From: "NAKAMURA, Hiroshi" <nakahiro@...>
Date: 2002-12-03T19:47:06+09:00
Subject: Re: inwoking irb from the middle of things

Hi, 

> From: "Radek Hnilica" <Radek@Hnilica.CZ>
> Sent: Friday, November 29, 2002 9:18 PM

> The far goal is to have fully interactive environment where in time of
> failure the program doesn't end but fires interactive session.

$ cat catch.rb
require 'irb'

module IRB
  def IRB.start2(eval_binding, ap_path)
    IRB.setup(ap_path)
    irb = Irb.new(WorkSpace.new(eval_binding))
    @CONF[:MAIN_CONTEXT] = irb.context
    trap("SIGINT") do
      irb.signal_handle
    end
    catch(:IRB_EXIT) do
      irb.eval_input
    end
  end
end

set_trace_func proc { |event, file, line, id, binding, *rest|
  if event == 'raise'
    $stdout.printf "%s:%d: `%s' (%s)\n", file, line, $!, $!.class
    tb = caller(0)[2..-1]
    for i in tb
      $stdout.printf "\tfrom %s\n", i
    end
    IRB.start2(binding, $stdin)
  end
}

$ ruby17 -rcatch -e 'a = 5; raise rescue RuntimeError; p a'

You can catch an exception and inspect a binding where
an error occurred.  But... after quitting IRB session,
your program will exit silently.  e.g. "p a" above won't
executed.

Hmm.  Doing catch/throw when "raise" before "rescue" might
let ruby confuse though I don't know anything about it.


Back to the topic, as ts stated, debug.rb could help you.

$ ruby -rdebug -e 'a = 5; raise rescue RuntimeError; p a'
Debug.rb
Emacs support available.

-e:1:a = 5; raise rescue RuntimeError; p a
(rdb:1) cont
-e:1: `' (RuntimeError)
        from -e:1
-e:1:a = 5; raise rescue RuntimeError; p a
(rdb:1) a = 6
6
(rdb:1) cont
6

Bear in mind you cannot recover(resume) the exception to
continue execution.  We don't have standard way to do it.

Regards,
// NaHi