Saxon

Now I have access to a system where I could try and indeed doing e.g.

        Processor processor = new Processor(true);

        XPathCompiler xpathCompiler = processor.newXPathCompiler();
        xpathCompiler.setLanguageVersion("4.0");

        XdmItem result = xpathCompiler.evaluateSingle("parse-html('<p id=p1>This is a test.<br>This is a test.<p>This is a test.')", null);

        System.out.println(result);

works fine (with 12.1 SaxonJ EE) if I add a dependency on e.g. nu.validator:htmlparser:1.4.6.

So it seems pure XPath 4.0 is already supported, just the documentation of setLanguageVersion needs to be updated to add "4.0" as a possible version string. And SaxonC might need a way to set the XPath version as well, at least I don't find a way to set it in the API https://www.saxonica.com/saxon-c/doc12/html/saxonc.html#PyXPathProcessor.

Thanks for letting us know. I've added bug #5995 to fix the documentation.

Feature #5967 has already been raised and resolved for the SaxonC issue.