inverse_of regression in 4.2

test_case.rb

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  # NOTE: tests pass on 4.1.x, fail on 4.2
  gem 'activerecord', '4.2.4'
  gem 'sqlite3'
end

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

# 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 :users, force: true do |t|
    t.integer :customer_id
    t.string :name
    t.string :role
  end

  create_table :customers, force: true do |t|
    t.string :name
  end

  create_table :programs, force: true do |t|
    t.integer :customer_id
    t.string :name
  end
end

class User < ActiveRecord::Base
  belongs_to :owned_customer, class_name: "Customer", inverse_of: :owner, foreign_key: :customer_id
  has_many :owned_programs, through: :owned_customer, source: :programs, inverse_of: :owner, class_name: 'Program'
end

class Customer < ActiveRecord::Base
  has_one :owner, -> { where(:role => 'owner') }, class_name: "User", inverse_of: :owned_customer, dependent: :destroy
  has_many :programs, inverse_of: :customer, dependent: :restrict_with_exception
end

class Program < ActiveRecord::Base
  belongs_to :customer, inverse_of: :programs
  has_one :owner, through: :customer, inverse_of: :owned_programs#, class_name: 'User'
end

class BugTest < Minitest::Test
  def test_inverses
    assert Program.reflect_on_association(:owner).inverse_of.present?
  end

  def test_association_stuff
    customer = Customer.create!(name: 'Nobody')
    program = Program.create!(name: 'Ed Norton Utilities', customer: customer)
    user = User.create!(name: 'Gorbypuff', role: 'owner', owned_customer: customer)

    new_program = Program.last
    assert new_program.customer.present?
    assert new_program.owner.present?
    new_program.name = 'foo'
    assert new_program.save
  end
end