Inspired by Common LISP conditions system, this code here uses continuations to inject "restart" options from the context where an Exception was raised and allowing to resume from the error line. Obs.: since this code relies on continuations, it is not supposed to work on Ruby implementations without this resource (such as JRuby, Ribinius, etc)

lisp-conditions-in-ruby.rb

require 'continuation'

class Restart < RuntimeError
  attr_accessor :menu

  def initialize(**menu)
    @menu = menu

    @menu.each do |name, proc|
      define_singleton_method "#{name}!" do
        proc.call
      end
    end
  end
end

begin
  x = 10

  callcc do |c|
    raise Restart.new \
      resume: -> {         c.call },
      inc_x:  -> { x += 1; c.call }
  end

  puts "x: #{x}"
rescue Restart => e
  # binding.irb
  puts "Restart options:"
  e.menu.keys.each_with_index do
    puts "  - #{_2 + 1}: #{_1}"
  end

  e.inc_x!
end

The output of running this using MRI Ruby is like:

Restart options:
  - 1: resume
  - 2: inc_x
x: 11

After I worked on this experiment, I found this blog post (from almost 20 years ago!) with a better approach and also porting the example from the Practical Common LISP book (which explains very well why to use this):

https://leahneukirchen.org/blog/archive/2005/03/restartable-exceptions.html