1 files changed, 29 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/date/behavior.rb b/activesupport/lib/active_support/core_ext/date/behavior.rb
index 011cc17cbf..bd378eb375 100644
--- a/activesupport/lib/active_support/core_ext/date/behavior.rb
+++ b/activesupport/lib/active_support/core_ext/date/behavior.rb
@@ -1,3 +1,5 @@
+require 'date'
+
 module ActiveSupport #:nodoc:
   module CoreExtensions #:nodoc:
     module Date #:nodoc:
@@ -7,6 +9,33 @@ module ActiveSupport #:nodoc:
         def acts_like_date?
           true
         end
+
+        # Date memoizes some instance methods using metaprogramming to wrap
+        # the methods with one that caches the result in an instance variable.
+        #
+        # If a Date is frozen but the memoized method hasn't been called, the
+        # first call will result in a frozen object error since the memo
+        # instance variable is uninitialized.
+        #
+        # Work around by eagerly memoizing before freezing.
+        #
+        # Ruby 1.9 uses a preinitialized instance variable so it's unaffected.
+        # This hack is as close as we can get to feature detection:
+        begin
+          ::Date.today.freeze.jd
+        rescue => frozen_object_error
+          if frozen_object_error.message =~ /frozen/
+            def freeze #:nodoc:
+              self.class.private_instance_methods(false).each do |m|
+                if m.to_s =~ /\A__\d+__\Z/
+                  instance_variable_set(:"@#{m}", [send(m)])
+                end
+              end
+
+              super
+            end
+          end
+        end
       end
     end
   end