Kaminari Issue #931: #page.size borks for certain AR relations (e.g., ordered by association attributes)

kaminari_issue_931.rb

# IMPORTANT: This bug report is specific to postgresql. Create the test DB with
#
# $ createdb kaminari
#
# before running this test case.

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 "railties", "5.1.4"
  gem "activerecord", "5.1.4"
  gem "pg"
  gem "kaminari-core"
  gem "kaminari-activerecord"
end

require "active_record"
require "minitest/autorun"
require "logger"

require "kaminari/core"
require "kaminari/activerecord"

Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)

ActiveRecord::Base.establish_connection(adapter: "postgresql", database: "kaminari")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts, force: true do |t|
    t.string :title
  end

  create_table :comments, force: true do |t|
    t.integer :post_id
  end
end

class Post < ActiveRecord::Base
  has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :post
end

class BugTest < Minitest::Test
  def test_pagination_stuff
    post = Post.create!(title: 'foo')
    post.comments << Comment.create!

    # PASSES
    assert_equal 1, Post.order('posts.title').page.size
    # PASSES
    assert_equal 1, Comment.left_outer_joins(:post).order('posts.title').page.size
    # RAISES DB ERROR
    assert_equal 1, Comment.includes(:post).order('posts.title').page.size
  end
end