rails_eager_load_assoication_with_joins

unless File.exist?('Gemfile')
  File.write('Gemfile', <<-GEMFILE)
    source 'https://rubygems.org'
    gem 'rails', github: 'rails/rails'
    gem 'arel', github: 'rails/arel'
    gem 'rack', github: 'rack/rack'
    gem 'i18n', github: 'svenfuchs/i18n'
    gem 'sqlite3'
  GEMFILE

  system 'bundle'
end

require 'bundler'
Bundler.setup(:default)

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 :posts do |t|
  end

  create_table :comments do |t|
    t.integer :post_id
    t.timestamps
  end
end

class Post < ActiveRecord::Base
  has_many :comments
  has_one :most_recent_comment, -> { most_recent }, class_name: 'Comment'
  has_many :most_recent_comments, -> { most_recent }, class_name: 'Comment'
end

class Comment < ActiveRecord::Base
  belongs_to :post
  scope :most_recent, -> {
    joins(<<-SQL).
      LEFT JOIN comments mrc ON mrc.post_id = comments.post_id
                AND mrc.updated_at > comments.updated_at
    SQL
    where('mrc.id IS NULL')
  }
end

class BugTest < Minitest::Test
  def test_association_eager_load_with_joins
    post = Post.create!
    comment = post.comments.create
    assert_equal comment, post.most_recent_comment
    assert_equal comment, post.most_recent_comments.first

    posts = Post.eager_load(:most_recent_comment)
    assert_equal comment, posts.first.most_recent_comment

    posts = Post.eager_load(:most_recent_comments)
    assert_equal comment, posts.first.most_recent_comments.first
  end
end