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.coding; 021 022import java.util.ArrayDeque; 023import java.util.Collections; 024import java.util.Deque; 025import java.util.HashSet; 026import java.util.Set; 027 028import com.puppycrawl.tools.checkstyle.FileStatefulCheck; 029import com.puppycrawl.tools.checkstyle.api.AbstractCheck; 030import com.puppycrawl.tools.checkstyle.api.DetailAST; 031import com.puppycrawl.tools.checkstyle.api.TokenTypes; 032import com.puppycrawl.tools.checkstyle.utils.CheckUtil; 033 034/** 035 * <p> 036 * Disallows assignment of parameters. 037 * </p> 038 * <p> 039 * Rationale: 040 * Parameter assignment is often considered poor 041 * programming practice. Forcing developers to declare 042 * parameters as final is often onerous. Having a check 043 * ensure that parameters are never assigned would give 044 * the best of both worlds. 045 * </p> 046 * <p> 047 * To configure the check: 048 * </p> 049 * <pre> 050 * <module name="ParameterAssignment"/> 051 * </pre> 052 * <p> 053 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker} 054 * </p> 055 * <p> 056 * Violation Message Keys: 057 * </p> 058 * <ul> 059 * <li> 060 * {@code parameter.assignment} 061 * </li> 062 * </ul> 063 * 064 * @since 3.2 065 */ 066@FileStatefulCheck 067public final class ParameterAssignmentCheck extends AbstractCheck { 068 069 /** 070 * A key is pointing to the warning message text in "messages.properties" 071 * file. 072 */ 073 public static final String MSG_KEY = "parameter.assignment"; 074 075 /** Stack of methods' parameters. */ 076 private final Deque<Set<String>> parameterNamesStack = new ArrayDeque<>(); 077 /** Current set of parameters. */ 078 private Set<String> parameterNames; 079 080 @Override 081 public int[] getDefaultTokens() { 082 return getRequiredTokens(); 083 } 084 085 @Override 086 public int[] getRequiredTokens() { 087 return new int[] { 088 TokenTypes.CTOR_DEF, 089 TokenTypes.METHOD_DEF, 090 TokenTypes.ASSIGN, 091 TokenTypes.PLUS_ASSIGN, 092 TokenTypes.MINUS_ASSIGN, 093 TokenTypes.STAR_ASSIGN, 094 TokenTypes.DIV_ASSIGN, 095 TokenTypes.MOD_ASSIGN, 096 TokenTypes.SR_ASSIGN, 097 TokenTypes.BSR_ASSIGN, 098 TokenTypes.SL_ASSIGN, 099 TokenTypes.BAND_ASSIGN, 100 TokenTypes.BXOR_ASSIGN, 101 TokenTypes.BOR_ASSIGN, 102 TokenTypes.INC, 103 TokenTypes.POST_INC, 104 TokenTypes.DEC, 105 TokenTypes.POST_DEC, 106 }; 107 } 108 109 @Override 110 public int[] getAcceptableTokens() { 111 return getRequiredTokens(); 112 } 113 114 @Override 115 public void beginTree(DetailAST rootAST) { 116 // clear data 117 parameterNamesStack.clear(); 118 parameterNames = Collections.emptySet(); 119 } 120 121 @Override 122 public void visitToken(DetailAST ast) { 123 switch (ast.getType()) { 124 case TokenTypes.CTOR_DEF: 125 case TokenTypes.METHOD_DEF: 126 visitMethodDef(ast); 127 break; 128 case TokenTypes.ASSIGN: 129 case TokenTypes.PLUS_ASSIGN: 130 case TokenTypes.MINUS_ASSIGN: 131 case TokenTypes.STAR_ASSIGN: 132 case TokenTypes.DIV_ASSIGN: 133 case TokenTypes.MOD_ASSIGN: 134 case TokenTypes.SR_ASSIGN: 135 