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com.google.errorprone.bugpatterns.EqualsWrongThing Maven / Gradle / Ivy
/*
* Copyright 2018 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.common.collect.ImmutableSet.toImmutableSet;
import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.matchers.Matchers.anyOf;
import static com.google.errorprone.matchers.Matchers.equalsMethodDeclaration;
import static com.google.errorprone.matchers.Matchers.instanceEqualsInvocation;
import static com.google.errorprone.matchers.Matchers.staticEqualsInvocation;
import static com.google.errorprone.matchers.Matchers.staticMethod;
import static com.google.errorprone.util.ASTHelpers.getReceiver;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static com.google.errorprone.util.ASTHelpers.isStatic;
import com.google.auto.value.AutoValue;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Sets;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.sun.source.tree.BinaryTree;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.IdentifierTree;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.Tree.Kind;
import com.sun.source.util.TreeScanner;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.code.Symbol.ClassSymbol;
import java.util.HashSet;
import java.util.Optional;
import java.util.Set;
import javax.lang.model.element.ElementKind;
/**
* Checks for {@code equals} implementations comparing non-corresponding fields.
*
* @author [email protected] (Graeme Morgan)
*/
@BugPattern(
summary =
"Comparing different pairs of fields/getters in an equals implementation is probably "
+ "a mistake.",
severity = ERROR)
public final class EqualsWrongThing extends BugChecker implements MethodTreeMatcher {
private static final Matcher COMPARISON_METHOD =
anyOf(staticMethod().onClass("java.util.Arrays").named("equals"), staticEqualsInvocation());
private static final ImmutableSet FIELD_TYPES =
Sets.immutableEnumSet(ElementKind.FIELD, ElementKind.METHOD);
@Override
public Description matchMethod(MethodTree tree, VisitorState state) {
if (!equalsMethodDeclaration().matches(tree, state)) {
return NO_MATCH;
}
ClassSymbol classSymbol = getSymbol(tree).enclClass();
Set suspiciousComparisons = new HashSet<>();
new TreeScanner() {
@Override
public Void visitBinary(BinaryTree node, Void unused) {
if (node.getKind() == Kind.EQUAL_TO || node.getKind() == Kind.NOT_EQUAL_TO) {
getDubiousComparison(classSymbol, node, node.getLeftOperand(), node.getRightOperand())
.ifPresent(suspiciousComparisons::add);
}
return super.visitBinary(node, null);
}
@Override
public Void visitMethodInvocation(MethodInvocationTree node, Void unused) {
var args = node.getArguments();
if (COMPARISON_METHOD.matches(node, state)) {
// args.size() / 2 handles the six-arg overload of Arrays.equals (the 0th and 3rd args are
// the arrays).
getDubiousComparison(classSymbol, node, args.get(0), args.get(args.size() / 2))
.ifPresent(suspiciousComparisons::add);
}
if (instanceEqualsInvocation().matches(node, state)) {
ExpressionTree receiver = getReceiver(node);
if (receiver != null) {
// Special-case super, for odd cases like `super.equals(this)`.
if (!(receiver instanceof IdentifierTree
&& ((IdentifierTree) receiver).getName().contentEquals("super"))) {
getDubiousComparison(classSymbol, node, receiver, args.get(0))
.ifPresent(suspiciousComparisons::add);
}
}
}
return super.visitMethodInvocation(node, null);
}
}.scan(tree, null);
// Fast path return.
if (suspiciousComparisons.isEmpty()) {
return NO_MATCH;
}
// Special case where comparisons are made of (a, b) and (b, a) to imply that order doesn't
// matter.
ImmutableSet suspiciousPairs =
suspiciousComparisons.stream().map(ComparisonSite::pair).collect(toImmutableSet());
suspiciousComparisons.stream()
.filter(p -> !suspiciousPairs.contains(p.pair().reversed()))
.map(
c ->
buildDescription(c.tree())
.setMessage(
String.format(
"Suspicious comparison between `%s` and `%s`",
c.pair().lhs(), c.pair().rhs()))
.build())
.forEach(state::reportMatch);
return NO_MATCH;
}
private static Optional getDubiousComparison(
ClassSymbol encl, Tree tree, ExpressionTree lhs, ExpressionTree rhs) {
Symbol lhsSymbol = getSymbol(lhs);
Symbol rhsSymbol = getSymbol(rhs);
if (lhsSymbol == null || rhsSymbol == null || lhsSymbol.equals(rhsSymbol)) {
return Optional.empty();
}
if (isStatic(lhsSymbol) || isStatic(rhsSymbol)) {
return Optional.empty();
}
if (!encl.equals(lhsSymbol.enclClass()) || !encl.equals(rhsSymbol.enclClass())) {
return Optional.empty();
}
if (!FIELD_TYPES.contains(lhsSymbol.getKind()) || !FIELD_TYPES.contains(rhsSymbol.getKind())) {
return Optional.empty();
}
if (getKind(lhs) != getKind(rhs)) {
return Optional.empty();
}
return Optional.of(ComparisonSite.of(tree, lhsSymbol, rhsSymbol));
}
private static Kind getKind(Tree tree) {
Kind kind = tree.getKind();
// Treat identifiers as being similar to member selects for our purposes, as in a == that.a.
return kind == Kind.IDENTIFIER ? Kind.MEMBER_SELECT : kind;
}
@AutoValue
abstract static class ComparisonSite {
abstract Tree tree();
abstract ComparisonPair pair();
private static ComparisonSite of(Tree tree, Symbol lhs, Symbol rhs) {
return new AutoValue_EqualsWrongThing_ComparisonSite(tree, ComparisonPair.of(lhs, rhs));
}
}
@AutoValue
abstract static class ComparisonPair {
abstract Symbol lhs();
abstract Symbol rhs();
final ComparisonPair reversed() {
return of(rhs(), lhs());
}
private static ComparisonPair of(Symbol lhs, Symbol rhs) {
return new AutoValue_EqualsWrongThing_ComparisonPair(lhs, rhs);
}
}
}