class Rails::Application::Configuration

If an extension in the configurted list is not found, a LoadError will be thrown from here.

TrustyCms.configuration.expanded_extension_list # => [:name, :name, :name, :name]

of every extension found among gems and vendor/extensions directories.
(it is here that the :all entry is expanded to mean 'everything else'), or will default to an alphabetical list
The expanded and ordered list of extensions, including any that may later be ignored. This can be configured

def expanded_extension_list
  # NB. it should remain possible to say config.extensions = []
  @extension_list ||= extensions ? expand_and_check(extensions) : available_extensions
end