Merge pull request #4804 from adangel:issue-4309-xpath-cleanups

[core] XPath cleanups #4804

docs/pages/pmd/userdocs/extending/defining_properties.md

@@ -165,7 +165,6 @@ with a backslash when needed.
 ```xml
 <rule name="MyXpathRule" ...>
   <properties>
-    <property name="version" value="2.0" />
     <property name="intProp" type="List[Integer]" value="1,2,5" description="An IntegerMultiProperty." />
     <property name="reportedIdentifiers" type="List[String]" value="foo,bar"
               description="A StringMultiProperty." />

docs/pages/pmd/userdocs/extending/writing_rules_intro.md

@@ -104,7 +104,7 @@ instead of mentioning the `ref` attribute, it mentions the `class` attribute,
 with the implementation class of your rule.
 
 * **For Java rules:** this is the concrete class extending AbstractRule (transitively)
-* **For XPath rules:** this is `net.sourceforge.pmd.lang.rule.XPathRule`.
+* **For XPath rules:** this is `net.sourceforge.pmd.lang.rule.xpath.XPathRule`.
 * **For XPath rules analyzing XML-based languages:** this is `net.sourceforge.pmd.lang.xml.rule.DomXPathRule`.
   See [XPath rules in XML](pmd_languages_xml.html#xpath-rules-in-xml) for more info.
 
@@ -128,7 +128,7 @@ Example for XPath rule:
 <rule name="MyXPathRule"
       language="java"
       message="Violation!"
-      class="net.sourceforge.pmd.lang.rule.XPathRule">
+      class="net.sourceforge.pmd.lang.rule.xpath.XPathRule">
     <description>
         Description
     </description>

docs/pages/pmd/userdocs/extending/writing_xpath_rules.md

@@ -27,7 +27,8 @@ with opt-in support for XPath 2.0.
 See [the Saxonica documentation](https://www.saxonica.com/html/documentation/expressions/xpath31new.html)
 for an introduction to new features in XPath 3.1.
 
-The property `version` of {% jdoc core::lang.rule.XPathRule %} is deprecated and will be removed.
+The property `version` of {% jdoc core::lang.rule.XPathRule %} is deprecated and
+has been removed with PMD 7.
 
 
 ## DOM representation of ASTs

docs/pages/pmd/userdocs/extending/your_first_rule.md

@@ -127,7 +127,7 @@ copy-paste into your ruleset XML. The resulting element looks like so:
 <rule name="DontCallBossShort"
       language="java"
       message="Boss wants to talk to you."
-      class="net.sourceforge.pmd.lang.rule.XPathRule">
+      class="net.sourceforge.pmd.lang.rule.xpath.XPathRule">
     <description>
         TODO
     </description>

docs/pages/pmd/userdocs/migrating_to_pmd7.md

@@ -109,9 +109,11 @@ XPath 2.0 is available in PMD 6 already and can be used right away. PMD 7 will u
 won't support XPath 1.0 anymore. The difference between XPath 2.0 and XPath 3.1 is not big, so your XPath 2.0
 can be expected to work in PMD 7 without any further changes. So the migration path is to simply migrate to XPath 2.0.
 
-After you have migrated your XPath rules to XPath 2.0, remove the "version" property, since that will be removed
+After you have migrated your XPath rules to XPath 2.0, remove the "version" property, since that has been removed
-with PMD 7. PMD 7 by default uses XPath 3.1.
+with PMD 7. PMD 7 by default uses XPath 3.1. See below [XPath](#xpath-migrating-from-10-to-20) for details.
-See below [XPath](#xpath-migrating-from-10-to-20) for details.
+
+Then change the `class` attribute of your rule to `net.sourceforge.pmd.lang.rule.xpath.XPathRule` - because the
+class {%jdoc core::lang.rule.xpath.XPathRule %} has been moved into subpackage {% jdoc_package core::lang.rule.xpath %}.
 
 There are some general changes for AST nodes regarding the `@Image` attribute.
 See below [General AST Changes to avoid @Image](#general-ast-changes-to-avoid-image).

docs/pages/release_notes.md

@@ -175,6 +175,7 @@ The rules have been moved into categories with PMD 6.
   * [#3903](https://github.com/pmd/pmd/issues/3903): \[core] Consolidate `n.s.pmd.reporting` package
   * [#3917](https://github.com/pmd/pmd/issues/3917): \[core] Consolidate `n.s.pmd.lang.rule` package
   * [#4065](https://github.com/pmd/pmd/issues/4065): \[core] Rename TokenMgrError to LexException, Tokenizer to CpdLexer
+  * [#4309](https://github.com/pmd/pmd/issues/4309): \[core] Cleanups in XPath area
   * [#4312](https://github.com/pmd/pmd/issues/4312): \[core] Remove unnecessary property `color` and system property `pmd.color` in `TextColorRenderer`
   * [#4313](https://github.com/pmd/pmd/issues/4313): \[core] Remove support for <lang>-<ruleset> hyphen notation for ruleset references
   * [#4314](https://github.com/pmd/pmd/issues/4314): \[core] Remove ruleset compatibility filter (RuleSetFactoryCompatibility) and CLI option `--no-ruleset-compatibility`
@@ -235,6 +236,11 @@ The rules have been moved into categories with PMD 6.
 See [General AST Changes to avoid @Image]({{ baseurl }}pmd_userdocs_migrating_to_pmd7.html#general-ast-changes-to-avoid-image)
 in the migration guide for details.
 
+**XPath Rules**
+* The property `version` was already deprecated and has finally been removed. Please don't define the version
+  property anymore in your custom XPath rules. By default, the latest XPath version will be used, which
+  is XPath 3.1.
+
 **Moved classes/consolidated packages**
 
 * pmd-core
@@ -252,6 +258,7 @@ in the migration guide for details.
     * {%jdoc core::reporting.RuleViolation %}
     * {%jdoc core::reporting.ViolationSuppressor %}
     * {%jdoc core::reporting.ParametricRuleViolation %} (moved from `net.sourcceforge.pmd.lang.rule`)
+  * {%jdoc core::lang.rule.xpath.XPathRule %} has been moved into subpackage {% jdoc_package core::lang.rule.xpath %}.
 
 **Internalized classes**
 
@@ -746,6 +753,7 @@ See also [Detailed Release Notes for PMD 7]({{ baseurl }}pmd_release_notes_pmd7.
