[xml] xmlDocCopyNode and local namespace copies

[Callum Gibson <callum_r_gibson yahoo com au>]

Hi,
As part of my xsd -> xml translation thing I've been working on (you may
recall my emails of several weeks ago), I've created a "template" xml
document (largely using the tree api). The schema I'm working with has
some elements that need to be qualified. The template document is just
a skeleton of elements with no text values. Here's a cut down example.

<Top:Top xmlns:Top="http://thing.com/Top"; xmlns:Qual="http://thing.com/Qual";>
    <Foo>
        <Qual:Bar/>
        <Qual:Splodge/>
        ...
    </Foo>
    <Other>
        <Things>
    ...
        </Things>
    </Other>
</Top:Top>

So everything inside <Foo> needs to be a qualified element. No problem,
you just need to create the node "Bar" with the necessary namespace which
was defined at the root node, Top. If I dump out this document with
xmlDocFormatDump I can see the desired result. However, in the process
of doing this I discovered that if you assign a copy of the namespace
(with same prefix and href) it will instead redefine the namespace locally
within each node.

        <Qual:Bar xmlns:Qual="http://thing.com/Qual"; />

That was fine, I just search for the namespace up to the doc root using
xmlSearchNsByHref() when I need to create that node and it worked. Problem
one solved, however this same issue would come back again.

Now, I want to take this template document and populate it with data
values. I'm doing this by traversing the node tree of the template
document and calling a callback function back into my application to
collect the required data. The callback has the option of excluding
elements with minOccurs = 0, or duplicating elements with maxOccurs >
1. This is all done in my template -> instance engine.

As I traverse the tree I'm using the following:

    instance_node = xmlDocCopyNode(template_node, instance_doc, 2);

So I want to copy properties and namespaces, but not recursive children
as I'm performing the recursion myself. Now, the problem is, that while
instance_doc has xmlns:Qual="http://thing.com/Qual"; defined at this
stage, and while template_node has a namespace which matches template_doc's
namespace (hence qualified elements dump correctly), this function will
make a duplicate COPY of the namespace, not refer to the template_doc's
definition of it. This has the effect of redefining the namespace in
the output, which is functionally the same, but looks a bit ugly.

Should xmlDocCopyNode handle this a bit smarter (imagine what would
happen in the recursive case)? Or should I just use:

xmlDocCopyNode(template_node, instance_doc, 0);

and handle all the namespace (and properties) copies myself, and re-search
the instance_doc for each (copied) namespace definition as required?

regards,
    Callum

-- 

Callum Gibson @ home