Ruby: get a list of extended modules?

Question

When you include modules in a class or other module you can call

@mymod.included_modules

to get a list of modules included.

Is there an equivalent for listing the modules a module was extended by?

module Feature1
end

module Feature2
  extend Feature1
end

Feature2.extended_modules #=> [Feature1]

Answer 1

Feature2.singleton_class.included_modules # => [Feature1, ...]

Answer 2

They're there, you just have to look in the right place:

(class << Feature2; self end).included_modules   # [Feature1, Kernel]

We can generalize like this:

class Module
  # Return any modules we +extend+
  def extended_modules
    (class << self; self end).included_modules
  end
end

# Now get those extended modules peculiar to Feature2
Feature2.extended_modules - Module.extended_modules # [Feature1]

Answer 3

All Ruby modules can be listed from CLI (Command Line), itself as follows:

ruby -e 'puts Gem::Specification.all().map{|g| [g.name, g.version.to_s] }'

OR

ruby -rubygems -e 'puts Gem::Specification.all().map{|g| [g.name, g.version.to_s] }'

Hope this helps to some extent!!!