Fix ActiveModel::Errors#dup

Since ActiveModel::Errors instance keeps all error messages as hash
we should duplicate this object as well.

Previously ActiveModel::Errors was a subclass of ActiveSupport::OrderedHash,
which results in different behavior on `dup`, this may result in regression for
people relying on it.

1 files changed, 5 insertions, 0 deletions

diff --git a/activemodel/lib/active_model/errors.rb b/activemodel/lib/active_model/errors.rb
index c6535082d3..4a0ad618bc 100644
--- a/activemodel/lib/active_model/errors.rb
+++ b/activemodel/lib/active_model/errors.rb
@@ -78,6 +78,11 @@ module ActiveModel
       @messages = ActiveSupport::OrderedHash.new
     end
 
+    def initialize_dup(other)
+      @messages = other.messages.dup
+      super
+    end
+
     # Clear the messages
     def clear
       messages.clear