[Israel.pm] Perl and Debugging question

[Peter Gordon]

If you have a look it dumpvar.pl, you will find my name there. Once upon
a time, during the birth pangs of Perl 5,  I did bang my head against
it. 

I agree with you that the debugger is a Real Mess (tm) and hopefully in
Perl 6 it will be a lot nicer. 

Another way would be make an opaque object so that the values don't get
dumped down.  

Peter


On Mon, 2007-05-14 at 09:30 +0300, Gaal Yahas wrote:
> I disagree on both counts. :-)
> 
> Simplicity isn't one of the best descriptions of the debugger code.
> (By which I mean
> the actual debugger, perl5db.pl.) I mean sure, you could tweak around lines:
> 2434
> 654
> 5547
> 
> But you'd still have to bang your head against dumpvar.pl.
> 
> And how to make the interface for it? Just hardcode some arbitrary
> limit? Yet another config option? What happens when your members are
> actually tied scalars that when read do some expensive operation like
> compute a value or read from the network? Maybe you want to skip those
> fields too... How?
> 
> If what guides you is a sense that debuggability features don't seem
> clean to leave in production code, I hear you, but consider that they
> would be implemented in a separate unit of modularity (a Role, in the
> case of Perl 6) and have declarative, thus uncluttering,
> configuration. Incidentally, in Perl 6 Roles can be composed at
> runtime, so your production program has absolutely no trace of this
> filterable dumpage, until you drop into the debugger and add it to a
> particular instance. Then you also have a consistent interface to mess
> around with its properties.
> 
> On 5/14/07, Peter Gordon <peter at pg-consultants.com> wrote:
> > It might be simpler and more consistent to add an option to the debugger
> > itself.
> >
> > On Sun, 2007-05-13 at 21:50 +0300, Gaal Yahas wrote:
> > > On 5/13/07, Peter Gordon <peter at pg-consultants.com> wrote:
> > > > On this occasion, one of the elements is a string a few megabytes long,
> > > > and I don't really want to dump the whole string.
> > > >
> > > > What would be the nicest way to suppress printing of this particular
> > > > element.
> > > >
> > > > I could print each element in turn, but that is inelegant.
> > >
> > > I'm afraid I don't have an elegant solution to offer. (A related
> > > problem that does
> > > have debugger support is deeply recursive structures. Saying "x 3
> > > $that" limits to
> > > depth 3 print.)
> > >
> > > What you might do -- and I'm not saying this is significantly
> > > different from printing each element in turn -- is add a to_debug
> > > method to the object. This copies the object but only leaves a digest
> > > version of the long string, say with the first 100 characters.
> > >
> > > Not that I've searched CPAN for prior art, but you might want to make
> > > this into a reusable module. (With Moose.pm or Perl 6, it would more
> > > properly be a Role.) Something like:
> > >
> > > package MyModuleWithLongMember;
> > >
> > > use Debug::Dump::Digest qw(long_memb1 huge_memb2);
> > >
> > > And then in the debugger:
> > >
> > > x $self->to_debug;
> > >
> >
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> >
> 
>