has_one associations with a nil target may be safely marshaled. Closes #6279.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@5188 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* has_one associations with a nil target may be safely marshaled.  #6279 [norbauer, Jeremy Kemper]
+
 * Duplicate the hash provided to AR::Base#to_xml to prevent unexpected side effects [Koz]
 
 * Add a :namespace option to  AR::Base#to_xml [Koz]

activerecord/lib/active_record/associations/association_proxy.rb

@@ -125,6 +125,8 @@ module ActiveRecord
         end
 
         def load_target
+          return nil unless defined?(@loaded)
+
           if !loaded? and (!@owner.new_record? || foreign_key_present)
             @target = find_target
           end

activerecord/test/associations_test.rb

@@ -102,13 +102,26 @@ class HasOneAssociationsTest < Test::Unit::TestCase
   end
 
   def test_has_one_cache_nils
-    assert_nil companies(:another_firm).account
-    assert_queries(0) { companies(:another_firm).account }
+    firm = companies(:another_firm)
+    assert_queries(1) { assert_nil firm.account }
+    assert_queries(0) { assert_nil firm.account }
 
     firms = Firm.find(:all, :include => :account)
     assert_queries(0) { firms.each(&:account) }
   end
 
+  def test_can_marshal_has_one_association_with_nil_target
+    firm = Firm.new
+    assert_nothing_raised do
+      assert_equal firm.attributes, Marshal.load(Marshal.dump(firm)).attributes
+    end
+
+    firm.account
+    assert_nothing_raised do
+      assert_equal firm.attributes, Marshal.load(Marshal.dump(firm)).attributes
+    end
+  end
+
   def test_proxy_assignment
     company = companies(:first_firm)
     assert_nothing_raised { company.account = company.account }