ClassMemberImpliedModifierCheck.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.modifier;
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.ScopeUtil;
/**
* <p>
* Checks for implicit modifiers on nested types in classes and records.
* </p>
* <p>
* This check is effectively the opposite of
* <a href="https://checkstyle.org/config_modifier.html#RedundantModifier">RedundantModifier</a>.
* It checks the modifiers on nested types in classes and records, ensuring that certain modifiers
* are explicitly specified even though they are actually redundant.
* </p>
* <p>
* Nested enums, interfaces, and records within a class are always {@code static} and as such the
* compiler does not require the {@code static} modifier. This check provides the ability to enforce
* that the {@code static} modifier is explicitly coded and not implicitly added by the compiler.
* </p>
* <pre>
* public final class Person {
* enum Age { // violation
* CHILD, ADULT
* }
* }
* </pre>
* <p>
* Rationale for this check: Nested enums, interfaces, and records are treated differently from
* nested classes as they are only allowed to be {@code static}. Developers should not need to
* remember this rule, and this check provides the means to enforce that the modifier is coded
* explicitly.
* </p>
* <ul>
* <li>
* Property {@code violateImpliedStaticOnNestedEnum} - Control whether to enforce that
* {@code static} is explicitly coded on nested enums in classes and records.
* Type is {@code boolean}.
* Default value is {@code true}.
* </li>
* <li>
* Property {@code violateImpliedStaticOnNestedInterface} - Control whether to enforce that
* {@code static} is explicitly coded on nested interfaces in classes and records.
* Type is {@code boolean}.
* Default value is {@code true}.
* </li>
* <li>
* Property {@code violateImpliedStaticOnNestedRecord} - Control whether to enforce that
* {@code static} is explicitly coded on nested records in classes and records.
* Type is {@code boolean}.
* Default value is {@code true}.
* </li>
* </ul>
* <p>
* To configure the check so that it checks that all implicit modifiers on nested interfaces, enums,
* and records are explicitly specified in classes and records.
* </p>
* <p>
* Configuration:
* </p>
* <pre>
* <module name="ClassMemberImpliedModifier" />
* </pre>
* <p>
* Code:
* </p>
* <pre>
* public final class Person {
* static interface Address1 { // valid
* }
*
* interface Address2 { // violation
* }
*
* static enum Age1 { // valid
* CHILD, ADULT
* }
*
* enum Age2 { // violation
* CHILD, ADULT
* }
*
* public static record GoodRecord() {} // valid
* public record BadRecord() {} // violation
*
* public static record OuterRecord() {
* static record InnerRecord1(){} // valid
* record InnerRecord2(){} // violation
* }
* }
* </pre>
* <p>
* Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
* </p>
* <p>
* Violation Message Keys:
* </p>
* <ul>
* <li>
* {@code class.implied.modifier}
* </li>
* </ul>
*
* @since 8.16
*/
@StatelessCheck
public class ClassMemberImpliedModifierCheck
extends AbstractCheck {
/**
* A key is pointing to the warning message text in "messages.properties" file.
*/
public static final String MSG_KEY = "class.implied.modifier";
/** Name for 'static' keyword. */
private static final String STATIC_KEYWORD = "static";
/**
* Control whether to enforce that {@code static} is explicitly coded
* on nested enums in classes and records.
*/
private boolean violateImpliedStaticOnNestedEnum = true;
/**
* Control whether to enforce that {@code static} is explicitly coded
* on nested interfaces in classes and records.
*/
private boolean violateImpliedStaticOnNestedInterface = true;
/**
* Control whether to enforce that {@code static} is explicitly coded
* on nested records in classes and records.
*/
private boolean violateImpliedStaticOnNestedRecord = true;
/**
* Setter to control whether to enforce that {@code static} is explicitly coded
* on nested enums in classes and records.
*
* @param violateImplied
* True to perform the check, false to turn the check off.
*/
public void setViolateImpliedStaticOnNestedEnum(boolean violateImplied) {
violateImpliedStaticOnNestedEnum = violateImplied;
}
/**
* Setter to control whether to enforce that {@code static} is explicitly coded
* on nested interfaces in classes and records.
*
* @param violateImplied
* True to perform the check, false to turn the check off.
*/
public void setViolateImpliedStaticOnNestedInterface(boolean violateImplied) {
violateImpliedStaticOnNestedInterface = violateImplied;
}
/**
* Setter to control whether to enforce that {@code static} is explicitly coded
* on nested records in classes and records.
*
* @param violateImplied
* True to perform the check, false to turn the check off.
*/
public void setViolateImpliedStaticOnNestedRecord(boolean violateImplied) {
violateImpliedStaticOnNestedRecord = violateImplied;
}
@Override
public int[] getDefaultTokens() {
return getAcceptableTokens();
}
@Override
public int[] getRequiredTokens() {
return getAcceptableTokens();
}
@Override
public int[] getAcceptableTokens() {
return new int[] {
TokenTypes.INTERFACE_DEF,
TokenTypes.ENUM_DEF,
TokenTypes.RECORD_DEF,
};
}
@Override
public void visitToken(DetailAST ast) {
if (isInTypeBlock(ast)) {
final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
switch (ast.getType()) {
case TokenTypes.ENUM_DEF:
if (violateImpliedStaticOnNestedEnum
&& modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
log(ast, MSG_KEY, STATIC_KEYWORD);
}
break;
case TokenTypes.INTERFACE_DEF:
if (violateImpliedStaticOnNestedInterface
&& modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
log(ast, MSG_KEY, STATIC_KEYWORD);
}
break;
case TokenTypes.RECORD_DEF:
if (violateImpliedStaticOnNestedRecord
&& modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
log(ast, MSG_KEY, STATIC_KEYWORD);
}
break;
default:
throw new IllegalStateException(ast.toString());
}
}
}
/**
* Checks if ast is in a class, enum, or record block.
*
* @param ast the current ast
* @return true if ast is in a class, enum, or record
*/
private static boolean isInTypeBlock(DetailAST ast) {
return ScopeUtil.isInClassBlock(ast)
|| ScopeUtil.isInEnumBlock(ast)
|| ScopeUtil.isInRecordBlock(ast);
}
}