& XSLT On Monday 13 August 2007, Steve Hay wrote:
>  I've just upgraded from 1.58_01 to 1.63 and I've been bitten by a change
>  of behaviour that was introduced in 1.62, namely, that
>  $elt->cloneNode(0) now copies namespace information.
> 
>  Thus, the following program:
> 
>  use XML::LibXML;
>  use XML::LibXML::XPathContext;
>  my $parser = XML::LibXML->new();
>  my $olddoc = $parser->parse_string(<<'EOX');
>  <?xml version="1.0" encoding="UTF-8"?>
>  <root xmlns="http://www.foo.org"/>
>  EOX
>  my $ctx = XML::LibXML::XPathContext->new();
>  $ctx->registerNs('foo', 'http://www.foo.org');
>  $ctx->setContextNode($olddoc);
>  my($oldelt) = $ctx->findnodes('/foo:root');
>  my $newelt = $oldelt->cloneNode(0);
>  my $newdoc = XML::LibXML::Document->createDocument('1.0', 'UTF-8');
>  $newdoc->setDocumentElement($newelt);
>  print $newdoc->toString();
> 
>  now prints:
> 
>  <?xml version="1.0" encoding="UTF-8"?>
>  <root xmlns="http://www.foo.org"/>
> 
>  whereas it used to print:
> 
>  <?xml version="1.0" encoding="UTF-8"?>
>  <root/>
> 
>  I see in Node.pod that this is an intentional change for a good reason
>  (and suitably documented too) so I'm not complaining about it, but I do
>  need some way of getting the old behaviour, or something equivalent to
>  it, back.

In such cases it seems more apropriate to create a new element and copying all 
attributes by hand; anyway ... read below

>  I'm copying an element from within a document that has an xmlns
>  declaration in its document element, and making a new document out of
>  it. The new document must not have any xmlns declaration when it is
>  output, otherwise it'll break lots of XSL code further down the line.
> 
>  I had been using cloneNode(0) recursively (and copying any attributes
>  present "manually") to achieve the desired behaviour, but as shown above
>  I now find that cloneNode(0) copies the namespace too.
> 
>  I tried using the new setNamespaceDeclPrefix() on the copied element to
>  try to clear its namespace:
> 
>  ...
>  my $newelt = $oldelt->cloneNode(0);
>  $newelt->setNamespaceDeclPrefix('foo', undef);
>  ...
> 
>  but that gives me an error:
> 
>  setNamespaceDeclPrefix: prefix '(null)' is in use at test.pl line 13.
>  Why does that cause an error? 

Well, this seems ok to me. Your document is

<root xmlns="http://www.foo.org"/> 

and the command above tries to turn a (non-existing) xmlns:foo="..." 
declaration into xmlns="" (aka default namespace), but the void prefix is 
already taken by http://www.foo.org. It would seem more natural if 
XML::LibXML first detected that you in fact do not have any xmlns:foo="..." 
declaration in your document and complain about that, but that's just an 
implementation issue. The error messages tries to tell you that if your 
document looked like

<root xmlns="http://www.foo.org" xmlns:foo="http://some.other.foo"/> 

after a

$newelt-> setNamespaceDeclPrefix('foo', undef);

(if it didn't err) you would get, 

<root xmlns="http://www.foo.org" xmlns="http://some.other.foo"/> 

which is "ill-formed" XML. 

>  Is there some way to remove the xmlns
>  using setNamespaceDeclPrefix() or setNamespaceDeclURI()?

Yes, you are supposed to do

$newelt-> setNamespaceDeclURI('',undef);  # or (undef,undef)

which reads: undefine the namespace declaration for the empty prefix.

-- Petr
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