001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2022 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.whitespace;
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.CodePointUtil;
027import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
028
029/**
030 * <p>
031 * Checks that there is no whitespace before a token.
032 * More specifically, it checks that it is not preceded with whitespace,
033 * or (if linebreaks are allowed) all characters on the line before are
034 * whitespace. To allow linebreaks before a token, set property
035 * {@code allowLineBreaks} to {@code true}. No check occurs before semi-colons in empty
036 * for loop initializers or conditions.
037 * </p>
038 * <ul>
039 * <li>
040 * Property {@code allowLineBreaks} - Control whether whitespace is allowed
041 * if the token is at a linebreak.
042 * Type is {@code boolean}.
043 * Default value is {@code false}.
044 * </li>
045 * <li>
046 * Property {@code tokens} - tokens to check
047 * Type is {@code java.lang.String[]}.
048 * Validation type is {@code tokenSet}.
049 * Default value is:
050 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#COMMA">
051 * COMMA</a>,
052 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#SEMI">
053 * SEMI</a>,
054 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#POST_INC">
055 * POST_INC</a>,
056 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#POST_DEC">
057 * POST_DEC</a>,
058 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#ELLIPSIS">
059 * ELLIPSIS</a>,
060 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#LABELED_STAT">
061 * LABELED_STAT</a>.
062 * </li>
063 * </ul>
064 * <p>
065 * To configure the check:
066 * </p>
067 * <pre>
068 * &lt;module name=&quot;NoWhitespaceBefore&quot;/&gt;
069 * </pre>
070 * <p>Example:</p>
071 * <pre>
072 * int foo;
073 * foo ++; // violation, whitespace before '++' is not allowed
074 * foo++; // OK
075 * for (int i = 0 ; i &lt; 5; i++) {}  // violation
076 *            // ^ whitespace before ';' is not allowed
077 * for (int i = 0; i &lt; 5; i++) {} // OK
078 * int[][] array = { { 1, 2 }
079 *                 , { 3, 4 } }; // violation, whitespace before ',' is not allowed
080 * int[][] array2 = { { 1, 2 },
081 *                    { 3, 4 } }; // OK
082 * Lists.charactersOf("foo").listIterator()
083 *        .forEachRemaining(System.out::print)
084 *        ; // violation, whitespace before ';' is not allowed
085 *   {
086 *     label1 : // violation, whitespace before ':' is not allowed
087 *     for (int i = 0; i &lt; 10; i++) {}
088 *   }
089 *
090 *   {
091 *     label2: // OK
092 *     while (true) {}
093 *   }
094 * </pre>
095 * <p>To configure the check to allow linebreaks before default tokens:</p>
096 * <pre>
097 * &lt;module name=&quot;NoWhitespaceBefore&quot;&gt;
098 *   &lt;property name=&quot;allowLineBreaks&quot; value=&quot;true&quot;/&gt;
099 * &lt;/module&gt;
100 * </pre>
101 * <p>Example:</p>
102 * <pre>
103 * int[][] array = { { 1, 2 }
104 *                 , { 3, 4 } }; // OK, linebreak is allowed before ','
105 * int[][] array2 = { { 1, 2 },
106 *                    { 3, 4 } }; // OK, ideal code
107 * void ellipsisExample(String ...params) {}; // violation, whitespace before '...' is not allowed
108 * void ellipsisExample2(String
109 *                         ...params) {}; //OK, linebreak is allowed before '...'
