Included relationships of the same class type is broken

[caseyprovost]

Working through implementing includes I have discovered what appears to be a bug. All my other code like this works as expected and the only difference I can find is that the association is the same class as the requested object.

You will not there is no "included" section even though the relationships section clearly reflects the data.

Controller

users = User.includes(:managers, :direct_reports).page(params[:page]).per(params[:per_page])
render jsonapi: users,
             include: ['managers', 'direct_reports'],
             links: pagination_links(users, User)

Serializer

class SerializableUser < JSONAPI::Serializable::Resource
  type 'users'

  belongs_to :role
  belongs_to :parent
  has_many :managers, class 'SerializableUser
  has_many :direct_reports, class 'SerializableUser
end

The response looks nearly correct, except the includes are missing at the end. I have provided a sample below.

{
  "data": [
    {
      "id": "1",
      "type": "users",
      "attributes": {
        "name": "Meghan Wilkinson",
        "email": "mauricio@lang.com",
        "threshold": null
      },
      "relationships": {
        "direct_reports": {
          "links": {
            "self": "http://localhost:3000/v1/users/1/relationships/direct_reports",
            "related": "http://localhost:3000/v1/users"
          },
          "data": []
        },
        "managers": {
          "links": {
            "self": "http://localhost:3000/v1/users/1/relationships/managers",
            "related": "http://localhost:3000/v1/users"
          },
          "data": []
        }
      }
    },
    {
      "id": "2",
      "type": "users",
      "attributes": {
        "name": "Dora Nitzsche",
        "email": "albin.legros@waters.io",
        "threshold": null
      },
      "relationships": {
        "parent": {
          "meta": {
            "included": false
          }
        },
        "role": {
          "meta": {
            "included": false
          }
        },
        "direct_reports": {
          "links": {
            "self": "http://localhost:3000/v1/users/2/relationships/direct_reports",
            "related": "http://localhost:3000/v1/users"
          },
          "data": [
            {
              "type": "users",
              "id": "5"
            }
          ]
        },
        "managers": {
          "links": {
            "self": "http://localhost:3000/v1/users/2/relationships/managers",
            "related": "http://localhost:3000/v1/users"
          },
          "data": [
            {
              "type": "users",
              "id": "4"
            }
          ]
        }
      }
    }
  ],
  "links": {
    "self": "http://localhost/v1/users?page=1&per_page=50",
    "first": "http://localhost/v1/users?page=1&per_page=50",
    "prev": null,
    "next": null,
    "last": "http://localhost/v1/users?page=1&per_page=50"
  },
  "jsonapi": {
    "version": "1.0"
  }
}