Source code

001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2026 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 * &#64;&#64; -32,4 +32,5 &#64;&#64; 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>This check verifies only the presence of a single line separator at the end of the file.
080 * It does not report violations for multiple trailing blank lines
081 * or additional newline characters beyond the final separator.
082 * </p>
083 *
084 * <p>
085 * It is also possible to enforce the use of a specific line-separator across
086 * platforms, with the {@code lineSeparator} property.
087 * </p>
088 *
089 * @since 3.1
090 */
091@StatelessCheck
092public class NewlineAtEndOfFileCheck
093    extends AbstractFileSetCheck {
094
095    /**
096     * A key is pointing to the warning message text in "messages.properties"
097     * file.
098     */
099    public static final String MSG_KEY_UNABLE_OPEN = "unable.open";
100
101    /**
102     * A key is pointing to the warning message text in "messages.properties"
103     * file.
104     */
105    public static final String MSG_KEY_NO_NEWLINE_EOF = "noNewlineAtEOF";
106
107    /**
108     * A key is pointing to the warning message text in "messages.properties"
109     * file.
110     */
111    public static final String MSG_KEY_NO_NEWLINE_EOF_WITH_SEPARATOR =
112            "noNewlineAtEofWithSeparator";
113
114    /**
115     * A key is pointing to the warning message text in "messages.properties"
116     * file.
117     */
118    public static final String MSG_KEY_WRONG_ENDING = "wrong.line.end";
119
120    /** Specify the type of line separator. */
121    private LineSeparatorOption lineSeparator = LineSeparatorOption.LF_CR_CRLF;
122
123    /**
124     * Creates a new {@code NewlineAtEndOfFileCheck} instance.
125     */
126    public NewlineAtEndOfFileCheck() {
127        // no code by default
128    }
129
130    @Override
131    protected void processFiltered(File file, FileText fileText) {
132        try {
133            readAndCheckFile(file);
134        }
135        catch (final IOException ignored) {
136            log(1, MSG_KEY_UNABLE_OPEN, file.getPath());
137        }
138    }
139
140    /**
141     * Setter to specify the type of line separator.
142     *
143     * @param lineSeparatorParam The line separator to set
144     * @throws IllegalArgumentException If the specified line separator is not
145     *         one of 'crlf', 'lf', 'cr', 'lf_cr_crlf' or 'system'
146     * @since 3.1
147     */
148    public void setLineSeparator(String lineSeparatorParam) {
149        lineSeparator =
150            Enum.valueOf(LineSeparatorOption.class, lineSeparatorParam.trim()
151                .toUpperCase(Locale.ENGLISH));
152    }
153
154    /**
155     * Reads the file provided and checks line separators.
156     *
157     * @param file the file to be processed
158     * @throws IOException When an IO error occurred while reading from the
159     *         file provided
160     */
161    private void readAndCheckFile(File file) throws IOException {
162        // Cannot use lines as the line separators have been removed!
163        try (RandomAccessFile randomAccessFile = new RandomAccessFile(file, "r")) {
164            if (lineSeparator == LineSeparatorOption.LF
165                    && endsWithNewline(randomAccessFile, LineSeparatorOption.CRLF)) {
166                log(1, MSG_KEY_WRONG_ENDING);
167            }
168            else if (!endsWithNewline(randomAccessFile, lineSeparator)) {
169                if (lineSeparator == LineSeparatorOption.LF
170                        || lineSeparator == LineSeparatorOption.CR
171                        || lineSeparator == LineSeparatorOption.CRLF) {
172                    log(1, MSG_KEY_NO_NEWLINE_EOF_WITH_SEPARATOR,
173                            lineSeparator.toString().toLowerCase(Locale.ENGLISH));
174                }
175                else {
176                    log(1, MSG_KEY_NO_NEWLINE_EOF);
177                }
178            }
179        }
180    }
181
182    /**
183     * Checks whether the content provided by the Reader ends with the platform
184     * specific line separator.
185     *
186     * @param file The reader for the content to check
187     * @param separator The line separator
188     * @return boolean Whether the content ends with a line separator
189     * @throws IOException When an IO error occurred while reading from the
190     *         provided reader
191     */
192    private static boolean endsWithNewline(RandomAccessFile file, LineSeparatorOption separator)
193            throws IOException {
194        final boolean result;
195        final int len = separator.length();
196        if (file.length() == 0) {
197            result = true;
198        }
199        else if (file.length() < len) {
200            result = false;
201        }
202        else {
203            file.seek(file.length() - len);
204            final byte[] lastBytes = new byte[len];
205            final int readBytes = file.read(lastBytes);
206            if (readBytes != len) {
207                throw new IOException("Unable to read " + len + " bytes, got "
208                        + readBytes);
209            }
210            result = separator.matches(lastBytes);
211        }
212        return result;
213    }
214
215}