dumping variables automatically with their name?

[LanX]

Hi

It's somehow a p!ta (or more diplomatic "not a pleasure") to dump variables together with their names.

Data::Dumper has a very cumbersome way to do it, where the variables have to be repeated, once as reference and then as string holding the name.

Data::Dump has no mechanism at all for names and expects me to handle the printing of the name.

Before I reinvent the wheel¹, is their already a good way to simply say

dmp \@a;

and to automatically get something like

\@a     => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

edit

When offering answers please keep in mind that different symbols can hold the same references or globs.

Reverse engineering the name is not trivial.

¹) well I already invented using B::Deparse, but IIRC when I asked some years ago and there was no clean way ...

updated

it helps to think about how such a module should be named! :)

see

Data::Dumper::Simple (uses source filter)

Data::Dumper::Names (depends on PadWalker and has limitations)

and maybe also Smart::Comments should be mentioned (another sourcefilter)

anything else?

[choroba]

when I asked some years ago

Link: Inspecting the name of a variable

[LanX]

yep thx! :)

... but still an open issue...

update

actually many thanks, I searched my hard disk for this posted code, I forgot that I "stored" it in the cloud... ;-)

[tobyink]

As well as Data::Dumper::Simple and Data::Dumper::Names I wrote Data::Dumper::Declare (but it's BackPAN-only now). I think my version provides slightly nicer output than the other two, but I removed it from CPAN because I think there are enough modules to do this already.

[Rhandom]

There is another method to get the name other than pad walking or name passing. I used this method in the 11 year old CGI::Ex::Dump module (looks like the POD for that module is rather lackluster - guess I should update it after 11 years). We've used a variant of this for some time.

Whenever we debug we also like to see the line location - once we have parsed for the line location it is trivial to open the code and look for that line and do a very barebones parse. Apologist notes: This may not be academically correct, but we don't care - we're debugging. The output will also not be right if the source file changes, or the debug line is too complex - but again I don't care about a perfect solution - I want a fast good enough solution. Maybe someday we'll update it to a padwalker, but it is really rather trivial as it is. Here is a sample:



$ cat sample.pl 
use strict;
use CGI::Ex::Dump qw(debug);
my $a = 123;
my @b = qw(1..10);
my $obj = bless {}, __PACKAGE__;
debug;
debug $a, \@b, $obj;
debug "Arbitrary String "x2;
debug {"a".."f"};

$ perl sample.pl 
debug: sample.pl line 6
debug: sample.pl line 7
  $a = 123;
  \@b = [
            "1..10"
          ];
  $obj = bless( {}, 'main' );
debug: sample.pl line 8
  String = "Arbitrary String Arbitrary String ";
debug: sample.pl line 9
  {"a".."f"} = {
            a => "b",
            c => "d",
            e => "f"
          };

The actual dumping is done by Data::Dumper, so setting all Data::Dumper options will control the output. It should be easy enough to replace the output with Data::Dump, or Data::Dumper::Simple, or even JSON or YAML, or any of the other 100 ways to dump out data. We used Data::Dumper because 11 years ago it was what there was.

Internally we use a variation of this codebase called simply "Debug". By default debug goes to STDOUT, but we have variants called debug_warn that goes to STDERR and a debug_dlog variant that will go directly to our perl based system logger.

[LanX]

Thanks! :)

... took a look into the source...

May I ask why you are reopening (i.e. reading again) the files if DATA is already pointing to them?

[trwww]

I use Data::Dumper->Dump( ARRAYREF, ARRAYREF ). You have to pass in the name, but it gives you what you're asking for:

use warnings;
use strict;
use Data::Dumper;

my @data = (qw(foo bar bazz));

print Data::Dumper->Dump([\@data], ["data"]);

outputs:

$data = [
          'foo',
          'bar',
          'bazz'
        ];

[LanX]

I knew, thats what I tried to avoid.