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.metrics;
021
022import java.util.ArrayDeque;
023import java.util.Deque;
024
025import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
026import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
027import com.puppycrawl.tools.checkstyle.api.DetailAST;
028import com.puppycrawl.tools.checkstyle.api.TokenTypes;
029import com.puppycrawl.tools.checkstyle.utils.CheckUtil;
030
031/**
032 * <div>
033 * Restricts the number of boolean operators ({@code &amp;&amp;}, {@code ||},
034 * {@code &amp;}, {@code |} and {@code ^}) in an expression.
035 * </div>
036 *
037 * <p>
038 * Rationale: Too many conditions leads to code that is difficult to read
039 * and hence debug and maintain.
040 * </p>
041 *
042 * <p>
043 * Note that the operators {@code &amp;} and {@code |} are not only integer bitwise
044 * operators, they are also the
045 * <a href="https://docs.oracle.com/javase/specs/jls/se11/html/jls-15.html#jls-15.22.2">
046 * non-shortcut versions</a> of the boolean operators {@code &amp;&amp;} and {@code ||}.
047 * </p>
048 *
049 * <p>
050 * Note that {@code &amp;}, {@code |} and {@code ^} are not checked if they are part
051 * of constructor or method call because they can be applied to non-boolean
052 * variables and Checkstyle does not know types of methods from different classes.
053 * </p>
054 *
055 * @since 3.4
056 */
057@FileStatefulCheck
058public final class BooleanExpressionComplexityCheck extends AbstractCheck {
059
060    /**
061     * A key is pointing to the warning message text in "messages.properties"
062     * file.
063     */
064    public static final String MSG_KEY = "booleanExpressionComplexity";
065
066    /** Default allowed complexity. */
067    private static final int DEFAULT_MAX = 3;
068
069    /** Stack of contexts. */
070    private final Deque<Context> contextStack = new ArrayDeque<>();
071    /** Specify the maximum number of boolean operations allowed in one expression. */
072    private int max;
073    /** Current context. */
074    private Context context = new Context(false);
075
076    /** Creates new instance of the check. */
077    public BooleanExpressionComplexityCheck() {
078        max = DEFAULT_MAX;
079    }
080
081    @Override
082    public int[] getDefaultTokens() {
083        return new int[] {
084            TokenTypes.CTOR_DEF,
085            TokenTypes.METHOD_DEF,
086            TokenTypes.EXPR,
087            TokenTypes.LAND,
088            TokenTypes.BAND,
089            TokenTypes.LOR,
090            TokenTypes.BOR,
091            TokenTypes.BXOR,
092            TokenTypes.COMPACT_CTOR_DEF,
093        };
094    }
095
096    @Override
097    public int[] getRequiredTokens() {
098        return new int[] {
099            TokenTypes.CTOR_DEF,
100            TokenTypes.METHOD_DEF,
101            TokenTypes.EXPR,
102            TokenTypes.COMPACT_CTOR_DEF,
103        };
104    }
105
106    @Override
107    public int[] getAcceptableTokens() {
108        return new int[] {
109            TokenTypes.CTOR_DEF,
110            TokenTypes.METHOD_DEF,
111            TokenTypes.EXPR,
112            TokenTypes.LAND,
113            TokenTypes.BAND,
114            TokenTypes.LOR,
115            TokenTypes.BOR,
116            TokenTypes.BXOR,
117            TokenTypes.COMPACT_CTOR_DEF,
118        };
119    }
120
121    /**
122     * Setter to specify the maximum number of boolean operations allowed in one expression.
123     *
124     * @param max new maximum allowed complexity.
