Ensure results returned by a memoized method are immutable

2 files changed, 7 insertions, 2 deletions

diff --git a/activesupport/lib/active_support/memoizable.rb b/activesupport/lib/active_support/memoizable.rb
index 5aa73bce52..6506238ac0 100644
--- a/activesupport/lib/active_support/memoizable.rb
+++ b/activesupport/lib/active_support/memoizable.rb
@@ -51,7 +51,7 @@ module ActiveSupport
           if instance_method(:#{symbol}).arity == 0
             def #{symbol}(reload = false)
               if reload || !defined?(#{memoized_ivar}) || #{memoized_ivar}.empty?
-                #{memoized_ivar} = [#{original_method}]
+                #{memoized_ivar} = [#{original_method}.freeze]
               end
               #{memoized_ivar}[0]
             end
@@ -64,7 +64,7 @@ module ActiveSupport
                 if !reload && #{memoized_ivar}.has_key?(args)
                   #{memoized_ivar}[args]
                 elsif #{memoized_ivar}
-                  #{memoized_ivar}[args] = #{original_method}(*args)
+                  #{memoized_ivar}[args] = #{original_method}(*args).freeze
                 end
               else
                 #{original_method}(*args)
diff --git a/activesupport/test/memoizable_test.rb b/activesupport/test/memoizable_test.rb
index 99d9240ea1..135d56f14a 100644
--- a/activesupport/test/memoizable_test.rb
+++ b/activesupport/test/memoizable_test.rb
@@ -110,6 +110,11 @@ uses_mocha 'Memoizable' do
       assert_equal 1, @person.age_calls
     end
 
+    def test_memorized_results_are_immutable
+      assert_equal "Josh", @person.name
+      assert_raise(ActiveSupport::FrozenObjectError) { @person.name.gsub!("Josh", "Gosh") }
+    end
+
     def test_reloadable
       counter = @calculator.counter
       assert_equal 1, @calculator.counter