////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2017 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 java.util.Arrays;
import java.util.Optional;
import java.util.Set;
import java.util.function.Predicate;
import java.util.stream.Collectors;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.Scope;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
import com.puppycrawl.tools.checkstyle.utils.ScopeUtils;
import com.puppycrawl.tools.checkstyle.utils.TokenUtils;
/**
* The check finds classes that are designed for extension (subclass creation).
*
* <p>
* Nothing wrong could be with founded classes.
* This check makes sense only for library projects (not an application projects)
* which care of ideal OOP-design to make sure that class works in all cases even misusage.
* Even in library projects this check most likely will find classes that are designed for extension
* by somebody. User needs to use suppressions extensively to got a benefit from this check,
* and keep in suppressions all confirmed/known classes that are deigned for inheritance
* intentionally to let the check catch only new classes, and bring this to team/user attention.
* </p>
*
* <p>
* ATTENTION: Only user can decide whether a class is designed for extension or not.
* The check just shows all classes which are possibly designed for extension.
* If smth inappropriate is found please use suppression.
* </p>
*
* <p>
* ATTENTION: If the method which can be overridden in a subclass has a javadoc comment
* (a good practise is to explain its self-use of overridable methods) the check will not
* rise a violation. The violation can also be skipped if the method which can be overridden
* in a subclass has one or more annotations that are specified in ignoredAnnotations
* option. Note, that by default @Override annotation is not included in the
* ignoredAnnotations set as in a subclass the method which has the annotation can also be
* overridden in its subclass.
* </p>
*
* <p>
* More specifically, the check enforces a programming style where superclasses provide empty
* "hooks" that can be implemented by subclasses.
* </p>
*
* <p>
* The check finds classes that have overridable methods (public or protected methods
* that are non-static, not-final, non-abstract) and have non-empty implementation.
* </p>
*
* <p>
* This protects superclasses against being broken by subclasses. The downside is that subclasses
* are limited in their flexibility, in particular, they cannot prevent execution of code in the
* superclass, but that also means that subclasses cannot forget to call their super method.
* </p>
*
* <p>
* The check has the following options:
* </p>
* <ul>
* <li>
* ignoredAnnotations - annotations which allow the check to skip the method from validation.
* Default value is <b>Test, Before, After, BeforeClass, AfterClass</b>.
* </li>
* </ul>
*
* @author lkuehne
* @author Andrei Selkin
*/
public class DesignForExtensionCheck extends AbstractCheck {
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_KEY = "design.forExtension";
/**
* A set of annotations which allow the check to skip the method from validation.
*/
private Set<String> ignoredAnnotations = Arrays.stream(new String[] {"Test", "Before", "After",
"BeforeClass", "AfterClass", }).collect(Collectors.toSet());
/**
* Sets annotations which allow the check to skip the method from validation.
* @param ignoredAnnotations method annotations.
*/
public void setIgnoredAnnotations(String... ignoredAnnotations) {
this.ignoredAnnotations = Arrays.stream(ignoredAnnotations).collect(Collectors.toSet());
}
@Override
public int[] getDefaultTokens() {
return getAcceptableTokens();
}
@Override
public int[] getAcceptableTokens() {
// The check does not subscribe to CLASS_DEF token as now it is stateless. If the check
// subscribes to CLASS_DEF token it will become stateful, since we need to have additional
// stack to hold CLASS_DEF tokens.
return new int[] {TokenTypes.METHOD_DEF};
}
@Override
public int[] getRequiredTokens() {
return getAcceptableTokens();
}
@Override
public boolean isCommentNodesRequired() {
return true;
}
@Override
public void visitToken(DetailAST ast) {
if (!hasJavadocComment(ast)
&& canBeOverridden(ast)
&& (isNativeMethod(ast)
|| !hasEmptyImplementation(ast))
&& !hasIgnoredAnnotation(ast, ignoredAnnotations)) {
final DetailAST classDef = getNearestClassOrEnumDefinition(ast);
if (canBeSubclassed(classDef)) {
final String className = classDef.findFirstToken(TokenTypes.IDENT).getText();
final String methodName = ast.findFirstToken(TokenTypes.IDENT).getText();
log(ast.getLineNo(), ast.getColumnNo(), MSG_KEY, className, methodName);
}
}
}
/**
* Checks whether a method has a javadoc comment.
* @param methodDef method definition token.
* @return true if a method has a javadoc comment.
*/
private boolean hasJavadocComment(DetailAST methodDef) {
final DetailAST modifiers = methodDef.findFirstToken(TokenTypes.MODIFIERS);
return modifiers.branchContains(TokenTypes.BLOCK_COMMENT_BEGIN);
}
/**
* Checks whether a methods is native.
* @param ast method definition token.
* @return true if a methods is native.
*/
private boolean isNativeMethod(DetailAST ast) {
final DetailAST mods = ast.findFirstToken(TokenTypes.MODIFIERS);
return mods.branchContains(TokenTypes.LITERAL_NATIVE);
}
/**
* Checks whether a method has only comments in the body (has an empty implementation).
* Method is OK if its implementation is empty.
* @param ast method definition token.
* @return true if a method has only comments in the body.
