00_gist_index.md

OmniAuth in Rails

Rails Template:

rails new \
  --database postgresql \
  --webpack \
  -m https://raw.githubusercontent.com/lewagon/rails-templates/master/devise.rb \
  github-omniauth

In the Gemfile:

gem 'omniauth-github', github: 'omniauth/omniauth-github', branch: 'master'

In .env:

APP_ID=YOUR_APP_ID
APP_SECRET=YOUR_APP_SECRET

01_config_routes.rb

# app/config/routes

Rails.application.routes.draw do
  devise_for :users, controllers: { omniauth_callbacks: 'users/omniauth_callbacks' }
  # [...]
end

02_app_models_user.rb

# app/models/user.b

class User < ApplicationRecord
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable, :trackable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :validatable,
         :omniauthable, :omniauth_providers => [:github]

  def self.from_omniauth(auth)
    where(provider: auth.provider, uid: auth.uid).first_or_create do |user|
      user.email = auth.info.email
      user.password = Devise.friendly_token[0, 20]
      # user.githubname = auth.info.nickname.downcase # assuming the user model has agithubnickname
      # user.avatar_url = auth.info.image # assuming the user model has an image
      user.save
    end
  end
end

03_config_initializers_devise.rb

# config/initializers/devise.rb

Devise.setup do |config|
  # [...]
  # ==> OmniAuth
  # Add a new OmniAuth provider. Check the wiki for more information on setting
  # up on your models and hooks.
  config.omniauth :github, ENV['APP_ID'], ENV['APP_SECRET'], scope: 'user,public_repo'
  # [...]
  # When using OmniAuth, Devise cannot automatically set OmniAuth path,
  # so you need to do it manually. For the users scope, it would be:
  config.omniauth_path_prefix = '/my_engine/users/auth'
  # [...]
end

04_app_controllers_users_omniauth_callbacks_controller.rb

# app/controllers/users/omniauth_callbacks_controller.rb

class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
  def github
    @user = User.from_omniauth(request.env["omniauth.auth"])

    if @user.persisted?
      sign_in_and_redirect @user, event: :authentication
      set_flash_message(:notice, :success, kind: "Github") if is_navigational_format?
    else
      session["devise.github_data"] = request.env["omniauth.auth"].except(:extra)
      redirect_to new_user_registration_url
    end
  end

  def failure
    redirect_to root_path
  end
end

05_home.html.erb

<!-- app/views/home.html.erb -->

<%= link_to user_github_omniauth_authorize_path, class: "github-link home-login-cta" do %>
  <button class="github-login">
    <i class="fab fa-github github-social"></i>
    Sign in with GitHub
  </button>
<% end %>

<style>
  .github-login {
    display:block;
    width:100%;
    max-width:680px;
    margin:20px auto;
    height:50px;
    cursor:pointer;
    font-size:14px;
    font-family: 'Montserrat', sans-serif;
    border-radius:8px;
    border:none;
    line-height:40px;
    background:#25282d;
    color:white;
    box-shadow:0 0 0 rgba(#25282d,.0);
    transition:.2s linear;
  }
</style>