org.sonar.java.checks.UselessExtendsCheck Maven / Gradle / Ivy

Go to download
/*
 * SonarQube Java
 * Copyright (C) 2012-2024 SonarSource SA
 * mailto:info AT sonarsource DOT com
 *
 * This program 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 3 of the License, or (at your option) any later version.
 *
 * This program 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 program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */
package org.sonar.java.checks;

import org.sonar.check.Rule;
import org.sonar.java.model.SyntacticEquivalence;
import org.sonar.plugins.java.api.IssuableSubscriptionVisitor;
import org.sonar.plugins.java.api.semantic.Symbol.TypeSymbol;
import org.sonar.plugins.java.api.semantic.Type;
import org.sonar.plugins.java.api.tree.ClassTree;
import org.sonar.plugins.java.api.tree.IdentifierTree;
import org.sonar.plugins.java.api.tree.ListTree;
import org.sonar.plugins.java.api.tree.MemberSelectExpressionTree;
import org.sonar.plugins.java.api.tree.ParameterizedTypeTree;
import org.sonar.plugins.java.api.tree.Tree;
import org.sonar.plugins.java.api.tree.TypeTree;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

@Rule(key = "S1939")
public class UselessExtendsCheck extends IssuableSubscriptionVisitor {

  @Override
  public List nodesToVisit() {
    return Arrays.asList(Tree.Kind.CLASS, Tree.Kind.INTERFACE, Tree.Kind.ENUM, Tree.Kind.RECORD);
  }

  @Override
  public void visitNode(Tree tree) {
    ClassTree classTree = (ClassTree) tree;
    checkExtendsObject(classTree);

    ListTree superInterfaces = classTree.superInterfaces();
    if (superInterfaces.isEmpty()) {
      return;
    }

    List superInterfacesTypes = getTypes(superInterfaces);
    List superTypes = new ArrayList<>(classTree.symbol().superTypes());
    superTypes.sort(new SuperTypeComparator(superInterfacesTypes));

    Set reportedNames = new HashSet<>();
    for (TypeTree superInterface : superInterfaces) {
      String superInterfaceName = extractInterfaceName(superInterface);
      if (isDuplicate(superInterfaces, superInterface) && !reportedNames.add(superInterfaceName)) {
        // add an issue on a duplicated interface the second time it is encountered
        reportIssue(superInterface, "\"" + superInterfaceName + "\" is listed multiple times.");
      }
      if (!superInterface.symbolType().isUnknown()) {
        checkRedundancy(superInterface, superInterfacesTypes, superTypes);
      }
    }
  }

  private void checkExtendsObject(ClassTree classTree) {
    TypeTree superClassTree = classTree.superClass();
    if (superClassTree != null && superClassTree.symbolType().is("java.lang.Object")) {
      reportIssue(superClassTree, "\"Object\" should not be explicitly extended.");
    }
  }

  private static boolean isDuplicate(ListTree superInterfaces, TypeTree currentInterfaceTree) {
    for (TypeTree superInterfaceTree : superInterfaces) {
      if (!currentInterfaceTree.equals(superInterfaceTree) && SyntacticEquivalence.areEquivalent(currentInterfaceTree, superInterfaceTree)) {
        return true;
      }
    }
    return false;
  }

  private static List getTypes(ListTree superInterfaces) {
    List types = new ArrayList<>(superInterfaces.size());
    for (TypeTree superInterface : superInterfaces) {
      types.add(superInterface.symbolType());
    }
    return types;
  }

  private void checkRedundancy(TypeTree currentInterface, List superInterfacesTypes, List superTypes) {
    Type interfaceType = currentInterface.symbolType();
    for (Type superType : superTypes) {
      TypeSymbol superTypeSymbol = superType.symbol();
      if (superTypeSymbol.interfaces().contains(interfaceType)) {
        String typeOfParentMsg = "implemented by a super class";
        if (superTypeSymbol.isInterface() && superInterfacesTypes.contains(superType)) {
          typeOfParentMsg = "already extended by \"" + superTypeSymbol.name() + "\"";
        }
        reportIssue(currentInterface, "\"" + interfaceType.name() + "\" is " + typeOfParentMsg + "; there is no need to implement it here.");
        break;
      }
    }
  }

  private static String extractInterfaceName(Tree interfaceTree) {
    if (interfaceTree.is(Tree.Kind.IDENTIFIER)) {
      return ((IdentifierTree) interfaceTree).name();
    }
    if (interfaceTree.is(Tree.Kind.MEMBER_SELECT)) {
      MemberSelectExpressionTree mset = (MemberSelectExpressionTree) interfaceTree;
      return extractInterfaceName(mset.expression()) + "." + mset.identifier().name();
    }
    return extractInterfaceName(((ParameterizedTypeTree) interfaceTree).type());
  }

  /**
   * Sort super types according to their declaration order in the list of interfaces
   */
  private static class SuperTypeComparator implements Comparator {

    private final List declaredSuperInterfaces;

    SuperTypeComparator(List declaredSuperInterfaces) {
      this.declaredSuperInterfaces = declaredSuperInterfaces;
    }

    @Override
    public int compare(Type t1, Type t2) {
      int indexT1 = declaredSuperInterfaces.indexOf(t1);
      int indexT2 = declaredSuperInterfaces.indexOf(t2);
      if (indexT1 != -1 && indexT2 != -1) {
        return Integer.compare(indexT1, indexT2);
      }
      if (indexT1 != -1) {
        // t1 should be placed before
        return -1;
      }
      if (indexT2 != -1) {
        // t2 should be placed before
        return +1;
      }
      // sort by name if none of t1 and t2 is present in declaration list
      return t1.name().compareTo(t2.name());
    }
  }
}