Re: XML Newbie

[mirod]

An XML::Twig version that does not load the entire XML in memory:

#!/usr/bin/perl

use strict;
use warnings;

use XML::Twig;

my $t=XML::Twig->new( start_tag_handlers => 
                       {  _all_ => \&store_line_number, },
              twig_handlers =>
                       { _all_  => \&warn_on_empty_elt, },
                     );
$t->parsefile( "so_line_numbers.xml");

sub store_line_number
  { my( $twig, $elt)= @_;
     $elt->set_att( '#line' => $twig->current_line); 
     $elt->parent->set_att( '#not_empty') if $elt->parent; 
  }

sub warn_on_empty_elt
  { my( $twig, $elt)= @_;
    if( ! $elt->att( '#not_empty') && $elt->text !~ m{\S}) { print $el
+t->att( '#line'), "\n"; }
    $twig->purge;
  }

The little bit of cleverness here is that the code manages whether an element is empty or not itself, which allows it to purge the twig after each element (otherwise an enclosing element would have no content and trigger the warning).

[remiah]

Hello mirod.

I read your post and tried. And found it seems not working good. This prints

3
4
1

And the script is like this. Just added example xml with your script.
Read more... (1114 Bytes)
As you see the DATA, empty tag will be ddd, and eee(line 3,4). And print out of "1" means "gibsonca" tag. I wonder this has relation with parsing of twig, as document says,

Remember that element handlers are called when the element is CLOSED, so if you have handlers for nested elements the inner handlers will be called first.

So, as a result of purging inner elements, gibsonca tag is empty for twig, I guess.

If I comment out purge, it prints line number 3 and 4.

regards.

update: Large XML files may have some cluster that may be easy to purge. For example item tag in the below case. Maybe this will print line number of end tag(not as correct as yours), but I would like to purge like this.
Read more... (1146 Bytes)

[mirod]

Duh! you need to set #not_empty to a true value. That will teach me to change tested code right before posting it.

So it should be $elt->parent->set_att( '#not_empty', 1) if $elt->parent;

regarding the update: in the code I wrote, the twig is purged after each element, that's why you need the #not_empty attribute, because within the twig handler, every single element appears empty, except if it contains text.

[remiah]

Thanks for reply.

It works fine.