PLATFORMSに入っているべき値を強制するCop

gistfile1.txt

# lib/rubocop/cop/bundler/required_platforms.rb
module RuboCop
  module Cop
    module Bundler
      class RequiredPlatforms < Cop
        def on_new_investigation
          required = Array(cop_config['RequiredPlatforms'])
          lockfile = File.read('Gemfile.lock')
          platforms = lockfile[/^PLATFORMS\n(.+?)\n\n/m, 1].to_s.lines.map(&:strip)
          (required - platforms).each do |missing|
            add_offense(nil, message: "Gemfile.lock に #{missing} が含まれていません")
          end
        end
      end
    end
  end
end