make devise work with turbo streams

devise.rb

# need to update devise config with these settings
config.parent_controller = 'Users::DeviseController'

devise_controller.rb

class Users::DeviseController < ApplicationController
  self.responder = TurboDeviseResponder
  respond_to :turbo_stream, :html
end

package.json

 "dependencies": {
    "@hotwired/turbo": "https://github.com/hotwired/turbo/archive/dev-builds/latest.tar.gz",
  }

turbo_devise_responder.rb

class TurboDeviseResponder < ActionController::Responder
  def initialize(controller, resources, options = nil)
    super

    options[:formats] = :html
  end

  def to_turbo_stream
    return to_html if get?

    unless has_errors?
      return redirect_to navigation_location
    end

    display_errors
  end

  protected

  def display_errors
    controller.render(rendering_options.merge(status: :unprocessable_entity))
  end

  def rendering_options
    super.merge! formats: :html
  end

  def has_errors?
    return true if controller.flash.alert.present?
    super
  end
end

I don't even have the failure app and I seem to be pretty close. What does that portion provide for us?

I don't even have the failure app and I seem to be pretty close. What does that portion provide for us?

I run into some issues where it adds .turbo_stream to the url 🤷‍♂️ but since this PR hotwired/turbo#39 got merged, all we need to do now is to return 422 if there are any errors. I updated the example, seems to work good for me.