cmd/protoc-gen-go-grpc: fix camel-casing of names in generated code

Fix a few points of divergence between the v1 and v2 generators around
when to apply camel-casing to service and method names.

Change-Id: I862f89c0995c540e4862013316d7af772e1ab0d8
Reviewed-on: https://go-review.googlesource.com/c/153658
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>

cmd/protoc-gen-go-grpc/internal_gengogrpc/grpc.go

@@ -150,7 +150,7 @@ func genService(gen *protogen.Plugin, file *protogen.File, g *protogen.Generated
 			continue
 		}
 		g.P("{")
-		g.P("MethodName: ", strconv.Quote(method.GoName), ",")
+		g.P("MethodName: ", strconv.Quote(string(method.Desc.Name())), ",")
 		g.P("Handler: ", handlerNames[i], ",")
 		g.P("},")
 	}
@@ -161,7 +161,7 @@ func genService(gen *protogen.Plugin, file *protogen.File, g *protogen.Generated
 			continue
 		}
 		g.P("{")
-		g.P("StreamName: ", strconv.Quote(method.GoName), ",")
+		g.P("StreamName: ", strconv.Quote(string(method.Desc.Name())), ",")
 		g.P("Handler: ", handlerNames[i], ",")
 		if method.Desc.IsStreamingServer() {
 			g.P("ServerStreams: true,")
@@ -298,7 +298,7 @@ func genServerMethod(gen *protogen.Plugin, file *protogen.File, g *protogen.Gene
 		g.P("if interceptor == nil { return srv.(", service.GoName, "Server).", method.GoName, "(ctx, in) }")
 		g.P("info := &", grpcPackage.Ident("UnaryServerInfo"), "{")
 		g.P("Server: srv,")
-		g.P("FullMethod: ", strconv.Quote(fmt.Sprintf("/%s/%s", service.Desc.FullName(), method.Desc.Name())), ",")
+		g.P("FullMethod: ", strconv.Quote(fmt.Sprintf("/%s/%s", service.Desc.FullName(), method.GoName)), ",")
 		g.P("}")
 		g.P("handler := func(ctx ", contextPackage.Ident("Context"), ", req interface{}) (interface{}, error) {")
 		g.P("return srv.(", service.GoName, "Server).", method.GoName, "(ctx, req.(*", method.InputType.GoIdent, "))")

cmd/protoc-gen-go-grpc/testdata/grpc/grpc_grpc.pb.go

@@ -167,7 +167,7 @@ func _TestService_UnaryCall_Handler(srv interface{}, ctx context.Context, dec fu
 	}
 	info := &grpc.UnaryServerInfo{
 		Server:     srv,
-		FullMethod: "/goproto.protoc.grpc.test_service/unary_call",
+		FullMethod: "/goproto.protoc.grpc.test_service/UnaryCall",
 	}
 	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
 		return srv.(TestServiceServer).UnaryCall(ctx, req.(*Request))
@@ -253,23 +253,23 @@ var _TestService_serviceDesc = grpc.ServiceDesc{
 	HandlerType: (*TestServiceServer)(nil),
 	Methods: []grpc.MethodDesc{
 		{
-			MethodName: "UnaryCall",
+			MethodName: "unary_call",
 			Handler:    _TestService_UnaryCall_Handler,
 		},
 	},
 	Streams: []grpc.StreamDesc{
 		{
-			StreamName:    "DownstreamCall",
+			StreamName:    "downstream_call",
 			Handler:       _TestService_DownstreamCall_Handler,
 			ServerStreams: true,
 		},
 		{
-			StreamName:    "UpstreamCall",
+			StreamName:    "upstream_call",
 			Handler:       _TestService_UpstreamCall_Handler,
 			ClientStreams: true,
 		},
 		{
-			StreamName:    "BidiCall",
+			StreamName:    "bidi_call",
 			Handler:       _TestService_BidiCall_Handler,
 			ServerStreams: true,
 			ClientStreams: true,