     * [#4204](https://github.com/pmd/pmd/issues/4204): \[core] Provide a CpdAnalysis class as a programmatic entry point into CPD
     * [#4301](https://github.com/pmd/pmd/issues/4301): \[core] Remove deprecated property concrete classes
     * [#4302](https://github.com/pmd/pmd/issues/4302): \[core] Migrate Property Framework API to Java 8
+    * [#4309](https://github.com/pmd/pmd/issues/4309): \[core] Cleanups in XPath area
     * [#4312](https://github.com/pmd/pmd/issues/4312): \[core] Remove unnecessary property `color` and system property `pmd.color` in `TextColorRenderer`
     * [#4313](https://github.com/pmd/pmd/issues/4313): \[core] Remove support for <lang>-<ruleset> hyphen notation for ruleset references
     * [#4314](https://github.com/pmd/pmd/issues/4314): \[core] Remove ruleset compatibility filter (RuleSetFactoryCompatibility) and CLI option `--no-ruleset-compatibility`

pmd-apex/src/main/resources/category/apex/bestpractices.xml

@@ -106,7 +106,7 @@ private class TestRunAs {
           since="6.13.0"
           language="apex"
           message="Apex test methods should have @isTest annotation."
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_bestpractices.html#apexunittestmethodshouldhaveistestannotation">
         <description>
 Apex test methods should have `@isTest` annotation instead of the `testMethod` keyword,
@@ -116,7 +116,6 @@ annotation for test classes and methods.
         </description>
         <priority>3</priority>
         <properties>
-            <property name="version" value="2.0"/>
             <property name="xpath">
                 <value>
 <![CDATA[
@@ -231,7 +230,7 @@ trigger Accounts on Account (before insert, before update, before delete, after
           since="6.18.0"
           language="apex"
           message="Calls to System.debug should specify a logging level."
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_bestpractices.html#debugsshoulduselogginglevel">
        <description>
 The first parameter of System.debug, when using the signature with two parameters, is a LoggingLevel enum.

pmd-apex/src/main/resources/category/apex/codestyle.xml

@@ -37,7 +37,7 @@ public class fooClass { } // This will be reported unless you change the regex
           language="apex"
           since="5.6.0"
           message="Avoid using 'if...else' statements without curly braces"
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_codestyle.html#ifelsestmtsmustusebraces">
         <description>
 Avoid using if..else statements without using surrounding braces. If the code formatting
@@ -74,7 +74,7 @@ else
           language="apex"
           since="5.6.0"
           message="Avoid using if statements without curly braces"
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_codestyle.html#ifstmtsmustusebraces">
         <description>
 Avoid using if statements without using braces to surround the code block. If the code
@@ -156,7 +156,7 @@ public class Foo {
           language="apex"
           since="5.6.0"
           message="Avoid using 'for' statements without curly braces"
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_codestyle.html#forloopsmustusebraces">
         <description>
 Avoid using 'for' statements without using surrounding braces. If the code formatting or
@@ -270,7 +270,7 @@ public class Foo {
           language="apex"
           since="6.7.0"
           message="Use one statement for each line, it enhances code readability."
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_codestyle.html#onedeclarationperline">
         <description>
 Apex allows the use of several variables declaration of the same type on one line. However, it
@@ -338,7 +338,7 @@ public class Foo {
           language="apex"
           since="5.6.0"
           message="Avoid using 'while' statements without curly braces"
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_codestyle.html#whileloopsmustusebraces">
         <description>
 Avoid using 'while' statements without using braces to surround the code block. If the code

pmd-apex/src/main/resources/category/apex/errorprone.xml

@@ -54,7 +54,7 @@ public class Foo {
           language="apex"
           since="6.0.0"
           message="Avoid directly accessing Trigger.old and Trigger.new"
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_errorprone.html#avoiddirectaccesstriggermap">
         <description>
 Avoid directly accessing Trigger.old and Trigger.new as it can lead to a bug. Triggers should be bulkified and iterate through the map to handle the actions for each item separately.
@@ -138,7 +138,7 @@ public without sharing class Foo {
           language="apex"
           since="6.0.0"
           message="Avoid empty catch blocks"
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_errorprone.html#emptycatchblock">
         <description>
 Empty Catch Block finds instances where an exception is caught, but nothing is done.
@@ -177,7 +177,7 @@ public void doSomething() {
           language="apex"
           since="6.0.0"
           message="Avoid empty 'if' statements"
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_errorprone.html#emptyifstmt">
         <description>
 Empty If Statement finds instances where a condition is checked but nothing is done about it.
@@ -210,7 +210,7 @@ public class Foo {
           language="apex"
           since="6.0.0"
           message="Avoid empty block statements."
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_errorprone.html#emptystatementblock">
         <description>
 Empty block statements serve no purpose and should be removed.
@@ -247,7 +247,7 @@ public class Foo {
           language="apex"
           since="6.0.0"
           message="Avoid empty try or finally blocks"
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_errorprone.html#emptytryorfinallyblock">
         <description>
 Avoid empty try or finally blocks - what's the point?
@@ -291,7 +291,7 @@ public class Foo {
           language="apex"
           since="6.0.0"
           message="Avoid empty 'while' statements"
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_errorprone.html#emptywhilestmt">
         <description>
 Empty While Statement finds all instances where a while statement does nothing.
@@ -445,7 +445,7 @@ public class Foo {        // perfect, both methods provided
           language="apex"
           since="6.22.0"
           message="Test methods must be in test classes"
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_errorprone.html#testmethodsmustbeintestclasses">
        <description>
           Test methods marked as a testMethod or annotated with @IsTest,

pmd-apex/src/main/resources/category/apex/performance.xml

@@ -13,7 +13,7 @@ Rules that flag suboptimal code.
           language="apex"
           since="6.36.0"
           message="Avoid debug statements since they impact on performance"
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_performance.html#avoiddebugstatements">
         <description>
 Debug statements contribute to longer transactions and consume Apex CPU time even when debug logs are not being captured.
@@ -24,7 +24,6 @@ For other valid use cases that the statement is in fact valid make use of the `@
         </description>
         <priority>3</priority>
         <properties>
-            <property name="version" value="2.0"/>
             <property name="xpath">
                 <value>
 <![CDATA[
@@ -141,7 +140,7 @@ public class Something {
           language="apex"
           since="6.40.0"
           message="DescribeSObjectResult could be being loaded eagerly with all child relationships."
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
           externalInfoUrl="${pmd.website.baseurl}/pmd_rules_apex_performance.html#eagerlyloadeddescribesobjectresult">
         <description>
 This rule finds `DescribeSObjectResult`s which could have been loaded eagerly via `SObjectType.getDescribe()`.
