has_many through obeys order on through association

fixes #10016

activerecord/CHANGELOG.md

 ## Rails 4.0.0 (unreleased) ##
 
+*   `has_many` using `:through` now obeys the order clause mentioned in
+    through association. Fixes #10016.
+
+    *Neeraj Singh*
+
 *   `belongs_to :touch` behavior now touches old association when
     transitioning to new association.
 

activerecord/lib/active_record/associations/association_scope.rb

@@ -101,6 +101,7 @@ def add_constraints(scope)
 
             scope.includes! item.includes_values
             scope.where_values += item.where_values
+            scope.order_values += (item.order_values - scope.order_values)
           end
         end
 

activerecord/test/cases/associations/eager_test.rb

@@ -302,7 +302,7 @@ def test_nested_loading_through_has_one_association_with_conditions_on_nested_as
 
   def test_eager_association_loading_with_belongs_to_and_foreign_keys
     pets = Pet.all.merge!(:includes => :owner).to_a
-    assert_equal 3, pets.length
+    assert_equal 4, pets.length
   end
 
   def test_eager_association_loading_with_belongs_to

activerecord/test/cases/associations/has_many_through_associations_test.rb

@@ -583,7 +583,7 @@ def test_has_many_association_through_a_belongs_to_association
   end
 
   def test_has_many_association_through_a_has_many_association_with_nonstandard_primary_keys
-    assert_equal 1, owners(:blackbeard).toys.count
+    assert_equal 2, owners(:blackbeard).toys.count
   end
 
   def test_find_on_has_many_association_collection_with_include_and_conditions
@@ -882,6 +882,12 @@ def test_has_many_through_with_polymorphic_source
     assert_equal [tags(:general)], post.reload.tags
   end
 
+  def test_has_many_through_obeys_order_on_through_association
+    owner = owners(:blackbeard)
+    assert owner.toys.to_sql.include?("pets.name desc")
+    assert_equal ["parrot", "bulbul"], owner.toys.map { |r| r.pet.name }
+  end
+
   test "has many through associations on new records use null relations" do
     person = Person.new
 

activerecord/test/fixtures/pets.yml

@@ -12,3 +12,8 @@ mochi:
   pet_id: 3
   name: mochi
   owner_id: 2
+
+bulbul:
+  pet_id: 4
+  name: bulbul
+  owner_id: 1

activerecord/test/fixtures/toys.yml

@@ -2,7 +2,13 @@ bone:
   toy_id: 1
   name: Bone
   pet_id: 1
+
 doll:
   toy_id: 2
   name: Doll
   pet_id: 2
+
+bulbuli:
+  toy_id: 3
+  name: Bulbuli
+  pet_id: 4

activerecord/test/models/owner.rb

 class Owner < ActiveRecord::Base
   self.primary_key = :owner_id
-  has_many :pets
+  has_many :pets, -> { order 'pets.name desc' }
   has_many :toys, :through => :pets
 end