Package imported but not used

[fische]

Hi!
When a service method uses a type T from an imported proto and does not define the option google.api.http to get exposed by the grpc-gateway, protoc-gen-grpc-gateway tries anyway to import the package, where the type T is defined, and therefore I get the following message when I try to compile the gateway:

./main.pb.gw.go:17: imported and not used: "github.com/golang/protobuf/ptypes/empty"

Here's an example of such service:

syntax = "proto3";

import "google/api/annotations.proto";
import "github.com/golang/protobuf/ptypes/empty/empty.proto";

package tester;

service Service {
  rpc MethodExposed (Message) returns (Message) {
    option (google.api.http) = {
      post: "/exposed"
      body: "*"
    };
  }

  rpc MethodImportingEmpty (google.protobuf.Empty) returns (google.protobuf.Empty) {}
}

message Message {
	string value = 1;
}

[tmc]

@fische thanks for the report -- could you put an example into a failing test case?

[fische]

The example I've put above is a failing test case.
It tries to import the empty.proto which defines the message type Empty. However the method of Service, that uses this message type, does not define the option google.api.http, so that it does not get exposed by the grpc-gateway. During the code generation of the gateway, protoc-gen-grpc-gateway will add anyway the import of the empty package to the pb.gw.go, even if it is not used.

Edit: I have quickly checked this issue with a mate. It seems that it appeared between 5e41241 and 199c40a.

[tmc]

@fische I mean can you add a test case that demonstrates the failure (perhaps to #312)