Gab Social. All are welcome.

app/validators/unreserved_username_validator.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+class UnreservedUsernameValidator < ActiveModel::Validator
+  def validate(account)
+    @username = account.username
+    return if @username.nil?
+
+    account.errors.add(:username, I18n.t('accounts.reserved_username')) if reserved_username?
+  end
+
+  private
+
+  def pam_controlled?
+    return false unless Devise.pam_authentication && Devise.pam_controlled_service
+    Rpam2.account(Devise.pam_controlled_service, @username).present?
+  end
+
+  def reserved_username?
+    return true if pam_controlled?
+    return false unless Setting.reserved_usernames
+    Setting.reserved_usernames.include?(@username.downcase)
+  end
+end