001//////////////////////////////////////////////////////////////////////////////// 002// checkstyle: Checks Java source code for adherence to a set of rules. 003// Copyright (C) 2001-2018 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 antlr.collections.AST; 023import com.puppycrawl.tools.checkstyle.StatelessCheck; 024import com.puppycrawl.tools.checkstyle.api.AbstractCheck; 025import com.puppycrawl.tools.checkstyle.api.DetailAST; 026import com.puppycrawl.tools.checkstyle.api.TokenTypes; 027 028/** 029 * <p> 030 * Checks for overly complicated boolean return statements. 031 * Idea shamelessly stolen from the equivalent PMD rule (pmd.sourceforge.net). 032 * </p> 033 * <p> 034 * An example of how to configure the check is: 035 * </p> 036 * <pre> 037 * <module name="SimplifyBooleanReturn"/> 038 * </pre> 039 * @author Lars Kühne 040 */ 041@StatelessCheck 042public class SimplifyBooleanReturnCheck 043 extends AbstractCheck { 044 045 /** 046 * A key is pointing to the warning message text in "messages.properties" 047 * file. 048 */ 049 public static final String MSG_KEY = "simplify.boolReturn"; 050 051 @Override 052 public int[] getAcceptableTokens() { 053 return getRequiredTokens(); 054 } 055 056 @Override 057 public int[] getDefaultTokens() { 058 return getRequiredTokens(); 059 } 060 061 @Override 062 public int[] getRequiredTokens() { 063 return new int[] {TokenTypes.LITERAL_IF}; 064 } 065 066 @Override 067 public void visitToken(DetailAST ast) { 068 // LITERAL_IF has the following four or five children: 069 // '(' 070 // condition 071 // ')' 072 // thenStatement 073 // [ LITERAL_ELSE (with the elseStatement as a child) ] 074 075 // don't bother if this is not if then else 076 final AST elseLiteral = 077 ast.findFirstToken(TokenTypes.LITERAL_ELSE); 078 if (elseLiteral != null) { 079 final AST elseStatement = elseLiteral.getFirstChild(); 080 081 // skip '(' and ')' 082 final AST condition = ast.getFirstChild().getNextSibling(); 083 final AST thenStatement = condition.getNextSibling().getNextSibling(); 084 085 if (canReturnOnlyBooleanLiteral(thenStatement) 086 && canReturnOnlyBooleanLiteral(elseStatement)) { 087 log(ast.getLineNo(), ast.getColumnNo(), MSG_KEY); 088 } 089 } 090 } 091 092 /** 093 * Returns if an AST is a return statement with a boolean literal 094 * or a compound statement that contains only such a return statement. 095 * 096 * <p>Returns {@code true} iff ast represents 097 * <br/> 098 * <pre> 099 * return true/false; 100 * </pre> 101 * or 102 * <br/> 103 * <pre> 104 * { 105 * return true/false; 106 * } 107 * </pre> 108 * 109 * @param ast the syntax tree to check 110 * @return if ast is a return statement with a boolean literal. 111 */ 112 private static boolean canReturnOnlyBooleanLiteral(AST ast) { 113 boolean result = true; 114 if (!isBooleanLiteralReturnStatement(ast)) { 115 final AST firstStatement = ast.getFirstChild(); 116 result = isBooleanLiteralReturnStatement(firstStatement); 117 } 118 return result; 119 } 120 121 /** 122 * Returns if an AST is a return statement with a boolean literal. 123 * 124 * <p>Returns {@code true} iff ast represents 125 * <br/> 126 * <pre> 127 * return true/false; 128 * </pre> 129 * 130 * @param ast the syntax tree to check 131 * @return if ast is a return statement with a boolean literal. 132 */ 133 private static boolean isBooleanLiteralReturnStatement(AST ast) { 134 boolean booleanReturnStatement = false; 135 136 if (ast != null && ast.getType() == TokenTypes.LITERAL_RETURN) { 137 final AST expr = ast.getFirstChild(); 138 139 if (expr.getType() != TokenTypes.SEMI) { 140 final AST value = expr.getFirstChild(); 141 booleanReturnStatement = isBooleanLiteralType(value.getType()); 142 } 143 } 144 return booleanReturnStatement; 145 } 146 147 /** 148 * Checks if a token type is a literal true or false. 149 * @param tokenType the TokenType 150 * @return true iff tokenType is LITERAL_TRUE or LITERAL_FALSE 151 */ 152 private static boolean isBooleanLiteralType(final int tokenType) { 153 final boolean isTrue = tokenType == TokenTypes.LITERAL_TRUE; 154 final boolean isFalse = tokenType == TokenTypes.LITERAL_FALSE; 155 return isTrue || isFalse; 156 } 157 158}