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Better
@MonotonicNonNull support (#1149)
Fixes #1148 We add explicit support for any annotation named `@MonotonicNonNull` and add our own version of the annotation to our annotations package. The main additional support is that we now reason that once assigned a non-null value, `@MonotonicNull` fields remain non-null when accessed from subsequent lambdas, even if the lambdas are invoked asynchronously.
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annotations/src/main/java/com/uber/nullaway/annotations/MonotonicNonNull.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,29 @@ | ||
| package com.uber.nullaway.annotations; | ||
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| import java.lang.annotation.ElementType; | ||
| import java.lang.annotation.Retention; | ||
| import java.lang.annotation.RetentionPolicy; | ||
| import java.lang.annotation.Target; | ||
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|
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| /** | ||
| * Indicates that once the field becomes non-null, it never becomes null again. Inspired by the | ||
| * identically-named annotation from the Checker Framework. A {@code @MonotonicNonNull} field can | ||
| * only be assigned non-null values. The key reason to use this annotation with NullAway is to | ||
| * enable reasoning about field non-nullness in nested lambdas / anonymous classes, e.g.: | ||
| * | ||
| * <pre> | ||
| * class Foo { | ||
| * {@literal @}MonotonicNonNull Object theField; | ||
| * void foo() { | ||
| * theField = new Object(); | ||
| * Runnable r = () -> { | ||
| * // No error, NullAway knows theField is non-null after assignment | ||
| * theField.toString(); | ||
| * } | ||
| * } | ||
| * } | ||
| * </pre> | ||
| */ | ||
| @Retention(RetentionPolicy.CLASS) | ||
| @Target(ElementType.FIELD) | ||
| public @interface MonotonicNonNull {} |
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186 changes: 186 additions & 0 deletions
186
nullaway/src/test/java/com/uber/nullaway/MonotonicNonNullTests.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,186 @@ | ||
| package com.uber.nullaway; | ||
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| import org.junit.Test; | ||
| import org.junit.runner.RunWith; | ||
| import org.junit.runners.JUnit4; | ||
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| @RunWith(JUnit4.class) | ||
| public class MonotonicNonNullTests extends NullAwayTestsBase { | ||
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| @Test | ||
| public void initializerExpression() { | ||
| defaultCompilationHelper | ||
| .addSourceLines( | ||
| "Test.java", | ||
| "package com.uber;", | ||
| "import com.uber.nullaway.annotations.MonotonicNonNull;", | ||
| "class Test {", | ||
| " // this is fine; same as implicit initialization", | ||
| " @MonotonicNonNull Object f1 = null;", | ||
| " @MonotonicNonNull Object f2 = new Object();", | ||
| "}") | ||
| .doTest(); | ||
| } | ||
|
|
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| @Test | ||
| public void assignments() { | ||
| defaultCompilationHelper | ||
| .addSourceLines( | ||
| "Test.java", | ||
| "package com.uber;", | ||
| "import com.uber.nullaway.annotations.MonotonicNonNull;", | ||
| "class Test {", | ||
| " @MonotonicNonNull Object f1;", | ||
| " void testPositive() {", | ||
| " // BUG: Diagnostic contains: assigning @Nullable expression", | ||
| " f1 = null;", | ||
| " }", | ||
| " void testNegative() {", | ||
| " f1 = new Object();", | ||
| " }", | ||
| "}") | ||
| .doTest(); | ||
| } | ||
|
|
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| @Test | ||
| public void lambdas() { | ||
| defaultCompilationHelper | ||
| .addSourceLines( | ||
| "Test.java", | ||
| "package com.uber;", | ||
| "import com.uber.nullaway.annotations.MonotonicNonNull;", | ||
| "class Test {", | ||
| " @MonotonicNonNull Object f1;", | ||
| " void testPositive() {", | ||
