gistfile1.rb

require 'active_record'
require 'logger'

# Print out what version we're running
puts "Active Record #{ActiveRecord::VERSION::STRING}"

ActiveRecord::Base.logger = Logger.new(STDOUT)

# Connect to an in-memory sqlite3 database
ActiveRecord::Base.establish_connection( :adapter  => 'sqlite3',
                                         :database => ':memory:' )

# Create the minimal database schema necessary to reproduce the bug
ActiveRecord::Schema.define do
  create_table "users" do |t|
  end

  create_table "contacts" do |t|
  end

  create_table "contact_aliases" do |t|
    t.integer :user_id
    t.integer :contact_id
  end
end

class User < ActiveRecord::Base
  has_many :contact_aliases
end

class ContactAlias < ActiveRecord::Base
  belongs_to :user
  belongs_to :contact
end

class Contact < ActiveRecord::Base
  has_many :contact_aliases
  has_one :contact_alias

  # I want this scope to eager load contact_aliases that are owned by the given
  # user.
  scope :as_user, -> user {
    joins(%(LEFT OUTER JOIN "contact_aliases" on "contact_aliases"."contact_id" = "contacts"."id" AND "contact_aliases"."user_id" = '#{user.id}'))
  }
end

user          = User.create
contact       = Contact.create
contact_alias = ContactAlias.create user: user, contact: contact

contact = Contact.includes.as_user(user).first

# This should be eager loaded but currently triggers another query.
contact.contact_alias