journey_router_patch.rb

module AppName::JourneyRouterPatch
  APP_NAME_GENERIC_ROUTING_INFO_KEY = "app_name.generic_routing_info".freeze

  def call(env)
    response_array = super

    # NOTE: When Journey::Router#call can't resolve a request, it returns an array like:
    # [404, {'X-Cascade' => 'pass'}, ['Not Found']]
    # ref. https://github.com/rails/journey/blob/v1.0.4/lib/journey/router.rb#L80
    if response_array[1]["X-Cascade"] != "pass" && env.key?(APP_NAME_GENERIC_ROUTING_INFO_KEY)
      # do something
    end

    response_array
  end

  def find_routes(env)
    routes = super
    _, params, route = routes.first

    # NOTE: When a path of the request (resolved by Generic routing) is something like
    # :controller/:action(/:id)(.:format), add the path parameters into Rack middleware's env.
    if like_generic_routing?(route) && params.key?(:controller) && params.key?(:action)
      env[APP_NAME_GENERIC_ROUTING_INFO_KEY] = params.slice(:controller, :action)
    end

    routes
  end

  private

  # NOTE: It can't tell the Generic routing from the requests for not existing pages.
  def like_generic_routing?(route)
    route &&
    route.verb == // &&       # return false if the routing is specified by get, post, and so on
    route.name != "root" &&   # return false if the routing is specified with "root to:"
    route.defaults.blank? &&  # return false if the routing is specified by match (not Generic routing)
    # return false if the request is for assets/**/*.[css|js]
    route.app.instance_of?(ActionDispatch::Routing::RouteSet::Dispatcher)
  end
end