Source code

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.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     * Creates a new {@code SuppressWarningsCheck} instance.
108     */
109    public SuppressWarningsCheck() {
110        // no code by default
111    }
112
113    /**
114     * Setter to specify the RegExp to match against warnings. Any warning
115     * being suppressed matching this pattern will be flagged.
116     *
117     * @param pattern the new pattern
118     * @since 5.0
119     */
120    public final void setFormat(Pattern pattern) {
121        format = pattern;
122    }
123
124    @Override
125    public final int[] getDefaultTokens() {
126        return getAcceptableTokens();
127    }
128
129    @Override
130    public final int[] getAcceptableTokens() {
131        return new int[] {
132            TokenTypes.CLASS_DEF,
133            TokenTypes.INTERFACE_DEF,
134            TokenTypes.ENUM_DEF,
135            TokenTypes.ANNOTATION_DEF,
136            TokenTypes.ANNOTATION_FIELD_DEF,
137            TokenTypes.ENUM_CONSTANT_DEF,
138            TokenTypes.PARAMETER_DEF,
139            TokenTypes.VARIABLE_DEF,
140            TokenTypes.METHOD_DEF,
141            TokenTypes.CTOR_DEF,
142            TokenTypes.COMPACT_CTOR_DEF,
143            TokenTypes.RECORD_DEF,
144            TokenTypes.PATTERN_VARIABLE_DEF,
145        };
146    }
147
148    @Override
149    public int[] getRequiredTokens() {
150        return CommonUtil.EMPTY_INT_ARRAY;
151    }
152
153    @Override
154    public void visitToken(final DetailAST ast) {
155        final DetailAST annotation = getSuppressWarnings(ast);
156
157        if (annotation != null) {
158            final DetailAST warningHolder =
159                findWarningsHolder(annotation);
160            final DetailAST token =
161                    warningHolder.findFirstToken(TokenTypes.ANNOTATION_MEMBER_VALUE_PAIR);
162
163            // case like '@SuppressWarnings(value = UNUSED)'
164            final DetailAST parent = Objects.requireNonNullElse(token, warningHolder);
165            final DetailAST warning = parent.findFirstToken(TokenTypes.EXPR);
166
167            if (warning == null) {
168                // check to see if empty warnings are forbidden -- are by default
169                logMatch(warningHolder, "");
170            }
171            else {
172                processWarnings(warning);
173            }
174        }
175    }
176
177    /**
178     * Processes all warning expressions starting from the given AST node.
179     *
180     * @param warning the first warning expression node to process
181     */
182    private void processWarnings(final DetailAST warning) {
183        for (DetailAST current = warning; current != null; current = current.getNextSibling()) {
184            if (current.getType() == TokenTypes.EXPR) {
185                processWarningExpr(current.getFirstChild(), current);
186            }
187        }
188    }
189
190    /**
191     * Processes a single warning expression.
192     *
193     * @param firstChild  the first child AST of the expression
194     * @param warning the parent warning AST node
195     */
196    private void processWarningExpr(final DetailAST firstChild, final DetailAST warning) {
197        switch (firstChild.getType()) {
198            case TokenTypes.STRING_LITERAL -> logMatch(warning,
199                    removeQuotes(warning.getFirstChild().getText()));
200
201            case TokenTypes.QUESTION ->
202                // ex: @SuppressWarnings((false) ? (true) ? "unchecked" : "foo" : "unused")
203                walkConditional(firstChild);
204
205            default -> {
206            // Known limitation: cases like @SuppressWarnings("un" + "used") or
207            // @SuppressWarnings((String) "unused") are not properly supported,
208            // but they should not cause exceptions.
209            // Also constants as params:
210            // ex: public static final String UNCHECKED = "unchecked";
211            // @SuppressWarnings(UNCHECKED)
212            // or
213            // @SuppressWarnings(SomeClass.UNCHECKED)
214            }
215        }
216    }
217
218    /**
219     * Gets the {@link SuppressWarnings SuppressWarnings} annotation
220     * that is annotating the AST.  If the annotation does not exist
221     * this method will return {@code null}.
