Poor error message when using message in path parameter

[th-m]

📚 Documentation

--grpc-gateway_out: aggregate type TYPE_MESSAGE in parameter of ScheduleAPI.BookAppointment: LocationID

rpc looks like this

 rpc BookAppointment(schedule.ScheduleRequest) returns (schedule.BookAppointmentResponse) {
    option (google.api.http) = {
      post: "/schedule/v2/{LocationID}/bookings/schedule-links"
    };
  }

import "protorepo/messages/shared/uuid.proto";

message ScheduleRequest {
  shared.UUID LocationID = 1;
  google.protobuf.Timestamp DateTime = 2;
  google.protobuf.Duration Duration = 3;
 ...
}

Given the example rpc and message I get the aforementioned error. I am unable to find any documentation on how to resolve this or what it means.

[johanbrandhorst]

I think the issue is the use of the type shared.UUID in a path parameter. I don't think we support this. The error message definitely needs improving, but I expect changing LocationID to string should fix your issue.

[gunadhya]

Hi @johanbrandhorst, I'm new to this project and I'd like to work on this issue. I think the error is framed on this line

grpc-gateway/internal/descriptor/services.go

Line 251 in 26104fd

return Parameter{}, fmt.Errorf("aggregate type %s in parameter of %s.%s: %s", target.Type, meth.Service.GetName(), meth.GetName(), path)

Could you help me figure out a better format?

[johanbrandhorst]

Hi @gunadhya, yes that seems like the place. I think for users that encounter this error we should make it clear that they can't use that protobuf type for a path parameter, and also maybe suggest a fix? How about

fmt.Errorf("%s.%s: %s is a protobuf message type. Protobuf message types cannot be used as path parameters, use a scalar value type (such as string) instead". meth.Service.GetName(), meth.GetName(), path)