@@ -172,7 +171,6 @@ Properties:
         <priority>3</priority>
         <properties>
             <property name="noDefault" type="Boolean" value="false" description="Do not allow SObjectDescribeOptions.DEFAULT option to ensure consistent results no matter where getDescribe is called"/>
-            <property name="version" value="2.0"/>
             <property name="xpath">
                 <value>
 <![CDATA[

pmd-apex/src/test/java/net/sourceforge/pmd/lang/apex/rule/ApexXPathRuleTest.java

@@ -10,7 +10,7 @@ import org.junit.jupiter.api.Test;
 
 import net.sourceforge.pmd.lang.apex.ast.ApexParserTestBase;
 import net.sourceforge.pmd.lang.document.FileId;
-import net.sourceforge.pmd.lang.rule.XPathRule;
+import net.sourceforge.pmd.lang.rule.xpath.XPathRule;
 import net.sourceforge.pmd.reporting.Report;
 
 /**

pmd-cli/src/test/resources/net/sourceforge/pmd/cli/RuleSetWithViolations.xml

@@ -7,7 +7,7 @@
   </description>
 
     <rule name="ReportAllRootNodes" language="dummy" since="1.0" message="Violation from ReportAllRootNodes"
-          class="net.sourceforge.pmd.lang.rule.XPathRule"
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule"
         externalInfoUrl="${pmd.website.baseurl}/rules/test/TestRuleset3.xml#Ruleset3Rule1">
         <description>Just for test</description>
         <priority>3</priority>

pmd-compat6/src/it/pmd-for-java/exception_ruleset.xml

@@ -2,7 +2,7 @@
     <description/>
     <rule name="ExceptionThrowingRule"
           language="java"
-          class="net.sourceforge.pmd.lang.rule.XPathRule">
+          class="net.sourceforge.pmd.lang.rule.xpath.XPathRule">
         <description>Use this rule to produce a processing error.</description>
         <priority>3</priority>
         <properties>

pmd-compat6/src/main/java/net/sourceforge/pmd/lang/rule/XPathRule.java

@@ -0,0 +1,8 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.rule;
+
+public class XPathRule extends net.sourceforge.pmd.lang.rule.xpath.XPathRule {
+}

pmd-compat6/src/main/java/net/sourceforge/pmd/lang/rule/xpath/XPathRule.java

@@ -0,0 +1,172 @@
+/**
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+// This class has been taken from 7.0.0-SNAPSHOT
+// Changes: not final anymore to allow a subclass in the old package
+
+package net.sourceforge.pmd.lang.rule.xpath;
+
+import java.util.List;
+import java.util.Objects;
+
+import org.apache.commons.lang3.StringUtils;
+import org.apache.commons.lang3.exception.ContextedRuntimeException;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import net.sourceforge.pmd.Rule;
+import net.sourceforge.pmd.RuleContext;
+import net.sourceforge.pmd.lang.LanguageProcessor;
+import net.sourceforge.pmd.lang.ast.Node;
+import net.sourceforge.pmd.lang.rule.AbstractRule;
+import net.sourceforge.pmd.lang.rule.RuleTargetSelector;
+import net.sourceforge.pmd.lang.rule.xpath.internal.DeprecatedAttrLogger;
+import net.sourceforge.pmd.lang.rule.xpath.internal.SaxonXPathRuleQuery;
+import net.sourceforge.pmd.properties.PropertyDescriptor;
+import net.sourceforge.pmd.properties.PropertyFactory;
+
+
+/**
+ * Rule that tries to match an XPath expression against a DOM view of an AST.
+ */
+public /*final*/ class XPathRule extends AbstractRule {
+
+    private static final Logger LOG = LoggerFactory.getLogger(XPathRule.class);
+
+    /**
+     * @deprecated Use {@link #XPathRule(XPathVersion, String)}
+     */
+    @Deprecated
+    public static final PropertyDescriptor<String> XPATH_DESCRIPTOR =
+            PropertyFactory.stringProperty("xpath")
+                    .desc("XPath expression")
+                    .defaultValue("")
+                    .build();
+
+    /**
+     * This is initialized only once when calling {@link #apply(Node, RuleContext)} or {@link #getTargetSelector()}.
+     */
+    private SaxonXPathRuleQuery xpathRuleQuery;
+
+
+    // this is shared with rules forked by deepCopy, used by the XPathRuleQuery
+    private DeprecatedAttrLogger attrLogger = DeprecatedAttrLogger.create(this);
+
+
+    /**
+     * @deprecated This is now only used by the ruleset loader. When
+     *     we have syntactic sugar for XPath rules in the XML, we won't
+     *     need this anymore.
+     */
+    @Deprecated
+    public XPathRule() {
+        definePropertyDescriptor(XPATH_DESCRIPTOR);
+    }
+
+    /**
+     * Make a new XPath rule with the given version + expression
+     *
+     * @param version    Version of the XPath language
+     * @param expression XPath expression
+     *
+     * @throws NullPointerException If any of the arguments is null
+     */
+    public XPathRule(XPathVersion version, String expression) {
+        this();
+
+        Objects.requireNonNull(version, "XPath version is null");
+        Objects.requireNonNull(expression, "XPath expression is null");
+
+        setProperty(XPathRule.XPATH_DESCRIPTOR, expression);
+    }
+
+
+    @Override
+    public Rule deepCopy() {
+        XPathRule rule = (XPathRule) super.deepCopy();
+        rule.attrLogger = this.attrLogger;
+        return rule;
+    }
+
+    /**
+     * Returns the XPath expression that implements this rule.