222     *
223     * @param ast the AST
224     * @return the {@link SuppressWarnings SuppressWarnings} annotation
225     */
226    private static DetailAST getSuppressWarnings(DetailAST ast) {
227        DetailAST annotation = AnnotationUtil.getAnnotation(ast, SUPPRESS_WARNINGS);
228
229        if (annotation == null) {
230            annotation = AnnotationUtil.getAnnotation(ast, FQ_SUPPRESS_WARNINGS);
231        }
232        return annotation;
233    }
234
235    /**
236     * This method looks for a warning that matches a configured expression.
237     * If found it logs a violation at the given AST.
238     *
239     * @param ast the location to place the violation
240     * @param warningText the warning.
241     */
242    private void logMatch(DetailAST ast, final String warningText) {
243        final Matcher matcher = format.matcher(warningText);
244        if (matcher.matches()) {
245            log(ast,
246                    MSG_KEY_SUPPRESSED_WARNING_NOT_ALLOWED, warningText);
247        }
248    }
249
250    /**
251     * Find the parent (holder) of the of the warnings (Expr).
252     *
253     * @param annotation the annotation
254     * @return a Token representing the expr.
255     */
256    private static DetailAST findWarningsHolder(final DetailAST annotation) {
257        final DetailAST annValuePair =
258            annotation.findFirstToken(TokenTypes.ANNOTATION_MEMBER_VALUE_PAIR);
259
260        final DetailAST annArrayInitParent = Objects.requireNonNullElse(annValuePair, annotation);
261        final DetailAST annArrayInit = annArrayInitParent
262                .findFirstToken(TokenTypes.ANNOTATION_ARRAY_INIT);
263        return Objects.requireNonNullElse(annArrayInit, annotation);
264    }
265
266    /**
267     * Strips a single double quote from the front and back of a string.
268     *
269     * <p>For example:</p>
270     * <pre>
271     * Input String = "unchecked"
272     * </pre>
273     * Output String = unchecked
274     *
275     * @param warning the warning string
276     * @return the string without two quotes
277     */
278    private static String removeQuotes(final String warning) {
279        return warning.substring(1, warning.length() - 1);
280    }
281
282    /**
283     * Walks a conditional expression checking the left
284     * and right sides, checking for matches and
285     * logging violations.
286     *
287     * @param cond a Conditional type
288     *     {@link TokenTypes#QUESTION QUESTION}
289     */
290    private void walkConditional(final DetailAST cond) {
291        final Deque<DetailAST> condStack = new ArrayDeque<>();
292        condStack.push(cond);
293
294        while (!condStack.isEmpty()) {
295            final DetailAST currentCond = condStack.pop();
296            if (currentCond.getType() == TokenTypes.QUESTION) {
297                condStack.push(getCondRight(currentCond));
298                condStack.push(getCondLeft(currentCond));
299            }
300            else {
301                final String warningText = removeQuotes(currentCond.getText());
302                logMatch(currentCond, warningText);
303            }
304        }
305    }
306
307    /**
308     * Retrieves the left side of a conditional.
309     *
310     * @param cond cond a conditional type
311     *     {@link TokenTypes#QUESTION QUESTION}
312     * @return either the value
313     *     or another conditional
314     */
315    private static DetailAST getCondLeft(final DetailAST cond) {
316        final DetailAST colon = cond.findFirstToken(TokenTypes.COLON);
317        return colon.getPreviousSibling();
318    }
319
320    /**
321     * Retrieves the right side of a conditional.
322     *
323     * @param cond a conditional type
324     *     {@link TokenTypes#QUESTION QUESTION}
325     * @return either the value
326     *     or another conditional
327     */
328    private static DetailAST getCondRight(final DetailAST cond) {
329        final DetailAST colon = cond.findFirstToken(TokenTypes.COLON);
330        return colon.getNextSibling();
331    }
332
333}