reciprocal_HABTM_with_STI.rb

# This file describe a bug found in Active Record while migrating an old
# application from rails 3.2 to rails 6.0.1.
#
# with active record > 6.0.0rc2, the line below raises the following error:
# ActiveModel::UnknownAttributeError: unknown attribute 'shop' for
# Shop::HABTM_Contents.
#
# The bug was introduced by the following commit: 
# https://github.com/rails/rails/commit/3b04715cda
# (https://github.com/rails/rails/pull/36776)
# The commit aimed at fixing https://github.com/rails/rails/issues/36742

require "bundler/inline"

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

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

  # The test pass with activerecord <= 6.0.0rc2 and fails >= 6.0.0
  gem 'activerecord', '6.0.0'
  gem 'sqlite3', '~> 1.4'
end

require 'active_record'

require 'minitest/autorun'
require 'logger'

ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :contents, force: true do |t|
    t.string :type
  end
  create_table :contents_shops, force: true do |t|
    t.integer :shop_id
    t.integer :content_id
  end
end

class Content < ActiveRecord::Base
  has_and_belongs_to_many :shops,
    foreign_key: :content_id,
    association_foreign_key: :shop_id,
    join_table: :contents_shops
end

class Shop < Content
  # Uncomment this re-declaration to make the test pass on ActiveRecord > 6.0.0.rc2
  # has_and_belongs_to_many :shops,
  #   foreign_key: :content_id,
  #   association_foreign_key: :shop_id,
  #   join_table: :contents_shops
  has_and_belongs_to_many :contents,
      foreign_key: :shop_id,
      association_foreign_key: :content_id,
      join_table: :contents_shops
end

class BugTest < Minitest::Test
  def test_association
    Shop.create!.shops = [Shop.create, Shop.create]
  end
end