has _one :through polymorphic association

has_one_polymorphic_association.rb

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  # Activate the gem you are reporting the issue against.
  gem "activerecord", "6.0.0"
  gem "sqlite3"
end

require "active_record"
require "minitest/autorun"
require "logger"

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do

  create_table :authors, force: true do |t|
  end

  create_table :hardbacks, force: true do |t|
  end

  create_table :paperbacks, force: true do |t|
  end

  create_table :books, force: true do |t|
    t.string :author_id
    t.string :format_type
    t.integer :format_id
  end

  create_table :dust_jackets, force: true do |t|
    t.string :hardback_id
  end
end

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true
end

class Author < ApplicationRecord
  has_one :book
  has_one :hardback, through: :book, source: :format, source_type: "Hardback"
  has_one :dust_jacket, through: :hardback
end

class Book < ApplicationRecord
  #has_one :format, polymorphic: true
  belongs_to :format, polymorphic: true
end

class Paperback < ApplicationRecord; end
class Hardback < ApplicationRecord
  has_one :dust_jacket
end

class DustJacket < ApplicationRecord; end

class AuthorTest < Minitest::Test
  def test_association
    author = Author.create!
    dust_jacket = DustJacket.new
    hardback = Hardback.create!
    hardback.dust_jacket = dust_jacket
    book = Book.new
    book.format = hardback
    book.author_id = author.id
    book.save!

    author.reload
    assert_equal dust_jacket, author.dust_jacket
  end
end

test.log

Finished in 0.029099s, 34.3660 runs/s, 34.3660 assertions/s.

1 runs, 1 assertions, 0 failures, 0 errors, 0 skips