Configure devise to use Google sign in

Followed the guides provided on omniauth-google-oauth2 repo (https://github.com/zquestz/omniauth-google-oauth2\#devise) and devise wiki (https://github.com/heartcombo/devise/wiki/OmniAuth:-Overview). Note that `data: { turbo: "false" }` is required to make this work, as was noted in a few different Github and Stack Overflow threads (e.g., https://github.com/heartcombo/devise/issues/5236\#issuecomment-1004028752).

.gitignore

@@ -42,4 +42,7 @@ coverage
 /node_modules
 
 # Ignore editor config files
-.vscode
+.vscode
+
+# Ignore .env
+.env

Gemfile

@@ -39,7 +39,9 @@ gem "tzinfo-data", platforms: [:mingw, :mswin, :x64_mingw, :jruby]
 # Reduces boot times through caching; required in config/boot.rb
 gem "bootsnap", require: false
 
-gem 'devise'
+gem "devise"
+gem "omniauth-google-oauth2"
+gem "omniauth-rails_csrf_protection", "~> 1.0"
 
 # Use Sass to process CSS
 # gem "sassc-rails"

Gemfile.lock

@@ -168,6 +168,7 @@ GEM
       rubocop-performance
       rubocop-rails (~> 2.2.0)
       thor
+    hashie (5.0.0)
     httparty (0.20.0)
       mime-types (~> 3.0)
       multi_xml (>= 0.5.2)
@@ -179,6 +180,7 @@ GEM
       activesupport (>= 5.0.0)
     jsbundling-rails (1.0.2)
       railties (>= 6.0.0)
+    jwt (2.3.0)
     launchy (2.5.0)
       addressable (~> 2.7)
     lol_dba (2.1.5)
@@ -200,6 +202,7 @@ GEM
     mini_portile2 (2.8.0)
     minitest (5.15.0)
     msgpack (1.5.0)
+    multi_json (1.15.0)
     multi_xml (0.6.0)
     multipart-post (2.1.1)
     net-imap (0.2.3)
@@ -222,10 +225,31 @@ GEM
       racc (~> 1.4)
     nokogiri (1.13.3-arm64-darwin)
       racc (~> 1.4)
+    oauth2 (1.4.9)
+      faraday (>= 0.17.3, < 3.0)
+      jwt (>= 1.0, < 3.0)
+      multi_json (~> 1.3)
+      multi_xml (~> 0.5)
+      rack (>= 1.2, < 3)
     octokit (4.22.0)
       faraday (>= 0.9)
       sawyer (~> 0.8.0, >= 0.5.3)
     okcomputer (1.18.4)
+    omniauth (2.0.4)
+      hashie (>= 3.4.6)
+      rack (>= 1.6.2, < 3)
+      rack-protection
+    omniauth-google-oauth2 (1.0.1)
+      jwt (>= 2.0)
+      oauth2 (~> 1.1)
+      omniauth (~> 2.0)
+      omniauth-oauth2 (~> 1.7.1)
+    omniauth-oauth2 (1.7.2)
+      oauth2 (~> 1.4)
+      omniauth (>= 1.9, < 3)
+    omniauth-rails_csrf_protection (1.0.1)
+      actionpack (>= 4.2)
+      omniauth (~> 2.0)
     orm_adapter (0.5.0)
     parallel (1.22.1)
     parser (3.1.1.0)
@@ -258,6 +282,8 @@ GEM
       nio4r (~> 2.0)
     racc (1.6.0)
     rack (2.2.3)
+    rack-protection (2.2.0)
+      rack
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rails (7.0.2.3)
@@ -411,6 +437,8 @@ DEPENDENCIES
   launchy
   lol_dba
   okcomputer
+  omniauth-google-oauth2
+  omniauth-rails_csrf_protection (~> 1.0)
   pg (~> 1.1)
   pronto
   pronto-brakeman

app/controllers/users/omniauth_callbacks_controller.rb

@@ -0,0 +1,15 @@
+class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
+  skip_before_action :verify_authenticity_token, only: :google_oauth2
+
+  def google_oauth2
+    @user = User.from_omniauth(request.env['omniauth.auth'])
+
+    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'].except('extra') # Removing extra as it can overflow some session stores
+      redirect_to new_user_registration_url, alert: @user.errors.full_messages.join("\n")
+    end
+  end
+end

app/models/user.rb

@@ -2,5 +2,18 @@ class User < ApplicationRecord
   # Include default devise modules. Others available are:
   # :confirmable, :lockable, :timeoutable, :trackable and :omniauthable
   devise :database_authenticatable, :registerable,
-         :recoverable, :rememberable, :validatable
+    :recoverable, :rememberable, :validatable,
+    :omniauthable, omniauth_providers: [:google_oauth2]
+
+  def self.from_omniauth(access_token)
+    data = access_token.info
+
+    User.find_by(email: data["email"]) ||
+      User.create(
+        uid: access_token["uid"],
+        provider: access_token["provider"] || nil,
+        email: data["email"] || nil,
+        password: Devise.friendly_token[0, 20],
+      )
+  end
 end

app/views/welcome/index.html.erb

@@ -1,4 +1,6 @@
 <h2 class="text-red-500">Hello World</h2>
 <p>
   The time is now: <%= Time.now %>
-</p>
+</p>
+
+<%= button_to "Sign in with Google", user_google_oauth2_omniauth_authorize_path, method: :post, data: { turbo: "false" } %>

config/initializers/devise.rb

@@ -272,6 +272,7 @@
   # Add a new OmniAuth provider. Check the wiki for more information on setting
   # up on your models and hooks.
   # config.omniauth :github, 'APP_ID', 'APP_SECRET', scope: 'user,public_repo'
+  config.omniauth :google_oauth2, ENV["GOOGLE_CLIENT_ID"], ENV["GOOGLE_CLIENT_SECRET"], { hd: ["gnar.dog"] }
 
   # ==> Warden configuration
   # If you want to use other strategies, that are not supported by Devise, or

config/routes.rb

@@ -1,4 +1,4 @@
 Rails.application.routes.draw do
-  devise_for :users
+  devise_for :users, controllers: { omniauth_callbacks: "users/omniauth_callbacks" }
   root "welcome#index"
 end

db/migrate/20220407201654_add_omniauth_to_users.rb

@@ -0,0 +1,6 @@
+class AddOmniauthToUsers < ActiveRecord::Migration[7.0]
+  def change
+    add_column :users, :provider, :string
+    add_column :users, :uid, :string
+  end
+end