Allow calling class methods on a Relation

activerecord/lib/active_record/relation.rb

@@ -301,6 +301,8 @@ module ActiveRecord
     def method_missing(method, *args, &block)
       if Array.method_defined?(method)
         to_a.send(method, *args, &block)
+      elsif @klass.respond_to?(method)
+        @klass.send(:with_scope, self) { @klass.send(method, *args, &block) }
       elsif arel.respond_to?(method)
         arel.send(method, *args, &block)
       elsif match = DynamicFinderMatch.match(method)

activerecord/test/cases/named_scope_test.rb

@@ -380,6 +380,15 @@ class NamedScopeTest < ActiveRecord::TestCase
     assert_deprecated('named_scope has been deprecated') { Topic.named_scope :deprecated_named_scope }
   end
 
+  def test_named_scopes_on_relations
+    # Topic.replied
+    approved_topics = Topic.scoped.approved.order('id DESC')
+    assert_equal topics(:fourth), approved_topics.first
+
+    replied_approved_topics = approved_topics.replied
+    assert_equal topics(:third), replied_approved_topics.first
+  end
+
   def test_index_on_named_scope
     approved = Topic.approved.order('id ASC')
     assert_equal topics(:second), approved[0]