Fix mit-teaching-systems-lab#32 make authentication based on username…

… only

lti_authenticator.rb

@@ -40,30 +40,24 @@ def after_authenticate(auth_token)
     auth_result.extra_data = omniauth_params.merge(lti_uid: lti_uid)
     log :info, "after_authenticate, auth_result: #{auth_result.inspect}"
 
-    # Lookup or create a new User record, requiring that both email and username match.
+    # Lookup or create a new User record
     # Discourse's User model patches some Rails methods, so we use their
     # methods here rather than reaching into details of how these fields are stored in the DB.
     # This appears related to changes in https://github.com/discourse/discourse/pull/4977
-    user_by_email = User.find_by_email(auth_result.email.downcase)
-    user_by_username = User.find_by_username(auth_result.username)
-    both_matches_found = user_by_email.present? && user_by_username.present?
-    no_matches_found = user_by_email.nil? && user_by_username.nil?
-    if both_matches_found && user_by_email.id == user_by_username.id
-      log :info, "after_authenticate, found user records by both username and email and they matched, using existing user..."
-      user = user_by_email
-    elsif no_matches_found
-      log :info, "after_authenticate, no matches found for email or username, creating user record for first-time user..."
+    #
+    # Making the assumption that Edx uses username as primary and cannot be changed
+    # See https://support.edx.org/hc/en-us/articles/115016004448-Can-I-change-my-edX-username-
+    user = User.find_by_username(auth_result.username)
+    if user.present?
+      log :info, "after_authenticate, found user records by username, using existing user..."
+    elsif user.nil?
+      log :info, "after_authenticate, no matches found username, creating user record for first-time user..."
       user = User.new(email: auth_result.email.downcase, username: auth_result.username)
       user.staged = false
       user.active = true
       user.password = SecureRandom.hex(32)
       user.save!
       user.reload
-    else
-      log :info, "after_authenticate, found user records that did not match by username and email"
-      log :info, "after_authenticate, user_by_email: #{user_by_email.inspect}"
-      log :info, "after_authenticate, user_by_username: #{user_by_username.inspect}"
-      raise ::ActiveRecord::RecordInvalid('LTIAuthenticator: edge case for finding User records where username and email did not match, aborting...')
     end
 
     # Return a reference to the User record.