Devise + Omniauth = undefined method `new_session_path'

Question

I'm trying to implement a login system that only supports login through a Google Account to access Analytics data.

I cannot get it working with the exception

undefined method `new_session_path' for #<Users::OmniauthCallbacksController:0x8f588b0>

I'm using omniauth with the omniauth-google-oauth2 strategy.

This is the Gemfile

source 'https://rubygems.org'

gem 'rails', '3.2.3'

# Bundle edge Rails instead:
# gem 'rails', :git => 'git://github.com/rails/rails.git'

gem 'mysql2'
gem 'haml'
gem 'haml-rails'
gem 'omniauth'
gem 'omniauth-google-oauth2'
gem 'devise'

# Gems used only for assets and not required
# in production environments by default.
group :assets do
  gem 'sass-rails',   '~> 3.2.3'
  gem 'coffee-rails', '~> 3.2.1'

  # See https://github.com/sstephenson/execjs#readme for more supported runtimes
  gem 'therubyracer', :platform => :ruby

  gem 'uglifier', '>= 1.0.3'
end

gem 'jquery-rails'

# To use ActiveModel has_secure_password
# gem 'bcrypt-ruby', '~> 3.0.0'

# To use Jbuilder templates for JSON
# gem 'jbuilder'

# Use unicorn as the app server
# gem 'unicorn'

# Deploy with Capistrano
# gem 'capistrano'

# To use debugger
# gem 'ruby-debug19', :require => 'ruby-debug'

group :test do
  gem 'capybara'
  gem 'database_cleaner'
  gem 'rspec-rails'
  gem 'cucumber-rails'
  gem 'factory_girl_rails'
end

This is the config/routes.rb

TestApp::Application.routes.draw do
  devise_for :users, :controllers => { :omniauth_callbacks => "users/omniauth_callbacks" }

  devise_scope :user do
    get 'sign_in', :to => 'users/sessions#new', :as => :new_user_session
    get 'sign_out', :to => 'users/sessions#destroy', :as => :destroy_user_session
  end

  root :to => "Landing#index"
end

app/model/user.rb:

class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :token_authenticatable, :confirmable,
  # :lockable, :timeoutable and :omniauthable
  # :database_authenticatable, :registerable
  # :recoverable, :rememberable, :trackable, :validatable

  devise :omniauthable

  # Setup accessible (or protected) attributes for your model
  # attr_accessible :email, :password, :password_confirmation, :remember_me
  # attr_accessible :title, :body
end

config/intitializers/omniauth.rb

Rails.application.config.middleware.use OmniAuth::Builder do
  provider :google_oauth2, 'ID', 'SECRET', :scope => 'https://www.googleapis.com/auth/analytics.readonly'
end

app/controllers/users/omniauth_callback_controller.rb

class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
  def google_oauth2
    # You need to implement the method below in your model
    @user = User.find_for_google_oauth2(request.env["omniauth.auth"], current_user)

    if @user.persisted?
      flash[:notice] = I18n.t "devise.omniauth_callbacks.success", :kind => "Google"
      sign_in_and_redirect @user, :event => :authentication
    else
      session["devise.google_data"] = request.env["omniauth.auth"]
      redirect_to new_user_registration_url
    end
  end
end

Can you please help me to understand what's wrong here?

P.S. this is the result I get running rake routes

user_omniauth_callback    /users/auth/:action/callback(.:format)  users/omniauth_callbacks#(?-mix:(?!))
new_user_session GET     /sign_in(.:format)                      users/sessions#new
destroy_user_session GET /sign_out(.:format)                     users/sessions#destroy
root                     /                                       Landing#index

Answer 1

What version of devise are you running? This closed issue seem to deal with the same problem, and assumes that it was gonna be fixed in version 1.4.9 and offers a quick and dirty fix.

But, if it doesn't help, try to change the named route for new session to:

get 'sign_in', :to => 'users/sessions#new', :as => :new_session

Also, I asked the question about Devise with Omniauth that you may find useful: Devise omniauthable breaks Omniauth authentication with `Could not find a valid mapping for path`