rails--rails/actionpack/lib/action_view/template/handlers/erb.rb

require 'erb'
require 'active_support/core_ext/class/attribute_accessors'

module ActionView
  module TemplateHandlers
    class ERB < TemplateHandler
      include Compilable

      ##
      # :singleton-method:
      # Specify trim mode for the ERB compiler. Defaults to '-'.
      # See ERb documentation for suitable values.
      cattr_accessor :erb_trim_mode
      self.erb_trim_mode = '-'

      self.default_format = Mime::HTML

      def compile(template)
        magic = $1 if template.source =~ /\A(<%#.*coding:\s*(\S+)\s*-?%>)/
        erb = "#{magic}<% __in_erb_template=true %>#{template.source}"
        ::ERB.new(erb, nil, erb_trim_mode, '@output_buffer').src
      end
    end
  end
end