repro.rb

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: 'postgresql', database: 'test123')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :movies, force: true do |t|
  end

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

  create_table :shows, force: true do |t|
    t.references :language
    t.references :movie
  end

  create_table :schedules, force: true do |t|
    t.references :show
    t.datetime :schedule_time
    t.references :theatre
  end
end

class Movie < ActiveRecord::Base
  has_many :schedules, through: :shows
  has_many :shows
end

class Schedule < ActiveRecord::Base
  belongs_to :show
  belongs_to :theatre
end

class Show < ActiveRecord::Base
  has_many :schedules

  belongs_to :language
  belongs_to :movie
end

class Language < ActiveRecord::Base
  has_many :shows
end

class BugTest < Minitest::Test
  def test_nested_includes
    movie = Movie.create!

    schedules = Movie.first.schedules.eager_load(show: [:language]).to_a

    # HINT:  Perhaps you meant to reference the table alias "shows_schedules".
  end
end