Properly cache association_collection#scopes calls having arguments

Author: lifo

activerecord/lib/active_record/associations/association_collection.rb

@@ -411,7 +411,8 @@ def method_missing(method, *args)
             end
           elsif @reflection.klass.scopes[method]
             @_named_scopes_cache ||= {}
-            @_named_scopes_cache[method] ||= with_scope(construct_scope) { @reflection.klass.send(method, *args) }
+            @_named_scopes_cache[method] ||= {}
+            @_named_scopes_cache[method][args] ||= with_scope(construct_scope) { @reflection.klass.send(method, *args) }
           else
             with_scope(construct_scope) do
               if block_given?

activerecord/test/cases/named_scope_test.rb

@@ -428,6 +428,19 @@ def test_named_scopes_are_cached_on_associations
     assert_no_queries { post.comments.containing_the_letter_e.all }
   end
 
+  def test_named_scopes_with_arguments_are_cached_on_associations
+    post = posts(:welcome)
+
+    one = post.comments.limit_by(1).all
+    assert_equal 1, one.size
+
+    two = post.comments.limit_by(2).all
+    assert_equal 2, two.size
+
+    assert_no_queries { post.comments.limit_by(1).all }
+    assert_no_queries { post.comments.limit_by(2).all }
+  end
+
   def test_named_scopes_are_reset_on_association_reload
     post = posts(:welcome)
 

activerecord/test/models/comment.rb

@@ -1,4 +1,5 @@
 class Comment < ActiveRecord::Base
+  scope :limit_by, lambda {|l| limit(l) }
   scope :containing_the_letter_e, :conditions => "comments.body LIKE '%e%'"
   scope :for_first_post, :conditions => { :post_id => 1 }
   scope :for_first_author,