Allow existing users to log-in with SSO

app/models/identity.rb

@@ -9,8 +9,10 @@ def self.find_with_omniauth(auth)
   def self.create_with_omniauth(auth)
     Rails.logger.debug('Creating user from')
     Rails.logger.debug(auth)
-    user = User.create_with_omniauth(auth.info, auth.provider)
-    Rails.logger.debug(user.inspect)
-    create(uid: auth['uid'], provider: auth['provider'], user_id: user.id)
+    transaction do
+      user = User.find_or_create_with_omniauth(auth.info, auth.provider)
+      Rails.logger.debug(user.inspect)
+      create!(uid: auth['uid'], provider: auth['provider'], user_id: user.id)
+    end
   end
 end

app/models/user.rb

@@ -573,16 +573,14 @@ def tag_recommendations(allow_run=true)
       .sort_by {|_tag, count| -count + rand}
   end
 
-  def self.create_with_omniauth(info, _provider)
-    user = {
-      email: info['email'],
-      password: Devise.friendly_token[0, 20],
-      confirmed_at: Time.now.utc.to_datetime.to_s,
-      confirmation_token: nil,
-      first_name: info.first_name,
-      last_name: info.last_name
-    }
-    create!(user)
+  def self.find_or_create_with_omniauth(info, _provider)
+    find_or_create_by!(email: info.email) do |user|
+      user.password = Devise.friendly_token[0, 20]
+      user.confirmed_at = Time.now.utc.to_datetime.to_s
+      user.confirmation_token = nil
+      user.first_name = info.first_name
+      user.last_name = info.last_name
+    end
   end
 
   def active_for_authentication?

test/models/identity_test.rb

@@ -0,0 +1,58 @@
+require 'test_helper'
+
+class IdentityTest < ActiveSupport::TestCase
+  def user_info
+    @user_info ||= OmniAuth::AuthHash.new(
+      name: 'Mr X',
+      first_name: 'Mr',
+      last_name: 'X',
+      email: 'mr.x@example.com',
+      nickname: 'mr.x@example.com'
+    )
+  end
+
+  def omniauth_hash
+    @omniauth_hash ||= OmniAuth::AuthHash.new(
+      provider: %w[azure_activedirectory_v2 facebook github gitlab google_oauth2 twitter].sample,
+      uid: 'e3b8c0b1-68de-454e-8cdb-d7e2d8e9390a',
+      info: user_info
+    )
+  end
+
+  def ensure_user_does_not_exist
+    User.destroy_by(email: user_info.email) # if it exists
+  end
+
+  def create_user
+    User.create!(
+      password: 'Password #123456',
+      **user_info.slice(:email, :first_name, :last_name)
+    )
+  end
+
+  setup do
+    ensure_user_does_not_exist
+  end
+
+  test 'it creates new users' do
+    identity = assert_difference -> {User.count + Identity.count}, 2 do
+      Identity.create_with_omniauth(omniauth_hash)
+    end
+
+    assert_equal omniauth_hash.uid, identity.uid
+
+    user = identity.user
+    assert_equal user_info.email, user.email
+    assert_equal user_info.first_name, user.first_name
+    assert_equal user_info.last_name, user.last_name
+  end
+
+  test 'it associates existing users with new SSO identities' do
+    user = create_user
+    identity = assert_difference -> {Identity.count} do
+      Identity.create_with_omniauth(omniauth_hash)
+    end
+
+    assert_equal user.id, identity.user_id
+  end
+end