Source code

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.annotation;
021
022import java.util.ArrayDeque;
023import java.util.Deque;
024import java.util.Objects;
025import java.util.regex.Matcher;
026import java.util.regex.Pattern;
027
028import com.puppycrawl.tools.checkstyle.StatelessCheck;
029import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
030import com.puppycrawl.tools.checkstyle.api.DetailAST;
031import com.puppycrawl.tools.checkstyle.api.TokenTypes;
032import com.puppycrawl.tools.checkstyle.utils.AnnotationUtil;
033import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
034
035/**
036 * <div>
037 * Allows to specify what warnings that
038 * {@code @SuppressWarnings} is not allowed to suppress.
039 * You can also specify a list of TokenTypes that
040 * the configured warning(s) cannot be suppressed on.
041 * </div>
042 *
043 * <p>
044 * Limitations:  This check does not consider conditionals
045 * inside the &#64;SuppressWarnings annotation.
046 * </p>
047 *
048 * <p>
049 * For example:
050 * {@code @SuppressWarnings((false) ? (true) ? "unchecked" : "foo" : "unused")}.
051 * According to the above example, the "unused" warning is being suppressed
052 * not the "unchecked" or "foo" warnings.  All of these warnings will be
053 * considered and matched against regardless of what the conditional
054 * evaluates to.
055 * The check also does not support code like {@code @SuppressWarnings("un" + "used")},
056 * {@code @SuppressWarnings((String) "unused")} or
057 * {@code @SuppressWarnings({('u' + (char)'n') + (""+("used" + (String)"")),})}.
058 * </p>
059 *
060 * <p>
061 * By default, any warning specified will be disallowed on
062 * all legal TokenTypes unless otherwise specified via
063 * the tokens property.
064 * </p>
065 *
066 * <p>
067 * Also, by default warnings that are empty strings or all
068 * whitespace (regex: ^$|^\s+$) are flagged.  By specifying,
069 * the format property these defaults no longer apply.
070 * </p>
071 *
072 * <p>This check can be configured so that the "unchecked"
073 * and "unused" warnings cannot be suppressed on
074 * anything but variable and parameter declarations.
075 * See below of an example.
076 * </p>
077 *
078 * @since 5.0
079 */
080@StatelessCheck
081public class SuppressWarningsCheck extends AbstractCheck {
082
083    /**
084     * A key is pointing to the warning message text in "messages.properties"
085     * file.
086     */
087    public static final String MSG_KEY_SUPPRESSED_WARNING_NOT_ALLOWED =
088        "suppressed.warning.not.allowed";
089
090    /** {@link SuppressWarnings SuppressWarnings} annotation name. */
091    private static final String SUPPRESS_WARNINGS = "SuppressWarnings";
092
093    /**
094     * Fully-qualified {@link SuppressWarnings SuppressWarnings}
095     * annotation name.
096     */
097    private static final String FQ_SUPPRESS_WARNINGS =
098        "java.lang." + SUPPRESS_WARNINGS;
099
100    /**
101     * Specify the RegExp to match against warnings. Any warning
102     * being suppressed matching this pattern will be flagged.
103     */
104    private Pattern format = Pattern.compile("^\\s*+$");
105
106    /**
107     * Setter to specify the RegExp to match against warnings. Any warning
108     * being suppressed matching this pattern will be flagged.
109     *
110     * @param pattern the new pattern
111     * @since 5.0
112     */
113    public final void setFormat(Pattern pattern) {
114        format = pattern;
115    }
116
117    @Override
118    public final int[] getDefaultTokens() {
119        return getAcceptableTokens();
120    }
121
122    @Override
123    public final int[] getAcceptableTokens() {
124        return new int[] {
125            TokenTypes.CLASS_DEF,
126            TokenTypes.INTERFACE_DEF,
127            TokenTypes.ENUM_DEF,
128            TokenTypes.ANNOTATION_DEF,
129            TokenTypes.ANNOTATION_FIELD_DEF,
130            TokenTypes.ENUM_CONSTANT_DEF,
131            TokenTypes.PARAMETER_DEF,
132            TokenTypes.VARIABLE_DEF,
133            TokenTypes.METHOD_DEF,
134            TokenTypes.CTOR_DEF,
135            TokenTypes.COMPACT_CTOR_DEF,
136            TokenTypes.RECORD_DEF,
137            TokenTypes.PATTERN_VARIABLE_DEF,
138        };
139    }
140
141    @Override
142    public int[] getRequiredTokens() {
143        return CommonUtil.EMPTY_INT_ARRAY;
144    }
145
146    @Override
147    public void visitToken(final DetailAST ast) {
148        final DetailAST annotation = getSuppressWarnings(ast);
149
150        if (annotation != null) {
151            final DetailAST warningHolder =
152                findWarningsHolder(annotation);
153            final DetailAST token =
154                    warningHolder.findFirstToken(TokenTypes.ANNOTATION_MEMBER_VALUE_PAIR);
155
156            // case like '@SuppressWarnings(value = UNUSED)'
157            final DetailAST parent = Objects.requireNonNullElse(token, warningHolder);
158            final DetailAST warning = parent.findFirstToken(TokenTypes.EXPR);
159
160            if (warning == null) {
161                // check to see if empty warnings are forbidden -- are by default
162                logMatch(warningHolder, "");
163            }
164            else {
165                processWarnings(warning);
166            }
167        }
168    }
169
170    /**
171     * Processes all warning expressions starting from the given AST node.
