NoWhitespaceBeforeCheck.java
////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2021 the original author or authors.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
////////////////////////////////////////////////////////////////////////////////
package com.puppycrawl.tools.checkstyle.checks.whitespace;
import com.puppycrawl.tools.checkstyle.StatelessCheck;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
/**
* <p>
* Checks that there is no whitespace before a token.
* More specifically, it checks that it is not preceded with whitespace,
* or (if linebreaks are allowed) all characters on the line before are
* whitespace. To allow linebreaks before a token, set property
* {@code allowLineBreaks} to {@code true}. No check occurs before semi-colons in empty
* for loop initializers or conditions.
* </p>
* <ul>
* <li>
* Property {@code allowLineBreaks} - Control whether whitespace is allowed
* if the token is at a linebreak.
* Type is {@code boolean}.
* Default value is {@code false}.
* </li>
* <li>
* Property {@code tokens} - tokens to check
* Type is {@code java.lang.String[]}.
* Validation type is {@code tokenSet}.
* Default value is:
* <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#COMMA">
* COMMA</a>,
* <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#SEMI">
* SEMI</a>,
* <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#POST_INC">
* POST_INC</a>,
* <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#POST_DEC">
* POST_DEC</a>,
* <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#ELLIPSIS">
* ELLIPSIS</a>,
* <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#LABELED_STAT">
* LABELED_STAT</a>.
* </li>
* </ul>
* <p>
* To configure the check:
* </p>
* <pre>
* <module name="NoWhitespaceBefore"/>
* </pre>
* <p>Example:</p>
* <pre>
* int foo;
* foo ++; // violation, whitespace before '++' is not allowed
* foo++; // OK
* for (int i = 0 ; i < 5; i++) {} // violation
* // ^ whitespace before ';' is not allowed
* for (int i = 0; i < 5; i++) {} // OK
* int[][] array = { { 1, 2 }
* , { 3, 4 } }; // violation, whitespace before ',' is not allowed
* int[][] array2 = { { 1, 2 },
* { 3, 4 } }; // OK
* Lists.charactersOf("foo").listIterator()
* .forEachRemaining(System.out::print)
* ; // violation, whitespace before ';' is not allowed
* {
* label1 : // violation, whitespace before ':' is not allowed
* for (int i = 0; i < 10; i++) {}
* }
*
* {
* label2: // OK
* while (true) {}
* }
* </pre>
* <p>To configure the check to allow linebreaks before default tokens:</p>
* <pre>
* <module name="NoWhitespaceBefore">
* <property name="allowLineBreaks" value="true"/>
* </module>
* </pre>
* <p>Example:</p>
* <pre>
* int[][] array = { { 1, 2 }
* , { 3, 4 } }; // OK, linebreak is allowed before ','
* int[][] array2 = { { 1, 2 },
* { 3, 4 } }; // OK, ideal code
* void ellipsisExample(String ...params) {}; // violation, whitespace before '...' is not allowed
* void ellipsisExample2(String
* ...params) {}; //OK, linebreak is allowed before '...'
* Lists.charactersOf("foo")
* .listIterator()
* .forEachRemaining(System.out::print); // OK
* </pre>
* <p>
* To Configure the check to restrict the use of whitespace before METHOD_REF and DOT tokens:
* </p>
* <pre>
* <module name="NoWhitespaceBefore">
* <property name="tokens" value="METHOD_REF"/>
* <property name="tokens" value="DOT"/>
* </module>
* </pre>
* <p>Example:</p>
* <pre>
* Lists.charactersOf("foo").listIterator()
* .forEachRemaining(System.out::print); // violation, whitespace before '.' is not allowed
* Lists.charactersOf("foo").listIterator().forEachRemaining(System.out ::print); // violation,
* // whitespace before '::' is not allowed ^
* Lists.charactersOf("foo").listIterator().forEachRemaining(System.out::print); // OK
* </pre>
* <p>
* To configure the check to allow linebreak before METHOD_REF and DOT tokens:
* </p>
* <pre>
* <module name="NoWhitespaceBefore">
* <property name="tokens" value="METHOD_REF"/>
* <property name="tokens" value="DOT"/>
* <property name="allowLineBreaks" value="true"/>
* </module>
* </pre>
* <p>Example:</p>
* <pre>
* Lists .charactersOf("foo") //violation, whitespace before '.' is not allowed
* .listIterator()
* .forEachRemaining(System.out ::print); // violation,
* // ^ whitespace before '::' is not allowed
* Lists.charactersOf("foo")
* .listIterator()
* .forEachRemaining(System.out::print); // OK
* </pre>
* <p>
* Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
* </p>
* <p>
* Violation Message Keys:
* </p>
* <ul>
* <li>
* {@code ws.preceded}
* </li>
* </ul>
*
* @since 3.0
*/
@StatelessCheck
public class NoWhitespaceBeforeCheck
extends AbstractCheck {
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_KEY = "ws.preceded";
/** Control whether whitespace is allowed if the token is at a linebreak. */
private boolean allowLineBreaks;
@Override
public int[] getDefaultTokens() {
return new int[] {
TokenTypes.COMMA,
TokenTypes.SEMI,
TokenTypes.POST_INC,
TokenTypes.POST_DEC,
TokenTypes.ELLIPSIS,
TokenTypes.LABELED_STAT,
};
}
@Override
public int[] getAcceptableTokens() {
return new int[] {
TokenTypes.COMMA,
TokenTypes.SEMI,
TokenTypes.POST_INC,
TokenTypes.POST_DEC,
TokenTypes.DOT,
TokenTypes.GENERIC_START,
TokenTypes.GENERIC_END,
TokenTypes.ELLIPSIS,
TokenTypes.LABELED_STAT,
TokenTypes.METHOD_REF,
};
}
@Override
public int[] getRequiredTokens() {
return CommonUtil.EMPTY_INT_ARRAY;
}
@Override
public void visitToken(DetailAST ast) {
final String line = getLine(ast.getLineNo() - 1);
final int before = ast.getColumnNo() - 1;
if ((before == -1 || Character.isWhitespace(line.charAt(before)))
&& !isInEmptyForInitializerOrCondition(ast)) {
boolean flag = !allowLineBreaks;
// verify all characters before '.' are whitespace
for (int i = 0; i <= before - 1; i++) {
if (!Character.isWhitespace(line.charAt(i))) {
flag = true;
break;
}
}
if (flag) {
log(ast, MSG_KEY, ast.getText());
}
}
}
/**
* Checks that semicolon is in empty for initializer or condition.
*
* @param semicolonAst DetailAST of semicolon.
* @return true if semicolon is in empty for initializer or condition.
*/
private static boolean isInEmptyForInitializerOrCondition(DetailAST semicolonAst) {
boolean result = false;
final DetailAST sibling = semicolonAst.getPreviousSibling();
if (sibling != null
&& (sibling.getType() == TokenTypes.FOR_INIT
|| sibling.getType() == TokenTypes.FOR_CONDITION)
&& !sibling.hasChildren()) {
result = true;
}
return result;
}
/**
* Setter to control whether whitespace is allowed if the token is at a linebreak.
*
* @param allowLineBreaks whether whitespace should be
* flagged at line breaks.
*/
public void setAllowLineBreaks(boolean allowLineBreaks) {
this.allowLineBreaks = allowLineBreaks;
}
}