InterfaceMemberImpliedModifierCheck.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 interface members and nested types.
* </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 interface members, ensuring that certain modifiers are explicitly
* specified even though they are actually redundant.
* </p>
* <p>
* Methods in interfaces are {@code public} by default, however from Java 9 they can also be
* {@code private}. This check provides the ability to enforce that {@code public} is explicitly
* coded and not implicitly added by the compiler.
* </p>
* <p>
* From Java 8, there are three types of methods in interfaces - static methods marked with
* {@code static}, default methods marked with {@code default} and abstract methods which do not
* have to be marked with anything. From Java 9, there are also private methods marked with
* {@code private}. This check provides the ability to enforce that {@code abstract} is
* explicitly coded and not implicitly added by the compiler.
* </p>
* <p>
* Fields in interfaces are always {@code public static final} and as such the compiler does not
* require these modifiers. This check provides the ability to enforce that these modifiers are
* explicitly coded and not implicitly added by the compiler.
* </p>
* <p>
* Nested types within an interface are always {@code public static} and as such the compiler
* does not require the {@code public static} modifiers. This check provides the ability to
* enforce that the {@code public} and {@code static} modifiers are explicitly coded and not
* implicitly added by the compiler.
* </p>
* <pre>
* public interface AddressFactory {
* // check enforces code contains "public static final"
* public static final String UNKNOWN = "Unknown";
*
* String OTHER = "Other"; // violation
*
* // check enforces code contains "public" or "private"
* public static AddressFactory instance();
*
* // check enforces code contains "public abstract"
* public abstract Address createAddress(String addressLine, String city);
*
* List<Address> findAddresses(String city); // violation
*
* // check enforces default methods are explicitly declared "public"
* public default Address createAddress(String city) {
* return createAddress(UNKNOWN, city);
* }
*
* default Address createOtherAddress() { // violation
* return createAddress(OTHER, OTHER);
* }
* }
* </pre>
* <p>
* Rationale for this check: Methods, fields and nested types are treated differently
* depending on whether they are part of an interface or part of a class. For example, by
* default methods are package-scoped on classes, but public in interfaces. However, from
* Java 8 onwards, interfaces have changed to be much more like abstract classes.
* Interfaces now have static and instance methods with code. Developers should not have to
* remember which modifiers are required and which are implied. This check allows the simpler
* alternative approach to be adopted where the implied modifiers must always be coded explicitly.
* </p>
* <ul>
* <li>
* Property {@code violateImpliedPublicField} - Control whether to enforce that {@code public}
* is explicitly coded on interface fields.
* Type is {@code boolean}.
* Default value is {@code true}.
* </li>
* <li>
* Property {@code violateImpliedStaticField} - Control whether to enforce that {@code static}
* is explicitly coded on interface fields.
* Type is {@code boolean}.
* Default value is {@code true}.
* </li>
* <li>
* Property {@code violateImpliedFinalField} - Control whether to enforce that {@code final}
* is explicitly coded on interface fields.
* Type is {@code boolean}.
* Default value is {@code true}.
* </li>
* <li>
* Property {@code violateImpliedPublicMethod} - Control whether to enforce that {@code public}
* is explicitly coded on interface methods.
* Type is {@code boolean}.
* Default value is {@code true}.
* </li>
* <li>
* Property {@code violateImpliedAbstractMethod} - Control whether to enforce that {@code abstract}
* is explicitly coded on interface methods.
* Type is {@code boolean}.
* Default value is {@code true}.
* </li>
* <li>
* Property {@code violateImpliedPublicNested} - Control whether to enforce that {@code public}
* is explicitly coded on interface nested types.
* Type is {@code boolean}.
* Default value is {@code true}.
* </li>
* <li>
* Property {@code violateImpliedStaticNested} - Control whether to enforce that {@code static}
* is explicitly coded on interface nested types.
* 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 methods, fields
* and nested types are explicitly specified in interfaces.