+     */
+    public String getXPathExpression() {
+        return getProperty(XPATH_DESCRIPTOR);
+    }
+
+
+    @Override
+    public void apply(Node target, RuleContext ctx) {
+        SaxonXPathRuleQuery query = getQueryMaybeInitialize();
+
+        List<Node> nodesWithViolation;
+        try {
+            nodesWithViolation = query.evaluate(target);
+        } catch (PmdXPathException e) {
+            throw addExceptionContext(e);
+        }
+
+        for (Node nodeWithViolation : nodesWithViolation) {
+            addViolation(ctx, nodeWithViolation, nodeWithViolation.getImage());
+        }
+    }
+
+    private ContextedRuntimeException addExceptionContext(PmdXPathException e) {
+        return e.addRuleName(getName());
+    }
+
+    @Override
+    public void initialize(LanguageProcessor languageProcessor) {
+        String xpath = getXPathExpression();
+        XPathVersion version = XPathVersion.DEFAULT;
+
+        try {
+            xpathRuleQuery = new SaxonXPathRuleQuery(xpath,
+                    version,
+                    getPropertiesByPropertyDescriptor(),
+                    languageProcessor.services().getXPathHandler(),
+                    attrLogger);
+        } catch (PmdXPathException e) {
+            throw addExceptionContext(e);
+        }
+    }
+
+    private SaxonXPathRuleQuery getQueryMaybeInitialize() throws PmdXPathException {
+        if (xpathRuleQuery == null) {
+            throw new IllegalStateException("Not initialized");
+        }
+        return xpathRuleQuery;
+    }
+
+
+    @Override
+    protected @NonNull RuleTargetSelector buildTargetSelector() {
+
+        List<String> visits = getQueryMaybeInitialize().getRuleChainVisits();
+
+        logXPathRuleChainUsage(!visits.isEmpty());
+
+        return visits.isEmpty() ? RuleTargetSelector.forRootOnly()
+                : RuleTargetSelector.forXPathNames(visits);
+    }
+
+
+    private void logXPathRuleChainUsage(boolean usesRuleChain) {
+        LOG.debug("{} rule chain for XPath rule: {} ({})",
+                usesRuleChain ? "Using" : "no",
+                getName(),
+                getRuleSetName());
+    }
+
+
+    @Override
+    public String dysfunctionReason() {
+        if (StringUtils.isBlank(getXPathExpression())) {
+            return "Missing XPath expression";
+        }
+        return null;
+    }
+}

pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/RuleSet.java

@@ -27,6 +27,7 @@ import net.sourceforge.pmd.lang.LanguageVersion;
 import net.sourceforge.pmd.lang.document.FileId;
 import net.sourceforge.pmd.lang.document.TextFile;
 import net.sourceforge.pmd.lang.rule.internal.RuleSetReference;
+import net.sourceforge.pmd.lang.rule.xpath.XPathRule;
 
 /**
  * This class represents a collection of rules along with some optional filter

pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/xpath/XPathRule.java

@@ -2,12 +2,9 @@
  * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
  */
 
-package net.sourceforge.pmd.lang.rule;
+package net.sourceforge.pmd.lang.rule.xpath;
 
-import java.util.Collections;
-import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
 import java.util.Objects;
 
 import org.apache.commons.lang3.StringUtils;
@@ -16,11 +13,11 @@ import org.checkerframework.checker.nullness.qual.NonNull;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import net.sourceforge.pmd.annotation.DeprecatedUntil700;
 import net.sourceforge.pmd.lang.LanguageProcessor;
 import net.sourceforge.pmd.lang.ast.Node;
-import net.sourceforge.pmd.lang.rule.xpath.PmdXPathException;
+import net.sourceforge.pmd.lang.rule.AbstractRule;
-import net.sourceforge.pmd.lang.rule.xpath.XPathVersion;
+import net.sourceforge.pmd.lang.rule.Rule;
+import net.sourceforge.pmd.lang.rule.RuleTargetSelector;
 import net.sourceforge.pmd.lang.rule.xpath.internal.DeprecatedAttrLogger;
 import net.sourceforge.pmd.lang.rule.xpath.internal.SaxonXPathRuleQuery;
 import net.sourceforge.pmd.properties.PropertyDescriptor;
@@ -35,8 +32,6 @@ public final class XPathRule extends AbstractRule {
 
     private static final Logger LOG = LoggerFactory.getLogger(XPathRule.class);
 
-    // TODO move to XPath subpackage
-
     /**
      * @deprecated Use {@link #XPathRule(XPathVersion, String)}
      */
@@ -47,17 +42,6 @@ public final class XPathRule extends AbstractRule {
                        .defaultValue("")
                        .build();
 
-    /**
-     * @deprecated Use {@link #XPathRule(XPathVersion, String)}
-     */
-    @Deprecated
-    @DeprecatedUntil700
-    public static final PropertyDescriptor<XPathVersion> VERSION_DESCRIPTOR =
-        PropertyFactory.enumProperty("version", getXPathVersions())
-                       .desc("XPath specification version")
-                       .defaultValue(XPathVersion.DEFAULT)
-                       .build();
-
     /**
      * This is initialized only once when calling {@link #apply(Node, RuleContext)} or {@link #getTargetSelector()}.
      */
@@ -76,7 +60,6 @@ public final class XPathRule extends AbstractRule {
     @Deprecated
     public XPathRule() {
         definePropertyDescriptor(XPATH_DESCRIPTOR);
-        definePropertyDescriptor(VERSION_DESCRIPTOR);
     }
 
     /**
@@ -94,7 +77,6 @@ public final class XPathRule extends AbstractRule {
         Objects.requireNonNull(expression, "XPath expression is null");
 
         setProperty(XPathRule.XPATH_DESCRIPTOR, expression);
-        setProperty(XPathRule.VERSION_DESCRIPTOR, XPathVersion.ofId(version.getXmlName()));
     }
 
 
@@ -105,14 +87,6 @@ public final class XPathRule extends AbstractRule {
         return rule;
     }
 
-    /**
-     * Returns the version for this rule. Returns null if this is not
-     * set or invalid.
-     */
-    public XPathVersion getVersion() {
-        return getProperty(VERSION_DESCRIPTOR);
-    }
-
     /**
      * Returns the XPath expression that implements this rule.
      */
@@ -144,11 +118,7 @@ public final class XPathRule extends AbstractRule {
     @Override
     public void initialize(LanguageProcessor languageProcessor) {
         String xpath = getXPathExpression();
-        XPathVersion version = getVersion();
+        XPathVersion version = XPathVersion.DEFAULT;
-
-        if (version == null) {
-            throw new IllegalStateException("Invalid XPath version, should have been caught by Rule::dysfunctionReason");
-        }
 
         try {
             xpathRuleQuery = new SaxonXPathRuleQuery(xpath,
@@ -182,9 +152,8 @@ public final class XPathRule extends AbstractRule {
 
 
     private void logXPathRuleChainUsage(boolean usesRuleChain) {
-        LOG.debug("{} rule chain for XPath {} rule: {} ({})",
+        LOG.debug("{} rule chain for XPath rule: {} ({})",
                 usesRuleChain ? "Using" : "no",
-                getProperty(XPathRule.VERSION_DESCRIPTOR),
                 getName(),
                 getRuleSetName());
     }
@@ -192,19 +161,9 @@ public final class XPathRule extends AbstractRule {
 
     @Override
     public String dysfunctionReason() {
-        if (getVersion() == null) {
+        if (StringUtils.isBlank(getXPathExpression())) {
-            return "Invalid XPath version '" + getProperty(VERSION_DESCRIPTOR) + "'";
-        } else if (StringUtils.isBlank(getXPathExpression())) {
             return "Missing XPath expression";
         }
         return null;
     }
-
-    private static Map<String, XPathVersion> getXPathVersions() {
-        Map<String, XPathVersion> tmp = new HashMap<>();
-        for (XPathVersion v : XPathVersion.values()) {
-            tmp.put(v.getXmlName(), v);
-        }
-        return Collections.unmodifiableMap(tmp);
-    }
 }

pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/xpath/impl/AbstractXPathFunctionDef.java

@@ -1,40 +0,0 @@
-/*
- * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
- */
-
-package net.sourceforge.pmd.lang.rule.xpath.impl;
-
-import net.sourceforge.pmd.lang.Language;
-
-import net.sf.saxon.lib.ExtensionFunctionDefinition;
-import net.sf.saxon.om.StructuredQName;
-
-
-/**
- * Base impl for an XPath function definition.
- * This uses Saxon API.
