Use JSpecify annotations in the public release.

We've been using these internally for over a year. With JSpecify 1.0 not far off and wider adoption to gradually follow, now seems like the time to expand our public usage of the annotations. We've already been using them in a few projects, but Truth may become the mostly widely used project that users actually link against to use them. At the same time, it's a library that's used only in testing code, so the stakes remain relatively low.

Most users will see no effect from this change, since most users don't use nullness checking and since we already used some nullness annotations in our public release. The main effect users are likely to see is if they pass nullable values for parameters that are now recognized as non-nullable. Under Kotlin, the effect should normally be a warning, not an error, at least until [Kotlin 2.1 or so](https://youtrack.jetbrains.com/issue/KT-55586/Handle-nullability-from-jspecify-annotations-properly#focus=Comments-27-8368666.0-0). Please still [report any problems](https://github.com/google/truth/issues/new).

(progress toward JSpecify adoption in our projects in general, including google/guava#2960)

RELNOTES=Added more nullness information to our APIs (in the form of [JSpecify](https://jspecify.dev/) annotations). This could lead to additional warnings (or even errors) for users of Kotlin and other nullness checkers. Please [report any problems](https://github.com/google/truth/issues/new).
PiperOrigin-RevId: 647012817

Author: cpovirk

core/pom.xml

@@ -15,8 +15,8 @@
       <artifactId>guava</artifactId>
     </dependency>
     <dependency>
-      <groupId>org.checkerframework</groupId>
-      <artifactId>checker-qual</artifactId>
+      <groupId>org.jspecify</groupId>
+      <artifactId>jspecify</artifactId>
     </dependency>
     <dependency>
       <groupId>junit</groupId>

core/src/main/java/com/google/common/truth/AbstractArraySubject.java

@@ -20,13 +20,15 @@
 import static com.google.common.truth.Fact.simpleFact;
 
 import java.lang.reflect.Array;
-import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
 
 /**
  * A common supertype for Array subjects, abstracting some common display and error infrastructure.
  *
  * @author Christian Gruber ([email protected])
  */
+@NullMarked
 abstract class AbstractArraySubject extends Subject {
   private final @Nullable Object actual;
 

core/src/main/java/com/google/common/truth/ActualValueInference.java

@@ -33,7 +33,8 @@
 import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.Map.Entry;
-import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
 import org.objectweb.asm.ClassReader;
 import org.objectweb.asm.ClassVisitor;
 import org.objectweb.asm.Handle;
@@ -69,6 +70,7 @@
  */
 @GwtIncompatible
 @J2ktIncompatible
+@NullMarked
 final class ActualValueInference {
   /** <b>Call {@link Platform#inferDescription} rather than calling this directly.</b> */
   static @Nullable String describeActualValue(String className, String methodName, int lineNumber) {

core/src/main/java/com/google/common/truth/AssertionErrorWithFacts.java

@@ -19,13 +19,15 @@
 import static com.google.common.truth.Fact.makeMessage;
 
 import com.google.common.collect.ImmutableList;
-import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
 
 /**
  * An {@link AssertionError} composed of structured {@link Fact} instances and other string
  * messages.
  */
 @SuppressWarnings("OverrideThrowableToString") // We intentionally hide the class name.
+@NullMarked
 final class AssertionErrorWithFacts extends AssertionError implements ErrorWithFacts {
   private final ImmutableList<Fact> facts;
 

core/src/main/java/com/google/common/truth/BigDecimalSubject.java

@@ -20,13 +20,15 @@
 import static com.google.common.truth.Fact.simpleFact;
 
 import java.math.BigDecimal;
-import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Propositions for {@link BigDecimal} typed subjects.
  *
  * @author Kurt Alfred Kluever
  */
+@NullMarked
 public final class BigDecimalSubject extends ComparableSubject<BigDecimal> {
   private final @Nullable BigDecimal actual;
 

core/src/main/java/com/google/common/truth/BooleanSubject.java

@@ -17,13 +17,15 @@
 
 import static com.google.common.truth.Fact.simpleFact;
 
-import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Propositions for boolean subjects.
  *
  * @author Christian Gruber ([email protected])
  */
+@NullMarked
 public final class BooleanSubject extends Subject {
   private final @Nullable Boolean actual;
 

core/src/main/java/com/google/common/truth/ClassSubject.java

@@ -18,13 +18,15 @@
 import static com.google.common.base.Preconditions.checkNotNull;
 
 import com.google.common.annotations.GwtIncompatible;
-import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Propositions for {@link Class} subjects.
  *
  * @author Kurt Alfred Kluever
  */
+@NullMarked
 @GwtIncompatible("reflection")
 @J2ktIncompatible
 public final class ClassSubject extends Subject {

core/src/main/java/com/google/common/truth/ComparableSubject.java

@@ -18,14 +18,16 @@
 import static com.google.common.base.Preconditions.checkNotNull;
 
 import com.google.common.collect.Range;
-import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Propositions for {@link Comparable} typed subjects.
  *
  * @author Kurt Alfred Kluever
  * @param <T> the type of the object being tested by this {@code ComparableSubject}
  */
+@NullMarked
 // TODO(b/136040841): Consider further tightening this to the proper `extends Comparable<? super T>`
 public abstract class ComparableSubject<T extends Comparable<?>> extends Subject {
   /**

core/src/main/java/com/google/common/truth/ComparisonFailureWithFacts.java

@@ -21,12 +21,14 @@
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.truth.Platform.PlatformComparisonFailure;
-import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
 
 /**
  * An {@link AssertionError} (usually a JUnit {@code ComparisonFailure}, but not under GWT) composed
  * of structured {@link Fact} instances and other string messages.
  */
+@NullMarked
 final class ComparisonFailureWithFacts extends PlatformComparisonFailure implements ErrorWithFacts {
   private final ImmutableList<Fact> facts;
 

core/src/main/java/com/google/common/truth/ComparisonFailures.java

@@ -26,7 +26,8 @@
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.ImmutableList;
-import org.checkerframework.checker.nullness.qual.Nullable;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Contains part of the code responsible for creating a JUnit {@code ComparisonFailure} (if
@@ -42,6 +43,7 @@
  * different implementation under GWT/j2cl, where {@code ComparisonFailure} is also unavailable but
  * we can't just recover from that at runtime.
  */
+@NullMarked
 final class ComparisonFailures {
   static ImmutableList<Fact> makeComparisonFailureFacts(
       ImmutableList<Fact> headFacts,