Source code

001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2020 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;
021
022import java.util.Arrays;
023import java.util.Collections;
024import java.util.Set;
025import java.util.stream.Collectors;
026
027import com.puppycrawl.tools.checkstyle.StatelessCheck;
028import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
029import com.puppycrawl.tools.checkstyle.api.DetailAST;
030import com.puppycrawl.tools.checkstyle.api.TokenTypes;
031import com.puppycrawl.tools.checkstyle.utils.CheckUtil;
032import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
033
034/**
035 * <p>
036 * Checks that parameters for methods, constructors, catch and for-each blocks are final.
037 * Interface, abstract, and native methods are not checked: the final keyword
038 * does not make sense for interface, abstract, and native method parameters as
039 * there is no code that could modify the parameter.
040 * </p>
041 * <p>
042 * Rationale: Changing the value of parameters during the execution of the method's
043 * algorithm can be confusing and should be avoided. A great way to let the Java compiler
044 * prevent this coding style is to declare parameters final.
045 * </p>
046 * <ul>
047 * <li>
048 * Property {@code ignorePrimitiveTypes} - Ignore primitive types as parameters.
049 * Type is {@code boolean}.
050 * Default value is {@code false}.
051 * </li>
052 * <li>
053 * Property {@code tokens} - tokens to check
054 * Type is {@code int[]}.
055 * Default value is:
056 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#METHOD_DEF">
057 * METHOD_DEF</a>,
058 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#CTOR_DEF">
059 * CTOR_DEF</a>.
060 * </li>
061 * </ul>
062 * <p>
063 * To configure the check to enforce final parameters for methods and constructors:
064 * </p>
065 * <pre>
066 * &lt;module name=&quot;FinalParameters&quot;/&gt;
067 * </pre>
068 * <p>
069 * To configure the check to enforce final parameters only for constructors:
070 * </p>
071 * <pre>
072 * &lt;module name=&quot;FinalParameters&quot;&gt;
073 *   &lt;property name=&quot;tokens&quot; value=&quot;CTOR_DEF&quot;/&gt;
074 * &lt;/module&gt;
075 * </pre>
076 * <p>
077 * To configure the check to allow ignoring
078 * <a href="https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html">
079 * primitive datatypes</a> as parameters:
080 * </p>
081 * <pre>
082 * &lt;module name=&quot;FinalParameters&quot;&gt;
083 *   &lt;property name=&quot;ignorePrimitiveTypes&quot; value=&quot;true&quot;/&gt;
084 * &lt;/module&gt;
085 * </pre>
086 * <p>
087 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
088 * </p>
089 * <p>
090 * Violation Message Keys:
091 * </p>
092 * <ul>
093 * <li>
094 * {@code final.parameter}
095 * </li>
096 * </ul>
097 *
098 * @since 3.0
099 */
100@StatelessCheck
101public class FinalParametersCheck extends AbstractCheck {
102
103    /**
104     * A key is pointing to the warning message text in "messages.properties"
105     * file.
106     */
107    public static final String MSG_KEY = "final.parameter";
108
109    /**
110     * Contains
111     * <a href="https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html">
112     * primitive datatypes</a>.
113     */
114    private final Set<Integer> primitiveDataTypes = Collections.unmodifiableSet(
115        Arrays.stream(new Integer[] {
116            TokenTypes.LITERAL_BYTE,
117            TokenTypes.LITERAL_SHORT,
118            TokenTypes.LITERAL_INT,
119            TokenTypes.LITERAL_LONG,
120            TokenTypes.LITERAL_FLOAT,
121            TokenTypes.LITERAL_DOUBLE,
122            TokenTypes.LITERAL_BOOLEAN,
123            TokenTypes.LITERAL_CHAR, })
124        .collect(Collectors.toSet()));
125
126    /**
127     * Ignore primitive types as parameters.
128     */
129    private boolean ignorePrimitiveTypes;
130
131    /**
132     * Setter to ignore primitive types as parameters.
133     *
134     * @param ignorePrimitiveTypes true or false.
