class Rack::Response

def finish(&block)
  if no_entity_body?
    delete_header CONTENT_TYPE
    delete_header CONTENT_LENGTH
    close
    return [@status, @headers, []]
  else
    if block_given?
      # We don't add the content-length here as the user has provided a block that can #write additional chunks to the body.
      @block = block
      return [@status, @headers, self]
    else
      # If we know the length of the body, set the content-length header... except if we are chunked? which is a legacy special case where the body might already be encoded and thus the actual encoded body length and the content-length are likely to be different.
      if @length && !chunked?
        @headers[CONTENT_LENGTH] = @length.to_s
      end
      return [@status, @headers, @body]
    end
  end
end