Using a well-known type inside a RPC argument results in weird code generation

[Marcoru97]

Currently we are trying to generate Typescript files out of our proto files to use them in our frontend. We have a gRPC file with the following:

...
    rpc GetApp (google.protobuf.Int32Value) returns (App);
...

This results into the following generated code:

...
  GetApp(request: DeepPartial<number>, metadata?: grpc.Metadata): Promise<App> {
    return this.rpc.unary(
      ServiceGetAppDesc,
      number.fromPartial(request), // <---
      metadata
    );
  }
...

As you can see in the sample above, the generated code calls a function on a primitive js type, which results in an error:

semantic error TS2693: 'number' only refers to a type, but is being used as a value here.

We use these arguments:

  --ts_proto_opt=esModuleInterop=true 
  --ts_proto_opt=env=web 
  --ts_proto_opt=useOptionals=true 
  --ts_proto_opt=oneof=unions 
  --ts_proto_opt=unrecognizedEnum=false 
  --ts_proto_opt=outputClientImpl=grpc-web 
  --ts_proto_opt=fileSuffix=.pb 

[stephenh]

Hm, yeah, so that part of the output comes from:

https://github.com/stephenh/ts-proto/blob/main/src/generate-grpc-web.ts#L64

And we can inputType from:

  const inputType = requestType(ctx, methodDesc);

Which uses methodDesc.inputType (which is normally .package.SomeMessage) to resolve that into an import-able type.

I don't think we have an existing way to detect whether the return type of requestType is a primitive or not, but you could probably make an isPrimitive(ctx, typeName) helper method that uses ctx.typeName to see if typeName is in the map, and if it is, it's a message, and if it's not, it should be a primitive.

I.e. add a condition like:

const usePartial = isPrimitive(ctx, methodDesc.inputType);

And then use that to adjust the contents of partialInputType.

I don't have time to personally flush this out more than that, but hopefully that's enough pointers to get a PR going if you'd like to fix it. Thanks!