Add support for HttpRule types to gRPC JSON transcoding (dotnet#48194)

src/Grpc/JsonTranscoding/src/Shared/ServiceDescriptorHelpers.cs

@@ -324,10 +324,27 @@ public static void SetValue(IMessage message, FieldDescriptor field, object? val
         }
     }
 
+    // Transcoding assumes that the app is referencing Google.Api.CommonProtos and HttpRule is from that assembly.
+    // However, it's possible the app has compiled http.proto with Grpc.Tools, so the extension value is HttpRule from a different assembly.
+    // This custom extension uses the HttpRule field number but has a return type of object.
+    // The method always returns the extension value, and the calling code can convert it to the expected type.
+    // See https://github.com/protocolbuffers/protobuf/issues/9626 for more details.
+    private static readonly Extension<MethodOptions, object> UntypedHttpExtension =
+        new Extension<MethodOptions, object>(AnnotationsExtensions.Http.FieldNumber, codec: null);
+
     public static bool TryGetHttpRule(MethodDescriptor methodDescriptor, [NotNullWhen(true)] out HttpRule? httpRule)
     {
         var options = methodDescriptor.GetOptions();
-        httpRule = options?.GetExtension(AnnotationsExtensions.Http);
+
+        // The untyped extension always returns the extension value. If the type is already the expected HttpRule then use it directly.
+        // A different message indicates a custom HttpRule was used. Convert the message to bytes and reparse it to the known HttpRule type.
+        var extensionValue = options?.GetExtension(UntypedHttpExtension);
+        httpRule = extensionValue switch
+        {
+            HttpRule rule => rule,
+            IMessage message => HttpRule.Parser.ParseFrom(message.ToByteArray()),
+            _ => null
+        };
 
         return httpRule != null;
     }

src/Grpc/JsonTranscoding/test/Microsoft.AspNetCore.Grpc.JsonTranscoding.Tests/Microsoft.AspNetCore.Grpc.JsonTranscoding.Tests.csproj

@@ -1,15 +1,19 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>$(DefaultNetCoreTargetFramework)</TargetFramework>
     <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>
     <Protobuf Include="Proto\httpbody.proto" GrpcServices="Both" />
-    <Protobuf Include="Proto\Issue047349\message.proto" GrpcServices="Both" />
     <Protobuf Include="Proto\transcoding.proto" GrpcServices="Both" />
+
     <Protobuf Include="Proto\Issue045270\hello.proto" GrpcServices="Both" />
     <Protobuf Include="Proto\Issue045270\country.proto" GrpcServices="Both" />
+    <Protobuf Include="Proto\Issue047349\message.proto" GrpcServices="Both" />    
+    <Protobuf Include="Proto\Issue048192\hello.proto" GrpcServices="Both" />
+    <Protobuf Include="Proto\Issue048192\customhttp.proto" GrpcServices="Both" />
+    <Protobuf Include="Proto\Issue048192\customannotations.proto" GrpcServices="Both" />
 
     <Compile Include="..\Shared\TestGrpcServiceActivator.cs" Link="Infrastructure\TestGrpcServiceActivator.cs" />
 

src/Grpc/JsonTranscoding/test/Microsoft.AspNetCore.Grpc.JsonTranscoding.Tests/Proto/Issue048192/customannotations.proto

@@ -0,0 +1,35 @@
+// Copyright (c) 2015, Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+// This is a copy of annotations.proto and is used to test loading the HttpRule for a
+// message when the .NET type doesn't match the version in Google.Api.CommonProtos.
+option csharp_namespace = "CustomHttpRule";
+
+package google.api;
+
+import "Proto/Issue048192/customhttp.proto";
+import "google/protobuf/descriptor.proto";
+
+option go_package = "google.golang.org/genproto/googleapis/api/annotations;annotations";
+option java_multiple_files = true;
+option java_outer_classname = "AnnotationsProto";
+option java_package = "com.google.api";
+option objc_class_prefix = "GAPI";
+
+extend google.protobuf.MethodOptions {
+  // See `HttpRule`.
+  HttpRule http = 72295728;
+}