Coverage Report - com.puppycrawl.tools.checkstyle.checks.design.DesignForExtensionCheck
 
Classes in this File Line Coverage Branch Coverage Complexity
DesignForExtensionCheck
83%
30/36
67%
23/34
8.333
 
 1  
 ////////////////////////////////////////////////////////////////////////////////
 2  
 // checkstyle: Checks Java source code for adherence to a set of rules.
 3  
 // Copyright (C) 2001-2014  Oliver Burn
 4  
 //
 5  
 // This library is free software; you can redistribute it and/or
 6  
 // modify it under the terms of the GNU Lesser General Public
 7  
 // License as published by the Free Software Foundation; either
 8  
 // version 2.1 of the License, or (at your option) any later version.
 9  
 //
 10  
 // This library is distributed in the hope that it will be useful,
 11  
 // but WITHOUT ANY WARRANTY; without even the implied warranty of
 12  
 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 13  
 // Lesser General Public License for more details.
 14  
 //
 15  
 // You should have received a copy of the GNU Lesser General Public
 16  
 // License along with this library; if not, write to the Free Software
 17  
 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 18  
 ////////////////////////////////////////////////////////////////////////////////
 19  
 package com.puppycrawl.tools.checkstyle.checks.design;
 20  
 
 21  
 import com.puppycrawl.tools.checkstyle.api.Check;
 22  
 import com.puppycrawl.tools.checkstyle.api.DetailAST;
 23  
 import com.puppycrawl.tools.checkstyle.api.Scope;
 24  
 import com.puppycrawl.tools.checkstyle.api.ScopeUtils;
 25  
 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
 26  
 
 27  
 /**
 28  
  * Checks that classes are designed for inheritance.
 29  
  *
 30  
  * <p>
 31  
  * More specifically, it enforces a programming style
 32  
  * where superclasses provide empty "hooks" that can be
 33  
  * implemented by subclasses.
 34  
  * </p>
 35  
  *
 36  
  * <p>
 37  
  * The exact rule is that nonprivate, nonstatic methods in
 38  
  * nonfinal classes (or classes that do not
 39  
  * only have private constructors) must either be
 40  
  * <ul>
 41  
  * <li>abstract or</li>
 42  
  * <li>final or</li>
 43  
  * <li>have an empty implementation</li>
 44  
  * </ul>
 45  
  * </p>
 46  
  *
 47  
  * <p>
 48  
  * This protects superclasses against being broken by
 49  
  * subclasses. The downside is that subclasses are limited
 50  
  * in their flexibility, in particular they cannot prevent
 51  
  * execution of code in the superclass, but that also
 52  
  * means that subclasses can't forget to call their super
 53  
  * method.
 54  
  * </p>
 55  
  *
 56  
  * @author lkuehne
 57  
  */
 58  1
 public class DesignForExtensionCheck extends Check
 59  
 {
 60  
     @Override
 61  
     public int[] getDefaultTokens()
 62  
     {
 63  1
         return new int[] {TokenTypes.METHOD_DEF};
 64  
     }
 65  
 
 66  
     @Override
 67  
     public void visitToken(DetailAST aAST)
 68  
     {
 69  
         // nothing to do for Interfaces
 70  10
         if (ScopeUtils.inInterfaceOrAnnotationBlock(aAST)) {
 71  1
             return;
 72  
         }
 73  
 
 74  
         // method is ok if it is private or abstract or final
 75  9
         final DetailAST modifiers = aAST.findFirstToken(TokenTypes.MODIFIERS);
 76  9
         if (modifiers.branchContains(TokenTypes.LITERAL_PRIVATE)
 77  
             || modifiers.branchContains(TokenTypes.ABSTRACT)
 78  
             || modifiers.branchContains(TokenTypes.FINAL)
 79  
             || modifiers.branchContains(TokenTypes.LITERAL_STATIC))
 80  
         {
 81  2
             return;
 82  
         }
 83  
 
 84  
         // method is ok if containing class is not visible in API and
 85  
         // cannot be extended by 3rd parties (bug #884035)
 86  7
         if (!ScopeUtils.getSurroundingScope(aAST).isIn(Scope.PROTECTED)) {
 87  3
             return;
 88  
         }
 89  
 
 90  
         // method is ok if it is implementation can verified to be empty
 91  
         // Note: native methods don't have impl in java code, so
 92  
         // implementation can be null even if method not abstract
 93  4
         final DetailAST implementation = aAST.findFirstToken(TokenTypes.SLIST);
 94  4
         if ((implementation != null)
 95  
             && (implementation.getFirstChild().getType() == TokenTypes.RCURLY))
 96  
         {
 97  2
             return;
 98  
         }
 99  
 
 100  
         // check if the containing class can be subclassed
 101  2
         final DetailAST classDef = findContainingClass(aAST);
 102  2
         final DetailAST classMods =
 103  
             classDef.findFirstToken(TokenTypes.MODIFIERS);
 104  2
         if ((classDef.getType() == TokenTypes.ENUM_DEF)
 105  
             || classMods.branchContains(TokenTypes.FINAL))
 106  
         {
 107  0
             return;
 108  
         }
 109  
 
 110  
         // check if subclassing is prevented by having only private ctors
 111  2
         final DetailAST objBlock = classDef.findFirstToken(TokenTypes.OBJBLOCK);
 112  
 
 113  2
         boolean hasDefaultConstructor = true;
 114  2
         boolean hasExplNonPrivateCtor = false;
 115  
 
 116  2
         DetailAST candidate = objBlock.getFirstChild();
 117  
 
 118  24
         while (candidate != null) {
 119  22
             if (candidate.getType() == TokenTypes.CTOR_DEF) {
 120  0
                 hasDefaultConstructor = false;
 121  
 
 122  0
                 final DetailAST ctorMods =
 123  
                     candidate.findFirstToken(TokenTypes.MODIFIERS);
 124  0
                 if (!ctorMods.branchContains(TokenTypes.LITERAL_PRIVATE)) {
 125  0
                     hasExplNonPrivateCtor = true;
 126  0
                     break;
 127  
                 }
 128  
             }
 129  22
             candidate = candidate.getNextSibling();
 130  
         }
 131  
 
 132  2
         if (hasDefaultConstructor || hasExplNonPrivateCtor) {
 133  2
             final String name = aAST.findFirstToken(TokenTypes.IDENT).getText();
 134  2
             log(aAST.getLineNo(), aAST.getColumnNo(),
 135  
                 "design.forExtension", name);
 136  
         }
 137  
 
 138  
 
 139  
 
 140  2
     }
 141  
 
 142  
     /**
 143  
      * Searches the tree towards the root until it finds a CLASS_DEF node.
 144  
      * @param aAST the start node for searching
 145  
      * @return the CLASS_DEF node.
 146  
      */
 147  
     private DetailAST findContainingClass(DetailAST aAST)
 148  
     {
 149  2
         DetailAST searchAST = aAST;
 150  
         while ((searchAST.getType() != TokenTypes.CLASS_DEF)
 151  6
                && (searchAST.getType() != TokenTypes.ENUM_DEF))
 152  
         {
 153  4
             searchAST = searchAST.getParent();
 154  
         }
 155  2
         return searchAST;
 156  
     }
 157  
 }