Including composed relationships

I want to find out how to handle symmetric relationships with JSON API (and an Ember.js front-end). I have the following models:

class Person < ActiveRecord::Base
  has_many :friended, through: :friender_friendships, class_name: Person
  has_many :friended_by, through: :friended_friendships, source: :friended, class_name: Person
  has_many :friender_friendships, class_name: Friendship, foreign_key: "friender_id"
  has_many :friended_friendships, class_name: Friendship, foreign_key: "friended_id"

  def friendships
    Friendship.where("friender_id = ? OR friended_id = ?", id, id);
  end

end

class Friendship < ActiveRecord::Base
  belongs_to :friender, class_name: Person
  belongs_to :friended, class_name: Person
end

And the current resources:

class PersonResource < JSONAPI::Resource
  attributes :name
  relationship :friender, to: :many, class_name: "Person"
  relationship :friended_by, to: :many, class_name: "Person"
  relationship :friender_friendships, to: :many, class_name: "Friendship"
  relationship :friended_friendships, to: :many, class_name: "Friendship"
  relationship :friendships, to: :many, class_name: "Friendship"
end

class FriendshipResource < JSONAPI::Resource
  has_one :friender
  has_one :friended
  attributes :strength
end

When looking at a person's profile, I would like to show all friendships of that person, whether they are on the "friender" or the "friended" end of the relationship. When I'm fetching the person resource, I pass include=friendships so that all friendships are also returned and I don't need further requests to fetch friendship data.

However, that fails with the following error:

Association named 'friendships' was not found on Person; perhaps you misspelled it?

The reason for this is that jsonapi_resources eventually calls records.includes(relationship) (see here), and since friendships is not a real relationship, ActiveRecord throws an error.

I'm not really sure how to solve this with jsonapi_resources. It might be possible to turn friendships into a "real" hasMany relationship with AR, but I haven't found a way to do that (although it's possible my AR-fu is just lacking).

If not with AR, is there a way to solve this problem with jsonapi_resources? (without making an extra roundtrip to the server). Thank you.

Đọc lib/jsonapi/resource.rb#L533-L541 và các định nghĩa PersonResource và FriendshipResource được nêu trong issue. Theo dõi cách include=friendships đi tới records.includes(relationship), sau đó xác định relationship hoặc đường dẫn inclusion được hỗ trợ nào có thể biểu diễn cả hai đầu của friendship. Hoàn tất khi response của một person bao gồm tất cả friendship trong một request mà không có missing-association error.