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java-team-github-botError Prone Team
java-team-github-bot
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Error Prone Team
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Automatic code cleanup.
PiperOrigin-RevId: 551640093
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‎core/src/main/java/com/google/errorprone/bugpatterns/NullableOptional.java

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/*
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* Copyright 2023 The Error Prone Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.errorprone.bugpatterns;
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import com.google.common.collect.ImmutableSet;
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import com.google.errorprone.BugPattern;
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import com.google.errorprone.BugPattern.SeverityLevel;
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import com.google.errorprone.VisitorState;
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import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
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import com.google.errorprone.bugpatterns.BugChecker.VariableTreeMatcher;
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import com.google.errorprone.matchers.Description;
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import com.google.errorprone.predicates.TypePredicate;
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import com.google.errorprone.predicates.TypePredicates;
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import com.google.errorprone.util.ASTHelpers;
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import com.sun.source.tree.MethodTree;
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import com.sun.source.tree.ModifiersTree;
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import com.sun.source.tree.VariableTree;
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import com.sun.tools.javac.code.Type;
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/**
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* A Checker that catches {@link java.util.Optional}/{@link com.google.common.base.Optional} with
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* {@code Nullable} annotation.
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*/
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@BugPattern(
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summary =
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"Using an Optional variable which is expected to possibly be null is discouraged. It is"
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+ " best to indicate the absence of the value by assigning it an empty optional.",
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severity = SeverityLevel.WARNING)
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public final class NullableOptional extends BugChecker
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implements MethodTreeMatcher, VariableTreeMatcher {
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private static final TypePredicate IS_OPTIONAL_TYPE =
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TypePredicates.isExactTypeAny(
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ImmutableSet.of(
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java.util.Optional.class.getCanonicalName(),
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com.google.common.base.Optional.class.getCanonicalName()));
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@Override
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public Description matchMethod(MethodTree tree, VisitorState state) {
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if (hasNullableAnnotation(tree.getModifiers())
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&& isOptional(ASTHelpers.getType(tree.getReturnType()), state)) {
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return describeMatch(tree);
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}
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return Description.NO_MATCH;
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}
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@Override
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public Description matchVariable(VariableTree tree, VisitorState state) {
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if (hasNullableAnnotation(tree.getModifiers()) && isOptional(ASTHelpers.getType(tree), state)) {
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return describeMatch(tree);
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}
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return Description.NO_MATCH;
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}
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/** Check if the input ModifiersTree has any kind of "Nullable" annotation. */
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private static boolean hasNullableAnnotation(ModifiersTree modifiersTree) {
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return ASTHelpers.getAnnotationWithSimpleName(modifiersTree.getAnnotations(), "Nullable")
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!= null;
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}
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/**
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* Check if the input Type is either {@link java.util.Optional} or{@link
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* com.google.common.base.Optional}.
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*/
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private static boolean isOptional(Type type, VisitorState state) {
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return IS_OPTIONAL_TYPE.apply(type, state);
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}
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}

‎core/src/main/java/com/google/errorprone/scanner/BuiltInCheckerSuppliers.java

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import com.google.errorprone.bugpatterns.NullTernary;
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import com.google.errorprone.bugpatterns.NullableConstructor;
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import com.google.errorprone.bugpatterns.NullableOnContainingClass;
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import com.google.errorprone.bugpatterns.NullableOptional;
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import com.google.errorprone.bugpatterns.NullablePrimitive;
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import com.google.errorprone.bugpatterns.NullablePrimitiveArray;
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import com.google.errorprone.bugpatterns.NullableVoid;
@@ -979,6 +980,7 @@ public static ScannerSupplier warningChecks() {
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NotJavadoc.class,
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NullOptional.class,
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NullableConstructor.class,
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NullableOptional.class,
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NullablePrimitive.class,
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NullablePrimitiveArray.class,
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NullableVoid.class,

