indifferent access should recurse Hash subclasses

This commit makes Hash subclasses convert to HWIA by default for nested
objects of subclasses of Hash, but allows certain subclasses to prevent nested
conversion by introducing Hash#nested_under_indifferent_access that subclasses
can overwrite.

ActiveSupport::OrderedHash is one such subclass that overwrites
+nested_under_indifferent_access+, since implicitly converting it to HWIA would
remove the ordering of keys and values in Ruby 1.8.

This change is necessary because commit ce9456e broke nested indifferent access
conversion for all subclasses of Hash.

1 files changed, 12 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb b/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb
index aad4b61e16..c2a6476604 100644
--- a/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb
+++ b/activesupport/lib/active_support/core_ext/hash/indifferent_access.rb
@@ -9,4 +9,16 @@ class Hash
   def with_indifferent_access
     ActiveSupport::HashWithIndifferentAccess.new_from_hash_copying_default(self)
   end
+
+  # Called when object is nested under an object that receives
+  # #with_indifferent_access. This method with be called on the current object
+  # by the enclosing object and is aliased to #with_indifferent_access by
+  # default. Subclasses of Hash may overwrite this method to return +self+ if
+  # converting to an +ActiveSupport::HashWithIndifferentAccess+ would not be
+  # desirable.
+  #
+  #   b = {:b => 1}
+  #   {:a => b}.with_indifferent_access["a"] # calls b.nested_under_indifferent_access
+  #
+  alias nested_under_indifferent_access with_indifferent_access
 end