has_many_through_ordering.rb

unless File.exist?('Gemfile')
  File.write('Gemfile', <<-GEMFILE)
    source 'https://rubygems.org'
    gem 'rails', github: 'rails/rails'
    gem 'arel', github: 'rails/arel'
    gem 'sqlite3'
  GEMFILE

  system 'bundle'
end

require 'bundler'
Bundler.setup(:default)

require 'active_record'
require 'minitest/autorun'
require 'logger'

# Ensure backward compatibility with Minitest 4
Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)

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

# Schema
ActiveRecord::Schema.define do
  ActiveRecord::Base.connection.create_table(:articles)

  ActiveRecord::Base.connection.create_table(:by_lines) do |t|
    t.integer :article_id
    t.integer :author_id
    t.integer :position
  end

  ActiveRecord::Base.connection.create_table(:authors)
end

# Models
class Article < ActiveRecord::Base
  has_many :by_lines, -> { order(:position) }
  has_many :authors, through: :by_lines
end

class ByLine < ActiveRecord::Base
  belongs_to :author
  belongs_to :article
end

class Author < ActiveRecord::Base

end

class BugTest < Minitest::Test

  def setup
    Article.delete_all
    ByLine.delete_all
    Author.delete_all

    @article1 = Article.create!
    @article2 = Article.create!

    @author1 = Author.create!
    @author2 = Author.create!

    @article1.by_lines.create!(author: @author1, position: 1)
    @article1.by_lines.create!(author: @author2, position: 2)
    @article2.by_lines.create!(author: @author2, position: 1)
    @article2.by_lines.create!(author: @author1, position: 2)
  end

  # Just make sure it works as expected with lazy loading
  def test_lazy_loading
    @article1.reload
    @article2.reload

    assert_equal([@author1, @author2], @article1.authors)
    assert_equal([@author2, @author1], @article2.authors)
  end

  def test_eager_load
    loaded_article1 = Article.where(id: @article1.id).includes(:authors).first!
    loaded_article2 = Article.where(id: @article2.id).includes(:authors).first!
    
    assert_equal([@author1, @author2], loaded_article1.authors)
    assert_equal([@author2, @author1], loaded_article2.authors)
  end
end