do_not_dump.rb

# frozen_string_literal: true

class DoNotDump < Module
  class << self
    alias [] new
  end

  attr_reader :ignored_ivars

  def initialize *ignored_ivars
    @ignored_ivars = ignored_ivars.freeze

    super() do
      define_method :marshal_load do |pairs|
        pairs.each { |ivar, value| instance_variable_set ivar, value }
      end

      define_method :marshal_dump do
        instance_variables.each_with_object [] do |ivar, pairs|
          pairs << [ivar, instance_variable_get(ivar)] unless ignored_ivars.include? ivar
        end
      end
    end
  end

  alias to_a ignored_ivars

  def == other
    other.instance_of?(self.class) && other.ignored_ivars.sort == @ignored_ivars.sort
  end

  def inspect
    "#{self.class.name}#{@ignored_ivars.inspect}"
  end
  alias to_s inspect

  def marshal_dump
    @ignored_ivars
  end

  def marshal_load data
    @ignored_ivars = data
  end
end