172     *
173     * @param warning the first warning expression node to process
174     */
175    private void processWarnings(final DetailAST warning) {
176        for (DetailAST current = warning; current != null; current = current.getNextSibling()) {
177            if (current.getType() == TokenTypes.EXPR) {
178                processWarningExpr(current.getFirstChild(), current);
179            }
180        }
181    }
182
183    /**
184     * Processes a single warning expression.
185     *
186     * @param fChild  the first child AST of the expression
187     * @param warning the parent warning AST node
188     */
189    private void processWarningExpr(final DetailAST fChild, final DetailAST warning) {
190        switch (fChild.getType()) {
191            case TokenTypes.STRING_LITERAL -> logMatch(warning,
192                    removeQuotes(warning.getFirstChild().getText()));
193
194            case TokenTypes.QUESTION ->
195                // ex: @SuppressWarnings((false) ? (true) ? "unchecked" : "foo" : "unused")
196                walkConditional(fChild);
197
198            default -> {
199            // Known limitation: cases like @SuppressWarnings("un" + "used") or
200            // @SuppressWarnings((String) "unused") are not properly supported,
201            // but they should not cause exceptions.
202            // Also constants as params:
203            // ex: public static final String UNCHECKED = "unchecked";
204            // @SuppressWarnings(UNCHECKED)
205            // or
206            // @SuppressWarnings(SomeClass.UNCHECKED)
207            }
208        }
209    }
210
211    /**
212     * Gets the {@link SuppressWarnings SuppressWarnings} annotation
213     * that is annotating the AST.  If the annotation does not exist
214     * this method will return {@code null}.
215     *
216     * @param ast the AST
217     * @return the {@link SuppressWarnings SuppressWarnings} annotation
218     */
219    private static DetailAST getSuppressWarnings(DetailAST ast) {
220        DetailAST annotation = AnnotationUtil.getAnnotation(ast, SUPPRESS_WARNINGS);
221
222        if (annotation == null) {
223            annotation = AnnotationUtil.getAnnotation(ast, FQ_SUPPRESS_WARNINGS);
224        }
225        return annotation;
226    }
227
228    /**
229     * This method looks for a warning that matches a configured expression.
230     * If found it logs a violation at the given AST.
231     *
232     * @param ast the location to place the violation
233     * @param warningText the warning.
234     */
235    private void logMatch(DetailAST ast, final String warningText) {
236        final Matcher matcher = format.matcher(warningText);
237        if (matcher.matches()) {
238            log(ast,
239                    MSG_KEY_SUPPRESSED_WARNING_NOT_ALLOWED, warningText);
240        }
241    }
242
243    /**
244     * Find the parent (holder) of the of the warnings (Expr).
245     *
246     * @param annotation the annotation
247     * @return a Token representing the expr.
248     */
249    private static DetailAST findWarningsHolder(final DetailAST annotation) {
250        final DetailAST annValuePair =
251            annotation.findFirstToken(TokenTypes.ANNOTATION_MEMBER_VALUE_PAIR);
252
253        final DetailAST annArrayInitParent = Objects.requireNonNullElse(annValuePair, annotation);
254        final DetailAST annArrayInit = annArrayInitParent
255                .findFirstToken(TokenTypes.ANNOTATION_ARRAY_INIT);
256        return Objects.requireNonNullElse(annArrayInit, annotation);
257    }
258
259    /**
260     * Strips a single double quote from the front and back of a string.
261     *
262     * <p>For example:</p>
263     * <pre>
264     * Input String = "unchecked"
265     * </pre>
266     * Output String = unchecked
267     *
268     * @param warning the warning string
269     * @return the string without two quotes
270     */
271    private static String removeQuotes(final String warning) {
272        return warning.substring(1, warning.length() - 1);
273    }
274
275    /**
276     * Walks a conditional expression checking the left
277     * and right sides, checking for matches and
278     * logging violations.
279     *
280     * @param cond a Conditional type
281     *     {@link TokenTypes#QUESTION QUESTION}
282     */
283    private void walkConditional(final DetailAST cond) {
284        final Deque<DetailAST> condStack = new ArrayDeque<>();
285        condStack.push(cond);
286
287        while (!condStack.isEmpty()) {
288            final DetailAST currentCond = condStack.pop();
289            if (currentCond.getType() == TokenTypes.QUESTION) {
290                condStack.push(getCondRight(currentCond));
291                condStack.push(getCondLeft(currentCond));
292            }
293            else {
294                final String warningText = removeQuotes(currentCond.getText());
295                logMatch(currentCond, warningText);
296            }
297        }
298    }
299
300    /**
301     * Retrieves the left side of a conditional.
302     *
303     * @param cond cond a conditional type
304     *     {@link TokenTypes#QUESTION QUESTION}
305     * @return either the value
306     *     or another conditional
307     */
308    private static DetailAST getCondLeft(final DetailAST cond) {
309        final DetailAST colon = cond.findFirstToken(TokenTypes.COLON);
310        return colon.getPreviousSibling();
311    }
312
313    /**
314     * Retrieves the right side of a conditional.
315     *
316     * @param cond a conditional type
317     *     {@link TokenTypes#QUESTION QUESTION}
318     * @return either the value
319     *     or another conditional
320     */
321    private static DetailAST getCondRight(final DetailAST cond) {
322        final DetailAST colon = cond.findFirstToken(TokenTypes.COLON);
323        return colon.getNextSibling();
324    }
325
326}