Avoid using meta-programming for solving code duplication. (#1457)

* Add feature spec for twitter login

* Avoid using class eval for solving code duplication.

This change make code easier to change in the future.

* Fix codeclimate issues

* Introduce explanatory methods

app/controllers/omniauth_callbacks_controller.rb

@@ -1,29 +1,39 @@
 class OmniauthCallbacksController < Devise::OmniauthCallbacksController
   # Don't need a policy for this since this is our sign up/in route
   include Devise::Controllers::Rememberable
-  def self.provides_callback_for(provider)
-    # raise ApplicationConfig["omniauth.auth"].to_yaml
-    class_eval %{
-      def #{provider}
-        cta_variant = request.env["omniauth.params"]['state'].to_s
-        @user = AuthorizationService.new(request.env["omniauth.auth"], current_user, cta_variant).get_user
-        if @user.persisted? && @user.valid?
-          remember_me(@user)
-          sign_in_and_redirect @user, event: :authentication
-          set_flash_message(:notice, :success, kind: "#{provider}".capitalize) if is_navigational_format?
-        elsif @user.persisted? && @user.errors.full_messages.join(", ").include?("username has already been taken")
-          redirect_to "/settings?state=previous-registration"
-        else
-          session["devise.#{provider}_data"] = request.env["omniauth.auth"]
-          user_errors = @user.errors.full_messages
-          flash[:alert] = user_errors
-          redirect_to new_user_registration_url
-        end
-      end
-    }
+
+  def twitter
+    callback_for("twitter")
   end
 
-  %i[twitter github].each do |provider|
-    provides_callback_for provider
+  def github
+    callback_for("github")
+  end
+
+  private
+
+  def callback_for(provider)
+    cta_variant = request.env["omniauth.params"]["state"].to_s
+    @user = AuthorizationService.new(request.env["omniauth.auth"], current_user, cta_variant).get_user
+    if persisted_and_valid?
+      remember_me(@user)
+      sign_in_and_redirect @user, event: :authentication
+      set_flash_message(:notice, :success, kind: provider.to_s.capitalize) if is_navigational_format?
+    elsif persisted_but_username_taken?
+      redirect_to "/settings?state=previous-registration"
+    else
+      session["devise.#{provider}_data"] = request.env["omniauth.auth"]
+      user_errors = @user.errors.full_messages
+      flash[:alert] = user_errors
+      redirect_to new_user_registration_url
+    end
+  end
+
+  def persisted_and_valid?
+    @user.persisted? && @user.valid?
+  end
+
+  def persisted_but_username_taken?
+    @user.persisted? && @user.errors.full_messages.join(", ").include?("username has already been taken")
   end
 end

spec/features/user_logs_in_with_twitter_spec.rb

@@ -0,0 +1,58 @@
+require 'rails_helper'
+
+def user_grants_authorization_on_twitter_popup(twitter_callback_hash)
+  OmniAuth.config.add_mock(:twitter, twitter_callback_hash)
+end
+
+def user_do_not_grants_authorization_on_twitter_popup
+  OmniAuth.config.mock_auth[:twitter] = :invalid_credentials
+end
+
+RSpec.feature "Authenticating with twitter" do
+  let(:twitter_callback_hash) do
+    {
+      :provider => 'twitter',
+      :uid => '111111',
+      :credentials => {
+        :token => "222222",
+        :secret => "333333"
+      },
+      :extra => {
+        :access_token => "",
+        :raw_info => {
+          :name => "Bruce Wayne",
+          :created_at => "Thu Jul 4 00:00:00 +0000 2013", # This is mandatory
+        }
+      },
+      :info => {
+        :nickname => "batman",
+        :name => "Bruce Wayne",
+        :email => "batman@batcave.com",
+      }
+    }
+  end
+
+  context "when user is new on dev.to" do
+    scenario "logging in with twitter using valid credentials" do
+      user_grants_authorization_on_twitter_popup(twitter_callback_hash)
+
+      visit root_path
+      click_link "SIGN IN VIA TWITTER"
+
+      expect(page).to have_link("Write your first post now")
+      expect(page).to have_link("Welcome Thread")
+    end
+
+    scenario "logging in with twitter using invalid credentials" do
+      user_do_not_grants_authorization_on_twitter_popup
+
+      visit root_path
+      click_link "SIGN IN VIA TWITTER"
+
+      expect(page).to have_link "Sign In/Up"
+      expect(page).to have_link "Via Twitter"
+      expect(page).to have_link "Via GitHub"
+      expect(page).to have_link "All about dev.to"
+    end
+  end
+end