From: Daniel Nugent <nugend@...>
Date: 2005-07-05T05:39:35+09:00
Subject: REXML and namespace axis troubles

Hello,

I've been trying to use the namespace:: in an XPath query to get at
the namespaces for some XML elements and I've been having some seirous
difficulty with it.

I kept getting a bunch of errors about nil not having a '<<' method
defined.  So I went back and checked my query string and it turns out
to be fine as far as a I can tell.  Then I tried a bunch of simple
query strings using he namespace:: axis and they all failed too.

For example: "REXML::XPath.match(xml.root, 'namespace::*')"

This errored and I'm not sure how much more simple I can make a query
using the namespace axis so I decided to go in and check the code in
REXML.

Going through the call chain, I came upon one section in
REXML::XPath_Parser.rb that caught my eye:

      when :namespace
        new_set = []
        for node in nodeset
          new_nodeset << node.namespace if node.node_type == :element
or node.node_type == :attribute
        end
        return new_nodeset

This section is near the end of the method internal_parse if you're curious.

Two things I noted that would cause problems here:

1) new_nodeset is going to be nil on that shift operation (which is
what gave me the original error message).

2) new_nodeset will only contain the default namespace for each node,
not all of the namespaces as "namespace::*" is supposed to return.

I corrected the typo for new_nodeset and tried again and I got a
different error, basically that the string that new_nodeset was
assigned was being treated as a node when it couldn't.

I'm not sure how to fix this, and I can't get to the REXML homepage
right now (it seems to be down).

Does anybody have any advice on this?  Have I really misunderstood something?
-- 
-Dan Nugent