Find rails routes with no corresponding controller action

find_unused_routes.rake

desc 'Finds unused routes (routes with no corresponding controller action)'
task find_unused_routes: :environment do
  checked_actions = %i[create destroy edit index new show update]

  Rails.application.eager_load!

  endpoints = Rails.application.routes.routes.map do |route|
    ActionDispatch::Routing::RouteWrapper.new(route).endpoint
  end
  
  checked_endpoints = endpoints.
    grep(/#(?:#{checked_actions.join('|')})\z/).
    grep_v(/^(?:action_|active_|rails)/)

  controllers = ObjectSpace.each_object(Class).select do |klass|
    klass < ActionController::Base
  end

  controller_actions = controllers.flat_map do |ctrl|
    actions = ctrl.public_instance_methods & checked_actions
    actions.map do |action|
      "#{ctrl.name.underscore.chomp('_controller')}##{action}"
    end
  end

  unused = (checked_endpoints - controller_actions).uniq

  puts unused.sort, "#{unused.count} unused routes, may include false positives"
end