125     * @since 3.4
126     */
127    public void setMax(int max) {
128        this.max = max;
129    }
130
131    @Override
132    public void visitToken(DetailAST ast) {
133        switch (ast.getType()) {
134            case TokenTypes.CTOR_DEF,
135                 TokenTypes.METHOD_DEF,
136                 TokenTypes.COMPACT_CTOR_DEF -> visitMethodDef(ast);
137
138            case TokenTypes.EXPR -> visitExpr();
139
140            case TokenTypes.BOR -> {
141                if (!isPipeOperator(ast) && !isPassedInParameter(ast)) {
142                    context.visitBooleanOperator();
143                }
144            }
145
146            case TokenTypes.BAND,
147                 TokenTypes.BXOR -> {
148                if (!isPassedInParameter(ast)) {
149                    context.visitBooleanOperator();
150                }
151            }
152
153            case TokenTypes.LAND,
154                 TokenTypes.LOR -> context.visitBooleanOperator();
155
156            default -> throw new IllegalArgumentException("Unknown type: " + ast);
157        }
158    }
159
160    /**
161     * Checks if logical operator is part of constructor or method call.
162     *
163     * @param logicalOperator logical operator
164     * @return true if logical operator is part of constructor or method call
165     */
166    private static boolean isPassedInParameter(DetailAST logicalOperator) {
167        return logicalOperator.getParent().getParent().getType() == TokenTypes.ELIST;
168    }
169
170    /**
171     * Checks if {@link TokenTypes#BOR binary OR} is applied to exceptions
172     * in
173     * <a href="https://docs.oracle.com/javase/specs/jls/se8/html/jls-14.html#jls-14.20">
174     * multi-catch</a> (pipe-syntax).
175     *
176     * @param binaryOr {@link TokenTypes#BOR binary or}
177     * @return true if binary or is applied to exceptions in multi-catch.
178     */
179    private static boolean isPipeOperator(DetailAST binaryOr) {
180        return binaryOr.getParent().getType() == TokenTypes.TYPE;
181    }
182
183    @Override
184    public void leaveToken(DetailAST ast) {
185        switch (ast.getType()) {
186            case TokenTypes.CTOR_DEF,
187                 TokenTypes.METHOD_DEF,
188                 TokenTypes.COMPACT_CTOR_DEF -> leaveMethodDef();
189
190            case TokenTypes.EXPR -> leaveExpr(ast);
191
192            default -> {
193                // Do nothing
194            }
195        }
196    }
197
198    /**
199     * Creates new context for a given method.
200     *
201     * @param ast a method we start to check.
202     */
203    private void visitMethodDef(DetailAST ast) {
204        contextStack.push(context);
205        final boolean check = !CheckUtil.isEqualsMethod(ast);
206        context = new Context(check);
207    }
208
209    /** Removes old context. */
210    private void leaveMethodDef() {
211        context = contextStack.pop();
212    }
213
214    /** Creates and pushes new context. */
215    private void visitExpr() {
216        contextStack.push(context);
217        context = new Context(context.isChecking());
218    }
219
220    /**
221     * Restores previous context.
222     *
223     * @param ast expression we leave.
224     */
225    private void leaveExpr(DetailAST ast) {
226        context.checkCount(ast);
227        context = contextStack.pop();
228    }
229
230    /**
231     * Represents context (method/expression) in which we check complexity.
232     *
233     */
234    private final class Context {
235
236        /**
237         * Should we perform check in current context or not.
238         * Usually false if we are inside equals() method.
239         */
240        private final boolean checking;
241        /** Count of boolean operators. */
242        private int count;
243
244        /**
245         * Creates new instance.
246         *
247         * @param checking should we check in current context or not.
248         */
249        private Context(boolean checking) {
250            this.checking = checking;
251        }
252
253        /**
254         * Getter for checking property.
255         *
256         * @return should we check in current context or not.
257         */
258        public boolean isChecking() {
259            return checking;
260        }
261
262        /** Increases operator counter. */
263        public void visitBooleanOperator() {
264            ++count;
265        }
266
267        /**
268         * Checks if we violate maximum allowed complexity.
269         *
270         * @param ast a node we check now.
271         */
272        public void checkCount(DetailAST ast) {
273            if (checking && count > max) {
274                final DetailAST parentAST = ast.getParent();
275
276                log(parentAST, MSG_KEY, count, max);
277            }
278        }
279
280    }
281
282}