*/
private static boolean hasEmptyImplementation(DetailAST ast) {
boolean hasEmptyBody = true;
final DetailAST methodImplOpenBrace = ast.findFirstToken(TokenTypes.SLIST);
final DetailAST methodImplCloseBrace = methodImplOpenBrace.getLastChild();
final Predicate<DetailAST> predicate = currentNode -> {
return currentNode != methodImplCloseBrace
&& !TokenUtils.isCommentType(currentNode.getType());
};
final Optional<DetailAST> methodBody =
TokenUtils.findFirstTokenByPredicate(methodImplOpenBrace, predicate);
if (methodBody.isPresent()) {
hasEmptyBody = false;
}
return hasEmptyBody;
}
/**
* Checks whether a method can be overridden.
* Method can be overridden if it is not private, abstract, final or static.
* Note that the check has nothing to do for interfaces.
* @param methodDef method definition token.
* @return true if a method can be overridden in a subclass.
*/
private boolean canBeOverridden(DetailAST methodDef) {
final DetailAST modifiers = methodDef.findFirstToken(TokenTypes.MODIFIERS);
return ScopeUtils.getSurroundingScope(methodDef).isIn(Scope.PROTECTED)
&& !ScopeUtils.isInInterfaceOrAnnotationBlock(methodDef)
&& !modifiers.branchContains(TokenTypes.LITERAL_PRIVATE)
&& !modifiers.branchContains(TokenTypes.ABSTRACT)
&& !modifiers.branchContains(TokenTypes.FINAL)
&& !modifiers.branchContains(TokenTypes.LITERAL_STATIC);
}
/**
* Checks whether a method has any of ignored annotations.
* @param methodDef method definition token.
* @param annotations a set of ignored annotations.
* @return true if a method has any of ignored annotations.
*/
private static boolean hasIgnoredAnnotation(DetailAST methodDef, Set<String> annotations) {
final DetailAST modifiers = methodDef.findFirstToken(TokenTypes.MODIFIERS);
boolean hasIgnoredAnnotation = false;
if (modifiers.branchContains(TokenTypes.ANNOTATION)) {
final Optional<DetailAST> annotation = TokenUtils.findFirstTokenByPredicate(modifiers,
currentToken -> {
return currentToken.getType() == TokenTypes.ANNOTATION
&& annotations.contains(getAnnotationName(currentToken));
});
if (annotation.isPresent()) {
hasIgnoredAnnotation = true;
}
}
return hasIgnoredAnnotation;
}
/**
* Gets the name of the annotation.
* @param annotation to get name of.
* @return the name of the annotation.
*/
private static String getAnnotationName(DetailAST annotation) {
final DetailAST dotAst = annotation.findFirstToken(TokenTypes.DOT);
final String name;
if (dotAst == null) {
name = annotation.findFirstToken(TokenTypes.IDENT).getText();
}
else {
name = dotAst.findFirstToken(TokenTypes.IDENT).getText();
}
return name;
}
/**
* Returns CLASS_DEF or ENUM_DEF token which is the nearest to the given ast node.
* Searches the tree towards the root until it finds a CLASS_DEF or ENUM_DEF node.
* @param ast the start node for searching.
* @return the CLASS_DEF or ENUM_DEF token.
*/
private static DetailAST getNearestClassOrEnumDefinition(DetailAST ast) {
DetailAST searchAST = ast;
while (searchAST.getType() != TokenTypes.CLASS_DEF
&& searchAST.getType() != TokenTypes.ENUM_DEF) {
searchAST = searchAST.getParent();
}
return searchAST;
}
/**
* Checks if the given class (given CLASS_DEF node) can be subclassed.
* @param classDef class definition token.
* @return true if the containing class can be subclassed.
*/
private static boolean canBeSubclassed(DetailAST classDef) {
final DetailAST modifiers = classDef.findFirstToken(TokenTypes.MODIFIERS);
return classDef.getType() != TokenTypes.ENUM_DEF
&& !modifiers.branchContains(TokenTypes.FINAL)
&& hasDefaultOrExplicitNonPrivateCtor(classDef);
}
/**
* Checks whether a class has default or explicit non-private constructor.
* @param classDef class ast token.
* @return true if a class has default or explicit non-private constructor.
*/
private static boolean hasDefaultOrExplicitNonPrivateCtor(DetailAST classDef) {
// check if subclassing is prevented by having only private ctors
final DetailAST objBlock = classDef.findFirstToken(TokenTypes.OBJBLOCK);
boolean hasDefaultConstructor = true;
boolean hasExplicitNonPrivateCtor = false;
DetailAST candidate = objBlock.getFirstChild();
while (candidate != null) {
if (candidate.getType() == TokenTypes.CTOR_DEF) {
hasDefaultConstructor = false;
final DetailAST ctorMods =
candidate.findFirstToken(TokenTypes.MODIFIERS);
if (!ctorMods.branchContains(TokenTypes.LITERAL_PRIVATE)) {
hasExplicitNonPrivateCtor = true;
break;
}
}
candidate = candidate.getNextSibling();
}
return hasDefaultConstructor || hasExplicitNonPrivateCtor;
}
}