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