Optimize Class Inheritable Attributes so that unnecessary hashes are not created. Closes #7472 [Bruce Perens]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@6110 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

2 files changed, 16 insertions, 5 deletions

diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index 9e21a8beab..0add31cb50 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Optimize Class Inheritable Attributes so that unnecessary hashes are not created.  Closes #7472 [Bruce Perens]
+
 * Ruby 1.8-cvs and 1.9 define a private Time#to_date that overrides Active
 Support. Make it public to preserve compatibility.  [Jeremy Kemper]
 
diff --git a/activesupport/lib/active_support/core_ext/class/inheritable_attributes.rb b/activesupport/lib/active_support/core_ext/class/inheritable_attributes.rb
index 3c5b2b8340..d8283760b9 100644
--- a/activesupport/lib/active_support/core_ext/class/inheritable_attributes.rb
+++ b/activesupport/lib/active_support/core_ext/class/inheritable_attributes.rb
@@ -89,10 +89,13 @@ class Class # :nodoc:
   end
 
   def inheritable_attributes
-    @inheritable_attributes ||= {}
+    @inheritable_attributes ||= EMPTY_INHERITABLE_ATTRIBUTES
   end
   
   def write_inheritable_attribute(key, value)
+    if inheritable_attributes.equal?(EMPTY_INHERITABLE_ATTRIBUTES)
+      inheritable_attributes = {}
+    end
     inheritable_attributes[key] = value
   end
   
@@ -111,15 +114,21 @@ class Class # :nodoc:
   end
   
   def reset_inheritable_attributes
-    inheritable_attributes.clear
+    @inheritable_attributes = EMPTY_INHERITABLE_ATTRIBUTES
   end
 
-  private 
+  private
+    EMPTY_INHERITABLE_ATTRIBUTES = {}.freeze
+
     def inherited_with_inheritable_attributes(child)
       inherited_without_inheritable_attributes(child) if respond_to?(:inherited_without_inheritable_attributes)
       
-      new_inheritable_attributes = inheritable_attributes.inject({}) do |memo, (key, value)|
-        memo.update(key => (value.dup rescue value))
+      if inheritable_attributes.equal?(EMPTY_INHERITABLE_ATTRIBUTES)
+        new_inheritable_attributes = EMPTY_INHERITABLE_ATTRIBUTES
+      else
+        new_inheritable_attributes = inheritable_attributes.inject({}) do |memo, (key, value)|
+          memo.update(key => (value.dup rescue value))
+        end
       end
       
       child.instance_variable_set('@inheritable_attributes', new_inheritable_attributes)