- *
- * @since 7.0.0
- */
-public abstract class AbstractXPathFunctionDef extends ExtensionFunctionDefinition {
-
-    private static final String PMD_URI_PREFIX = "http://pmd.sourceforge.net/";
-    private final StructuredQName qname;
-
-    private AbstractXPathFunctionDef(String localName, String namespacePrefix, String uri) {
-        this.qname = new StructuredQName(namespacePrefix, uri, localName);
-    }
-
-    protected AbstractXPathFunctionDef(String localName) {
-        this(localName, "pmd", PMD_URI_PREFIX + "pmd-core");
-    }
-
-    protected AbstractXPathFunctionDef(String localName, Language language) {
-        this(localName, "pmd-" + language.getId(), PMD_URI_PREFIX + "pmd-" + language.getId());
-    }
-
-    @Override
-    public final StructuredQName getFunctionQName() {
-        return qname;
-    }
-}

pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/xpath/impl/XPathFunctionDefinition.java

@@ -0,0 +1,126 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.rule.xpath.impl;
+
+import javax.xml.namespace.QName;
+
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+import net.sourceforge.pmd.lang.Language;
+import net.sourceforge.pmd.lang.ast.Node;
+
+/**
+ * Base impl for an XPath function definition.
+ *
+ * @since 7.0.0
+ */
+public abstract class XPathFunctionDefinition {
+
+    private static final String PMD_URI_PREFIX = "http://pmd.sourceforge.net/";
+    private final QName qname;
+
+    private XPathFunctionDefinition(String localName, String namespacePrefix, String uri) {
+        this.qname = new QName(uri, localName, namespacePrefix);
+    }
+
+    protected XPathFunctionDefinition(String localName) {
+        this(localName, "pmd", PMD_URI_PREFIX + "pmd-core");
+    }
+
+    protected XPathFunctionDefinition(String localName, Language language) {
+        this(localName, "pmd-" + language.getId(), PMD_URI_PREFIX + "pmd-" + language.getId());
+    }
+
+    public final QName getQName() {
+        return qname;
+    }
+
+    /**
+     * Defines the types of the function arguments. By default, an empty array is returned, indicating
+     * that the function takes no arguments.
+     */
+    public Type[] getArgumentTypes() {
+        return new Type[0];
+    }
+
+    /**
+     * Defines the return type of the function.
+     */
+    public abstract Type getResultType();
+
+    /**
+     * If the function depends on the context item, then
+     * this method should return {@code true}.
+     *
+     * <p>Note: Only if this is true, the contextNode parameter will be present in the
+     * {@link FunctionCall#call(Node, Object[])} method.
+     */
+    public boolean dependsOnContext() {
+        return false;
+    }
+
+    /**
+     * Create a call on this function. This method is called, when a function call
+     * is found in the XPath expression.
+     */
+    public abstract FunctionCall makeCallExpression();
+
+    /**
+     * Supported types of a custom XPath function. These can be used as {@link #getResultType() result types}
+     * or {@link #getArgumentTypes() argument types}.
+     */
+    public enum Type {
+        /** Represents {@link String}. */
+        SINGLE_STRING,
+        /** Represents {@link Boolean}. */
+        SINGLE_BOOLEAN,
+        /** Represents {@link Integer}. */
+        SINGLE_INTEGER,
+        /** Represents any node. Usually used as an argument type. */
+        SINGLE_ELEMENT,
+        /** Represents a {@link java.util.List} of {@link String}, potentially empty. */
+        STRING_SEQUENCE,
+        /** Represents a {@link java.util.Optional} {@link String}. */
+        OPTIONAL_STRING,
+        /** Represents a {@link java.util.Optional} {@link Double}. */
+        OPTIONAL_DECIMAL,
+    }
+
+    /**
+     * Provides the actual implementation of a custom XPath function.
+     */
+    public interface FunctionCall {
+        /**
+         * This method is called at runtime to evaluate the XPath function expression.
+         *
+         * @param contextNode the context node or {@code null}, if this function doesn't depend on the context.
+         *                    See {@link XPathFunctionDefinition#dependsOnContext()}.
+         * @param arguments The arguments converted as the corresponding java types.
+         *                  See {@link XPathFunctionDefinition#getArgumentTypes()}.
+         * @return The result of the function. This should be the corresponding java type of
+         * {@link XPathFunctionDefinition#getResultType()}.
+         * @throws XPathFunctionException when any problem during evaluation occurs, like invalid arguments.
+         */
+        Object call(@Nullable Node contextNode, Object[] arguments) throws XPathFunctionException;
+
+        /**
+         * This is called once before the function is evaluated. It can be used to optimize the
+         * implementation by doing expensive operations only once and cache the result.
+         * This is useful, if the argument of the function is of type {@link String} and is provided
+         * as a String literal in the XPath expression.
+         *
+         * <p>This is an optional step. The default implementation does nothing.
+         *
+         * @param arguments The arguments converted as the corresponding java types.
+         *                  See {@link XPathFunctionDefinition#getArgumentTypes()}.
+         *                  Note: This array might contain {@code null} elements, if the values are
+         *                  not known yet because they are dynamic. Only literal values are available.
+         * @throws XPathFunctionException when any problem during initialization occurs, like invalid arguments.
+         */
+        default void staticInit(Object[] arguments) throws XPathFunctionException {
+            // default implementation does nothing
+        }
+    }
+}

pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/xpath/impl/XPathFunctionException.java

@@ -0,0 +1,19 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.rule.xpath.impl;
+
+/**
+ * Indicates a problem during the execution of a custom
+ * XPath function.
+ */
+public class XPathFunctionException extends Exception {
+    public XPathFunctionException(String message) {
+        super(message);
+    }
+
+    public XPathFunctionException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}

pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/xpath/impl/XPathHandler.java

@@ -11,8 +11,6 @@ import java.util.Set;
 import net.sourceforge.pmd.lang.rule.xpath.internal.DefaultXPathFunctions;
 import net.sourceforge.pmd.util.CollectionUtil;
 
-import net.sf.saxon.lib.ExtensionFunctionDefinition;
-
 
 /**
  * Interface for performing Language specific XPath handling, such as
@@ -24,7 +22,7 @@ public interface XPathHandler {
      * Returns the set of extension functions for this language module.
      * These are the additional functions available in XPath queries.
      */
-    Set<ExtensionFunctionDefinition> getRegisteredExtensionFunctions();
+    Set<XPathFunctionDefinition> getRegisteredExtensionFunctions();
 
 
     static XPathHandler noFunctionDefinitions() {
@@ -34,8 +32,8 @@ public interface XPathHandler {
     /**
      * Returns a default XPath handler.
