From: Stefan Lang <perfectly.normal.hacker@...>
Date: 2008-10-11T00:23:45+09:00
Subject: Re: rescue clause

2008/10/10 Patrick Doyle <wpdster@gmail.com>:
> I have been looking at the source code for rake (as you can probably tell
> from my previous questions), in an attempt to study a reasonable sized Ruby
> application and see what I can learn from the exercise.  I've come across
> something that looks like it could be an innocuous typo in the code, or it
> could be doing something that I just don't understand.  Here is the code
> snippet:
>
>    def standard_exception_handling
>      begin
>        yield
>      rescue SystemExit => ex
>        # Exit silently with current status
>        exit(ex.status)
>      rescue SystemExit, OptionParser::InvalidOption => ex
>        # Exit silently
>        exit(1)
>      end
>    end
>
> I am curious as to why SystemExit shows up in 2 different rescue clauses.
> Is that a typo?  Or is something else going on?

The the first rescue clause and the SystemExit in the second clause
can be removed without changing the semantics of the code.

As a sidenote, something being popular does not necessarily
mean it should be used as a model for good Ruby code.
Sometimes the techniques used only make sense in a
historical context.

Stefan