SealedShouldHavePermitsListCheck.java
///////////////////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
// Copyright (C) 2001-2024 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.design;
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;
/**
* <p>
* Checks that sealed classes and interfaces have a permits list.
* </p>
* <p>
* Rationale: When a permits clause is omitted from a sealed class,
* any class within the same compilation unit can extend it. This differs
* from other sealed classes where permitted subclasses are explicitly
* declared, making them readily visible to the reader. Without a permits
* clause, identifying potential subclasses requires searching the entire
* compilation unit, which can be challenging, especially in large files
* with complex class hierarchies.
* </p>
* <p>
* See the <a href="https://docs.oracle.com/javase/specs/jls/se22/html/jls-13.html#jls-13.4.2">
* Java Language Specification</a> for more information about sealed classes.
* </p>
* <p>
* Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
* </p>
* <p>
* Violation Message Keys:
* </p>
* <ul>
* <li>
* {@code sealed.should.have.permits}
* </li>
* </ul>
*
* @since 10.18.0
*/
@StatelessCheck
public class SealedShouldHavePermitsListCheck extends AbstractCheck {
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_KEY = "sealed.should.have.permits";
@Override
public int[] getDefaultTokens() {
return getRequiredTokens();
}
@Override
public int[] getAcceptableTokens() {
return getRequiredTokens();
}
@Override
public int[] getRequiredTokens() {
return new int[] {
TokenTypes.CLASS_DEF,
TokenTypes.INTERFACE_DEF,
};
}
@Override
public void visitToken(DetailAST ast) {
final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
final boolean isSealed = modifiers.findFirstToken(TokenTypes.LITERAL_SEALED) != null;
final boolean hasPermitsList = ast.findFirstToken(TokenTypes.PERMITS_CLAUSE) != null;
if (isSealed && !hasPermitsList) {
log(ast, MSG_KEY);
}
}
}