HttpApi doesn't write empty strings

[GerardSmit]

Not sure if I need to make an issue about HttpApi here. #167 is for feedback, however there are 47 people subscribed to the thread which I don't want to notify. Also https://github.com/aspnet/AspLabs has issues disabled which brings me here.

What version of gRPC and what language are you using?

Grpc.AspNetCore						: 2.32.0
Microsoft.AspNetCore.Grpc.HttpApi	: 0.1.0-alpha.20580.2
Microsoft.AspNetCore.Grpc.Swagger	: 0.1.0-alpha.20580.2

What operating system (Linux, Windows,...) and version?

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19042
 OS Platform: Windows
 RID:         win10-x64

What runtime / compiler are you using (e.g. .NET Core SDK version dotnet --info)

.NET SDK (reflecting any global.json):
 Version:   5.0.100
 Commit:    5044b93829

Host (useful for support):
  Version: 5.0.0
  Commit:  cf258a14b7

What did you do?

I've created a gRPC service that returns the following message:

message GuildUser {
    uint64 id = 1;
    string username = 2;
    string discriminator = 3;
    string nickname = 4;
}

After that I've followed https://docs.microsoft.com/en-us/aspnet/core/grpc/httpapi to create a REST API for the service.

What did you expect to see?

Messages with all their fields.

What did you see instead?

Messages with missing fields.

When an empty string is being written, the field is omitted. On the client-side this would cause the value to be null (or undefined in JavaScript), while it should be an empty string.

Screenshot:

[JamesNK]

Empty string is the default value and default values aren't written by Protobuf serializer or is equivilent JSON serializer. You could try making the property type StringValue.

[GerardSmit]

I see, with StringValue I get the expected result.

default values aren't written by Protobuf serializer or is equivilent JSON serializer

Is this the expected behavior for HttpApi? For typed languages (e.g. C#) this doesn't matter since it's using the default value, but for untyped languages (e.g. JavaScript) this means you'll always get undefined, even with numbers.

A workaround would be to change everything to XValue (e.g. int32 to Int32Value) but I'm not sure if that's the most prettiest solution...

[JamesNK]

Is this the expected behavior for HttpApi

I think so but I haven't compared against grpc-gateway to see what it does (HttpApi is based on it).

[JamesNK]

Closing as answered

[GerardSmit]

I thought you wanted to compare against grpc-gateway to see what it did, excuse me for not answering.

grpc-gateway had an open issue about this as well. In v2 they emit default values.

References:
Issue: grpc-ecosystem/grpc-gateway#233
V2 release planning: grpc-ecosystem/grpc-gateway#1223
PR enabling default values: grpc-ecosystem/grpc-gateway#1377.

---

If HttpApi doesn't want to omit default values by default: currently the UnaryServerCallHandler always uses the default formatter (JsonFormatter.Default):

https://github.com/aspnet/AspLabs/blob/07ebdf55d59814a85ec0efaded572e88729cc04c/src/GrpcHttpApi/src/Microsoft.AspNetCore.Grpc.HttpApi/UnaryServerCallHandler.cs#L278

If it were possible to provide your own JsonFormatter, then the settings FormatDefaultValues could be enabled:

services.AddGrpcSwagger(config =>
{
	config.JsonFormatter = new JsonFormatter(new JsonFormatter.Settings(true));
});

According to the docs the default values should then be written: https://developers.google.com/protocol-buffers/docs/reference/csharp/class/google/protobuf/json-formatter/settings

[JamesNK]

It looks like emitting default values is on by default in grpc-gateway V2. I didn't know it had changed.

In that case it should be turned on in HttpApi.

[JamesNK]

Done. I'm not sure when the package on NuGet will next be updated but you should be able to get the changes by adding this feed and using the latest version: https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet6/nuget/v3/index.json

[GerardSmit]

Alright, thanks! 😄

[ghost]

how to turn it on to not emit the default value in json response? i am currently use go and find no way to do this