* </p>
* <p>
* Configuration:
* </p>
* <pre>
* <module name="InterfaceMemberImpliedModifier"/>
* </pre>
* <p>
* Code:
* </p>
* <pre>
* public interface AddressFactory {
*
* public static final String UNKNOWN = "Unknown"; // valid
*
* String OTHER = "Other"; // violation
*
* public static AddressFactory instance(); // valid
*
* public abstract Address createAddress(String addressLine, String city); // valid
*
* List<Address> findAddresses(String city); // violation
*
* interface Address { // violation
*
* String getCity(); // violation
* }
* }
* </pre>
* <p>
* This example checks that all implicit modifiers on methods and fields are
* explicitly specified, but nested types do not need to be.
* </p>
* <p>
* Configuration:
* </p>
* <pre>
* <module name="InterfaceMemberImpliedModifier">
* <property name="violateImpliedPublicNested" value="false"/>
* <property name="violateImpliedStaticNested" value="false"/>
* </module>
* </pre>
* <p>
* Code:
* </p>
* <pre>
* public interface RoadFeature {
*
* String STOP = "Stop"; // violation
*
* enum Lights { // valid because of configured properties
*
* RED, YELLOW, GREEN;
* }
* }
* </pre>
* <p>
* Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
* </p>
* <p>
* Violation Message Keys:
* </p>
* <ul>
* <li>
* {@code interface.implied.modifier}
* </li>
* </ul>
*
* @since 8.12
*/
@StatelessCheck
public class InterfaceMemberImpliedModifierCheck
extends AbstractCheck {
/**
* A key is pointing to the warning message text in "messages.properties" file.
*/
public static final String MSG_KEY = "interface.implied.modifier";
/** Name for 'public' access modifier. */
private static final String PUBLIC_ACCESS_MODIFIER = "public";
/** Name for 'abstract' keyword. */
private static final String ABSTRACT_KEYWORD = "abstract";
/** Name for 'static' keyword. */
private static final String STATIC_KEYWORD = "static";
/** Name for 'final' keyword. */
private static final String FINAL_KEYWORD = "final";
/**
* Control whether to enforce that {@code public} is explicitly coded
* on interface fields.
*/
private boolean violateImpliedPublicField = true;
/**
* Control whether to enforce that {@code static} is explicitly coded
* on interface fields.
*/
private boolean violateImpliedStaticField = true;
/**
* Control whether to enforce that {@code final} is explicitly coded
* on interface fields.
*/
private boolean violateImpliedFinalField = true;
/**
* Control whether to enforce that {@code public} is explicitly coded
* on interface methods.
*/
private boolean violateImpliedPublicMethod = true;
/**
* Control whether to enforce that {@code abstract} is explicitly coded
* on interface methods.
*/
private boolean violateImpliedAbstractMethod = true;
/**
* Control whether to enforce that {@code public} is explicitly coded
* on interface nested types.
*/
private boolean violateImpliedPublicNested = true;
/**
* Control whether to enforce that {@code static} is explicitly coded
* on interface nested types.
*/
private boolean violateImpliedStaticNested = true;
/**
* Setter to control whether to enforce that {@code public} is explicitly coded
* on interface fields.
*
* @param violateImpliedPublicField
* True to perform the check, false to turn the check off.
*/
public void setViolateImpliedPublicField(boolean violateImpliedPublicField) {
this.violateImpliedPublicField = violateImpliedPublicField;
}
/**
* Setter to control whether to enforce that {@code static} is explicitly coded
* on interface fields.
*
* @param violateImpliedStaticField
* True to perform the check, false to turn the check off.
*/
public void setViolateImpliedStaticField(boolean violateImpliedStaticField) {
this.violateImpliedStaticField = violateImpliedStaticField;
}
/**
* Setter to control whether to enforce that {@code final} is explicitly coded
* on interface fields.
*
* @param violateImpliedFinalField
* True to perform the check, false to turn the check off.
*/
public void setViolateImpliedFinalField(boolean violateImpliedFinalField) {
this.violateImpliedFinalField = violateImpliedFinalField;
}
/**
* Setter to control whether to enforce that {@code public} is explicitly coded
* on interface methods.
*
* @param violateImpliedPublicMethod
* True to perform the check, false to turn the check off.
