001/////////////////////////////////////////////////////////////////////////////////////////////// 002// checkstyle: Checks Java source code and other text files for adherence to a set of rules. 003// Copyright (C) 2001-2025 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; 021 022import java.io.File; 023import java.io.IOException; 024import java.io.RandomAccessFile; 025import java.util.Locale; 026 027import com.puppycrawl.tools.checkstyle.StatelessCheck; 028import com.puppycrawl.tools.checkstyle.api.AbstractFileSetCheck; 029import com.puppycrawl.tools.checkstyle.api.FileText; 030 031/** 032 * <div> 033 * Checks whether files end with a line separator. 034 * </div> 035 * 036 * <p> 037 * Rationale: Any not empty source files and text files in general should end with a line 038 * separator to let other easily add new content at the end of file and "diff" 039 * command does not show previous lines as changed. 040 * </p> 041 * 042 * <p> 043 * Example (the line with 'No newline at end of file' should not be in the diff): 044 * </p> 045 * <div class="wrapper"><pre class="prettyprint"><code class="language-text"> 046 * @@ -32,4 +32,5 @@ ForbidWildcardAsReturnTypeCheck.returnTypeClassNamesIgnoreRegex 047 * PublicReferenceToPrivateTypeCheck.name = Public Reference To Private Type 048 * 049 * StaticMethodCandidateCheck.name = Static Method Candidate 050 * -StaticMethodCandidateCheck.desc = Checks whether private methods should be declared as static. 051 * \ No newline at end of file 052 * +StaticMethodCandidateCheck.desc = Checks whether private methods should be declared as static. 053 * +StaticMethodCandidateCheck.skippedMethods = Method names to skip during the check. 054 * </code></pre></div> 055 * 056 * <p> 057 * It can also trick the VCS to report the wrong owner for such lines. 058 * An engineer who has added nothing but a newline character becomes the last 059 * known author for the entire line. As a result, a mate can ask him a question 060 * to which he will not give the correct answer. 061 * </p> 062 * 063 * <p> 064 * Old Rationale: CVS source control management systems will even print 065 * a warning when it encounters a file that doesn't end with a line separator. 066 * </p> 067 * 068 * <p> 069 * Attention: property fileExtensions works with files that are passed by similar 070 * property for at <a href="https://checkstyle.org/config.html#Checker">Checker</a>. 071 * Please make sure required file extensions are mentioned at Checker's fileExtensions property. 072 * </p> 073 * 074 * <p> 075 * Notes: 076 * This will check against the platform-specific default line separator. 077 * </p> 078 * 079 * <p> 080 * It is also possible to enforce the use of a specific line-separator across 081 * platforms, with the {@code lineSeparator} property. 082 * </p> 083 * <ul> 084 * <li> 085 * Property {@code fileExtensions} - Specify the file extensions of the files to process. 086 * Type is {@code java.lang.String[]}. 087 * Default value is {@code ""}. 088 * </li> 089 * <li> 090 * Property {@code lineSeparator} - Specify the type of line separator. 091 * Type is {@code com.puppycrawl.tools.checkstyle.checks.LineSeparatorOption}. 092 * Default value is {@code lf_cr_crlf}. 093 * </li> 094 * </ul> 095 * 096 * <p> 097 * Parent is {@code com.puppycrawl.tools.checkstyle.Checker} 098 * </p> 099 * 100 * <p> 101 * Violation Message Keys: 102 * </p> 103 * <ul> 104 * <li> 105 * {@code noNewlineAtEOF} 106 * </li> 107 * <li> 108 * {@code unable.open} 109 * </li> 110 * <li> 111 * {@code wrong.line.end} 112 * </li> 113 * </ul> 114 * 115 * @since 3.1 116 */ 117@StatelessCheck 118public class NewlineAtEndOfFileCheck 119 extends AbstractFileSetCheck { 120 121 /** 122 * A key is pointing to the warning message text in "messages.properties" 123 * file. 124 */ 125 public static final String MSG_KEY_UNABLE_OPEN = "unable.open"; 126 127 /** 128 * A key is pointing to the warning message text in "messages.properties" 129 * file. 130 */ 131 public static final String MSG_KEY_NO_NEWLINE_EOF = "noNewlineAtEOF"; 132 133 /** 134 * A key is pointing to the warning message text in "messages.properties" 135 * file. 136 */ 137 public static final String MSG_KEY_WRONG_ENDING = "wrong.line.end"; 138 139 /** Specify the type of line separator. */ 140 private LineSeparatorOption lineSeparator = LineSeparatorOption.LF_CR_CRLF; 141 142 @Override 143 protected void processFiltered(File file, FileText fileText) { 144 try { 145 readAndCheckFile(file); 146 } 147 catch (final IOException ignored) { 148 log(1, MSG_KEY_UNABLE_OPEN, file.getPath()); 149 } 150 } 151 152 /** 153 * Setter to specify the type of line separator. 154 * 155 * @param lineSeparatorParam The line separator to set 156 * @throws IllegalArgumentException If the specified line separator is not 157 * one of 'crlf', 'lf', 'cr', 'lf_cr_crlf' or 'system' 158 * @since 3.1 159 */ 160 public void setLineSeparator(String lineSeparatorParam) { 161 lineSeparator = 162 Enum.valueOf(LineSeparatorOption.class, lineSeparatorParam.trim() 163 .toUpperCase(Locale.ENGLISH)); 164 } 165 166 /** 167 * Reads the file provided and checks line separators. 168 * 169 * @param file the file to be processed 170 * @throws IOException When an IO error occurred while reading from the 171 * file provided 172 */ 173 private void readAndCheckFile(File file) throws IOException { 174 // Cannot use lines as the line separators have been removed! 175 try (RandomAccessFile randomAccessFile = new RandomAccessFile(file, "r")) { 176 if (lineSeparator == LineSeparatorOption.LF 177 && endsWithNewline(randomAccessFile, LineSeparatorOption.CRLF)) { 178 log(1, MSG_KEY_WRONG_ENDING); 179 } 180 else if (!endsWithNewline(randomAccessFile, lineSeparator)) { 181 log(1, MSG_KEY_NO_NEWLINE_EOF); 182 } 183 } 184 } 185 186 /** 187 * Checks whether the content provided by the Reader ends with the platform 188 * specific line separator. 189 * 190 * @param file The reader for the content to check 191 * @param separator The line separator 192 * @return boolean Whether the content ends with a line separator 193 * @throws IOException When an IO error occurred while reading from the 194 * provided reader 195 */ 196 private static boolean endsWithNewline(RandomAccessFile file, LineSeparatorOption separator) 197 throws IOException { 198 final boolean result; 199 final int len = separator.length(); 200 if (file.length() == 0) { 201 result = true; 202 } 203 else if (file.length() < len) { 204 result = false; 205 } 206 else { 207 file.seek(file.length() - len); 208 final byte[] lastBytes = new byte[len]; 209 final int readBytes = file.read(lastBytes); 210 if (readBytes != len) { 211 throw new IOException("Unable to read " + len + " bytes, got " 212 + readBytes); 213 } 214 result = separator.matches(lastBytes); 215 } 216 return result; 217 } 218 219}