Allow a Date to be frozen more than once without an error in Ruby 1.8.x

activesupport/lib/active_support/core_ext/date/freeze.rb

@@ -5,7 +5,7 @@
 # first call will result in a frozen object error since the memo
 # instance variable is uninitialized.
 #
-# Work around by eagerly memoizing before freezing.
+# Work around by eagerly memoizing before the first freeze.
 #
 # Ruby 1.9 uses a preinitialized instance variable so it's unaffected.
 # This hack is as close as we can get to feature detection:
@@ -17,9 +17,11 @@
     if frozen_object_error.message =~ /frozen/
       class Date #:nodoc:
         def freeze
-          self.class.private_instance_methods(false).each do |m|
-            if m.to_s =~ /\A__\d+__\Z/
-              instance_variable_set(:"@#{m}", [send(m)])
+          unless frozen?
+            self.class.private_instance_methods(false).each do |m|
+              if m.to_s =~ /\A__\d+__\Z/
+                instance_variable_set(:"@#{m}", [send(m)])
+              end
             end
           end
 

activesupport/test/core_ext/date_ext_test.rb

@@ -454,4 +454,10 @@ def test_freeze_doesnt_clobber_memoized_instance_methods
       Date.today.freeze.inspect
     end
   end
+
+  def test_can_freeze_twice
+    assert_nothing_raised do
+      Date.today.freeze.freeze
+    end
+  end
 end