Illustrates forcing inclusion of a module by another included module in Ruby.

force_class_inclusion_of_module.rb

#!/usr/bin/env ruby

# From solution at https://stackoverflow.com/questions/73676857/guaranteeing-that-module-includer-classes-include-another-module-in-ruby.

module M1
  def m1; puts 'M1 was included by M2.'; end
end

module M2
  def self.included(including_class)
    including_class.class_exec { include M1 }
  end
end

class C
  include M2
end

C.new.m1  # => M1 was included by M2.