      */
-    static XPathHandler getHandlerForFunctionDefs(ExtensionFunctionDefinition first, ExtensionFunctionDefinition... defs) {
+    static XPathHandler getHandlerForFunctionDefs(XPathFunctionDefinition first, XPathFunctionDefinition... defs) {
-        Set<ExtensionFunctionDefinition> set = new HashSet<>(CollectionUtil.setOf(first, defs));
+        Set<XPathFunctionDefinition> set = new HashSet<>(CollectionUtil.setOf(first, defs));
         set.addAll(DefaultXPathFunctions.getDefaultFunctions());
 
         return () -> Collections.unmodifiableSet(set);

pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/xpath/internal/CoordinateXPathFunction.java

@@ -7,23 +7,15 @@ package net.sourceforge.pmd.lang.rule.xpath.internal;
 import java.util.function.ToIntFunction;
 
 import net.sourceforge.pmd.lang.ast.Node;
-import net.sourceforge.pmd.lang.rule.xpath.impl.AbstractXPathFunctionDef;
+import net.sourceforge.pmd.lang.rule.xpath.impl.XPathFunctionDefinition;
-
+import net.sourceforge.pmd.lang.rule.xpath.impl.XPathFunctionException;
-import net.sf.saxon.expr.XPathContext;
-import net.sf.saxon.lib.ExtensionFunctionCall;
-import net.sf.saxon.om.Sequence;
-import net.sf.saxon.pattern.NodeKindTest;
-import net.sf.saxon.trans.XPathException;
-import net.sf.saxon.type.Type;
-import net.sf.saxon.value.Int64Value;
-import net.sf.saxon.value.SequenceType;
 
 /**
  * A function that returns the current file name.
  *
  * @author Clément Fournier
  */
-public final class CoordinateXPathFunction extends AbstractXPathFunctionDef {
+public final class CoordinateXPathFunction extends XPathFunctionDefinition {
 
     public static final CoordinateXPathFunction START_LINE =
         new CoordinateXPathFunction("startLine", Node::getBeginLine);
@@ -34,9 +26,7 @@ public final class CoordinateXPathFunction extends AbstractXPathFunctionDef {
     public static final CoordinateXPathFunction END_COLUMN =
         new CoordinateXPathFunction("endColumn", Node::getEndColumn);
 
-    private static final SequenceType[] A_SINGLE_ELEMENT = {
+    private static final Type[] A_SINGLE_ELEMENT = { Type.SINGLE_ELEMENT };
-        NodeKindTest.makeNodeKindTest(Type.ELEMENT).one(),
-    };
     public static final String PMD_NODE_USER_DATA = "pmd.node";
     private final ToIntFunction<Node> getter;
 
@@ -46,32 +36,26 @@ public final class CoordinateXPathFunction extends AbstractXPathFunctionDef {
     }
 
     @Override
-    public SequenceType[] getArgumentTypes() {
+    public Type[] getArgumentTypes() {
         return A_SINGLE_ELEMENT;
     }
 
     @Override
-    public SequenceType getResultType(SequenceType[] suppliedArgumentTypes) {
+    public Type getResultType() {
-        return SequenceType.SINGLE_INTEGER;
+        return Type.SINGLE_INTEGER;
     }
 
     @Override
-    public ExtensionFunctionCall makeCallExpression() {
+    public FunctionCall makeCallExpression() {
-        return new ExtensionFunctionCall() {
+        return (contextNode, arguments) -> {
-
+            Node node = XPathElementToNodeHelper.itemToNode(arguments[0]);
-            @Override
+            if (node == null) {
-            public Sequence call(XPathContext context, Sequence[] arguments) throws XPathException {
+                throw new XPathFunctionException(
-                Node node = XPathElementToNodeHelper.itemToNode(arguments[0]);
+                    "Cannot call function '" + getQName().getLocalPart()
-                if (node == null) {
+                        + "' on argument " + arguments[0]
-                    throw new XPathException(
+                );
-                        "Cannot call function '" + getFunctionQName().getLocalPart()
-                            + "' on argument " + arguments[0]
-                    );
-                }
-                return Int64Value.makeIntegerValue(getter.applyAsInt(node));
             }
+            return getter.applyAsInt(node);
         };
     }
-
-
 }

pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/xpath/internal/DefaultXPathFunctions.java

@@ -7,16 +7,15 @@ package net.sourceforge.pmd.lang.rule.xpath.internal;
 
 import java.util.Set;
 
+import net.sourceforge.pmd.lang.rule.xpath.impl.XPathFunctionDefinition;
 import net.sourceforge.pmd.util.CollectionUtil;
 
-import net.sf.saxon.lib.ExtensionFunctionDefinition;
-
 /**
  * Default XPath functions provided by pmd-core.
  */
 public final class DefaultXPathFunctions {
 
-    private static final Set<ExtensionFunctionDefinition> DEFAULTS =
+    private static final Set<XPathFunctionDefinition> DEFAULTS =
         CollectionUtil.immutableSetOf(
             FileNameXPathFunction.INSTANCE,
             CoordinateXPathFunction.START_LINE,
@@ -29,7 +28,7 @@ public final class DefaultXPathFunctions {
         // utility class
     }
 
-    public static Set<ExtensionFunctionDefinition> getDefaultFunctions() {
+    public static Set<XPathFunctionDefinition> getDefaultFunctions() {
         return DEFAULTS;
     }
 }

pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/xpath/internal/DeprecatedAttrLogger.java

@@ -11,8 +11,8 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import net.sourceforge.pmd.lang.rule.Rule;
-import net.sourceforge.pmd.lang.rule.XPathRule;
 import net.sourceforge.pmd.lang.rule.xpath.Attribute;
+import net.sourceforge.pmd.lang.rule.xpath.XPathRule;
 
 /**
  * Records usages of deprecated attributes in XPath rules. This needs

pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/xpath/internal/FileNameXPathFunction.java

@@ -6,23 +6,16 @@ package net.sourceforge.pmd.lang.rule.xpath.internal;
 
 import java.util.Objects;
 
-import net.sourceforge.pmd.lang.ast.Node;
 import net.sourceforge.pmd.lang.ast.RootNode;
-import net.sourceforge.pmd.lang.rule.xpath.impl.AbstractXPathFunctionDef;
+import net.sourceforge.pmd.lang.rule.xpath.impl.XPathFunctionDefinition;
-
+import net.sourceforge.pmd.lang.rule.xpath.impl.XPathFunctionException;
-import net.sf.saxon.expr.XPathContext;
-import net.sf.saxon.lib.ExtensionFunctionCall;
-import net.sf.saxon.om.Sequence;
-import net.sf.saxon.trans.XPathException;
-import net.sf.saxon.value.SequenceType;
-import net.sf.saxon.value.StringValue;
 
 /**
  * A function that returns the current file name.