case TokenTypes.BSR_ASSIGN: 136 case TokenTypes.SL_ASSIGN: 137 case TokenTypes.BAND_ASSIGN: 138 case TokenTypes.BXOR_ASSIGN: 139 case TokenTypes.BOR_ASSIGN: 140 visitAssign(ast); 141 break; 142 case TokenTypes.INC: 143 case TokenTypes.POST_INC: 144 case TokenTypes.DEC: 145 case TokenTypes.POST_DEC: 146 visitIncDec(ast); 147 break; 148 default: 149 throw new IllegalStateException(ast.toString()); 150 } 151 } 152 153 @Override 154 public void leaveToken(DetailAST ast) { 155 switch (ast.getType()) { 156 case TokenTypes.CTOR_DEF: 157 case TokenTypes.METHOD_DEF: 158 leaveMethodDef(); 159 break; 160 case TokenTypes.ASSIGN: 161 case TokenTypes.PLUS_ASSIGN: 162 case TokenTypes.MINUS_ASSIGN: 163 case TokenTypes.STAR_ASSIGN: 164 case TokenTypes.DIV_ASSIGN: 165 case TokenTypes.MOD_ASSIGN: 166 case TokenTypes.SR_ASSIGN: 167 case TokenTypes.BSR_ASSIGN: 168 case TokenTypes.SL_ASSIGN: 169 case TokenTypes.BAND_ASSIGN: 170 case TokenTypes.BXOR_ASSIGN: 171 case TokenTypes.BOR_ASSIGN: 172 case TokenTypes.INC: 173 case TokenTypes.POST_INC: 174 case TokenTypes.DEC: 175 case TokenTypes.POST_DEC: 176 // Do nothing 177 break; 178 default: 179 throw new IllegalStateException(ast.toString()); 180 } 181 } 182 183 /** 184 * Checks if this is assignments of parameter. 185 * 186 * @param ast assignment to check. 187 */ 188 private void visitAssign(DetailAST ast) { 189 checkIdent(ast); 190 } 191 192 /** 193 * Checks if this is increment/decrement of parameter. 194 * 195 * @param ast dec/inc to check. 196 */ 197 private void visitIncDec(DetailAST ast) { 198 checkIdent(ast); 199 } 200 201 /** 202 * Check if ident is parameter. 203 * 204 * @param ast ident to check. 205 */ 206 private void checkIdent(DetailAST ast) { 207 final DetailAST identAST = ast.getFirstChild(); 208 209 if (identAST != null 210 && identAST.getType() == TokenTypes.IDENT 211 && parameterNames.contains(identAST.getText())) { 212 log(ast, MSG_KEY, identAST.getText()); 213 } 214 } 215 216 /** 217 * Creates new set of parameters and store old one in stack. 218 * 219 * @param ast a method to process. 220 */ 221 private void visitMethodDef(DetailAST ast) { 222 parameterNamesStack.push(parameterNames); 223 parameterNames = new HashSet<>(); 224 225 visitMethodParameters(ast.findFirstToken(TokenTypes.PARAMETERS)); 226 } 227 228 /** Restores old set of parameters. */ 229 private void leaveMethodDef() { 230 parameterNames = parameterNamesStack.pop(); 231 } 232 233 /** 234 * Creates new parameter set for given method. 235 * 236 * @param ast a method for process. 237 */ 238 private void visitMethodParameters(DetailAST ast) { 239 DetailAST parameterDefAST = 240 ast.findFirstToken(TokenTypes.PARAMETER_DEF); 241 242 while (parameterDefAST != null) { 243 if (parameterDefAST.getType() == TokenTypes.PARAMETER_DEF 244 && !CheckUtil.isReceiverParameter(parameterDefAST)) { 245 final DetailAST param = 246 parameterDefAST.findFirstToken(TokenTypes.IDENT); 247 parameterNames.add(param.getText()); 248 } 249 parameterDefAST = parameterDefAST.getNextSibling(); 250 } 251 } 252 253}