Support Values as service return values

[moufmouf]

First of all, thanks a ton for ts-proto. This lib really is a game changer ❤️

I believe I found a bug in the way ts-proto handles "Value" object in services.

Here is a sample service:

service RoomApi {
    rpc readVariable(VariableRequest) returns (google.protobuf.Value);
}

See how readVariable returns directly a google.protobuf.Value ?

When I look at the code generated for the service, I have this:

export const RoomApiService = {
  readVariable: {
    path: "/roomApi.RoomApi/readVariable",
    requestStream: false,
    responseStream: false,
    requestSerialize: (value: VariableRequest) => Buffer.from(VariableRequest.encode(value).finish()),
    requestDeserialize: (value: Buffer) => VariableRequest.decode(value),
    responseSerialize: (value: any | undefined) => Buffer.from(Value.encode(value).finish()),
    responseDeserialize: (value: Buffer) => Value.decode(value),
  },
}

The responseSerialize is typed to "any", but Value.encode expects the value to be a "Value" object.
Same thing, responseDeserialize will return a "Value" object, but the end user probably expects a plain object instead.

As a result, when reading the result of a call to readVariable, the end user needs to manually call Value.unwrap.

The code looks like this:

const value = Value.unwrap(await client.readVariable({ /*...*/ });

Same thing server-side where we need to manually call Value.wrap.

I believe the correct implementation should generate something like:

    responseSerialize: (value: any | undefined) => Buffer.from(Value.encode(Value.wrap(value)).finish()),
    responseDeserialize: (value: Buffer) => Value.unwrap(Value.decode(value)),

What do you think?

Also, the same issue happens with streamed return values. For instance:

service RoomApi {
    rpc listenVariable(VariableRequest) returns (stream google.protobuf.Value);
}

But, the issue does not happen if the Value is part of a message:

message DispatchGlobalEventRequest {
  string name = 1;
  google.protobuf.Value value = 2; // This is correctly serialized/unserialized to "any"
}

Bonus: could it be possible have an option to cast protobuf Value to Typescript unknown (instead of any) for type safety?

[stephenh]

Hi @moufmouf ; yeah, I am not entirely surprised this is an issue.

As you noticed, we have code inside of the main "generate encode/decode" methods to handle value types:

https://github.com/stephenh/ts-proto/blob/main/src/main.ts#L1024

Doesn't seem to be using it:

https://github.com/stephenh/ts-proto/blob/main/src/generate-grpc-js.ts#L91

https://github.com/stephenh/ts-proto/blob/main/src/encode.ts#L7

If you'd like to submit a PR that moves/copy/pastes the Value-related code into the encode/decode handling, that'd be great! Thanks!

[moufmouf]

Hey @stephenh ,

Thanks a lot for this quick response. Thanks to your help, it was easy enough to fix the issue.

PR is here : #951