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NullableTest.java
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NullableTest.java
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package org.anyname.nullsafety;
import org.anyname.nullsafety.NullableTest.NonNullApiClass.StandardApiExtention;
import org.anyname.nullsafety.NullableTest.StandardClass.NonNullApiExtention;
import org.junit.Test;
import org.junit.matchers.JUnitMatchers;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
/**
* Tests with idioms interesting for null-safety analysis. They more document behaviour of how nullable annotations are
* interpreted by various tools then test anything.
*/
@SuppressWarnings("ResultOfMethodCallIgnored")
public class NullableTest {
private final StandardClass standardApiClass = new StandardClass();
private final NonNullApiClass nonNullApiClass = new NonNullApiClass();
private final NonNullFieldsClass nonNullFieldsClass = new NonNullFieldsClass();
private final NonNullApiExtention nonNullApiInStandardScope = new NonNullApiExtention();
private final StandardApiExtention standardApiInNonNullScope = new StandardApiExtention();
private final List<@Nullable Object> listOfNullables = new ArrayList<>();
private final List<Object> listOfUnknowns = new ArrayList<>();
@Test(expected = NullPointerException.class)
public void dereferencingNullable_isPrevented() {
// [NullAway] dereferenced expression this.nonNullFieldsClass.nullableField is @Nullable
// IJ warns: method invocation 'toString' may produce 'NullPointerException'
this.nonNullFieldsClass.nullableField.toString();
this.standardApiClass.returnsNullable().toString();
this.nonNullApiClass.returnsNullable().toString();
this.nonNullFieldsClass.returnsNullable().toString();
// detected by IJ, not detected by NullAway
this.standardApiInNonNullScope.returnsNullable().toString(); // not specified, IJ: inherited from super
this.listOfNullables.get(0).toString();
synchronized (this.standardApiClass.returnsNullable()) {
}
}
@Test
public void dereferencingNullable_afterNullCheck_isOK() {
final Object nullableField = this.nonNullFieldsClass.nullableField;
if (nullableField != null) {
nullableField.toString();
}
final Object nullableReturn = this.standardApiClass.returnsNullable();
if (Objects.nonNull(nullableReturn)) {
nullableReturn.toString(); // [NullAway] dereferenced expression nullableReturn is @Nullable
}
try {
// could be useful at system boundaries if everything that comes from 3rd party libs was nullable by default
Objects.requireNonNull(this.nonNullApiClass.returnsNullable()).toString();
} catch (NullPointerException ignore) {
// expected if we believed it is never null but actually at runtime it turns out to be null
// (better detect incorrect data sooner than later)
}
}
@Test
public void dereferencingNonNull_isOK() {
this.nonNullFieldsClass.nonNullField.toString();
this.nonNullApiClass.returnsNonNull().toString();
this.standardApiInNonNullScope.returnsNonNull().toString();
}
@Test(expected = NullPointerException.class)
public void dereferencingUnknown_couldBePrevented() {
this.standardApiClass.unknownField.toString();
this.nonNullApiClass.unknownField.toString();
this.standardApiClass.returnsUnknown().toString();
this.standardApiInNonNullScope.returnsUnknown().toString();
this.nonNullFieldsClass.returnsUnknown().toString();
this.listOfUnknowns.get(0).toString();
}
@Test(expected = NullPointerException.class)
public void externalLibraryCalls_couldBeDefensiveByDefault() {
// NullAway, IJ: optimistically assumes non-null return
System.getSecurityManager().toString();
// NullAway, IJ: optimistically assumes nullable param
JUnitMatchers.isException(null);
}
@Test(expected = NullPointerException.class)
public void assigningNullToNonNull_isPrevented() {
// [NullAway] passing @Nullable parameter 'null' where @NonNull is required
// IJ warns: passing 'null' argument to parameter annotated as '@NonNull`
this.nonNullApiClass.acceptsNonNull(null);
this.nonNullApiInStandardScope.acceptsNonNull(null); // inherited from super
this.standardApiInNonNullScope.acceptsNonNull(null); // unspecified reset by scope's default
// [NullAway] assigning @Nullable expression to @NonNull field
// IJ warns: 'null' is assigned to a variable that is annotated with @NotNull
this.nonNullFieldsClass.nonNullField = null;
}
@Test
public void assigningNullToNullable_isOK() {
this.nonNullFieldsClass.nullableField = null;
this.standardApiClass.nullableField = null;
this.nonNullApiClass.nullableField = null;
this.nonNullFieldsClass.acceptsNullable(null);
this.standardApiClass.acceptsNullable(null);
this.standardApiInNonNullScope.acceptsNullable(null); // inherited from super
this.nonNullApiClass.acceptsNullable(null);
this.listOfNullables.add(null);
}
@Test(expected = NullPointerException.class)
public void assigningNullToUnknown_couldBePrevented() {
// default NonNull not set, so no warn and NPE is thrown
// todo IJ: can be set with 'Suggest @Nullable annotations ...'
