[merb-auth-core] Improved active_model compatibility

merb-auth-core/lib/merb-auth-core/errors.rb

@@ -33,6 +33,17 @@ def full_messages
         end
       end
 
+      # Return validation errors for a particular field name or an empty array
+      #
+      # This method is a necessary requirement for active_model compatibility.
+      #
+      # @param [Symbol] field_name the name of the field you want an error for
+      # @return [Array<Array<String>>]
+      #   array of validation errors or empty array, if there are no errors on given field
+      def [](field_name)
+        errors[field_name] ||= []
+      end
+
       # Return authentication errors for a particular field_name.
       #
       # @param <Symbol> field_name the name of the field you want an error for