001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2017 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.coding;
021
022import java.util.HashSet;
023import java.util.Set;
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.FullIdent;
029import com.puppycrawl.tools.checkstyle.api.TokenTypes;
030import com.puppycrawl.tools.checkstyle.utils.CheckUtils;
031
032/**
033 * <p>Checks that if a class defines a covariant method equals,
034 * then it defines method equals(java.lang.Object).
035 * Inspired by findbugs,
036 * http://findbugs.sourceforge.net/bugDescriptions.html#EQ_SELF_NO_OBJECT
037 * </p>
038 * <p>
039 * An example of how to configure the check is:
040 * </p>
041 * <pre>
042 * &lt;module name="CovariantEquals"/&gt;
043 * </pre>
044 * @author Rick Giles
045 */
046@FileStatefulCheck
047public class CovariantEqualsCheck extends AbstractCheck {
048
049    /**
050     * A key is pointing to the warning message text in "messages.properties"
051     * file.
052     */
053    public static final String MSG_KEY = "covariant.equals";
054
055    /** Set of equals method definitions. */
056    private final Set<DetailAST> equalsMethods = new HashSet<>();
057
058    @Override
059    public int[] getDefaultTokens() {
060        return getRequiredTokens();
061    }
062
063    @Override
064    public int[] getRequiredTokens() {
065        return new int[] {TokenTypes.CLASS_DEF, TokenTypes.LITERAL_NEW, TokenTypes.ENUM_DEF, };
066    }
067
068    @Override
069    public int[] getAcceptableTokens() {
070        return getRequiredTokens();
071    }
072
073    @Override
074    public void visitToken(DetailAST ast) {
075        equalsMethods.clear();
076
077        // examine method definitions for equals methods
078        final DetailAST objBlock = ast.findFirstToken(TokenTypes.OBJBLOCK);
079        if (objBlock != null) {
080            DetailAST child = objBlock.getFirstChild();
081            boolean hasEqualsObject = false;
082            while (child != null) {
083                if (child.getType() == TokenTypes.METHOD_DEF
084                        && CheckUtils.isEqualsMethod(child)) {
085                    if (isFirstParameterObject(child)) {
086                        hasEqualsObject = true;
087                    }
088                    else {
089                        equalsMethods.add(child);
090                    }
091                }
092                child = child.getNextSibling();
093            }
094
095            // report equals method definitions
096            if (!hasEqualsObject) {
097                for (DetailAST equalsAST : equalsMethods) {
098                    final DetailAST nameNode = equalsAST
099                            .findFirstToken(TokenTypes.IDENT);
100                    log(nameNode.getLineNo(), nameNode.getColumnNo(),
101                            MSG_KEY);
102                }
103            }
104        }
105    }
106
107    /**
108     * Tests whether a method's first parameter is an Object.
109     * @param methodDefAst the method definition AST to test.
110     *     Precondition: ast is a TokenTypes.METHOD_DEF node.
111     * @return true if ast has first parameter of type Object.
112     */
113    private static boolean isFirstParameterObject(DetailAST methodDefAst) {
114        final DetailAST paramsNode = methodDefAst.findFirstToken(TokenTypes.PARAMETERS);
115
116        // parameter type "Object"?
117        final DetailAST paramNode =
118            paramsNode.findFirstToken(TokenTypes.PARAMETER_DEF);
119        final DetailAST typeNode = paramNode.findFirstToken(TokenTypes.TYPE);
120        final FullIdent fullIdent = FullIdent.createFullIdentBelow(typeNode);
121        final String name = fullIdent.getText();
122        return "Object".equals(name) || "java.lang.Object".equals(name);
123    }
124}