Fix undefined method `owners' for NullPreloader:Class

* Fix undefined method `owners' for NullPreloader:Class

Fixing undefined method `owners' for
ActiveRecord::Associations::Preloader::NullPreloader:Class

* Use Ruby 1.9 hash format

Use Ruby 1.9 hash format

#24192

[Rafael Mendonça França + Ladislav Smola]

activerecord/lib/active_record/associations/preloader.rb

@@ -184,6 +184,7 @@ module ActiveRecord
         def self.new(klass, owners, reflection, preload_scope); self; end
         def self.run(preloader); end
         def self.preloaded_records; []; end
+        def self.owners; []; end
       end
 
       # Returns a class containing the logic needed to load preload the data

activerecord/test/cases/associations/has_many_through_associations_test.rb

@@ -11,7 +11,9 @@ require 'models/tagging'
 require 'models/author'
 require 'models/owner'
 require 'models/pet'
+require 'models/pet_treasure'
 require 'models/toy'
+require 'models/treasure'
 require 'models/contract'
 require 'models/company'
 require 'models/developer'
@@ -1082,6 +1084,18 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     assert_equal [], person.posts
   end
 
+  def test_preloading_empty_through_with_polymorphic_source_association
+    owner = Owner.create!(name: "Rainbow Unicat")
+    pet = Pet.create!(owner: owner)
+    person = Person.create!(first_name: "Gaga")
+    treasure = Treasure.create!(looter: person)
+    non_looted_treasure = Treasure.create!()
+    PetTreasure.create!(pet: pet, treasure: treasure, rainbow_color: "Ultra violet indigo")
+    PetTreasure.create!(pet: pet, treasure: non_looted_treasure, rainbow_color: "Ultra violet indigo")
+
+    assert_equal [person], Owner.where(name: "Rainbow Unicat").includes(pets: :persons).first.persons.to_a
+  end
+
   def test_explicitly_joining_join_table
     assert_equal owners(:blackbeard).toys, owners(:blackbeard).toys.with_pet
   end

activerecord/test/models/owner.rb

@@ -1,7 +1,8 @@
 class Owner < ActiveRecord::Base
   self.primary_key = :owner_id
   has_many :pets, -> { order 'pets.name desc' }
-  has_many :toys, :through => :pets
+  has_many :toys, through: :pets
+  has_many :persons, through: :pets
 
   belongs_to :last_pet, class_name: 'Pet'
   scope :including_last_pet, -> {

activerecord/test/models/pet.rb

@@ -4,6 +4,9 @@ class Pet < ActiveRecord::Base
   self.primary_key = :pet_id
   belongs_to :owner, :touch => true
   has_many :toys
+  has_many :pet_treasures
+  has_many :treasures, through: :pet_treasures
+  has_many :persons, through: :treasures, source: :looter, source_type: 'Person'
 
   class << self
     attr_accessor :after_destroy_output

activerecord/test/models/pet_treasure.rb

@@ -0,0 +1,6 @@
+class PetTreasure < ActiveRecord::Base
+  self.table_name = "pets_treasures"
+
+  belongs_to :pet
+  belongs_to :treasure
+end

activerecord/test/schema/schema.rb

@@ -614,6 +614,12 @@ ActiveRecord::Schema.define do
     end
   end
 
+  create_table :pets_treasures, force: true do |t|
+    t.column :treasure_id, :integer
+    t.column :pet_id, :integer
+    t.column :rainbow_color, :string
+  end
+
   create_table :pirates, force: true do |t|
     t.column :catchphrase, :string
     t.column :parrot_id, :integer