  *
  * @author Clément Fournier
  */
-public final class FileNameXPathFunction extends AbstractXPathFunctionDef {
+public final class FileNameXPathFunction extends XPathFunctionDefinition {
 
     public static final FileNameXPathFunction INSTANCE = new FileNameXPathFunction();
 
@@ -31,36 +24,31 @@ public final class FileNameXPathFunction extends AbstractXPathFunctionDef {
     }
 
     @Override
-    public SequenceType[] getArgumentTypes() {
+    public Type getResultType() {
-        return new SequenceType[0];
+        return Type.SINGLE_STRING;
     }
 
     @Override
-    public SequenceType getResultType(SequenceType[] suppliedArgumentTypes) {
+    public boolean dependsOnContext() {
-        return SequenceType.STRING_SEQUENCE;
+        return true;
     }
 
     @Override
-    public ExtensionFunctionCall makeCallExpression() {
+    public FunctionCall makeCallExpression() {
-        return new ExtensionFunctionCall() {
+        return (node, arguments) -> {
-
+            if (node == null) {
-            @Override
+                throw new XPathFunctionException(
-            public Sequence call(XPathContext context, Sequence[] arguments) throws XPathException {
+                    "Cannot call function '" + getQName().getLocalPart()
-                Node node = XPathElementToNodeHelper.itemToNode(context.getContextItem());
+                        + "' without context item"
-                if (node == null) {
+                );
-                    throw new XPathException(
-                        "Cannot call function '" + getFunctionQName().getLocalPart()
-                            + "' with context item " + context.getContextItem()
-                    );
-                }
-                RootNode root = node.getRoot();
-                Objects.requireNonNull(root, "No root node in tree?");
-
-                String fileName = root.getTextDocument().getFileId().getFileName();
-                Objects.requireNonNull(fileName, "File name was not set");
-
-                return new StringValue(fileName);
             }
+            RootNode root = node.getRoot();
+            Objects.requireNonNull(root, "No root node in tree?");
+
+            String fileName = root.getTextDocument().getFileId().getFileName();
+            Objects.requireNonNull(fileName, "File name was not set");
+
+            return fileName;
         };
     }
 }

pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/xpath/internal/SaxonExtensionFunctionDefinitionAdapter.java

@@ -0,0 +1,172 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.rule.xpath.internal;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Collectors;
+import javax.xml.namespace.QName;
+
+import net.sourceforge.pmd.lang.ast.Node;
+import net.sourceforge.pmd.lang.rule.xpath.impl.XPathFunctionDefinition;
+import net.sourceforge.pmd.lang.rule.xpath.impl.XPathFunctionException;
+
+import net.sf.saxon.expr.Expression;
+import net.sf.saxon.expr.StaticContext;
+import net.sf.saxon.expr.StringLiteral;
+import net.sf.saxon.expr.XPathContext;
+import net.sf.saxon.lib.ExtensionFunctionCall;
+import net.sf.saxon.lib.ExtensionFunctionDefinition;
+import net.sf.saxon.om.EmptyAtomicSequence;
+import net.sf.saxon.om.Sequence;
+import net.sf.saxon.om.StructuredQName;
+import net.sf.saxon.pattern.NodeKindTest;
+import net.sf.saxon.trans.XPathException;
+import net.sf.saxon.value.BigDecimalValue;
+import net.sf.saxon.value.BooleanValue;
+import net.sf.saxon.value.EmptySequence;
+import net.sf.saxon.value.Int64Value;
+import net.sf.saxon.value.SequenceExtent;
+import net.sf.saxon.value.SequenceType;
+import net.sf.saxon.value.StringValue;
+
+/**
+ * Converts PMD's {@link XPathFunctionDefinition} into Saxon's {@link ExtensionFunctionDefinition}.
+ */
+public class SaxonExtensionFunctionDefinitionAdapter extends ExtensionFunctionDefinition {
+    private static final SequenceType SINGLE_ELEMENT_SEQUENCE_TYPE = NodeKindTest.ELEMENT.one();
+
+    private final XPathFunctionDefinition definition;
+
+    public SaxonExtensionFunctionDefinitionAdapter(XPathFunctionDefinition definition) {
+        this.definition = definition;
+    }
+
+    private SequenceType convertToSequenceType(XPathFunctionDefinition.Type type) {
+        switch (type) {
+        case SINGLE_STRING: return SequenceType.SINGLE_STRING;
+        case SINGLE_BOOLEAN: return SequenceType.SINGLE_BOOLEAN;
+        case SINGLE_ELEMENT: return SINGLE_ELEMENT_SEQUENCE_TYPE;
+        case SINGLE_INTEGER: return SequenceType.SINGLE_INTEGER;
+        case STRING_SEQUENCE: return SequenceType.STRING_SEQUENCE;
+        case OPTIONAL_STRING: return SequenceType.OPTIONAL_STRING;
+        case OPTIONAL_DECIMAL: return SequenceType.OPTIONAL_DECIMAL;
+        default:
+            throw new UnsupportedOperationException("Type " + type + " is not supported");
+        }
+    }
+
+    private SequenceType[] convertToSequenceTypes(XPathFunctionDefinition.Type[] types) {
+        SequenceType[] result = new SequenceType[types.length];
+        for (int i = 0; i < types.length; i++) {
+            result[i] = convertToSequenceType(types[i]);
+        }
+        return result;
+    }
+
+    @Override
+    public StructuredQName getFunctionQName() {
+        QName qName = definition.getQName();
+        return new StructuredQName(qName.getPrefix(), qName.getNamespaceURI(), qName.getLocalPart());
+    }
+
+    @Override
+    public SequenceType[] getArgumentTypes() {
+        return convertToSequenceTypes(definition.getArgumentTypes());
+    }
+
+    @Override
+    public SequenceType getResultType(SequenceType[] suppliedArgumentTypes) {
+        return convertToSequenceType(definition.getResultType());
+    }
+
+    @Override
+    public boolean dependsOnFocus() {
+        return definition.dependsOnContext();
+    }
+
+    @Override
+    public ExtensionFunctionCall makeCallExpression() {
+        XPathFunctionDefinition.FunctionCall call = definition.makeCallExpression();
+        return new ExtensionFunctionCall() {
+            @Override
+            public Expression rewrite(StaticContext context, Expression[] arguments) throws XPathException {
+                Object[] convertedArguments = new Object[definition.getArgumentTypes().length];
+                for (int i = 0; i < convertedArguments.length; i++) {
+                    if (arguments[i] instanceof StringLiteral) {
+                        convertedArguments[i] = ((StringLiteral) arguments[i]).getStringValue();
+                    }
+                }
+                try {
+                    call.staticInit(convertedArguments);
+                } catch (XPathFunctionException e) {
+                    XPathException xPathException = new XPathException(e);
+                    xPathException.setIsStaticError(true);
+                    throw xPathException;
+                }
+                return null;
+            }
+
+            @Override
+            public Sequence call(XPathContext context, Sequence[] arguments) throws XPathException {
+                Node contextNode = null;
+                if (definition.dependsOnContext()) {
+                    contextNode = XPathElementToNodeHelper.itemToNode(context.getContextItem());
+                }
