Fix SSO login not using existing account when e-mail is verified (mastodon#11862)

Fix mastodon#11472

Author: Gargron

app/models/concerns/omniauthable.rb

@@ -4,7 +4,7 @@ module Omniauthable
   extend ActiveSupport::Concern
 
   TEMP_EMAIL_PREFIX = 'change@me'
-  TEMP_EMAIL_REGEX = /\Achange@me/
+  TEMP_EMAIL_REGEX  = /\A#{TEMP_EMAIL_PREFIX}/.freeze
 
   included do
     devise :omniauthable
@@ -28,8 +28,8 @@ def find_for_oauth(auth, signed_in_resource = nil)
       # to prevent the identity being locked with accidentally created accounts.
       # Note that this may leave zombie accounts (with no associated identity) which
       # can be cleaned up at a later date.
-      user = signed_in_resource || identity.user
-      user = create_for_oauth(auth) if user.nil?
+      user   = signed_in_resource || identity.user
+      user ||= create_for_oauth(auth)
 
       if identity.user.nil?
         identity.user = user
@@ -45,7 +45,18 @@ def create_for_oauth(auth)
       # exists, we assign a temporary email and ask the user to verify it on
       # the next step via Auth::SetupController.show
 
-      user = User.new(user_params_from_auth(auth))
+      strategy          = Devise.omniauth_configs[auth.provider.to_sym].strategy
+      assume_verified   = strategy&.security&.assume_email_is_verified
+      email_is_verified = auth.info.verified || auth.info.verified_email || assume_verified
+      email             = auth.info.verified_email || auth.info.email
+      email             = nil unless email_is_verified
+
+      user = User.find_by(email: email) if email_is_verified
+
+      return user unless user.nil?
+
+      user = User.new(user_params_from_auth(email, auth))
+
       user.account.avatar_remote_url = auth.info.image if auth.info.image =~ /\A#{URI.regexp(%w(http https))}\z/
       user.skip_confirmation!
       user.save!
@@ -54,22 +65,15 @@ def create_for_oauth(auth)
 
     private
 
-    def user_params_from_auth(auth)
-      strategy          = Devise.omniauth_configs[auth.provider.to_sym].strategy
-      assume_verified   = strategy.try(:security).try(:assume_email_is_verified)
-      email_is_verified = auth.info.verified || auth.info.verified_email || assume_verified
-      email             = auth.info.verified_email || auth.info.email
-      email             = email_is_verified && !User.exists?(email: auth.info.email) && email
-      display_name      = auth.info.full_name || [auth.info.first_name, auth.info.last_name].join(' ')
-
+    def user_params_from_auth(email, auth)
       {
         email: email || "#{TEMP_EMAIL_PREFIX}-#{auth.uid}-#{auth.provider}.com",
         password: Devise.friendly_token[0, 20],
         agreement: true,
         external: true,
         account_attributes: {
           username: ensure_unique_username(auth.uid),
-          display_name: display_name,
+          display_name: auth.info.full_name || [auth.info.first_name, auth.info.last_name].join(' '),
         },
       }
     end