XPath queries for namespaces are broken on JRuby

[flavorjones]

Discovered while working on #761 (test breakage on the issue-761 branch). Getting the following exception:

# NokogiriHelpers.java:105:in `getCachedNodeOrCreate': java.lang.ClassCastException: nokogiri.XmlNamespace cannot be cast to nokogiri.XmlDocument

I've found this behavior is different in the two following examples.

Example 1:

xml = <<EOXML
<root xmlns:foo="http://google.com/">
  <foo:node>hello</foo:node>
</root>
EOXML

doc = Nokogiri::XML xml
puts doc.xpath("//namespace::*").inspect # first time is OK
puts doc.xpath("//namespace::*").inspect # second time raises exception

Example 2:

xml = <<EOXML
<base>
  <root xmlns:foo="http://google.com/">
  </root>
</base>
EOXML

doc = Nokogiri::XML xml
puts doc.xpath("//namespace::*").inspect # raises exception

[soulcutter]

No test case included with the fix?

[jvshahid]

there was a failing test (test_collect_namespaces) on the issue-761 branch.

[soulcutter]

Awesome. I was going to circle back around this evening and add a test case, but you are on top of it! Apologies if I came across as critical.

[jvshahid]

No worries. Critical is better than sloppy. Thanks for following up.