ActionDispatch::Cookies::CookieOverflow in Users::OmniauthCallbacksController#google_oauth2

[AxelBriche]

Configuration

• Provider Gem: omniauth-google_oauth2
• Ruby Version: 3.0.0
• Framework: Ruby on Rails 6.1.2.1
• Platform: MacOs

Actual Behavior

ActionDispatch::Cookies::CookieOverflow in Users::OmniauthCallbacksController#google_oauth2

Line:
session["devise.google_oauth2_data"] = request.env["omniauth.auth"].except(:extra) # Removing extra as it can overflow some session stores

Controller:

class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
  # See https://github.com/omniauth/omniauth/wiki/FAQ#rails-session-is-clobbered-after-callback-on-developer-strategy
  skip_before_action :verify_authenticity_token, only: :google_oauth2

  def google_oauth2
    @user = User.from_omniauth(request.env["omniauth.auth"])

    if @user.persisted?
      sign_in_and_redirect @user, event: :authentication # this will throw if @user is not activated
      set_flash_message(:notice, :success, kind: "Google") if is_navigational_format?
    else
      session["devise.google_oauth2_data"] = request.env["omniauth.auth"].except(:extra) # Removing extra as it can overflow some session stores
      redirect_to new_user_registration_url
    end
  end

  def failure
    redirect_to root_path
  end
end

The scope for google inside the devise config file:
scope: 'userinfo.email,userinfo.profile'

[AxelBriche]

If I add except!(:extra) instead of except(:extra) the problem is solved.
It's an error inside the documentation ?

[rodolfobandeira]

An alternative for this issue is to switch your cookies (max 4kb capacity) to https://github.com/rails/activerecord-session_store which provides a key/value storage directly in your db