110 * Lists.charactersOf("foo")
111 *        .listIterator()
112 *        .forEachRemaining(System.out::print); // OK
113 * </pre>
114 * <p>
115 *     To Configure the check to restrict the use of whitespace before METHOD_REF and DOT tokens:
116 * </p>
117 * <pre>
118 * &lt;module name=&quot;NoWhitespaceBefore&quot;&gt;
119 *   &lt;property name=&quot;tokens&quot; value=&quot;METHOD_REF&quot;/&gt;
120 *   &lt;property name=&quot;tokens&quot; value=&quot;DOT&quot;/&gt;
121 * &lt;/module&gt;
122 * </pre>
123 * <p>Example:</p>
124 * <pre>
125 * Lists.charactersOf("foo").listIterator()
126 *        .forEachRemaining(System.out::print); // violation, whitespace before '.' is not allowed
127 * Lists.charactersOf("foo").listIterator().forEachRemaining(System.out ::print); // violation,
128 *                           // whitespace before '::' is not allowed  ^
129 * Lists.charactersOf("foo").listIterator().forEachRemaining(System.out::print); // OK
130 * </pre>
131 * <p>
132 *     To configure the check to allow linebreak before METHOD_REF and DOT tokens:
133 * </p>
134 * <pre>
135 * &lt;module name=&quot;NoWhitespaceBefore&quot;&gt;
136 *   &lt;property name=&quot;tokens&quot; value=&quot;METHOD_REF&quot;/&gt;
137 *   &lt;property name=&quot;tokens&quot; value=&quot;DOT&quot;/&gt;
138 *   &lt;property name=&quot;allowLineBreaks&quot; value=&quot;true&quot;/&gt;
139 * &lt;/module&gt;
140 * </pre>
141 * <p>Example:</p>
142 * <pre>
143 * Lists .charactersOf("foo") //violation, whitespace before '.' is not allowed
144 *         .listIterator()
145 *         .forEachRemaining(System.out ::print); // violation,
146 *                                  // ^ whitespace before '::' is not allowed
147 * Lists.charactersOf("foo")
148 *        .listIterator()
149 *        .forEachRemaining(System.out::print); // OK
150 * </pre>
151 * <p>
152 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
153 * </p>
154 * <p>
155 * Violation Message Keys:
156 * </p>
157 * <ul>
158 * <li>
159 * {@code ws.preceded}
160 * </li>
161 * </ul>
162 *
163 * @since 3.0
164 */
165@StatelessCheck
166public class NoWhitespaceBeforeCheck
167    extends AbstractCheck {
168
169    /**
170     * A key is pointing to the warning message text in "messages.properties"
171     * file.
172     */
173    public static final String MSG_KEY = "ws.preceded";
174
175    /** Control whether whitespace is allowed if the token is at a linebreak. */
176    private boolean allowLineBreaks;
177
178    @Override
179    public int[] getDefaultTokens() {
180        return new int[] {
181            TokenTypes.COMMA,
182            TokenTypes.SEMI,
183            TokenTypes.POST_INC,
184            TokenTypes.POST_DEC,
185            TokenTypes.ELLIPSIS,
186            TokenTypes.LABELED_STAT,
187        };
188    }
189
190    @Override
191    public int[] getAcceptableTokens() {
192        return new int[] {
193            TokenTypes.COMMA,
194            TokenTypes.SEMI,
195            TokenTypes.POST_INC,
196            TokenTypes.POST_DEC,
197            TokenTypes.DOT,
198            TokenTypes.GENERIC_START,
199            TokenTypes.GENERIC_END,
200            TokenTypes.ELLIPSIS,
201            TokenTypes.LABELED_STAT,
202            TokenTypes.METHOD_REF,
203        };
204    }
205
206    @Override
207    public int[] getRequiredTokens() {
208        return CommonUtil.EMPTY_INT_ARRAY;
209    }
210
211    @Override
212    public void visitToken(DetailAST ast) {
213        final int[] line = getLineCodePoints(ast.getLineNo() - 1);
214        final int columnNoBeforeToken = ast.getColumnNo() - 1;
215        final boolean isFirstToken = columnNoBeforeToken == -1;
216
217        if ((isFirstToken || CommonUtil.isCodePointWhitespace(line, columnNoBeforeToken))
218                && !isInEmptyForInitializerOrCondition(ast)) {
219            final boolean isViolation = !allowLineBreaks
220                    || !isFirstToken
221                    && !CodePointUtil.hasWhitespaceBefore(columnNoBeforeToken, line);
222
223            if (isViolation) {
224                log(ast, MSG_KEY, ast.getText());
225            }
226        }
227    }
228
229    /**
230     * Checks that semicolon is in empty for initializer or condition.
231     *
232     * @param semicolonAst DetailAST of semicolon.
233     * @return true if semicolon is in empty for initializer or condition.
234     */
235    private static boolean isInEmptyForInitializerOrCondition(DetailAST semicolonAst) {
236        boolean result = false;
237        final DetailAST sibling = semicolonAst.getPreviousSibling();
238        if (sibling != null
239                && (sibling.getType() == TokenTypes.FOR_INIT
240                        || sibling.getType() == TokenTypes.FOR_CONDITION)
241                && !sibling.hasChildren()) {
242            result = true;
243        }
244        return result;
245    }
246
247    /**
248     * Setter to control whether whitespace is allowed if the token is at a linebreak.
249     *
250     * @param allowLineBreaks whether whitespace should be
251     *     flagged at line breaks.
252     */
253    public void setAllowLineBreaks(boolean allowLineBreaks) {
254        this.allowLineBreaks = allowLineBreaks;
255    }
256
257}