decrement for counter_cache not updated in 4.2.7

issue_test_27169.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 "rails", github: "rails/rails", tag: "v4.2.7.1"
  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 :posts, force: true do |t|
    t.integer :nested_comments_count
    t.integer :un_nested_comments_count
    t.string :title
  end

  create_table :nested_comments, force: true do |t|
    t.integer :post_id
    t.string :title
  end

  create_table :un_nested_comments, force: true do |t|
    t.integer :post_id
    t.string :title
  end
end

class Post < ActiveRecord::Base
  has_many :nested_comments, inverse_of: :post
  has_many :un_nested_comments, inverse_of: :post
  accepts_nested_attributes_for :nested_comments, allow_destroy: true
end

class NestedComment < ActiveRecord::Base
  belongs_to :post, inverse_of: :nested_comments, counter_cache: true
end

class UnNestedComment < ActiveRecord::Base
  belongs_to :post, inverse_of: :un_nested_comments, counter_cache: true
end

class BugTest < Minitest::Test
  def setup
    Post.delete_all
    NestedComment.delete_all
    UnNestedComment.delete_all
  end

  def test_decreases_nested_associations_count_after_destroy
    post = Post.create(
      title: "Test Title", 
      nested_comments_attributes: { 
        0 => { title: ' NestedComment 1' }, 
      },
    )
    
    assert_equal 1, post.nested_comments_count
    assert_equal 1, post.nested_comments.count
    assert_equal 1, NestedComment.count
    assert_equal post.id, NestedComment.first.post.id

    post.nested_comments.first.destroy
    assert_equal 0, post.nested_comments.count
    assert_equal 0, post.nested_comments_count
  end

  def test_decreases_nested_associations_count_after_delete
    post = Post.create(
      title: "Test Title", 
      nested_comments_attributes: { 
        0 => { title: ' NestedComment 1' }, 
      },
    )

    post.nested_comments.last.delete
    assert_equal 0, post.nested_comments.count
    assert_equal 1, post.nested_comments_count
    post.title = "Change Test Title"
    post.save
    assert_equal 0, post.nested_comments_count
  end

  def test_decreases_un_nested_associations_count_after_destroy
    post = Post.create(title: "Test Title") 
    UnNestedComment.create(post: post, title: ' UnNestedComment 1')
    
    assert_equal 1, post.un_nested_comments_count
    assert_equal 1, post.un_nested_comments.count
    assert_equal 1, UnNestedComment.count
    assert_equal post.id, UnNestedComment.first.post.id

    post.un_nested_comments.first.destroy
    assert_equal 0, post.un_nested_comments.count
    assert_equal 0, post.un_nested_comments_count
  end

  def test_decreases_un_nested_associations_count_after_delete
    post = Post.create(title: "Test Title") 
    UnNestedComment.create(post: post, title: ' UnNestedComment 1')

    post.un_nested_comments.last.delete
    assert_equal 0, post.un_nested_comments.count
    assert_equal 1, post.un_nested_comments_count
    post.title = "Change Test Title"
    post.save
    assert_equal 0, post.un_nested_comments_count
  end
end