this.nonNullFieldsClass.acceptsUnknown(null);
this.standardApiClass.acceptsUnknown(null);
this.standardApiInNonNullScope.acceptsUnknown(null);
this.standardApiClass.unknownField = null;
this.nonNullApiClass.unknownField = null;
this.listOfUnknowns.add(null);
}
@Test
public void assigningNonNull_isAlwaysOK() {
this.nonNullFieldsClass.nullableField = new Object();
this.nonNullFieldsClass.nonNullField = new Object();
this.nonNullFieldsClass.acceptsNullable(new Object());
this.nonNullFieldsClass.acceptsUnknown(new Object());
this.standardApiClass.nullableField = new Object();
this.standardApiClass.unknownField = new Object();
this.standardApiClass.acceptsNullable(new Object());
this.standardApiClass.acceptsUnknown(new Object());
this.nonNullApiClass.nullableField = new Object();
this.nonNullApiClass.unknownField = new Object();
this.nonNullApiClass.acceptsNullable(new Object());
this.nonNullApiClass.acceptsNonNull(new Object());
}
static class StandardClass {
Object unknownField;
@Nullable
Object nullableField;
@Nullable
Object returnsNullable() {
return null;
}
Object returnsUnknown() {
return null;
}
void acceptsNullable(@Nullable final Object param) {
// IJ warns: method invocation 'toString' may produce 'NullPointerException'
// param.toString();
if (param != null) {
param.toString();
}
}
void acceptsUnknown(final Object param) throws NullPointerException {
param.toString();
}
static class NonNullApiExtention extends NonNullApiClass {
@Override
Object returnsNullable() {
return super.returnsNullable();
}
// if @Nullable annotation is used (note: returning 'null' would violate the contract)
// [NullAway] method returns @Nullable, but superclass method NonNullApiClass.returnsNonNull() returns @NonNull
// IJ warns: Method annotated with @Nullable must not overwrite @NonNullApi method
// currently IJ warns: Not annotated method overrides method annotated with @NonNullApi
@Override
Object returnsNonNull() {
return super.returnsNonNull();
}
@Override
void acceptsNullable(final Object param) {
super.acceptsNullable(param);
}
// IJ warns: Not annotated param overrides method annotated with @NonNullApi
@Override
void acceptsNonNull(final Object param) {
super.acceptsNonNull(param);
}
}
}
@NonNullApi
static class NonNullApiClass {
Object unknownField;
@Nullable
Object nullableField;
@Nullable
Object returnsNullable() {
return null;
}
Object returnsNonNull() {
// [NullAway] returning @Nullable expression from method with @NonNull return type
// IJ warns: 'null' is returned by the method declared as NonNullApi
// return null;
return new Object();
}
void acceptsNullable(@Nullable final Object param) {
// [NullAway] dereferenced expression param is @Nullable
// IJ warns: method invocation 'toString' may produce 'NullPointerException'
// param.toString();
if (param != null) {
param.toString();
}
}
// IJ warns: Overridden method parameters are not annotated
void acceptsNonNull(final Object param) {
param.toString();
}
// in scope of @NonNullApi
static class StandardApiExtention extends StandardClass {
Object returnsNonNull() {
return new Object();
}
void acceptsNonNull(final Object param) {
param.toString();
}
// IJ: inherits @Nullable from super :/
// [NullAway] returning @Nullable expression from method with @NonNull return type
@Override
Object returnsNullable() {
return super.returnsNullable();
}
// unknown remains unknown
@Override
Object returnsUnknown() {
return super.returnsUnknown();
}
@Override
void acceptsNullable(@Nullable final Object param) {
// if @Nullable on the param is missing (note: in non-null scope would violate the contract)
// [NullAway] parameter param is @NonNull, but parameter in superclass method
// StandardClass.acceptsNullable(@Nullable Object) is @Nullable
// IJ warns: 'Parameter annotated @Nullable must not override @Nullable parameter'
super.acceptsNullable(param);
}
@Override
void acceptsUnknown(final Object param) throws NullPointerException {
super.acceptsUnknown(param);
}
}
}
@NonNullFields
static class NonNullFieldsClass {
// if not initialized (either here or in constructor), IJ warns
// [NullAway] @NonNull field unknownField not initialized
Object nonNullField = new Object();
@Nullable
Object nullableField;
@Nullable
Object returnsNullable() {
return null;
}
Object returnsUnknown() {
return null;
}
void acceptsNullable(@Nullable final Object param) {
if (param != null) {
param.toString();
}
}
void acceptsUnknown(final Object param) throws NullPointerException {
param.toString();
}
}
}