`touch` leaves model with optimistic locking in changed state

[koppen]

TLDR: Using touch in Rails 5.0.0.1 leaves the ActiveRecord models with lock_version in a changed state:

Steps to reproduce

Set up a model with optimistic locking in a blank Rails application:

$ rails generate model Hammer lock_version
$ rails db:migrate
$ rails console

Create a new record and touch it:

2.3.0 :001 > mc = Hammer.create!
 => #<Hammer id: 1, lock_version: 0, created_at: "2016-09-14 14:06:12", updated_at: "2016-09-14 14:06:12">
2.3.0 :002 > mc.lock_version
 => 0
2.3.0 :003 > mc.touch
 => true

Actual behaviour

2.3.0 :004 > mc.changed?
 => true
2.3.0 :005 > mc.changes
 => {"lock_version"=>[0, "1"]}

Expected behaviour

2.3.0 :004 > mc.changed?
 => false
2.3.0 :005 > mc.changes
 => {}

A complete reproduction script can be found below.

System configuration

$ rails -v
Rails 5.0.0.1

$ ruby -v
ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-darwin15]

Reproduction script

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 "rails", github: "rails/rails"
  gem "sqlite3"
end

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 :hammers, force: true do |t|
    t.integer :lock_version
    t.timestamps
  end
end

class Hammer < ActiveRecord::Base
end

class TouchTest < Minitest::Test
  def test_touching_stuff
    hammer = Hammer.create!

    hammer.touch

    assert_equal 1, hammer.lock_version
    refute hammer.changed?, "Changes should be cleared: #{hammer.changes.inspect}"
  end
end

[alexcameron89]

The executable script passes on 4.2.7 and fails on master. It looks like issue occurred from 5e8d96c.

@koppen's PR fixes the behavior. 👍