protoc-gen-swagger missing definition issue

[warmans]

protoc-gen-swagger appears to have an issue where an entity is omitted from the definitions when a field is specified for the body rather than *.

Reproduce with the following code:

example.proto

syntax = "proto3";

package example;

import "google/api/annotations.proto";

service ExampleService {
    rpc DoSomething(DoSomethingRequest) returns (DoSomethingResponse) {
        option (google.api.http) = {
            post: "/do-something/{id}"
            body: "data"
        };
    }
}

message ExtraData {
    string foo = 1;
}

message DoSomethingRequest {
    string id = 1;
    ExtraData data = 2;
}

message DoSomethingResponse {
    string bar = 1;
}

Generate the code:

protoc -I. -I$GOPATH/src -I$GOPATH/src/github.com/grpc-ecosystem/grpc-gateway/third_party/googleapis --go_out=plugins=grpc:. --swagger_out=logtostderr=true:. ./example.proto

Results in:

{
  "swagger": "2.0",
  "info": {
    "title": "example.proto",
    "version": "version not set"
  },
  "schemes": [
    "http",
    "https"
  ],
  "consumes": [
    "application/json"
  ],
  "produces": [
    "application/json"
  ],
  "paths": {
    "/do-something/{id}": {
      "post": {
        "operationId": "DoSomething",
        "responses": {
          "200": {
            "description": "",
            "schema": {
              "$ref": "#/definitions/exampleDoSomethingResponse"
            }
          }
        },
        "parameters": [
          {
            "name": "id",
            "in": "path",
            "required": true,
            "type": "string"
          },
          {
            "name": "body",
            "in": "body",
            "required": true,
            "schema": {
              "$ref": "#/definitions/exampleExtraData"
            }
          }
        ],
        "tags": [
          "ExampleService"
        ]
      }
    }
  },
  "definitions": {
    "exampleDoSomethingResponse": {
      "type": "object",
      "properties": {
        "bar": {
          "type": "string"
        }
      }
    }
  }
}

Note that there is a $ref to #/definitions/exampleExtraData but it does not appear in the definitions.

edit: actually I don't know if the body attribute is relevant.