How do you find all modules and classes within a module, recursively?

Question

If you have:

module A
  class B
  end
end

You can find B and similar classes via A.constants. However, in Ruby 1.9.3, you cannot get B if i

Answer 1

class Module
  def all_the_modules
    [self] + constants.map {|const| const_get(const) }
      .select {|const| const.is_a? Module }
      .flat_map {|const| const.all_the_modules }
  end
end

A.all_the_modules
# => [A, A::Aa, A::Aa::B]

This code will break if you do have circular namespaces, aka A::Aa::B.const_set(:A, A).

Answer 2

I was getting stack overflows when I tried Reactormonk's answer on large libraries like RSpec. Here's a solution that should filter out circular references and foreign references by checking to make sure that "children" are really children of the parent module we're iterating through:

def parent_of(mod)
  parent_name = mod.name =~ /::[^:]+\Z/ ? $`.freeze : nil
  Object.const_get(parent_name) if parent_name
end

def all_modules(mod)
  [mod] + mod.constants.map { |c| mod.const_get(c) }
  .select {|c| c.is_a?(Module) && parent_of(c) == mod } 
  .flat_map {|m| all_modules(m) }
end

(The parent_of() method is adapted from ActiveSupport's Module#parent, which doesn't seem to work reliably for library classes.)

module Foo
  class Bar
    module Baz
      class Qux
        CORGE = Random::Formatter
        GARPLY = Foo::Bar::Baz
        module Quux
        end
      end
    end
  end
end

Foo::Bar::Baz::Qux::CORGE.is_a?(Module)
# => true 

all_modules(Foo)
# => [Foo, Foo::Bar, Foo::Bar::Baz, Foo::Bar::Baz::Qux, Foo::Bar::Baz::Qux::Quux]