‎core/src/test/java/com/google/errorprone/bugpatterns/NullableOptionalTest.java

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/*
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* Copyright 2023 The Error Prone Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.errorprone.bugpatterns;
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import com.google.errorprone.CompilationTestHelper;
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import org.junit.Test;
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import org.junit.runner.RunWith;
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import org.junit.runners.JUnit4;
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@RunWith(JUnit4.class)
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public final class NullableOptionalTest {
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private final CompilationTestHelper compilationHelper =
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CompilationTestHelper.newInstance(NullableOptional.class, getClass());
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@Test
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public void optionalFieldWithNullableAnnotation_showsError() {
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compilationHelper
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.addSourceLines(
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"Test.java",
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"import java.util.Optional;",
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"import javax.annotation.Nullable;",
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"final class Test {",
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" // BUG: Diagnostic contains:",
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" @Nullable private Optional<Object> foo;",
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"}")
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.doTest();
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}
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@Test
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public void guavaOptionalFieldWithNullableAnnotation_showsError() {
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compilationHelper
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.addSourceLines(
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"Test.java",
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"import com.google.common.base.Optional;",
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"import javax.annotation.Nullable;",
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"final class Test {",
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" @Nullable",
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" // BUG: Diagnostic contains:",
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" private Optional<Object> foo;",
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"}")
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.doTest();
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}
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@Test
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public void methodReturnsOptionalWithNullableAnnotation_showsError() {
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compilationHelper
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.addSourceLines(
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"Test.java",
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"import java.util.Optional;",
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"import javax.annotation.Nullable;",
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"final class Test {",
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" @Nullable",
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" // BUG: Diagnostic contains:",
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" private Optional<Object> foo() {",
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" return Optional.empty();",
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" }",
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"}")
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.doTest();
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}
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@Test
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public void methodReturnsOptionalWithAnotherNullableAnnotation_showsError() {
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compilationHelper
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.addSourceLines(
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"Test.java",
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"import java.util.Optional;",
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"import org.jspecify.nullness.Nullable;",
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"final class Test {",
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" @Nullable",
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" // BUG: Diagnostic contains:",
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" private Optional<Object> foo() {",
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" return Optional.empty();",
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" }",
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"}")
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.doTest();
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}
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@Test
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public void methodHasNullableOptionalAsParameter_showsError() {
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compilationHelper
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.addSourceLines(
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"Test.java",
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"import java.util.Optional;",
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"import javax.annotation.Nullable;",
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"final class Test {",
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" // BUG: Diagnostic contains:",
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" private void foo(@Nullable Optional<Object> optional) {}",
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"}")
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.doTest();
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}
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@Test
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public void objectFieldWithNullableAnnotation_noError() {
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compilationHelper
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.addSourceLines(
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"Test.java",
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"import javax.annotation.Nullable;",
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"final class Test {",
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" @Nullable Object field;",
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"}")
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.doTest();
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}
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@Test
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public void methodReturnsNonOptionalWithNullableAnnotation_noError() {
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compilationHelper
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.addSourceLines(
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"Test.java",
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"import javax.annotation.Nullable;",
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"final class Test {",
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" @Nullable",
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" private Object foo() {",
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" return null;",
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" }",
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"}")
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.doTest();
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}
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@Test
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public void methodReturnsNonOptionalWithAnotherNullableAnnotation_noError() {
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compilationHelper
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.addSourceLines(
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"Test.java",
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"import org.jspecify.nullness.Nullable;",
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"final class Test {",
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" @Nullable",
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" private Object foo() {",
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" return null;",
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" }",
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"}")
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.doTest();
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}
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@Test
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public void methodHasNullableNonOptionalAsParameter_noError() {
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compilationHelper
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.addSourceLines(
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"Test.java",
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"import org.jspecify.nullness.Nullable;",
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"final class Test {",
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" private void foo(@Nullable Object object) {}",
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"}")
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.doTest();
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}
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}

‎docs/bugpattern/NullableOptional.md

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`Optional` is a container object which may or may not contain a value. The
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presence or absence of the contained value should be demonstrated by the
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`Optional` object itself.
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Using an Optional variable which is expected to possibly be null is discouraged.
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An nullable Optional which uses `null` to indicate the absence of the value will
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lead to extra work for `null` checking when using the object and even cause
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exceptions such as `NullPointerException`. It is best to indicate the absence of
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the value by assigning it an empty optional.

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