Can I use the same model or enum for emitting both openapi and protobuf?

[flappyBug]

Hi, there. I'm new to typespec and I'd like to use typespec for defining messaging protos for my project. I'm using restful api for message between my frontend and my api server, and protobuf for my api server and other microservices.

I'm wondering if I can reuse models and enums to emitting different representations for openapi and protobuf. For example:

enum TradeDirection {
    @Protobuf.field(0)
    @Restful.field('buy')
    BUY;
    @Protobuf.field(1)
    @Restful.field('sell')
    SELL;
}

model Task {
    @Protobuf.field(1)
    direction: TradeDirection;
}

namespace HTTP {
    interface Service {
        createTask(Task) 
    }
}

namespace Protobuf {
    model TaskWithUserID extends Task {
        @Protobuf.field(2) userId: string;
    }
    interface Service {
        createTask(TaskWithUserID) 
    }
}

[timotheeguerin]

you can definitely do that, TypeSpec was designed with this scenario in mind. You do have to be mindful of course of how certain protocol might require certain structure(specially around operations) so you don't affect others but otherwise it should definitely work.

We have this example here showcasing multiple emitters https://typespec.io/multi-protocol

[flappyBug]

Thanks for the link. A more complex example can be helpful. For example, Can I have the same enum that serializes to number in profobuf, and serializes to string in openapi. Can I extends the base model for the specific proto.

[BenjaminTitmusGMSL]

I have a specific question related to this. If I want to use the @statusCode decorator on a model then this doesn't work with @typespec/protobuf unless I am using it wrong:

model Response {
  @statusCode _: 200;
}

This results in an error that I haven't specified a field for this. But I don't really want to because really the status code should be a decorator on the model, not a field within the model. In any case adding a @field decorator doesn't work because I can't give a single value for a field I need to give a type. I can do the following if I have a range:

model Response {
  @statusCode
  @minValue(200)
  @maxValue(201)
  @field(1)
  code: int32;
}

Even in this case it will still emit the code field which I don't want.