From: Andrew Johnson <ajohnson@...>
Date: 2006-03-29T07:43:42+09:00
Subject: Re: is -w really useful?

On Wed, 29 Mar 2006 07:17:10 +0900, Wybo Dekker <wybo@servalys.nl> wrote:
> 
> Well, you can already say: $VERBOSE = true or $VERBOSE = false.
> Isn't that the same?

Actually, $VERBOSE can take on three semantic values: nil, false, true.
Further, behaviour can differ slightly if -W0, -W1, -W2 (ie, nil, false,
true (and -w == -W2) are set from the command line as opposed to setting
$VERBOSE in the script (parse-time vs runtime). This means that doing
something akin to:

  module Kernel
    def no_warn
      begin
        verbose = $VERBOSE
        $VERBOSE = nil
        yield
        ensure
        $VERBOSE = verbose
      end
    end
  end

  no_warn do
    puts (0..5)
  end

doesn't quench the warning, but -W0 does. Strangely, changing that
block to:

  no_warn do
    puts "foo"
    puts (0..5)
  end

results in yet different warning behaviours.

At any rate, a catchable warning system might be a good idea and
encourage people to wrap 'warnable' code in blocks that don't emit
particular warnings -- so something like:

  no_warn :method_redefined do
    # (meta)code that redefines methods
  end

would explicitly turn off the method redefinition warning (presumably we
are doing that on purpose here), but still emit any other warnings the
code might generate.

Just a thought.

andrew

-- 
Andrew L. Johnson   http://www.siaris.net/
      The generation of random numbers is too 
      important to be left to chance.