Source code

001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2018 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.xpath;
021
022import java.util.ArrayList;
023import java.util.List;
024import java.util.stream.Collectors;
025
026import com.puppycrawl.tools.checkstyle.api.DetailAST;
027import com.puppycrawl.tools.checkstyle.api.FileText;
028import com.puppycrawl.tools.checkstyle.api.TokenTypes;
029import com.puppycrawl.tools.checkstyle.utils.CommonUtils;
030import com.puppycrawl.tools.checkstyle.utils.TokenUtils;
031
032/**
033 * Generates xpath queries. Xpath queries are generated based on received
034 * {@code DetailAst} element, line number and column number.
035 *
036 * <p>
037 *     Example class
038 * </p>
039 * <pre>
040 * public class Main {
041 *
042 *     public String sayHello(String name) {
043 *         return "Hello, " + name;
044 *     }
045 * }
046 * </pre>
047 *
048 * <p>
049 *     Following expression returns list of queries. Each query is the string representing full
050 *     path to the node inside Xpath tree, whose line number is 3 and column number is 4.
051 * </p>
052 * <pre>
053 *     new XpathQueryGenerator(rootAst, 3, 4).generate();
054 * </pre>
055 *
056 * <p>
057 *     Result list
058 * </p>
059 * <ul>
060 *     <li>
061 *         /CLASS_DEF[@text='Main']/OBJBLOCK/METHOD_DEF[@text='sayHello']
062 *     </li>
063 *     <li>
064 *         /CLASS_DEF[@text='Main']/OBJBLOCK/METHOD_DEF[@text='sayHello']/MODIFIERS
065 *     </li>
066 *     <li>
067 *         /CLASS_DEF[@text='Main']/OBJBLOCK/METHOD_DEF[@text='sayHello']/MODIFIERS/LITERAL_PUBLIC
068 *     </li>
069 * </ul>
070 *
071 * @author Timur Tibeyev.
072 */
073public class XpathQueryGenerator {
074
075    /** The root ast. */
076    private final DetailAST rootAst;
077    /** The line number of the element for which the query should be generated. */
078    private final int lineNumber;
079    /** The column number of the element for which the query should be generated. */
080    private final int columnNumber;
081    /** The {@code FileText} object, representing content of the file. */
082    private final FileText fileText;
083    /** The distance between tab stop position. */
084    private final int tabWidth;
085
086    /**
087     * Creates a new {@code XpathQueryGenerator} instance.
088     *
089     * @param rootAst root ast
090     * @param lineNumber line number of the element for which the query should be generated
091     * @param columnNumber column number of the element for which the query should be generated
092     * @param fileText the {@code FileText} object
093     * @param tabWidth distance between tab stop position
094     */
095    public XpathQueryGenerator(DetailAST rootAst, int lineNumber, int columnNumber,
096                               FileText fileText, int tabWidth) {
097        this.rootAst = rootAst;
098        this.lineNumber = lineNumber;
099        this.columnNumber = columnNumber;
100        this.fileText = fileText;
101        this.tabWidth = tabWidth;
102    }
103
104    /**
105     * Returns list of xpath queries of nodes, matching line and column number.
106     * This approach uses DetailAST traversal. DetailAST means detail abstract syntax tree.
107     * @return list of xpath queries of nodes, matching line and column number
108     */
109    public List<String> generate() {
110        return getMatchingAstElements()
111            .stream()
112            .map(XpathQueryGenerator::generateXpathQuery)
113            .collect(Collectors.toList());
114    }
115
116    /**
117     * Returns child {@code DetailAst} element of the given root,
118     * which has child element with token type equals to {@link TokenTypes#IDENT}.
119     * @param root {@code DetailAST} root ast
120     * @return child {@code DetailAst} element of the given root
121     */
122    private static DetailAST findChildWithIdent(DetailAST root) {
123        return TokenUtils.findFirstTokenByPredicate(root,
124            cur -> {
125                return cur.findFirstToken(TokenTypes.IDENT) != null;
126            }).orElse(null);
127    }
128
129    /**
130     * Returns full xpath query for given ast element.
131     * @param ast {@code DetailAST} ast element
132     * @return full xpath query for given ast element
133     */
134    private static String generateXpathQuery(DetailAST ast) {
135        String xpathQuery = getXpathQuery(null, ast);
136        if (!isUniqueAst(ast)) {
137            final DetailAST child = findChildWithIdent(ast);
138            if (child != null) {
139                xpathQuery += "[." + getXpathQuery(ast, child) + ']';
140            }
141        }
142        return xpathQuery;
143    }
144
145    /**
146     * Returns list of nodes matching defined line and column number.
