#endregion
+
+	#region Private Types
+
+	private sealed class Diamond : IDiamond
+	{
+		public int GetDiamond(int input) => input + 1000;
+
+		public int GetLevel1A(int input) => input + 100;
+
+		public int GetLevel1B(int input) => input + 200;
+
+		public int GetRoot(int input) => input;
+	}
+
+	#endregion
 }