Support mapping request body to map type

[wdec]

Is there a way tomap the message body to a keyed map?
I.e. with a proto definition containing:

    rpc UpdateConfig (ServiceConfig) returns (OpResult) {
        option (google.api.http) = {
			post: "/v1/robotctl/services/configure"
			body: "config"
		};
    }

message ServiceConfig {
    ServicesReq services            = 1;
    map<string, string> config                   = 2;
}

The idea being that the body of the received message would map to a key in the, eg map<config, body_of_message>

Currently on compiling for grpc-gateway, the following error is thrown - which is odd given that there is no repeated element:

--grpc-gateway_out: repeated field not allowed in field path: config in config

[johanbrandhorst]

Yeah I don't think this is possible, the proto3 map is just syntactic sugar for:

message map {
    string key = 1;
    string value = 2;
}

message ServiceConfig {
    repeated map config = 1;
}

So that's why you get this cryptic error message. I think technically there's no reason this couldn't work, but clearly it's not currently supported by the gateway. What can I do to help you get a pull request to implement this in?

[wdec]

Sounds like a nice feature I could add. I'll get looking into it.

[wora]

Recently, Google updated the gRPC Transcoding spec, aka google.api.http annotation, to allow repeated field and mapped field as HTTP request/response body. This is to allow third party implementations, such as gRPC Gateway, to provide advanced features that customers may need. Most implementations may not provide such advanced features. Except for backward compatibility, there is no general advantage to use such advanced features. It also creates more work to OpenAPI generator, documentation generator, and other tools. Just FYI.

Disclaim: I am a co-author of gRPC Transcoding spec.

[jwierzba-wish]

Is this still not supported?

[johanbrandhorst]

I don't believe it is. Are you interesting in implementing this?

[momom-i]

@johanbrandhorst Hi, I've contributed to this project's issues couple times and I'm interested in implementing this.
If I can and this is not supported yet, I'd appreciate it if you could give me some advice about it.

[johanbrandhorst]

Thanks for your interest! The thing I like to do first with something like this is to create a failing test. You can try adding an example like the one above to one of our example files or add a test to the generator tests. I went and looked at our code and discovered the allow_repeated_fields_in_body parameter:

grpc-gateway/protoc-gen-grpc-gateway/main.go

Line 29 in 963f1aa

allowRepeatedFieldsInBody = flag.Bool("allow_repeated_fields_in_body", false, "allows to use repeated field in `body` and `response_body` field of `google.api.http` annotation option")

. Maybe just setting this fixes the issue 🤔?

[momom-i]

Ahh, that parameter is exactly what I've been looking for, thank you!