What is the preferred way (better style) to name a namespace in Ruby? Singular or Plural?

Use:

module FooLib end
module FooLib::Plugins end
class  FooLib::Plugins::Plugin; end #the base for plugins
class  FooLib::Plugins::Bar < FooLib::Plugins::Plugin; end
class  FooLib::Plugins::Bar2 < FooLib::Plugins::Plugin; end

or in a different words:

module FooLib
  module Plugins
    class Plugin; end #the base for plugins
    class Bar < Plugin; end
    class Bar2 < Plugin; end
  end
end

Also arrange the files like this:

- foo_lib/
  - plugins/
    - plugin.rb
    - bar.rb
    - bar2.rb

This is how Rails does it (so this is the Rails Way). I.e. look at the Associations namespace and the Associations::Association class from which all of the classes form the Associations namespace inherits (i.e. Associations::SingularAssociation).

Assuming Plugin is a base class:

• class FooLib::Plugin::Bar < FooLib::Plugin

  This is the one I use and recommend. Bar is a Plugin in FooLib and it inherits from FooLib::Plugin. It also keeps the plugins provided by the FooLib library nested under the namespace of the general class, which reads naturally:

  # Assign the Bar Plugin of the FooLib library to p.
  p = FooLib::Plugin::Bar
  

  If I were to develop a third party plugin for your library, I would create the following structure:

  # Baz is a Plugin for the FooLib library provided by BarLib.
  class BarLib::FooLib::Plugin::Baz < ::FooLib::Plugin
  

  Note that I mirror the FooLib hierarchy, but under BarLib's namespace. I would not extend it directly.

• class FooLib::Plugins::Bar < FooLib::Plugin

  I have also used this one, and I think it makes the most sense. Bar extends FooLib::Plugin and is one of the Plugins provided by FooLib. However, it creates a potentially needless module.

  I think this would be a great choice if Plugins was a central plugin repository that implements methods like Plugins.add, Plugins.all and Plugins.loaded.

  Use it if you can justify the extra module.

• class FooLib::Plugins::Bar < FooLib::Plugins

  Doesn't make a lot of sense to me. Bar is one of the Plugins in FooLib, that part looks fine. However, it inherits from Plugins. Is it inheriting from more than one plugin? It sounds strange to me; the class name shouldn't suggest something that is impossible.