Remove duplication of conditions generated for associations when used…

… in conjunction with named_scopes [#4634 state: resolved]

activerecord/lib/active_record/named_scope.rb

@@ -120,7 +120,7 @@ def initialize(proxy_scope, options, &block)
         options ||= {}
         [options[:extend]].flatten.each { |extension| extend extension } if options[:extend]
         extend Module.new(&block) if block_given?
-        unless Scope === proxy_scope
+        unless (Scope === proxy_scope || ActiveRecord::Associations::AssociationCollection === proxy_scope)
           @current_scoped_methods_when_defined = proxy_scope.send(:current_scoped_methods)
         end
         @proxy_scope, @proxy_options = proxy_scope, options.except(:extend)

activerecord/test/cases/named_scope_test.rb

@@ -146,6 +146,12 @@ def test_has_many_associations_have_access_to_named_scopes
     assert_equal authors(:david).posts & Post.containing_the_letter_a, authors(:david).posts.containing_the_letter_a
   end
 
+  def test_nested_named_scopes_doesnt_duplicate_conditions_on_child_scopes
+    comments_scope = posts(:welcome).comments.send(:construct_sql)
+    named_scope_sql_conditions = posts(:welcome).comments.containing_the_letter_e.send(:current_scoped_methods)[:find][:conditions]
+    assert_no_match /#{comments_scope}.*#{comments_scope}/i, named_scope_sql_conditions
+  end
+
   def test_has_many_through_associations_have_access_to_named_scopes
     assert_not_equal Comment.containing_the_letter_e, authors(:david).comments
     assert !Comment.containing_the_letter_e.empty?