135     */
136    public void setIgnorePrimitiveTypes(boolean ignorePrimitiveTypes) {
137        this.ignorePrimitiveTypes = ignorePrimitiveTypes;
138    }
139
140    @Override
141    public int[] getDefaultTokens() {
142        return new int[] {
143            TokenTypes.METHOD_DEF,
144            TokenTypes.CTOR_DEF,
145        };
146    }
147
148    @Override
149    public int[] getAcceptableTokens() {
150        return new int[] {
151            TokenTypes.METHOD_DEF,
152            TokenTypes.CTOR_DEF,
153            TokenTypes.LITERAL_CATCH,
154            TokenTypes.FOR_EACH_CLAUSE,
155        };
156    }
157
158    @Override
159    public int[] getRequiredTokens() {
160        return CommonUtil.EMPTY_INT_ARRAY;
161    }
162
163    @Override
164    public void visitToken(DetailAST ast) {
165        // don't flag interfaces
166        final DetailAST container = ast.getParent().getParent();
167        if (container.getType() != TokenTypes.INTERFACE_DEF) {
168            if (ast.getType() == TokenTypes.LITERAL_CATCH) {
169                visitCatch(ast);
170            }
171            else if (ast.getType() == TokenTypes.FOR_EACH_CLAUSE) {
172                visitForEachClause(ast);
173            }
174            else {
175                visitMethod(ast);
176            }
177        }
178    }
179
180    /**
181     * Checks parameters of the method or ctor.
182     *
183     * @param method method or ctor to check.
184     */
185    private void visitMethod(final DetailAST method) {
186        final DetailAST modifiers =
187            method.findFirstToken(TokenTypes.MODIFIERS);
188
189        // ignore abstract and native methods
190        if (modifiers.findFirstToken(TokenTypes.ABSTRACT) == null
191                && modifiers.findFirstToken(TokenTypes.LITERAL_NATIVE) == null) {
192            final DetailAST parameters =
193                method.findFirstToken(TokenTypes.PARAMETERS);
194            DetailAST child = parameters.getFirstChild();
195            while (child != null) {
196                // children are PARAMETER_DEF and COMMA
197                if (child.getType() == TokenTypes.PARAMETER_DEF) {
198                    checkParam(child);
199                }
200                child = child.getNextSibling();
201            }
202        }
203    }
204
205    /**
206     * Checks parameter of the catch block.
207     *
208     * @param catchClause catch block to check.
209     */
210    private void visitCatch(final DetailAST catchClause) {
211        checkParam(catchClause.findFirstToken(TokenTypes.PARAMETER_DEF));
212    }
213
214    /**
215     * Checks parameter of the for each clause.
216     *
217     * @param forEachClause for each clause to check.
218     */
219    private void visitForEachClause(final DetailAST forEachClause) {
220        checkParam(forEachClause.findFirstToken(TokenTypes.VARIABLE_DEF));
221    }
222
223    /**
224     * Checks if the given parameter is final.
225     *
226     * @param param parameter to check.
227     */
228    private void checkParam(final DetailAST param) {
229        if (param.findFirstToken(TokenTypes.MODIFIERS).findFirstToken(TokenTypes.FINAL) == null
230                && !isIgnoredParam(param)
231                && !CheckUtil.isReceiverParameter(param)) {
232            final DetailAST paramName = param.findFirstToken(TokenTypes.IDENT);
233            final DetailAST firstNode = CheckUtil.getFirstNode(param);
234            log(firstNode,
235                MSG_KEY, paramName.getText());
236        }
237    }
238
239    /**
240     * Checks for skip current param due to <b>ignorePrimitiveTypes</b> option.
241     *
242     * @param paramDef {@link TokenTypes#PARAMETER_DEF PARAMETER_DEF}
243     * @return true if param has to be skipped.
244     */
245    private boolean isIgnoredParam(DetailAST paramDef) {
246        boolean result = false;
247        if (ignorePrimitiveTypes) {
248            final DetailAST parameterType = paramDef
249                .findFirstToken(TokenTypes.TYPE).getFirstChild();
250            if (primitiveDataTypes.contains(parameterType.getType())) {
251                result = true;
252            }
253        }
254        return result;
255    }
256
257}