Determine which keys in the given hash are "extra". Extra keys are those that were not used to generate a particular route. The extra keys also do not include those recalled from the prior request, nor do they include any keys that were implied in the route (like a :controller that is required, but not explicitly used in the text of the route.)

Source Code

# File action_controller/routing/route.rb, line 144
def extra_keys(hash, recall={})
  (hash || {}).keys.map { |k| k.to_sym } - (recall || {}).keys - significant_keys
end