Fix using gRPC reflection with services that have a base type

src/Grpc.AspNetCore.Server.Reflection/GrpcReflectionServiceExtensions.cs

@@ -21,6 +21,7 @@
 using System.Linq;
 using System.Reflection;
 using Grpc.AspNetCore.Server;
+using Grpc.Core;
 using Grpc.Reflection;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.Extensions.DependencyInjection.Extensions;
@@ -63,10 +64,7 @@ public static IServiceCollection AddGrpcReflection(this IServiceCollection servi
 
                 foreach (var serviceType in serviceTypes)
                 {
-                    var baseType = GetServiceBaseType(serviceType);
-                    var definitionType = baseType?.DeclaringType;
-
-                    var descriptorPropertyInfo = definitionType?.GetProperty("Descriptor", BindingFlags.Public | BindingFlags.Static);
+                    var descriptorPropertyInfo = GetDescriptorProperty(serviceType);
                     if (descriptorPropertyInfo != null)
                     {
                         if (descriptorPropertyInfo.GetValue(null) is Google.Protobuf.Reflection.ServiceDescriptor serviceDescriptor)
@@ -85,6 +83,59 @@ public static IServiceCollection AddGrpcReflection(this IServiceCollection servi
             return services;
         }
 
+        private static PropertyInfo? GetDescriptorProperty(Type serviceType)
+        {
+            // Prefer finding the descriptor property using attribute on the generated service
+            var descriptorPropertyInfo = GetDescriptorPropertyUsingAttribute(serviceType);
+
+            if (descriptorPropertyInfo == null)
+            {
+                // Fallback to searching for descriptor property using known type hierarchy that Grpc.Tools generates
+                descriptorPropertyInfo = GetDescriptorPropertyFallback(serviceType);
+            }
+
+            return descriptorPropertyInfo;
+        }
+
+        private static PropertyInfo? GetDescriptorPropertyUsingAttribute(Type serviceType)
+        {
+            Type? currentServiceType = serviceType;
+            BindServiceMethodAttribute? bindServiceMethod;
+            do
+            {
+                // Search through base types for bind service attribute.
+                bindServiceMethod = currentServiceType.GetCustomAttribute<BindServiceMethodAttribute>();
+                if (bindServiceMethod != null)
+                {
+                    // Descriptor property will be public and static and return ServiceDescriptor.
+                    return bindServiceMethod.BindType.GetProperty(
+                        "Descriptor",
+                        BindingFlags.Public | BindingFlags.Static,
+                        binder: null,
+                        typeof(Google.Protobuf.Reflection.ServiceDescriptor),
+                        Type.EmptyTypes,
+                        Array.Empty<ParameterModifier>());
+                }
+            } while ((currentServiceType = currentServiceType.BaseType) != null);
+
+            return null;
+        }
+
+        private static PropertyInfo? GetDescriptorPropertyFallback(Type serviceType)
+        {
+            // Search for the generated service base class
+            var baseType = GetServiceBaseType(serviceType);
+            var definitionType = baseType?.DeclaringType;
+
+            return definitionType?.GetProperty(
+                "Descriptor",
+                BindingFlags.Public | BindingFlags.Static,
+                binder: null,
+                typeof(Google.Protobuf.Reflection.ServiceDescriptor),
+                Type.EmptyTypes,
+                Array.Empty<ParameterModifier>());
+        }
+
         private static Type? GetServiceBaseType(Type serviceImplementation)
         {
             // TService is an implementation of the gRPC service. It ultimately derives from Foo.TServiceBase base class.

test/Grpc.AspNetCore.Server.Tests/Proto/greet.proto

@@ -26,6 +26,11 @@ service SecondGreeter {
   rpc SayHellos (HelloRequest) returns (stream HelloReply);
 }
 
+service ThirdGreeterWithBaseType {
+  rpc SayHello (HelloRequest) returns (HelloReply);
+  rpc SayHellos (HelloRequest) returns (stream HelloReply);
+}
+
 message HelloRequest {
   string name = 1;
 }

test/Grpc.AspNetCore.Server.Tests/Reflection/ReflectionGrpcServiceActivatorTests.cs

