Forbid Dir.chdir using rubocop custom cop

.rubocop.yml

require:
  - ./lib/rubocop/cop/hoge

hoge.rb

# frozen_string_literal: true

module RuboCop
  module Cop
    module Hoge
      # This cop is used to ban the use of Dir.chdir.
      #  Dir.chdir is NOT thread-safe.
      #
      # @see https://bugs.ruby-lang.org/issues/9785
      class DirChdir < ::RuboCop::Cop::Cop
        MSG = 'Do not use Dir.chdir as it is not thread-safe.'

        def_node_matcher :dir_chdir_node?, <<~PATTERN
          (send (const nil? :Dir) :chdir ...)
        PATTERN

        def on_send(node)
          return unless dir_chdir_node?(node)
          add_offense(node, location: :selector)
        end
      end
    end
  end
end

Note to others that find this, that it is now built into the rubocop-thread_safety gem (https://github.com/rubocop/rubocop-thread_safety/blob/master/docs/modules/ROOT/pages/cops_threadsafety.adoc#threadsafetydirchdir)

thx!