001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2025 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 * <ul>
062 * <li>
063 * Property {@code query} - Specify Xpath query.
064 * Type is {@code java.lang.String}.
065 * Default value is {@code ""}.
066 * </li>
067 * </ul>
068 *
069 * <p>
070 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
071 * </p>
072 *
073 * <p>
074 * Violation Message Keys:
075 * </p>
076 * <ul>
077 * <li>
078 * {@code matchxpath.match}
079 * </li>
080 * </ul>
081 *
082 * @since 8.39
083 */
084@StatelessCheck
085public class MatchXpathCheck extends AbstractCheck {
086
087    /**
088     * A key is pointing to the warning message text provided by user.
089     */
090    public static final String MSG_KEY = "matchxpath.match";
091
092    /** Specify Xpath query. */
093    private String query = "";
094
095    /** Xpath expression. */
096    private XPathExpression xpathExpression;
097
098    /**
099     * Setter to specify Xpath query.
100     *
101     * @param query Xpath query.
102     * @throws IllegalStateException if creation of xpath expression fails
103     * @since 8.39
104     */
105    public void setQuery(String query) {
106        this.query = query;
107        if (!query.isEmpty()) {
108            try {
109                final XPathEvaluator xpathEvaluator =
110                        new XPathEvaluator(Configuration.newConfiguration());
111                xpathExpression = xpathEvaluator.createExpression(query);
112            }
113            catch (XPathException exc) {
114                throw new IllegalStateException("Creating Xpath expression failed: " + query, exc);
115            }
116        }
117    }
118
119    @Override
120    public int[] getDefaultTokens() {
121        return getRequiredTokens();
122    }
123
124    @Override
125    public int[] getAcceptableTokens() {
126        return getRequiredTokens();
127    }
128
129    @Override
130    public int[] getRequiredTokens() {
131        return CommonUtil.EMPTY_INT_ARRAY;
132    }
133
134    @Override
135    public boolean isCommentNodesRequired() {
136        return true;
137    }
138
139    @Override
140    public void beginTree(DetailAST rootAST) {
141        if (!query.isEmpty()) {
142            final List<DetailAST> matchingNodes = findMatchingNodesByXpathQuery(rootAST);
143            matchingNodes.forEach(node -> log(node, MSG_KEY));
144        }
145    }
146
147    /**
148     * Find nodes that match query.
149     *
150     * @param rootAST root node
151     * @return list of matching nodes
152     * @throws IllegalStateException if evaluation of xpath query fails
153     */
154    private List<DetailAST> findMatchingNodesByXpathQuery(DetailAST rootAST) {
155        try {
156            final RootNode rootNode = new RootNode(rootAST);
157            final XPathDynamicContext xpathDynamicContext =
158                    xpathExpression.createDynamicContext(rootNode);
159            final List<Item> matchingItems = xpathExpression.evaluate(xpathDynamicContext);
160            return matchingItems.stream()
161                    .map(item -> (DetailAST) ((AbstractNode) item).getUnderlyingNode())
162                    .toList();
163        }
164        catch (XPathException exc) {
165            throw new IllegalStateException("Evaluation of Xpath query failed: " + query, exc);
166        }
167    }
168}