Detect unused routes (Rails 7.0)

unused_routes.rb

# frozen_string_literal: true

# Usage: bin/rails runner unused_routes.rb

def action_exists?(controller, action)
  controller_class = "#{controller.camelize}Controller".constantize
  controller_class.public_instance_methods.include?(action.to_sym)
rescue NameError
  false
end

def view_exists?(controller, action)
  Rails.root.join("app/views/#{controller}/#{action}.html.erb").exist?
end

routes = Rails.application.routes.routes.filter_map do |route|
  controller = route.requirements[:controller] or next
  action = route.requirements[:action] or next

  next if action_exists?(controller, action)
  next if view_exists?(controller, action)

  route
end

formatter = ActionDispatch::Routing::ConsoleFormatter::Expanded.new
inspector = ActionDispatch::Routing::RoutesInspector.new(routes)

puts inspector.format(formatter)