From: David Alan Black <dblack@...>
Date: 2002-07-19T10:09:16+09:00
Subject: Re: Can you only catch errors one level deep?

Hello --

On Fri, 19 Jul 2002, Philip Mak wrote:

> On Fri, Jul 19, 2002 at 09:31:02AM +0900, Alan Chen wrote:
> > On Fri, Jul 19, 2002 at 09:04:02AM +0900, Philip Mak wrote:
> > > The problem with "rescue LoadError" is that it will also catch errors
> > > it wasn't meant to! In my case, the file it loaded existed, but
> > > requiring that file threw a LoadError because there was some other
> > > problem with it. So the "rescue" caught an error it wasn't meant to
> > > catch, and just made debugging harder.
> >
> > What errors did rescue LoadError catch? Where they derived from LoadError?
>
> It caught a LoadError that was thrown by 'require <file>'. However,
> the LoadError was thrown not because <file> couldn't be loaded, but
> because <file> had a 'require' statement of its own which threw a
> LoadError.
>
> I think the problem is that people see code like this:
>
> begin
> 	require 'somefile'
> rescue LoadError
> 	# do something
> end
>
> and assume that if "# do something" is executed, then it means that
> 'somefile' did not exist or isn't readable.

I guess you could examine the backtrace:

  rescue LoadError => e
  b = e.backtrace

  # now look at the size of b ...

I'm sort of winging it here -- not sure if there are conditions under
which this would or wouldn't work.


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav