How to invoke "dynamic" XPaths with count() in Karate? [duplicate] - xpath

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I'm trying to invoke a "dynamic" XPath in Karate that uses the XPath count() function to return a number (or string representation).
[With Karate 0.9.2] I'm trying to invoke "dynamic" XPath expressions (originally read from a JSON-based configuration file) on an XML document.
There are (potentially) multiple XPath expressions so I am using Karate's karate.forEach() to invoke an XPath utility Javascript function repeatedly within Karate.
Within the embedded Javascript function I use karate.xmlPath() to invoke the "dynamic" XPath expression string.
This works fine for retrieving single nodes, node lists etc but it fails when the expression uses XPath's count() function as the result is a number rather than an XML node or XML NodeList.
Feature: General XPath based evaluator
Scenario: ....
# Omitting details around performing HTTP request to obtain XML response....
* xml payload = ..... $.requests[0].body ...
#
# A JS Function to invoke each XPath Query in our query dictionary
#
# queryDictionaryItem has a single XPath query in it with an expected
value
# { "xpath": <query>, "expectedValue", <string> }
#
* def checkXPathQueryFn =
"""
function(queryDictionaryItem) {
var requestXML = karate.get("payload");
var xpathQuery = queryDictionaryItem.xpath;
var expectedValue = queryDictionaryItem.expectedValue;
// [!!] This will blow up if the xpathQuery is of the form:
// "count(........)"
// --> Cannot return a NUMERIC value rather than a NODELIST
var actualValue = karate.xmlPath( requestXML, xpathQuery );
var match = karate.match( actualValue, expectedValue );
if (!match.pass)
{
karate.abort("Failed to match expectation..."); }
}
"""
# queryDictionary is a list of JSON objects of the form:
# { "xpath": <query>, "expectedValue", <string> }
* eval karate.forEach(queryDictionary, checkXPathQueryFn)
Expected result:
Receive a String/Number when an XPath based on count() is dynamically invoked.
Actual outcome:
Error:
javax.xml.xpath.XPathExpressionException: com.sun.org.apache.xpath.internal.XPathException: Can not convert #NUMBER to a NodeList!
javascript evaluation failed: karate.forEach(requestExpectations, oldCheckExpectation), javax.xml.xpath.XPathExpressionException: com.sun.org.apache.xpath.internal.XPathException: Can not convert #NUMBER to a NodeList!
For the Intuit Karate developers: [#ptrthomas]
In the v0.9.2 version of karate-core, there are provisions for use of count() in XPaths within Script#evalXmlPathOnXmlNode():
https://github.com/intuit/karate/blob/master/karate-core/src/main/java/com/intuit/karate/Script.java#L367 L367
but as we're using dynamic XPath, the call sequence does not use that "safeguard" and instead uses ScriptBridge#xmlPath()
https://github.com/intuit/karate/blob/master/karate-core/src/main/java/com/intuit/karate/core/ScriptBridge.java#L230 L230
This method has the line:
Node result = XmlUtils.getNodeByPath((Node) o, path, false);
which throws RuntimeExceptions when XPath expressions do not return NODESET shaped data.
https://github.com/intuit/karate/blob/master/karate-core/src/main/java/com/intuit/karate/XmlUtils.java#L152 L152.

Answer 1

Confirming this Karate Framework issue is fixed with the latest (as at 2019-04-23) Karate Core (Development branch build).
This fix is scheduled for release in Intuit Karate v0.9.3.
Java/Karate source further detailing the issue and an alternative (interim), Java-native workaround via direct Java XPath interop is listed at:
https://github.com/mhavilah/karateDynamicXPath
NB: The behaviour of the XPathHelper in the above project is slightly different to that of the karate.xmlPath() DSL service.
In particular for retrieving single XML elements, the karate DSL auto extracts the underlying text() node, whereas the Java native Helper requires explicit reference to the embedded text node within the XML element.