001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2019 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.CheckUtil;
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 */
045@FileStatefulCheck
046public class CovariantEqualsCheck extends AbstractCheck {
047
048    /**
049     * A key is pointing to the warning message text in "messages.properties"
050     * file.
051     */
052    public static final String MSG_KEY = "covariant.equals";
053
054    /** Set of equals method definitions. */
055    private final Set<DetailAST> equalsMethods = new HashSet<>();
056
057    @Override
058    public int[] getDefaultTokens() {
059        return getRequiredTokens();
060    }
061
062    @Override
063    public int[] getRequiredTokens() {
064        return new int[] {TokenTypes.CLASS_DEF, TokenTypes.LITERAL_NEW, TokenTypes.ENUM_DEF, };
065    }
066
067    @Override
068    public int[] getAcceptableTokens() {
069        return getRequiredTokens();
070    }
071
072    @Override
073    public void visitToken(DetailAST ast) {
074        equalsMethods.clear();
075
076        // examine method definitions for equals methods
077        final DetailAST objBlock = ast.findFirstToken(TokenTypes.OBJBLOCK);
078        if (objBlock != null) {
079            DetailAST child = objBlock.getFirstChild();
080            boolean hasEqualsObject = false;
081            while (child != null) {
082                if (child.getType() == TokenTypes.METHOD_DEF
083                        && CheckUtil.isEqualsMethod(child)) {
084                    if (isFirstParameterObject(child)) {
085                        hasEqualsObject = true;
086                    }
087                    else {
088                        equalsMethods.add(child);
089                    }
090                }
091                child = child.getNextSibling();
092            }
093
094            // report equals method definitions
095            if (!hasEqualsObject) {
096                for (DetailAST equalsAST : equalsMethods) {
097                    final DetailAST nameNode = equalsAST
098                            .findFirstToken(TokenTypes.IDENT);
099                    log(nameNode, MSG_KEY);
100                }
101            }
102        }
103    }
104
105    /**
106     * Tests whether a method's first parameter is an Object.
107     * @param methodDefAst the method definition AST to test.
108     *     Precondition: ast is a TokenTypes.METHOD_DEF node.
109     * @return true if ast has first parameter of type Object.
110     */
111    private static boolean isFirstParameterObject(DetailAST methodDefAst) {
112        final DetailAST paramsNode = methodDefAst.findFirstToken(TokenTypes.PARAMETERS);
113
114        // parameter type "Object"?
115        final DetailAST paramNode =
116            paramsNode.findFirstToken(TokenTypes.PARAMETER_DEF);
117        final DetailAST typeNode = paramNode.findFirstToken(TokenTypes.TYPE);
118        final FullIdent fullIdent = FullIdent.createFullIdentBelow(typeNode);
119        final String name = fullIdent.getText();
120        return "Object".equals(name) || "java.lang.Object".equals(name);
121    }
122
123}