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.coding;
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.api.TokenTypes;
026import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
027
028/**
029 * <div>
030 * Checks that array initialization contains a trailing comma.
031 * </div>
032 *
033 * <pre>
034 * int[] a = new int[]
035 * {
036 *   1,
037 *   2,
038 *   3,
039 * };
040 * </pre>
041 *
042 * <p>
043 * By default, the check demands a comma at the end if neither left nor right curly braces
044 * are on the same line as the last element of the array.
045 * </p>
046 * <pre>
047 * return new int[] { 0 };
048 * return new int[] { 0
049 *   };
050 * return new int[] {
051 *   0 };
052 * </pre>
053 *
054 * <p>
055 * Rationale: Putting this comma in makes it easier to change the
056 * order of the elements or add new elements on the end. Main benefit of a trailing
057 * comma is that when you add new entry to an array, no surrounding lines are changed.
058 * </p>
059 * <pre>
060 * {
061 *   100000000000000000000,
062 *   200000000000000000000, // OK
063 * }
064 *
065 * {
066 *   100000000000000000000,
067 *   200000000000000000000,
068 *   300000000000000000000,  // Just this line added, no other changes
069 * }
070 * </pre>
071 *
072 * <p>
073 * If closing brace is on the same line as trailing comma, this benefit is gone
074 * (as the check does not demand a certain location of curly braces the following
075 * two cases will not produce a violation):
076 * </p>
077 * <pre>
078 * {100000000000000000000,
079 *  200000000000000000000,} // Trailing comma not needed, line needs to be modified anyway
080 *
081 * {100000000000000000000,
082 *  200000000000000000000, // Modified line
083 *  300000000000000000000,} // Added line
084 * </pre>
085 *
086 * <p>
087 * If opening brace is on the same line as trailing comma there's also (more arguable) problem:
088 * </p>
089 * <pre>
090 * {100000000000000000000, // Line cannot be just duplicated to slightly modify entry
091 * }
092 *
093 * {100000000000000000000,
094 *  100000000000000000001, // More work needed to duplicate
095 * }
096 * </pre>
097 * <ul>
098 * <li>
099 * Property {@code alwaysDemandTrailingComma} - Control whether to always check for a trailing
100 * comma, even when an array is inline.
101 * Type is {@code boolean}.
102 * Default value is {@code false}.
103 * </li>
104 * </ul>
105 *
106 * <p>
107 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
108 * </p>
109 *
110 * <p>
111 * Violation Message Keys:
112 * </p>
113 * <ul>
114 * <li>
115 * {@code array.trailing.comma}
116 * </li>
117 * </ul>
118 *
119 * @since 3.2
120 */
121@StatelessCheck
122public class ArrayTrailingCommaCheck extends AbstractCheck {
123
124    /**
125     * A key is pointing to the warning message text in "messages.properties"
126     * file.
127     */
128    public static final String MSG_KEY = "array.trailing.comma";
129
130    /**
131     * Control whether to always check for a trailing comma, even when an array is inline.
132     */
133    private boolean alwaysDemandTrailingComma;
134
135    /**
136     * Setter to control whether to always check for a trailing comma, even when an array is inline.
137     *
138     * @param alwaysDemandTrailingComma whether to always check for a trailing comma.
139     * @since 8.33
140     */
141    public void setAlwaysDemandTrailingComma(boolean alwaysDemandTrailingComma) {
142        this.alwaysDemandTrailingComma = alwaysDemandTrailingComma;
143    }
144
145    @Override
146    public int[] getDefaultTokens() {
147        return getRequiredTokens();
148    }
149
150    @Override
151    public int[] getAcceptableTokens() {
152        return getRequiredTokens();
153    }
154
155    @Override
156    public int[] getRequiredTokens() {
157        return new int[] {TokenTypes.ARRAY_INIT};
158    }
159
160    @Override
161    public void visitToken(DetailAST arrayInit) {
162        final DetailAST rcurly = arrayInit.findFirstToken(TokenTypes.RCURLY);
163        final DetailAST previousSibling = rcurly.getPreviousSibling();
164
165        if (arrayInit.getChildCount() != 1
166                && (alwaysDemandTrailingComma
167                    || !TokenUtil.areOnSameLine(rcurly, previousSibling)
168                        && !TokenUtil.areOnSameLine(arrayInit, previousSibling))
169                && previousSibling.getType() != TokenTypes.COMMA) {
170            log(previousSibling, MSG_KEY);
171        }
172    }
173
174}