DJpumps has asked for the wisdom of the Perl Monks concerning the following question:

I'm using XML::Twig and have noticed that it replaces white-space characters to spaces. Something like s/\s/ /g on all attribute and element values.

See example code: 

#!/usr/bin/perl
use strict;
use warnings;
use XML::Twig;
my $twig=XML::Twig->new();
my $xml = qq{<root t="space tab\tnewline\nend"/>};
$twig->xparse($xml);
my $text=$twig->root->att('t');
print "|$text|\n";

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The expected output (contents of the scalar $text is the word space followed by a single space character, followed by the word tab, followed by a single tab character, followed by the word newline, followed by a single newline character, and then the word end.

Instead, the tab and the newline characters were replaced by a single space character each.

  1. Why?
  2. How can I force XML::Twig to preserve whitespaces and not alter the text in any form?

This relates to XML::Twig 3.29 and XML::Twig 3.30. I did not check this behavior in other versions of XML::Twig

Thanks.

-- DJpumps

Replies are listed 'Best First'.
Re: XML::Twig and whitespaces
by mirod (Canon) on Aug 23, 2007 at 15:06 UTC

    In attributes, the behaviour shown is normal, actually, it is required by the XML spec, see Attribute Value Normalization.

    I don't think the module does that in elements, except that it discards line returns followed by spaces between 2 tags (getting rid of non-significant whitespaces, as far as it can tell). you can turn this off using the keep_spaces option when you create the twig.

    You could not-normalize attribute values by using the keep_encoding method and writing your own start tag parser (based on XML::Twig's own parser in _parse_start_tag) and using it through the parse_start_tag option. Not really simple, but you are trying to do non XML processing with an XML processor here.

[reply]
      Hello, midod, and thanks for your quick reply. While you are right (and I was wrong) with regards to Attribute Value Normalization (see the correct updated reference from XML 1.0 4th edition at http://www.w3.org/TR/REC-xml/#AVNormalize), this behavior should not apply to element value. However, it does when using XML::Twig. I want to be able to read element values "as is" without applying any manipulation to these values, at least whitespace wise. So is there a way and if so what is the way of perserving whitespaces? Thanks.
      -- DJpumps
[reply]

        Did you try "using the keep_spaces option when you create the twig" as indicated in my previous answer? Did it not do what you want?

[reply]
Re: XML::Twig and whitespaces
by monkey_boy (Priest) on Aug 23, 2007 at 14:49 UTC
    I modified your code below to see how XML::Simple handles this, is seems to do the same thing, i suspect its one of the underlying modules possibly XML::Parser thats causing this: 
    #!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use XML::Simple;
my $xml = XMLin(qq{<root t="space tab\tnewline\nend"/>});
print Dumper $xml;

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    output: 
    $VAR1 = {
          't' => 'space tab newline end'
        };

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