The plugins that have been explicitly listed with config.plugins. If this list is nil then it means the client does not care which plugins or in what order they are loaded, so we load all in alphabetical order. If it is an empty array, we load no plugins, if it is non empty, we load the named plugins in the order specified.
# File railties/lib/rails/plugin/loader.rb, line 133 def registered_plugin_names configuration.plugins ? configuration.plugins.map(&:to_s) : nil end