001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2023 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 com.puppycrawl.tools.checkstyle.StatelessCheck;
023import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
024import com.puppycrawl.tools.checkstyle.api.DetailAST;
025import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
026
027/**
028 * <p>
029 * Checks whether file contains code. Files which are considered to have no code:
030 * </p>
031 * <ul>
032 * <li>
033 * File with no text
034 * </li>
035 * <li>
036 * File with single-line comment(s)
037 * </li>
038 * <li>
039 * File with a multi line comment(s).
040 * </li>
041 * </ul>
042 * <p>
043 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
044 * </p>
045 * <p>
046 * Violation Message Keys:
047 * </p>
048 * <ul>
049 * <li>
050 * {@code nocode.in.file}
051 * </li>
052 * </ul>
053 *
054 * @since 8.33
055 */
056@StatelessCheck
057public class NoCodeInFileCheck extends AbstractCheck {
058
059    /**
060     * A key is pointing to the warning message text in "messages.properties"
061     * file.
062     */
063    public static final String MSG_KEY_NO_CODE = "nocode.in.file";
064
065    /** Line number used to log violation when no AST nodes are present in file. */
066    private static final int DEFAULT_LINE_NUMBER = 1;
067
068    @Override
069    public int[] getDefaultTokens() {
070        return getRequiredTokens();
071    }
072
073    @Override
074    public int[] getAcceptableTokens() {
075        return getRequiredTokens();
076    }
077
078    @Override
079    public int[] getRequiredTokens() {
080        return CommonUtil.EMPTY_INT_ARRAY;
081    }
082
083    @Override
084    public void finishTree(DetailAST ast) {
085        if (ast == null) {
086            log(DEFAULT_LINE_NUMBER, MSG_KEY_NO_CODE);
087        }
088    }
089}