module ActionView::LookupContext::ViewPaths

def detail_args_for(options)

Compute details hash and key according to user options (e.g. passed from #render). 
def detail_args_for(options)
  return @details, details_key if options.empty? # most common path.
  user_details = @details.merge(options)
  [user_details, DetailsKey.get(user_details)]
end