Cache nil results for has_one associations so multiple calls don't call the database. Closes #5757. [Michael A. Schoen]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@4721 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Cache nil results for has_one associations so multiple calls don't call the database.  Closes #5757. [Michael A. Schoen]
+
 * Add documentation for how to disable timestamps on a per model basis. Closes #5684. [matt@mattmargolis.net Marcel Molina Jr.] 
 
 * Don't save has_one associations unnecessarily.  #5735 [Jonathan Viney]

activerecord/lib/active_record/associations.rb

@@ -656,7 +656,7 @@ module ActiveRecord
           module_eval do
             before_save <<-EOF
               association = instance_variable_get("@#{reflection.name}")
-              if !association.nil? 
+              if association && association.target
                 if association.new_record?
                   association.save(true)
                 end
@@ -841,14 +841,14 @@ module ActiveRecord
             if association.nil? || force_reload
               association = association_proxy_class.new(self, reflection)
               retval = association.reload
-              unless retval.nil?
+              if retval.nil? and association_proxy_class == BelongsToAssociation
-                instance_variable_set("@#{reflection.name}", association)
-              else
                 instance_variable_set("@#{reflection.name}", nil)
                 return nil
               end
+              instance_variable_set("@#{reflection.name}", association)
             end
-            association
+
+            association.target.nil? ? nil : association
           end
 
           define_method("#{reflection.name}=") do |new_value|

activerecord/lib/active_record/associations/association_proxy.rb

@@ -126,13 +126,13 @@ module ActiveRecord
         def load_target
           if !@owner.new_record? || foreign_key_present
             begin
-              @target = find_target if !loaded?
+              @target = find_target unless loaded?
             rescue ActiveRecord::RecordNotFound
               reset
             end
           end
 
-          loaded if target
+          loaded
           target
         end
 

activerecord/test/associations_test.rb

@@ -96,6 +96,11 @@ class HasOneAssociationsTest < Test::Unit::TestCase
     assert_equal Account.find(1).credit_limit, companies(:first_firm).account.credit_limit
   end
 
+  def test_has_one_cache_nils
+    assert_nil companies(:another_firm).account
+    assert_queries(0) { companies(:another_firm).account }
+  end
+
   def test_proxy_assignment
     company = companies(:first_firm)
     assert_nothing_raised { company.account = company.account }