Turbo Teapot

You probably shouldn’t do this, but anyway… I’ve been upgrading an app from Turbolinks to Turbo, and there are a number of controller actions that render successful responses after form submissions. Turbo expects the server to return an HTTP 303 See Other response in these cases, so returning 2xx won’t render anything. However, Turbo does render error responses (4xx and 5xx).

The HTTP status 418 I'm a teapot was an April Fools’ joke, so it’s basically nonsense, but we can use it as a temporary workround for Turbo’s requirements. For example:

class PostsController < ApplicationController
  def create
    if @post = Post.create(post_params)
      render status: (request.format.turbo_stream? ? 418 : :created)
    else
      render :new, status: :unprocessable_entity
    end
  end
end

My colleague Sam Oliver suggested wrapping this up in a patch, which ended up looking like this:

# lib/render_418_for_turbo.rb
module Render418ForTurbo
  def render(*args)
    message = "[Render418ForTurbo]: Responding with 418 status to work around Turbo's rendering limitation."

    if !request.get? && request.format.turbo_stream?
      if options = args.find { |arg| arg.is_a?(Hash) }
        unless options[:status]
          puts message # or my_logger.info message
          options[:status] = 418
        end
      else
        puts message # or my_logger.info message
        args.push(status: 418)
      end
    end

    super
  end
end

# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
  prepend Render418ForTurbo
end

This patch adds a 418 statuses for non-GET requests that were made via Turbo. It will only add the status if a status is not present, and will log the override.