147     * @return list of nodes matching defined line and column number
148     */
149    private List<DetailAST> getMatchingAstElements() {
150        final List<DetailAST> result = new ArrayList<>();
151        DetailAST curNode = rootAst;
152        while (curNode != null && curNode.getLineNo() <= lineNumber) {
153            if (isMatchingByLineAndColumnAndNotIdent(curNode)) {
154                result.add(curNode);
155            }
156            DetailAST toVisit = curNode.getFirstChild();
157            while (curNode != null && toVisit == null) {
158                toVisit = curNode.getNextSibling();
159                if (toVisit == null) {
160                    curNode = curNode.getParent();
161                }
162            }
163
164            curNode = toVisit;
165        }
166        return result;
167    }
168
169    /**
170     * Returns relative xpath query for given ast element from root.
171     * @param root {@code DetailAST} root element
172     * @param ast {@code DetailAST} ast element
173     * @return relative xpath query for given ast element from root
174     */
175    private static String getXpathQuery(DetailAST root, DetailAST ast) {
176        final StringBuilder resultBuilder = new StringBuilder(1024);
177        DetailAST cur = ast;
178        while (cur != root) {
179            final StringBuilder curNodeQueryBuilder = new StringBuilder(256);
180            curNodeQueryBuilder.append('/')
181                    .append(TokenUtils.getTokenName(cur.getType()));
182            final DetailAST identAst = cur.findFirstToken(TokenTypes.IDENT);
183            if (identAst != null) {
184                curNodeQueryBuilder.append("[@text='")
185                        .append(identAst.getText())
186                        .append("']");
187            }
188            resultBuilder.insert(0, curNodeQueryBuilder);
189            cur = cur.getParent();
190        }
191        return resultBuilder.toString();
192    }
193
194    /**
195     * Checks if the given ast element has unique {@code TokenTypes} among siblings.
196     * @param ast {@code DetailAST} ast element
197     * @return if the given ast element has unique {@code TokenTypes} among siblings
198     */
199    private static boolean hasAtLeastOneSiblingWithSameTokenType(DetailAST ast) {
200        boolean result = false;
201        if (ast.getParent() == null) {
202            DetailAST prev = ast.getPreviousSibling();
203            while (prev != null) {
204                if (prev.getType() == ast.getType()) {
205                    result = true;
206                    break;
207                }
208                prev = prev.getPreviousSibling();
209            }
210            if (!result) {
211                DetailAST next = ast.getNextSibling();
212                while (next != null) {
213                    if (next.getType() == ast.getType()) {
214                        result = true;
215                        break;
216                    }
217                    next = next.getNextSibling();
218                }
219            }
220        }
221        else {
222            result = ast.getParent().getChildCount(ast.getType()) > 1;
223        }
224        return result;
225    }
226
227    /**
228     * Returns the column number with tabs expanded.
229     * @param ast {@code DetailAST} root ast
230     * @return the column number with tabs expanded
231     */
232    private int expandedTabColumn(DetailAST ast) {
233        return 1 + CommonUtils.lengthExpandedTabs(fileText.get(lineNumber - 1),
234                ast.getColumnNo(), tabWidth);
235    }
236
237    /**
238     * Checks if the given {@code DetailAST} node is matching line and column number and
239     * it is not {@link TokenTypes#IDENT}.
240     * @param ast {@code DetailAST} ast element
241     * @return true if the given {@code DetailAST} node is matching
242     */
243    private boolean isMatchingByLineAndColumnAndNotIdent(DetailAST ast) {
244        return ast.getType() != TokenTypes.IDENT
245                && ast.getLineNo() == lineNumber
246                && expandedTabColumn(ast) == columnNumber;
247    }
248
249    /**
250     * To be sure that generated xpath query will return exactly required ast element, the element
251     * should be checked for uniqueness. If ast element has {@link TokenTypes#IDENT} as the child
252     * or there is no sibling with the same {@code TokenTypes} then element is supposed to be
253     * unique. This method finds if {@code DetailAst} element is unique.
254     * @param ast {@code DetailAST} ast element
255     * @return if {@code DetailAst} element is unique
256     */
257    private static boolean isUniqueAst(DetailAST ast) {
258        return ast.findFirstToken(TokenTypes.IDENT) != null
259            || !hasAtLeastOneSiblingWithSameTokenType(ast);
260    }
261
262}