ransack_has_one_though_join_dup.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', '5.1.2'
  gem 'sqlite3'
  gem 'ransack', require: false
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)
require 'ransack'

ActiveRecord::Schema.define do
  create_table :a_ancestors, force: true do |t|
  end

  create_table :b_ancestors, force: true do |t|
  end

  create_table :c_ancestors, force: true do |t|
  end

  create_table :parents, force: true do |t|
    t.integer :a_ancestor_id
    t.integer :b_ancestor_id
    t.integer :c_ancestor_id
  end

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

class Children < ActiveRecord::Base
  belongs_to :parent
  has_one :a_ancestor, through: :parent
  has_one :b_ancestor, through: :parent
  has_one :c_ancestor, through: :parent
end

class Parent < ActiveRecord::Base
  belongs_to :a_ancestor
  belongs_to :b_ancestor
  belongs_to :c_ancestor
end

class AAncestor < ActiveRecord::Base; end
class BAncestor < ActiveRecord::Base; end
class CAncestor < ActiveRecord::Base; end

class BugTest < Minitest::Test
  def setup
    c = Children.create
    p = c.create_parent
    p.create_a_ancestor
    p.create_b_ancestor
    p.create_c_ancestor
  end

  def test_duplicate_joins
    puts sql = Children.ransack(
      a_ancestor_id_eq: 1,
      b_ancestor_id_eq: 1,
      c_ancestor_id_eq: 1,
    ).result.to_sql
    assert_equal 1, sql.scan('LEFT OUTER JOIN "parents"').count
  end
end