com.google.errorprone.bugpatterns.EqualsHashCode Maven / Gradle / Ivy
/*
* Copyright 2014 The Error Prone Authors.
*
* 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.google.errorprone.bugpatterns;
import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.matchers.Matchers.allOf;
import static com.google.errorprone.matchers.Matchers.equalsMethodDeclaration;
import static com.google.errorprone.matchers.Matchers.instanceEqualsInvocation;
import static com.google.errorprone.matchers.Matchers.not;
import static com.google.errorprone.matchers.Matchers.singleStatementReturnMatcher;
import com.google.common.collect.ImmutableList;
import com.google.errorprone.BugPattern;
import com.google.errorprone.BugPattern.StandardTags;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.Tree;
import com.sun.tools.javac.code.Symbol.MethodSymbol;
import com.sun.tools.javac.code.Symbol.TypeSymbol;
import com.sun.tools.javac.code.Type;
import javax.annotation.Nullable;
import javax.lang.model.element.ElementKind;
/**
* Classes that override {@link Object#equals} should also override {@link Object#hashCode}.
*
* @author [email protected] (Liam Miller-Cushon)
*/
@BugPattern(
summary = "Classes that override equals should also override hashCode.",
severity = ERROR,
tags = StandardTags.FRAGILE_CODE)
public class EqualsHashCode extends BugChecker implements ClassTreeMatcher {
private static final Matcher NON_TRIVIAL_EQUALS =
allOf(
equalsMethodDeclaration(), not(singleStatementReturnMatcher(instanceEqualsInvocation())));
@Override
public Description matchClass(ClassTree classTree, VisitorState state) {
MethodTree methodTree = checkMethodPresence(classTree, state/* expectedNoArgMethod= */ );
if (methodTree == null || isSuppressed(methodTree, state)) {
return NO_MATCH;
}
return describeMatch(methodTree);
}
/**
* Returns the {@link MethodTree} node in the {@code classTree} if both :
*
*
* - there is a method matched by {@code requiredMethodPresenceMatcher}
*
- there is no additional method with name matching {@code expectedNoArgMethod}
*
*/
@Nullable
private static MethodTree checkMethodPresence(ClassTree classTree, VisitorState state) {
TypeSymbol symbol = ASTHelpers.getSymbol(classTree);
if (symbol.getKind() != ElementKind.CLASS) {
return null;
}
// don't flag java.lang.Object
if (symbol == state.getSymtab().objectType.tsym) {
return null;
}
MethodTree requiredMethod = null;
for (Tree member : classTree.getMembers()) {
if (!(member instanceof MethodTree)) {
continue;
}
MethodTree methodTree = (MethodTree) member;
if (EqualsHashCode.NON_TRIVIAL_EQUALS.matches(methodTree, state)) {
requiredMethod = methodTree;
}
}
if (requiredMethod == null) {
return null;
}
MethodSymbol expectedMethodSym =
ASTHelpers.resolveExistingMethod(
state,
symbol,
state.getName("hashCode"),
ImmutableList.of(),
ImmutableList.of());
if (!expectedMethodSym.owner.equals(state.getSymtab().objectType.tsym)) {
return null;
}
return requiredMethod;
}
}