001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2024 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 * <p>
033 * Checks whether files end with a line separator.
034 * </p>
035 * <p>
036 * Rationale: Any source files and text files in general should end with a line
037 * separator to let other easily add new content at the end of file and "diff"
038 * command does not show previous lines as changed.
039 * </p>
040 * <p>
041 * Example (the line with 'No newline at end of file' should not be in the diff):
042 * </p>
043 * <pre>
044 * &#64;&#64; -32,4 +32,5 &#64;&#64; ForbidWildcardAsReturnTypeCheck.returnTypeClassNamesIgnoreRegex
045 * PublicReferenceToPrivateTypeCheck.name = Public Reference To Private Type
046 *
047 * StaticMethodCandidateCheck.name = Static Method Candidate
048 * -StaticMethodCandidateCheck.desc = Checks whether private methods should be declared as static.
049 * \ No newline at end of file
050 * +StaticMethodCandidateCheck.desc = Checks whether private methods should be declared as static.
051 * +StaticMethodCandidateCheck.skippedMethods = Method names to skip during the check.
052 * </pre>
053 * <p>
054 * It can also trick the VCS to report the wrong owner for such lines.
055 * An engineer who has added nothing but a newline character becomes the last
056 * known author for the entire line. As a result, a mate can ask him a question
057 * to which he will not give the correct answer.
058 * </p>
059 * <p>
060 * Old Rationale: CVS source control management systems will even print
061 * a warning when it encounters a file that doesn't end with a line separator.
062 * </p>
063 * <p>
064 * Attention: property fileExtensions works with files that are passed by similar
065 * property for at <a href="https://checkstyle.org/config.html#Checker">Checker</a>.
066 * Please make sure required file extensions are mentioned at Checker's fileExtensions property.
067 * </p>
068 * <p>
069 * This will check against the platform-specific default line separator.
070 * </p>
071 * <p>
072 * It is also possible to enforce the use of a specific line-separator across
073 * platforms, with the {@code lineSeparator} property.
074 * </p>
075 * <ul>
076 * <li>
077 * Property {@code fileExtensions} - Specify the file extensions of the files to process.
078 * Type is {@code java.lang.String[]}.
079 * Default value is {@code ""}.
080 * </li>
081 * <li>
082 * Property {@code lineSeparator} - Specify the type of line separator.
083 * Type is {@code com.puppycrawl.tools.checkstyle.checks.LineSeparatorOption}.
084 * Default value is {@code lf_cr_crlf}.
085 * </li>
086 * </ul>
087 * <p>
088 * Parent is {@code com.puppycrawl.tools.checkstyle.Checker}
089 * </p>
090 * <p>
091 * Violation Message Keys:
092 * </p>
093 * <ul>
094 * <li>
095 * {@code noNewlineAtEOF}
096 * </li>
097 * <li>
098 * {@code unable.open}
099 * </li>
100 * <li>
101 * {@code wrong.line.end}
102 * </li>
103 * </ul>
104 *
105 * @since 3.1
106 */
107@StatelessCheck
108public class NewlineAtEndOfFileCheck
109    extends AbstractFileSetCheck {
110
111    /**
112     * A key is pointing to the warning message text in "messages.properties"
113     * file.
114     */
115    public static final String MSG_KEY_UNABLE_OPEN = "unable.open";
116
117    /**
118     * A key is pointing to the warning message text in "messages.properties"
119     * file.
120     */
121    public static final String MSG_KEY_NO_NEWLINE_EOF = "noNewlineAtEOF";
122
123    /**
124     * A key is pointing to the warning message text in "messages.properties"
125     * file.
126     */
127    public static final String MSG_KEY_WRONG_ENDING = "wrong.line.end";
128
129    /** Specify the type of line separator. */
130    private LineSeparatorOption lineSeparator = LineSeparatorOption.LF_CR_CRLF;
131
132    @Override
133    protected void processFiltered(File file, FileText fileText) {
134        try {
135            readAndCheckFile(file);
136        }
137        catch (final IOException ignored) {
138            log(1, MSG_KEY_UNABLE_OPEN, file.getPath());
139        }
140    }
141
142    /**
143     * Setter to specify the type of line separator.
144     *
145     * @param lineSeparatorParam The line separator to set
146     * @throws IllegalArgumentException If the specified line separator is not
147     *         one of 'crlf', 'lf', 'cr', 'lf_cr_crlf' or 'system'
148     * @since 3.1
149     */
150    public void setLineSeparator(String lineSeparatorParam) {
151        lineSeparator =
152            Enum.valueOf(LineSeparatorOption.class, lineSeparatorParam.trim()
153                .toUpperCase(Locale.ENGLISH));
154    }
155
156    /**
157     * Reads the file provided and checks line separators.
158     *
159     * @param file the file to be processed
160     * @throws IOException When an IO error occurred while reading from the
161     *         file provided
162     */
163    private void readAndCheckFile(File file) throws IOException {
164        // Cannot use lines as the line separators have been removed!
165        try (RandomAccessFile randomAccessFile = new RandomAccessFile(file, "r")) {
166            if (lineSeparator == LineSeparatorOption.LF
167                    && endsWithNewline(randomAccessFile, LineSeparatorOption.CRLF)) {
168                log(1, MSG_KEY_WRONG_ENDING);
169            }
170            else if (!endsWithNewline(randomAccessFile, lineSeparator)) {
171                log(1, MSG_KEY_NO_NEWLINE_EOF);
172            }
173        }
174    }
175
176    /**
177     * Checks whether the content provided by the Reader ends with the platform
178     * specific line separator.
179     *
180     * @param file The reader for the content to check
181     * @param separator The line separator
182     * @return boolean Whether the content ends with a line separator
183     * @throws IOException When an IO error occurred while reading from the
184     *         provided reader
185     */
186    private static boolean endsWithNewline(RandomAccessFile file, LineSeparatorOption separator)
187            throws IOException {
188        final boolean result;
189        final int len = separator.length();
190        if (file.length() < len) {
191            result = false;
192        }
193        else {
194            file.seek(file.length() - len);
195            final byte[] lastBytes = new byte[len];
196            final int readBytes = file.read(lastBytes);
197            if (readBytes != len) {
198                throw new IOException("Unable to read " + len + " bytes, got "
199                        + readBytes);
200            }
201            result = separator.matches(lastBytes);
202        }
203        return result;
204    }
205
206}