| " Runnable r = () -> {", | ||
| " // BUG: Diagnostic contains: dereferenced expression f1", | ||
| " f1.toString();", | ||
| " };", | ||
| " }", | ||
| " void testNegative() {", | ||
| " f1 = new Object();", | ||
| " Runnable r = () -> {", | ||
| " f1.toString();", | ||
| " };", | ||
| " }", | ||
| "}") | ||
| .doTest(); | ||
| } | ||
|
|
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| @Test | ||
| public void anonymousClasses() { | ||
| defaultCompilationHelper | ||
| .addSourceLines( | ||
| "Test.java", | ||
| "package com.uber;", | ||
| "import com.uber.nullaway.annotations.MonotonicNonNull;", | ||
| "class Test {", | ||
| " @MonotonicNonNull Object f1;", | ||
| " void testPositive() {", | ||
| " Runnable r = new Runnable() {", | ||
| " @Override", | ||
| " public void run() {", | ||
| " // BUG: Diagnostic contains: dereferenced expression f1", | ||
| " f1.toString();", | ||
| " }", | ||
| " };", | ||
| " }", | ||
| " void testNegative() {", | ||
| " f1 = new Object();", | ||
| " Runnable r = new Runnable() {", | ||
| " @Override", | ||
| " public void run() {", | ||
| " f1.toString();", | ||
| " }", | ||
| " };", | ||
| " }", | ||
| "}") | ||
| .doTest(); | ||
| } | ||
|
|
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| @Test | ||
| public void nestedObjects() { | ||
| defaultCompilationHelper | ||
| .addSourceLines( | ||
| "Test.java", | ||
| "package com.uber;", | ||
| "import com.uber.nullaway.annotations.MonotonicNonNull;", | ||
| "import org.jspecify.annotations.Nullable;", | ||
| "class Test {", | ||
| " class Foo {", | ||
| " @MonotonicNonNull Object x;", | ||
| " }", | ||
| " final Foo f1 = new Foo();", | ||
| " Foo f2 = new Foo(); // not final", | ||
| " @Nullable Foo f3;", | ||
| " void testPositive1() {", | ||
| " f2.x = new Object();", | ||
| " Runnable r = () -> {", | ||
| " // report a bug since f2 may be overwritten", | ||
| " // BUG: Diagnostic contains: dereferenced expression f2.x", | ||
| " f2.x.toString();", | ||
| " };", | ||
| " }", | ||
| " void testPositive2() {", | ||
| " f3 = new Foo();", | ||
| " f3.x = new Object();", | ||
| " Runnable r = () -> {", | ||
| " // report a bug since f3 may be overwritten", | ||
| " // BUG: Diagnostic contains: dereferenced expression f3.x", | ||
| " f3.x.toString();", | ||
| " };", | ||
| " }", | ||
| " void testNegative() {", | ||
| " f1.x = new Object();", | ||
| " Runnable r = () -> {", | ||
| " f1.x.toString();", | ||
| " };", | ||
| " }", | ||
| "}") | ||
| .doTest(); | ||
| } | ||
|
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| @Test | ||
| public void accessPathsWithMethodCalls() { | ||
| defaultCompilationHelper | ||
| .addSourceLines( | ||
| "Test.java", | ||
| "package com.uber;", | ||
| "import com.uber.nullaway.annotations.MonotonicNonNull;", | ||
| "import org.jspecify.annotations.Nullable;", | ||
| "class Test {", | ||
| " class Foo {", | ||
| " @MonotonicNonNull Object x;", | ||
| " }", | ||
| " Foo f1 = new Foo();", | ||
| " final Foo getF1() {", | ||
| " return f1;", | ||
| " }", | ||
| " final @Nullable Foo getOther() {", | ||
| " return null;", | ||
| " }", | ||
| " void testPositive1() {", | ||
| " getF1().x = new Object();", | ||
| " Runnable r = () -> {", | ||
| " // BUG: Diagnostic contains: dereferenced expression", | ||
| " getF1().x.toString();", | ||
| " };", | ||
| " }", | ||
| " void testPositive2() {", | ||
| " if (getOther() != null) {", | ||
| " getOther().x = new Object();", | ||
| " Runnable r1 = () -> {", | ||
| " // getOther() should be treated as @Nullable in the lambda", | ||
| " // BUG: Diagnostic contains: dereferenced expression", | ||
| " getOther().toString();", | ||
| " };", | ||
| " Runnable r2 = () -> {", | ||
| " // BUG: Diagnostic contains: dereferenced expression", | ||
| " getOther().x.toString();", | ||
| " };", | ||
| " }", | ||
| " }", | ||
| "}") | ||
| .doTest(); | ||
| } | ||
| } |
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