001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2026 the original author or authors.
004//
005// This library is free software; you can redistribute it and/or
006// modify it under the terms of the GNU Lesser General Public
007// License as published by the Free Software Foundation; either
008// version 2.1 of the License, or (at your option) any later version.
009//
010// This library is distributed in the hope that it will be useful,
011// but WITHOUT ANY WARRANTY; without even the implied warranty of
012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
013// Lesser General Public License for more details.
014//
015// You should have received a copy of the GNU Lesser General Public
016// License along with this library; if not, write to the Free Software
017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
018///////////////////////////////////////////////////////////////////////////////////////////////
019
020package com.puppycrawl.tools.checkstyle.checks.coding;
021
022import java.util.List;
023
024import com.puppycrawl.tools.checkstyle.StatelessCheck;
025import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
026import com.puppycrawl.tools.checkstyle.api.DetailAST;
027import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
028import com.puppycrawl.tools.checkstyle.xpath.AbstractNode;
029import com.puppycrawl.tools.checkstyle.xpath.RootNode;
030import net.sf.saxon.Configuration;
031import net.sf.saxon.om.Item;
032import net.sf.saxon.sxpath.XPathDynamicContext;
033import net.sf.saxon.sxpath.XPathEvaluator;
034import net.sf.saxon.sxpath.XPathExpression;
035import net.sf.saxon.trans.XPathException;
036
037/**
038 * <div>
039 * Evaluates Xpath query and report violation on all matching AST nodes. This check allows
040 * user to implement custom checks using Xpath. If Xpath query is not specified explicitly,
041 * then the check does nothing.
042 * </div>
043 *
044 * <p>
045 * It is recommended to define custom message for violation to explain what is not allowed and what
046 * to use instead, default message might be too abstract. To customize a message you need to
047 * add {@code message} element with <b>matchxpath.match</b> as {@code key} attribute and
048 * desired message as {@code value} attribute.
049 * </p>
050 *
051 * <p>
052 * Please read more about Xpath syntax at
053 * <a href="https://www.saxonica.com/html/documentation10/expressions/index.html">Xpath Syntax</a>.
054 * Information regarding Xpath functions can be found at
055 * <a href="https://www.saxonica.com/html/documentation10/functions/fn/index.html">
056 *     XSLT/XPath Reference</a>.
057 * Note, that <b>@text</b> attribute can be used only with token types that are listed in
058 * <a href="https://github.com/checkstyle/checkstyle/search?q=%22TOKEN_TYPES_WITH_TEXT_ATTRIBUTE+%3D+Arrays.asList%22">
059 *     XpathUtil</a>.
060 * </p>
061 *
062 * @since 8.39
063 */
064@StatelessCheck
065public class MatchXpathCheck extends AbstractCheck {
066
067    /**
068     * A key is pointing to the warning message text provided by user.
069     */
070    public static final String MSG_KEY = "matchxpath.match";
071
072    /** Specify Xpath query. */
073    private String query = "";
074
075    /** Xpath expression. */
076    private XPathExpression xpathExpression;
077
078    /**
079     * Creates a new {@code MatchXpathCheck} instance.
080     */
081    public MatchXpathCheck() {
082        // no code by default
083    }
084
085    /**
086     * Setter to specify Xpath query.
087     *
088     * @param query Xpath query.
089     * @throws IllegalStateException if creation of xpath expression fails
090     * @since 8.39
091     */
092    public void setQuery(String query) {
093        this.query = query;
094        if (!query.isEmpty()) {
095            try {
096                final XPathEvaluator xpathEvaluator =
097                        new XPathEvaluator(Configuration.newConfiguration());
098                xpathExpression = xpathEvaluator.createExpression(query);
099            }
100            catch (XPathException exc) {
101                throw new IllegalStateException("Creating Xpath expression failed: " + query, exc);
102            }
103        }
104    }
105
106    @Override
107    public int[] getDefaultTokens() {
108        return getRequiredTokens();
109    }
110
111    @Override
112    public int[] getAcceptableTokens() {
113        return getRequiredTokens();
114    }
115
116    @Override
117    public int[] getRequiredTokens() {
118        return CommonUtil.EMPTY_INT_ARRAY;
119    }
120
121    @Override
122    public boolean isCommentNodesRequired() {
123        return true;
124    }
125
126    @Override
127    public void beginTree(DetailAST rootAST) {
128        if (!query.isEmpty()) {
129            final List<DetailAST> matchingNodes = findMatchingNodesByXpathQuery(rootAST);
130            matchingNodes.forEach(node -> log(node, MSG_KEY));
131        }
132    }
133
134    /**
135     * Find nodes that match query.
136     *
137     * @param rootAST root node
138     * @return list of matching nodes
139     * @throws IllegalStateException if evaluation of xpath query fails
140     */
141    private List<DetailAST> findMatchingNodesByXpathQuery(DetailAST rootAST) {
142        try {
143            final RootNode rootNode = new RootNode(rootAST);
144            final XPathDynamicContext xpathDynamicContext =
145                    xpathExpression.createDynamicContext(rootNode);
146            final List<Item> matchingItems = xpathExpression.evaluate(xpathDynamicContext);
147            return matchingItems.stream()
148                    .map(item -> (DetailAST) ((AbstractNode) item).getUnderlyingNode())
149                    .toList();
150        }
151        catch (XPathException exc) {
152            throw new IllegalStateException("Evaluation of Xpath query failed: " + query, exc);
153        }
154    }
155
156}