com.google.errorprone.bugpatterns.EqualsNull Maven / Gradle / Ivy
/*
* Copyright 2021 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.BugPattern.StandardTags.FRAGILE_CODE;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.matchers.Matchers.allOf;
import static com.google.errorprone.matchers.Matchers.anyOf;
import static com.google.errorprone.matchers.Matchers.argument;
import static com.google.errorprone.matchers.Matchers.enclosingClass;
import static com.google.errorprone.matchers.Matchers.enclosingNode;
import static com.google.errorprone.matchers.Matchers.instanceEqualsInvocation;
import static com.google.errorprone.matchers.Matchers.isSubtypeOf;
import static com.google.errorprone.matchers.Matchers.kindIs;
import static com.google.errorprone.matchers.Matchers.toType;
import static com.google.errorprone.matchers.method.MethodMatchers.staticMethod;
import static com.google.errorprone.util.ASTHelpers.getReceiver;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.Tree.Kind;
/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
@BugPattern(
summary =
"The contract of Object.equals() states that for any non-null reference value x,"
+ " x.equals(null) should return false. If x is null, a NullPointerException is thrown."
+ " Consider replacing equals() with the == operator.",
tags = FRAGILE_CODE,
severity = ERROR)
public final class EqualsNull extends BugChecker implements MethodInvocationTreeMatcher {
private static final Matcher EQUALS_NULL =
allOf(instanceEqualsInvocation(), argument(0, kindIs(Kind.NULL_LITERAL)));
private static final Matcher INSIDE_ASSERT_CLASS =
enclosingClass(anyOf(isSubtypeOf("org.junit.Assert"), isSubtypeOf("junit.framework.Assert")));
private static final Matcher ENCLOSED_BY_ASSERT =
enclosingNode(
toType(
MethodInvocationTree.class,
staticMethod()
.onClassAny(
"com.google.common.truth.Truth",
"com.google.common.truth.Truth8",
"junit.framework.Assert",
"org.junit.Assert")));
@Override
public Description matchMethodInvocation(
MethodInvocationTree invocationTree, VisitorState state) {
if (!EQUALS_NULL.matches(invocationTree, state)) {
return NO_MATCH;
}
if (ASTHelpers.isJUnitTestCode(state)
|| ASTHelpers.isTestNgTestCode(state)
|| INSIDE_ASSERT_CLASS.matches(invocationTree, state)
|| ENCLOSED_BY_ASSERT.matches(invocationTree, state)) {
// Allow x.equals(null) in test code for testing the equals contract.
return NO_MATCH;
}
Tree parentTree = state.getPath().getParentPath().getLeaf();
boolean negated = parentTree.getKind() == Kind.LOGICAL_COMPLEMENT;
String operator = negated ? "!=" : "==";
Tree treeToFix = negated ? parentTree : invocationTree;
String fixedCode =
String.format("%s %s null", state.getSourceForNode(getReceiver(invocationTree)), operator);
return describeMatch(treeToFix, SuggestedFix.replace(treeToFix, fixedCode));
}
}