A common base exception object for Perl - RFC

[Pete Jordan <pjordan1@email.mot.com>]

OK, I suppose somebody's gonna do it; might as well be me...

These are my initial ideas, constructive suggestions are most welcome
bearing in mind that this is intentionally a fairly simple base class.

RATIONALE

To provide a common base exception object class for Perl to encourage
interoperability between specific implementations. Usage of this module
should not break any existing standard C<eval> and C<$@> processing.

NAMESPACE

I would like this to be Exception. This does, however, conflict with
Peter Seibel's[1] exception module and intersects with Joshua
Pritikin's[2] Exception::Cxx. This may or may not be a problem.

PROPOSED INTERFACE

	use Exception qw(-stacktrace);

	my $e=new Exception 'text';

	my $f=new Exception -text=>'foo', -class=>'Error',
			-name=>'bar', -errcode=>$!, -exitcode=>23;

	raise Exception 'text';

	raise Exception -text=>'foo', -class=>'Error',
			-name=>'bar', -errcode=>$!, -exitcode=>23;

	my $string=$e->render;	# overloaded from '""'

	my $text=$e->text;
	my $old=$e->text('new');

	my $class=$e->class;
	my $name=$e->name;
	my $exitcode=$e->exitcode;
	my $errcode=$e->errcode;

	Exception->stacktrace($yesno);
	my $stack=$e->stack;

	$e->croak;
	$e->confess;

There are a fair number of methods/fields in there; my guess (which may
be wrong) is that they're the set that most people are most likely to
want.

I'm not planning to put any code in to deal with specific values of
class or name, I just want to provide a standard interface for anyone
who does want to so do.

Exitcode will default as per standard C<die> processing, it's there so
programmers can specify their own if they wish.

Errcode gets its own field so its dual nature can be retained. For
example:

	eval {
	  open FOO, '<bar'
	    or raise Exception "Can't read bar", -errcode=>$!;
	  ...
	};

	print STDERR "$@\n" if $@;

might print:

	Can't read bar: [2] No such file or directory

on failure.

IMPLEMENTATION

As you'd expect; a blessed hash reference, with:

	use overload '""'=>sub {shift->render};

In deference to Larry, I'll not create a C<$SIG{__DIE__}> handler (by
default at least) so:

	eval {
	  die 'whatever';
	};

	$@ and $@->croak;

won't work.

Pete

[1] PSEIBEL   Peter Seibel <seibel@organic.com>
[2] JPRIT     Joshua N. Pritikin <jpritikin@pobox.com>
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Follow-Ups from:

Graham Barr <gbarr@pobox.com>

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