@@ -41,6 +41,56 @@ public class ReflectionGrpcServiceActivatorTests
     {
         [Test]
         public async Task Create_ConfiguredGrpcEndpoint_EndpointReturnedFromReflectionService()
+        {
+            // Arrange and act
+            TestServerStreamWriter<ServerReflectionResponse> writer = await ConfigureReflectionServerAndCallAsync(builder =>
+            {
+                builder.MapGrpcService<GreeterService>();
+            });
+
+            // Assert
+            Assert.AreEqual(1, writer.Responses.Count);
+            Assert.AreEqual(1, writer.Responses[0].ListServicesResponse.Service.Count);
+
+            var serviceResponse = writer.Responses[0].ListServicesResponse.Service[0];
+            Assert.AreEqual("greet.Greeter", serviceResponse.Name);
+        }
+
+        [Test]
+        public async Task Create_ConfiguredGrpcEndpointWithMultipleInheritenceLevel_EndpointReturnedFromReflectionService()
+        {
+            // Arrange and act
+            TestServerStreamWriter<ServerReflectionResponse> writer = await ConfigureReflectionServerAndCallAsync(builder =>
+            {
+                builder.MapGrpcService<InheritGreeterService>();
+            });
+
+            // Assert
+            Assert.AreEqual(1, writer.Responses.Count);
+            Assert.AreEqual(1, writer.Responses[0].ListServicesResponse.Service.Count);
+
+            var serviceResponse = writer.Responses[0].ListServicesResponse.Service[0];
+            Assert.AreEqual("greet.Greeter", serviceResponse.Name);
+        }
+
+        [Test]
+        public async Task Create_ConfiguredGrpcEndpointWithBaseType_EndpointReturnedFromReflectionService()
+        {
+            // Arrange and act
+            TestServerStreamWriter<ServerReflectionResponse> writer = await ConfigureReflectionServerAndCallAsync(builder =>
+            {
+                builder.MapGrpcService<GreeterServiceWithBaseType>();
+            });
+
+            // Assert
+            Assert.AreEqual(1, writer.Responses.Count);
+            Assert.AreEqual(1, writer.Responses[0].ListServicesResponse.Service.Count);
+
+            var serviceResponse = writer.Responses[0].ListServicesResponse.Service[0];
+            Assert.AreEqual("greet.ThirdGreeterWithBaseType", serviceResponse.Name);
+        }
+
+        private static async Task<TestServerStreamWriter<ServerReflectionResponse>> ConfigureReflectionServerAndCallAsync(Action<IEndpointRouteBuilder> action)
         {
             // Arrange
             var endpointRouteBuilder = new TestEndpointRouteBuilder();
@@ -56,7 +106,8 @@ public async Task Create_ConfiguredGrpcEndpoint_EndpointReturnedFromReflectionSe
             var serviceProvider = services.BuildServiceProvider(validateScopes: true);
 
             endpointRouteBuilder.ServiceProvider = serviceProvider;
-            endpointRouteBuilder.MapGrpcService<GreeterService>();
+
+            action(endpointRouteBuilder);
 
             // Act
             var service = serviceProvider.GetRequiredService<ReflectionServiceImpl>();
@@ -73,12 +124,16 @@ public async Task Create_ConfiguredGrpcEndpoint_EndpointReturnedFromReflectionSe
 
             await service.ServerReflectionInfo(reader, writer, context);
 
-            // Assert
-            Assert.AreEqual(1, writer.Responses.Count);
-            Assert.AreEqual(1, writer.Responses[0].ListServicesResponse.Service.Count);
+            return writer;
+        }
+
+        private class InheritGreeterService : GreeterService
+        {
+        }
+
+        private class GreeterServiceWithBaseType : ThirdGreeterWithBaseType.ThirdGreeterWithBaseTypeBase
+        {
 
-            var serviceResponse = writer.Responses[0].ListServicesResponse.Service[0];
-            Assert.AreEqual("greet.Greeter", serviceResponse.Name);
         }
 
         private class GreeterService : Greeter.GreeterBase
@@ -124,3 +179,18 @@ public IApplicationBuilder CreateApplicationBuilder()
         }
     }
 }
+
+namespace Greet
+{
+    public class ThirdGreeterBaseType
+    {
+
+    }
+
+    public static partial class ThirdGreeterWithBaseType
+    {
+        public partial class ThirdGreeterWithBaseTypeBase : ThirdGreeterBaseType
+        {
+        }
+    }
+}