Wrapping exceptions in Ruby

gistfile1.rb

class CustomError < StandardError
  def initialize(e = nil)
    super e
    set_backtrace e.backtrace if e
  end
end

def run
  r = Runner.new
  r.fail
end

class Runner
  def fail
    _fail
  end

  def _fail
    service = RunnerService.new
    service.fail
  rescue StandardError => e
    raise CustomError.new(e)
  end
end

class RunnerService
  def fail
    _fail
  end

  def _fail
    raise StandardError.new('Service failed')
  end
end

begin
  run
rescue CustomError => e
  puts e.message
  puts '  ' + e.backtrace.join("\n  ")
end

+1 for this!

Some tweaks:

class ClientError < StandardError
  def initialize(e = nil)
    super e
    # Preserve the original exception's data if provided
    if e && e.is_a?(Exception)
      set_backtrace e.backtrace
      message.prepend "#{e.class}: "
    end
  end
end

Fortunately, this is not needed anymore from Ruby 2.1 on:
http://devblog.avdi.org/2013/12/25/exception-causes-in-ruby-2-1/