Memoize association.named_scope calls

2 files changed, 12 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/associations/association_collection.rb b/activerecord/lib/active_record/associations/association_collection.rb
index 6eda70d0ce..5ecdf1ac8d 100644
--- a/activerecord/lib/active_record/associations/association_collection.rb
+++ b/activerecord/lib/active_record/associations/association_collection.rb
@@ -405,6 +405,9 @@ module ActiveRecord
             else
               super
             end
+          elsif @reflection.klass.scopes[method]
+            @_scopes ||= {}
+            @_scopes[method] ||= with_scope(construct_scope) { @reflection.klass.send(method, *args) }
           else
             with_scope(construct_scope) do
               if block_given?
diff --git a/activerecord/test/cases/named_scope_test.rb b/activerecord/test/cases/named_scope_test.rb
index 2396ca10b0..3d5ebb6cb8 100644
--- a/activerecord/test/cases/named_scope_test.rb
+++ b/activerecord/test/cases/named_scope_test.rb
@@ -413,6 +413,15 @@ class NamedScopeTest < ActiveRecord::TestCase
       Topic.approved.by_lifo.replied.written_before(Time.now).all
     end
   end
+
+  def test_named_scopes_are_cached_on_associations
+    post = posts(:welcome)
+
+    assert_equal post.comments.containing_the_letter_e.object_id, post.comments.containing_the_letter_e.object_id
+
+    post.comments.containing_the_letter_e.all # force load
+    assert_no_queries { post.comments.containing_the_letter_e.all }
+  end
 end
 
 class DynamicScopeMatchTest < ActiveRecord::TestCase