Using Nokogiri::XML::Builder in lieu of stock pure ruby Builder for Rails builder templates

nokogiri_builders.rb

# config/initializers/nokogiri_builders.rb
# Using Nokogiri::XML::Builder in lieu of stock pure ruby Builder for Rails builder templates

# unrelated, but you might want this too to enable parsing
# XML params with Nokogiri
#ActiveSupport::XmlMini.backend = 'Nokogiri'

module Nokogiri
  module XML
    class Builder
      # handle instruct! instead of emitting nonsense tag
      def instruct!(tag, options = {})
        case tag
        when :xml
          @version = options[:version]
          @encoding = options[:encoding]
        else
          raise NotImplementedError(tag.inspect)
        end
      end

      # redefined, to recover what instruct! gave us
      def to_xml(*args)
        if Nokogiri.jruby?
          options = args.first.is_a?(Hash) ? args.shift : {}
          unless options[:save_with]
            options[:save_with] = Node::SaveOptions::AS_BUILDER
          end
          args.insert(0, options)
        end

        if @version || @encoding
          # set options according to what was given previously
          args[0][:version] = @version if @version
          args[0][:encoding] = @encoding if @encoding
          # do emit a declaration
          args[0].delete(:save_with)
        end

        @doc.to_xml(*args)
      end
    end
  end
end

module ActionView
  module Template::Handlers
    class Builder
      # Default format used by Builder.
      class_attribute :default_format
      self.default_format = :xml

      def call(template)
        require_engine
        code = <<-CODE
          builder = Nokogiri::XML::Builder.new do |xml|
            #{template.source}
          end
          # default to not emit a declaration (use instruct! instead)
          save_options = Nokogiri::XML::Node::SaveOptions::NO_DECLARATION
          # default to UTF-8, as it's Rails default encoding
          options = { encoding: 'UTF-8', indent: 2, save_with: save_options }
          self.output_buffer = builder.to_xml(options)
        CODE

        code
      end

      protected

      def require_engine
        @required ||= begin
          require 'nokogiri'
          true
        end
      end
    end
  end
end