s-mage · June 27, 2017 17:40
diff --git a/no_previous_changes_on_autosave.rb b/no_previous_changes_on_autosave.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'
  gem 'activerecord', '5.1'
  gem 'pry'
  gem 'sqlite3'
 end

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

 # 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 :parents, force: true do |t|
    t.string :name
  end

  create_table :children, force: true do |t|
    t.string :name
    t.integer :parent_id
  end
 end

 class Parent < ActiveRecord::Base
  has_one :child, :inverse_of => :parent, :autosave => true

  @@foo = 0

  after_validation :foo

  def foo
    @@foo += 1
  end
 end

 class Child < ActiveRecord::Base
  belongs_to :parent, :inverse_of => :child, :autosave => true
 end

 class BugTest < Minitest::Test
  def setup
    @parent = Parent.create!(name: 'P')

    @child = Child.new(name: 'Hi!')
    @child.parent = @parent
    @child.save!
  end


  # The case below fail, because
  # https://github.com/rails/rails/blob/v4.2.7.1/activerecord/lib/active_record/autosave_association.rb#L441
  # there `record.changed_for_autosave?` is true through it's not changed.
  # It's true because `child` is changed.
  # Therefore child is being saved in the wrong place, then saved one more time
  # where it should be saved and as a result we see that `child.previous_changes` is {}
  def test_prev_changes
    assert_equal [nil, "Hi!"], @child.previous_changes[:name]
  end

  # This case pass because of another thing
  # https://github.com/rails/rails/blob/v4.2.7.1/activerecord/lib/active_record/autosave_association.rb#L432
  # association there is nil. But if I put debugger there and eval `parent` manually it would work
  # as the third case.
  def test_prev_changes_pass
    child2 = Child.create!(name: '2', parent_id: @parent.id)
    assert_equal [nil, "2"], child2.previous_changes[:name]
  end

  # This also fail for the same reason as test_prev_changes
  def test_prev_changes2
    child3 = Child.create!(name: '3', parent: @parent)
    assert_equal [nil, "3"], child3.previous_changes[:name]
  end

  # This case fails because of similar behaviour in different place
  def test_after_validation
    @parent.class.class_variable_set('@@foo', 0)
    @parent.update!(name: 'pp')
    assert_equal 1, @parent.class.class_variable_get('@@foo')
  end
 end
	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'
	gem 'activerecord', '5.1'
	gem 'pry'
	gem 'sqlite3'
	end

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

	# 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 :parents, force: true do \|t\|
	t.string :name
	end

	create_table :children, force: true do \|t\|
	t.string :name
	t.integer :parent_id
	end
	end

	class Parent < ActiveRecord::Base
	has_one :child, :inverse_of => :parent, :autosave => true

	@@foo = 0

	after_validation :foo

	def foo
	@@foo += 1
	end
	end

	class Child < ActiveRecord::Base
	belongs_to :parent, :inverse_of => :child, :autosave => true
	end

	class BugTest < Minitest::Test
	def setup
	@parent = Parent.create!(name: 'P')

	@child = Child.new(name: 'Hi!')
	@child.parent = @parent
	@child.save!
	end


	# The case below fail, because
	# https://github.com/rails/rails/blob/v4.2.7.1/activerecord/lib/active_record/autosave_association.rb#L441
	# there `record.changed_for_autosave?` is true through it's not changed.
	# It's true because `child` is changed.
	# Therefore child is being saved in the wrong place, then saved one more time
	# where it should be saved and as a result we see that `child.previous_changes` is {}
	def test_prev_changes
	assert_equal [nil, "Hi!"], @child.previous_changes[:name]
	end

	# This case pass because of another thing
	# https://github.com/rails/rails/blob/v4.2.7.1/activerecord/lib/active_record/autosave_association.rb#L432
	# association there is nil. But if I put debugger there and eval `parent` manually it would work
	# as the third case.
	def test_prev_changes_pass
	child2 = Child.create!(name: '2', parent_id: @parent.id)
	assert_equal [nil, "2"], child2.previous_changes[:name]
	end

	# This also fail for the same reason as test_prev_changes
	def test_prev_changes2
	child3 = Child.create!(name: '3', parent: @parent)
	assert_equal [nil, "3"], child3.previous_changes[:name]
	end

	# This case fails because of similar behaviour in different place
	def test_after_validation
	@parent.class.class_variable_set('@@foo', 0)
	@parent.update!(name: 'pp')
	assert_equal 1, @parent.class.class_variable_get('@@foo')
	end
	end