I feel there is something I'm missing in regards to namespace inheritance in XML::LibXML. Please consider the following:

<?xml version="1.0"?>
<root xmlns:foo="http://foo"><parent><foo:child/></parent></root>
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Element foo:child is valid without a xmlns:foo="http://foo" attribute since that appears further up the tree, in the root node. What I don't quite understand is the behavior of addChild or appendChild of XML::LibXML::Node which doesn't seem to realize that prefix is associated with a namespace further up the tree (in the root node) and doesn't properly split foo:child.

use strict;
use warnings;

use XML::LibXML;

my $d = XML::LibXML::Document->new;
$d->setDocumentElement(  my $r = $d->createElement( q{root} )  );
$r->setNamespace( q{http://foo}, q{foo}, 0 );
my $p = $r->addChild(  $d->createElement( q{parent} )  );
my $c = $p->addChild(  $d->createElement( q{foo:child} )  );

printf qq{child->prefix=%s, child->localname=%s\n}, $c->prefix, $c->lo
+calname;
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Which yields: child->prefix=, child->localname=foo:child
When I would have expected: child->prefix=foo, child->localname=child

I know createElementNS can be used, but that requires one to know what NS to pass rather than being able to rely on inheritance. What is even stranger is inheritance actually appears to work with attributes. If I add the following to the code above:

$c->setAttribute( q{foo:abc}, q{123} );
my $an = $c->getAttributeNode( q{foo:abc} );
printf qq{an->prefix=%s, an->name=%s\n}, $an->prefix, $an->name;
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I get this: an->prefix=foo, an->name=abc

Also note the lack of using setAttributeNS method, as this is about inheritance, rather than manually specifying the namespace uri each time an attribute is added.

So why doesn't this seem to work for elements? Maybe I'm really missing something, probably fairly obvious, as it seems this should be trivial.

Thanks.