+                Object[] convertedArguments = new Object[definition.getArgumentTypes().length];
+                for (int i = 0; i < convertedArguments.length; i++) {
+                    switch (definition.getArgumentTypes()[i]) {
+                        case SINGLE_STRING:
+                            convertedArguments[i] = arguments[i].head().getStringValue();
+                            break;
+                        case SINGLE_ELEMENT:
+                            convertedArguments[i] = arguments[i].head();
+                            break;
+                        default:
+                            throw new UnsupportedOperationException("Don't know how to convert argument type " + definition.getArgumentTypes()[i]);
+                    }
+                }
+
+
+                Object result = null;
+                try {
+                    result = call.call(contextNode, convertedArguments);
+                } catch (XPathFunctionException e) {
+                    throw new XPathException(e);
+                }
+                Sequence convertedResult = null;
+                switch (definition.getResultType()) {
+                    case SINGLE_BOOLEAN:
+                        convertedResult = BooleanValue.get((Boolean) result);
+                        break;
+                    case SINGLE_INTEGER:
+                        convertedResult = Int64Value.makeIntegerValue((Integer) result);
+                        break;
+                    case SINGLE_STRING:
+                        convertedResult = new StringValue((String) result);
+                        break;
+                    case OPTIONAL_STRING:
+                        convertedResult = result instanceof Optional && ((Optional<String>) result).isPresent()
+                                ? new StringValue(((Optional<String>) result).get())
+                                : EmptyAtomicSequence.INSTANCE;
+                        break;
+                    case STRING_SEQUENCE:
+                        convertedResult = result instanceof List
+                                ? new SequenceExtent(((List<String>) result).stream().map(StringValue::new).collect(Collectors.toList()))
+                                : EmptySequence.getInstance();
+                        break;
+                    case OPTIONAL_DECIMAL:
+                        convertedResult = result instanceof Optional && ((Optional<Double>) result).isPresent()
+                                ? new BigDecimalValue(((Optional<Double>) result).get())
+                                : EmptySequence.getInstance();
+                        break;
+                    default:
+                        throw new UnsupportedOperationException("Don't know how to convert result type " + definition.getResultType());
+                }
+                return convertedResult;
+            }
+        };
+    }
+}

pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/xpath/internal/SaxonXPathRuleQuery.java

@@ -17,10 +17,10 @@ import org.slf4j.LoggerFactory;
 
 import net.sourceforge.pmd.lang.ast.Node;
 import net.sourceforge.pmd.lang.ast.RootNode;
-import net.sourceforge.pmd.lang.rule.XPathRule;
 import net.sourceforge.pmd.lang.rule.xpath.PmdXPathException;
 import net.sourceforge.pmd.lang.rule.xpath.PmdXPathException.Phase;
 import net.sourceforge.pmd.lang.rule.xpath.XPathVersion;
+import net.sourceforge.pmd.lang.rule.xpath.impl.XPathFunctionDefinition;
 import net.sourceforge.pmd.lang.rule.xpath.impl.XPathHandler;
 import net.sourceforge.pmd.properties.PropertyDescriptor;
 import net.sourceforge.pmd.util.DataMap;
@@ -194,12 +194,13 @@ public class SaxonXPathRuleQuery {
 
         for (final PropertyDescriptor<?> propertyDescriptor : properties.keySet()) {
             final String name = propertyDescriptor.name();
-            if (!"xpath".equals(name) && !XPathRule.VERSION_DESCRIPTOR.name().equals(name)) {
+            if (!"xpath".equals(name)) {
                 staticCtx.declareProperty(propertyDescriptor);
             }
         }
 
-        for (ExtensionFunctionDefinition fun : xPathHandler.getRegisteredExtensionFunctions()) {
+        for (XPathFunctionDefinition xpathFun : xPathHandler.getRegisteredExtensionFunctions()) {
+            ExtensionFunctionDefinition fun = new SaxonExtensionFunctionDefinitionAdapter(xpathFun);
             StructuredQName qname = fun.getFunctionQName();
             staticCtx.declareNamespace(qname.getPrefix(), qname.getURI());
             this.configuration.registerExtensionFunction(fun);

pmd-core/src/test/java/net/sourceforge/pmd/lang/rule/RuleSetFactoryTest.java

@@ -241,7 +241,7 @@ class RuleSetFactoryTest extends RulesetFactoryTestBase {
                 "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" + "<ruleset name=\"test\">\n"
                     + "  <description>ruleset desc</description>\n"
                     + "     <rule deprecated=\"true\" ref=\"NewName\" name=\"OldName\"/>"
-                    + "     <rule name=\"NewName\" message=\"m\" class=\"net.sourceforge.pmd.lang.rule.XPathRule\" language=\"dummy\">"
+                    + "     <rule name=\"NewName\" message=\"m\" class=\"net.sourceforge.pmd.lang.rule.xpath.XPathRule\" language=\"dummy\">"
                     + "         <description>d</description>\n" + "         <priority>2</priority>\n" + "     </rule>"
                     + "</ruleset>");
             assertEquals(1, rs.getRules().size());
@@ -269,7 +269,7 @@ class RuleSetFactoryTest extends RulesetFactoryTestBase {
                                            "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" + "<ruleset name=\"test\">\n"
                                                + "  <description>ruleset desc</description>\n"
                                                + "     <rule deprecated=\"true\" ref=\"NewName\" name=\"OldName\"/>"
-                                               + "     <rule name=\"NewName\" message=\"m\" class=\"net.sourceforge.pmd.lang.rule.XPathRule\" language=\"dummy\">"
+                                               + "     <rule name=\"NewName\" message=\"m\" class=\"net.sourceforge.pmd.lang.rule.xpath.XPathRule\" language=\"dummy\">"
                                                + "         <description>d</description>\n"
                                                + "         <priority>2</priority>\n"
                                                + "     </rule>"

pmd-core/src/test/java/net/sourceforge/pmd/lang/rule/RuleSetWriterTest.java

@@ -20,6 +20,7 @@ import org.junit.jupiter.api.Test;
 
 import net.sourceforge.pmd.lang.rule.RuleSet.RuleSetBuilder;
 import net.sourceforge.pmd.lang.rule.internal.RuleSetReference;
+import net.sourceforge.pmd.lang.rule.xpath.XPathRule;
 import net.sourceforge.pmd.util.internal.xml.SchemaConstants;
 
 /**

pmd-core/src/test/java/net/sourceforge/pmd/lang/rule/XPathRuleTest.java

@@ -19,6 +19,7 @@ import net.sourceforge.pmd.lang.ast.DummyNode;
 import net.sourceforge.pmd.lang.ast.DummyNode.DummyRootNode;
 import net.sourceforge.pmd.lang.ast.DummyNodeWithDeprecatedAttribute;
 import net.sourceforge.pmd.lang.document.TextRegion;
+import net.sourceforge.pmd.lang.rule.xpath.XPathRule;
 import net.sourceforge.pmd.lang.rule.xpath.XPathVersion;
 import net.sourceforge.pmd.reporting.Report;