return an empty node set when xpath expression doesn't match

[clarkevans]

No description provided.

[bicycle1885]

Could you show me any examples that will cause a problem?

[bicycle1885]

For example, the following example does not fail even though there is no matching nodes for a query:

julia> doc = parsexml("""<root/>""")
EzXML.Document(EzXML.Node(<DOCUMENT_NODE@0x00007fc53d7e9b10>))

julia> find(doc, "//notexit")
0-element Array{EzXML.Node,1}

[clarkevans]

This seems to be a minimal test case where it fails (extracted from a huge input and messy xpath query)

using EzXML
doc = parsexml("""<root xmlns="urn:foo"/>""")
rs = find(root(doc), "//foo:notexit/*", [("foo", "urn:foo")])

Perhaps it is triggering some deep bug in libxml (v2.9.3) causing the null pointer, alas, this case happens everywhere in my data sets and I've been unable to write an xpath expression that avoids the issue.

BTW, thank you for the lovely EzXML library. It's very much appreciated.

[bicycle1885]

Thank you. I've quickly checked libxml2 and found the following macro in xpath.h:

/**
 * xmlXPathNodeSetIsEmpty:
 * @ns: a node-set
 *
 * Checks whether @ns is empty or not.
 *
 * Returns %TRUE if @ns is an empty node-set.
 */
#define xmlXPathNodeSetIsEmpty(ns)                                      \
    (((ns) == NULL) || ((ns)->nodeNr == 0) || ((ns)->nodeTab == NULL))

So, your patch looks good to me 👍 .

[Osirisxblack]

👌