*/
public void setViolateImpliedPublicMethod(boolean violateImpliedPublicMethod) {
this.violateImpliedPublicMethod = violateImpliedPublicMethod;
}
/**
* Setter to control whether to enforce that {@code abstract} is explicitly coded
* on interface methods.
*
* @param violateImpliedAbstractMethod
* True to perform the check, false to turn the check off.
*/
public void setViolateImpliedAbstractMethod(boolean violateImpliedAbstractMethod) {
this.violateImpliedAbstractMethod = violateImpliedAbstractMethod;
}
/**
* Setter to control whether to enforce that {@code public} is explicitly coded
* on interface nested types.
*
* @param violateImpliedPublicNested
* True to perform the check, false to turn the check off.
*/
public void setViolateImpliedPublicNested(boolean violateImpliedPublicNested) {
this.violateImpliedPublicNested = violateImpliedPublicNested;
}
/**
* Setter to control whether to enforce that {@code static} is explicitly coded
* on interface nested types.
*
* @param violateImpliedStaticNested
* True to perform the check, false to turn the check off.
*/
public void setViolateImpliedStaticNested(boolean violateImpliedStaticNested) {
this.violateImpliedStaticNested = violateImpliedStaticNested;
}
@Override
public int[] getDefaultTokens() {
return getAcceptableTokens();
}
@Override
public int[] getRequiredTokens() {
return getAcceptableTokens();
}
@Override
public int[] getAcceptableTokens() {
return new int[] {
TokenTypes.METHOD_DEF,
TokenTypes.VARIABLE_DEF,
TokenTypes.INTERFACE_DEF,
TokenTypes.CLASS_DEF,
TokenTypes.ENUM_DEF,
};
}
@Override
public void visitToken(DetailAST ast) {
if (ScopeUtil.isInInterfaceBlock(ast) && !ScopeUtil.isInCodeBlock(ast)) {
switch (ast.getType()) {
case TokenTypes.METHOD_DEF:
processMethod(ast);
break;
case TokenTypes.VARIABLE_DEF:
processField(ast);
break;
case TokenTypes.CLASS_DEF:
case TokenTypes.INTERFACE_DEF:
case TokenTypes.ENUM_DEF:
processNestedType(ast);
break;
default:
throw new IllegalStateException(ast.toString());
}
}
}
/**
* Check method in interface.
*
* @param ast the method AST
*/
private void processMethod(DetailAST ast) {
final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
if (violateImpliedPublicMethod
&& modifiers.findFirstToken(TokenTypes.LITERAL_PRIVATE) == null
&& modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) == null) {
log(ast, MSG_KEY, PUBLIC_ACCESS_MODIFIER);
}
if (violateImpliedAbstractMethod
&& modifiers.findFirstToken(TokenTypes.LITERAL_PRIVATE) == null
&& modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null
&& modifiers.findFirstToken(TokenTypes.LITERAL_DEFAULT) == null
&& modifiers.findFirstToken(TokenTypes.ABSTRACT) == null) {
log(ast, MSG_KEY, ABSTRACT_KEYWORD);
}
}
/**
* Check field in interface.
*
* @param ast the field AST
*/
private void processField(DetailAST ast) {
final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
if (violateImpliedPublicField
&& modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) == null) {
log(ast, MSG_KEY, PUBLIC_ACCESS_MODIFIER);
}
if (violateImpliedStaticField
&& modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
log(ast, MSG_KEY, STATIC_KEYWORD);
}
if (violateImpliedFinalField
&& modifiers.findFirstToken(TokenTypes.FINAL) == null) {
log(ast, MSG_KEY, FINAL_KEYWORD);
}
}
/**
* Check nested types in interface.
*
* @param ast the nested type AST
*/
private void processNestedType(DetailAST ast) {
final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
if (violateImpliedPublicNested
&& modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) == null) {
log(ast, MSG_KEY, PUBLIC_ACCESS_MODIFIER);
}
if (violateImpliedStaticNested
&& modifiers.findFirstToken(TokenTypes.LITERAL_STATIC) == null) {
log(ast, MSG_KEY, STATIC_KEYWORD);
}
}
}