recursive delete of Hash.

Hash#rdelete

class Hash
  def rdelete(other)
    new_hash = {}
    self.each do |key, value|
      if other.key?(key)
        if value.kind_of?(Hash)
          if other[key].kind_of?(Hash)
            new_hash[key] = value.rdelete(other[key])
            if new_hash[key].empty?
              new_hash.delete(key)
            end
          else
            new_hash[key] = value
          end
        else
          if other[key].kind_of?(Hash)
            new_hash[key] = value
          else
            # delete
          end
        end
      else
        new_hash[key] = value
      end
    end
    
    new_hash
  end
end

require 'yaml'

current_str = <<-EOS
en:
  activerecord:
    models:
      metadata: "Metadata"
      attributes:
    metadata:
      application_base_id: "ID Based on Application Form"
      entity_id: "entityID"
      certification: "Certificate"
      status: "Status"
  foo: "bar"
EOS
 
old_str = <<-EOS
en:
  activerecord:
    models:
      metadata: "Metadata"
      attributes:
    metadata:
      entity_id: "entityID"
      certification: "Certificate"
      status: "Status"
EOS
 
current_yaml = YAML.load(current_str)
old_yaml = YAML.load(old_str)
appended_yaml = current_yaml.rdelete(old_yaml)
puts YAML.dump(appended_yaml)
# ---
# en:
#   activerecord:
#     metadata:
#       application_base_id: ID Based on Application Form
#   foo: bar