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

require 'erb'

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 = '-'

      def compile(template)
        src = ::ERB.new("<% __in_erb_template=true %>#{template.source}", nil, erb_trim_mode, '@output_buffer').src

        # Ruby 1.9 prepends an encoding to the source. However this is
        # useless because you can only set an encoding on the first line
        RUBY_VERSION >= '1.9' ? src.sub(/\A#coding:.*\n/, '') : src
      end
    end
  end
end