StaticInheritanceInspection.java

/*
 * Copyright 2003-2014 Dave Griffith, Bas Leijdekkers
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.siyeh.ig.inheritance;

import com.intellij.psi.PsiClass;
import com.intellij.psi.PsiElement;
import com.intellij.psi.PsiJavaCodeReferenceElement;
import com.intellij.psi.PsiReferenceList;
import com.siyeh.InspectionGadgetsBundle;
import com.siyeh.ig.BaseInspection;
import com.siyeh.ig.BaseInspectionVisitor;
import com.siyeh.ig.InspectionGadgetsFix;
import org.jetbrains.annotations.NotNull;

import java.util.HashSet;
import java.util.Set;

public class StaticInheritanceInspection extends BaseInspection {

  @Override
  @NotNull
  public String getDisplayName() {
    return InspectionGadgetsBundle.message(
      "static.inheritance.display.name");
  }

  @Override
  @NotNull
  protected String buildErrorString(Object... infos) {
    return InspectionGadgetsBundle.message(
      "static.inheritance.problem.descriptor");
  }

  @NotNull
  @Override
  protected InspectionGadgetsFix[] buildFixes(Object... infos) {
    return new InspectionGadgetsFix[]{new StaticInheritanceFix(false), new StaticInheritanceFix(true)};
  }


  @Override
  public BaseInspectionVisitor buildVisitor() {
    return new StaticInheritanceVisitor();
  }

  private static class StaticInheritanceVisitor
    extends BaseInspectionVisitor {

    @Override
    public void visitClass(@NotNull PsiClass aClass) {
      // no call to super, so it doesn't drill down
      final PsiReferenceList implementsList = aClass.getImplementsList();
      if (implementsList == null) {
        return;
      }
      final PsiJavaCodeReferenceElement[] references =
        implementsList.getReferenceElements();
      for (final PsiJavaCodeReferenceElement reference : references) {
        final PsiElement target = reference.resolve();
        if (!(target instanceof PsiClass)) {
          return;
        }
        final PsiClass targetClass = (PsiClass)target;
        if (targetClass.isInterface() && interfaceContainsOnlyConstants(targetClass, new HashSet<>())) {
          registerError(reference);
        }
      }
    }

    private static boolean interfaceContainsOnlyConstants(PsiClass anInterface, Set<PsiClass> visitedInterfaces) {
      if (!visitedInterfaces.add(anInterface)) {
        return true;
      }
      if (anInterface.getAllFields().length == 0) {
        // ignore it, it's either a true interface or just a marker
        return false;
      }
      if (anInterface.getMethods().length != 0) {
        return false;
      }
      final PsiClass[] parentInterfaces = anInterface.getInterfaces();
      for (final PsiClass parentInterface : parentInterfaces) {
        if (!interfaceContainsOnlyConstants(parentInterface, visitedInterfaces)) {
          return false;
        }
      }
      return true;
    }
  }
}