chore: replace List<@nullable Object> with List<?>

The latter is easier to read, and it forbids list.add(...) at the compile-time.

See https://jspecify.dev/docs/user-guide/#wildcard-bounds

Author: vlsi

junit-jupiter-params/src/main/java/org/junit/jupiter/params/aggregator/ArgumentsAccessor.java

@@ -198,7 +198,7 @@ public interface ArgumentsAccessor {
 	/**
 	 * Get all arguments in this accessor as an immutable list.
 	 */
-	List<@Nullable Object> toList();
+	List<?> toList();
 
 	/**
 	 * Get the index of the current test invocation.

junit-jupiter-params/src/main/java/org/junit/jupiter/params/aggregator/DefaultArgumentsAccessor.java

@@ -139,7 +139,7 @@ public int size() {
 	}
 
 	@Override
-	public List<@Nullable Object> toList() {
+	public List<?> toList() {
 		return Collections.unmodifiableList(Arrays.asList(this.arguments));
 	}
 

junit-platform-commons/src/main/java/org/junit/platform/commons/support/AnnotationSupport.java

@@ -443,8 +443,7 @@ public static List<Field> findAnnotatedFields(Class<?> clazz, Class<? extends An
 	 * @see ReflectionSupport#tryToReadFieldValue(Field, Object)
 	 */
 	@API(status = MAINTAINED, since = "1.4")
-	public static List<@Nullable Object> findAnnotatedFieldValues(Object instance,
-			Class<? extends Annotation> annotationType) {
+	public static List<?> findAnnotatedFieldValues(Object instance, Class<? extends Annotation> annotationType) {
 		Preconditions.notNull(instance, "instance must not be null");
 
 		List<Field> fields = findAnnotatedFields(instance.getClass(), annotationType, ModifierSupport::isNotStatic,
@@ -476,8 +475,7 @@ public static List<Field> findAnnotatedFields(Class<?> clazz, Class<? extends An
 	 * @see ReflectionSupport#tryToReadFieldValue(Field, Object)
 	 */
 	@API(status = MAINTAINED, since = "1.4")
-	public static List<@Nullable Object> findAnnotatedFieldValues(Class<?> clazz,
-			Class<? extends Annotation> annotationType) {
+	public static List<?> findAnnotatedFieldValues(Class<?> clazz, Class<? extends Annotation> annotationType) {
 
 		List<Field> fields = findAnnotatedFields(clazz, annotationType, ModifierSupport::isStatic,
 			HierarchyTraversalMode.TOP_DOWN);

junit-platform-commons/src/main/java/org/junit/platform/commons/util/ReflectionUtils.java

@@ -656,7 +656,7 @@ public static <T> Try<Object> tryToReadFieldValue(Class<T> clazz, String fieldNa
 	 * @return an immutable list of the values of the specified fields; never
 	 * {@code null} but may be empty or contain {@code null} entries
 	 */
-	public static List<@Nullable Object> readFieldValues(List<Field> fields, @Nullable Object instance) {
+	public static List<?> readFieldValues(List<Field> fields, @Nullable Object instance) {
 		return readFieldValues(fields, instance, field -> true);
 	}
 
@@ -673,8 +673,7 @@ public static <T> Try<Object> tryToReadFieldValue(Class<T> clazz, String fieldNa
 	 * @return an immutable list of the values of the specified fields; never
 	 * {@code null} but may be empty or contain {@code null} entries
 	 */
-	public static List<@Nullable Object> readFieldValues(List<Field> fields, @Nullable Object instance,
-			Predicate<Field> predicate) {
+	public static List<?> readFieldValues(List<Field> fields, @Nullable Object instance, Predicate<Field> predicate) {
 		Preconditions.notNull(fields, "fields list must not be null");
 		Preconditions.notNull(predicate, "Predicate must not be null");
 

jupiter-tests/src/test/java/org/junit/jupiter/params/aggregator/DefaultArgumentsAccessorTests.java

@@ -157,7 +157,8 @@ void toList() {
 		assertIterableEquals(Arrays.asList("foo", "bar"), copy);
 
 		// Modify local copy:
-		assertThrows(UnsupportedOperationException.class, () -> copy.set(0, "Boom!"));
+		assertThrows(UnsupportedOperationException.class, () -> copy.set(0, null));
+		// Note that copy.set(0, "foo") does not compile
 	}
 
 	@Test

platform-tests/src/test/java/org/junit/platform/commons/support/AnnotationSupportTests.java

@@ -23,6 +23,7 @@
 import java.util.List;
 import java.util.Optional;
 
+import org.assertj.core.api.Assertions;
 import org.jspecify.annotations.NullUnmarked;
 import org.junit.jupiter.api.Tag;
 import org.junit.jupiter.api.Test;
@@ -247,15 +248,15 @@ void findAnnotatedFieldValuesForNonStaticFields() {
 
 		assertThat(AnnotationSupport.findAnnotatedFieldValues(instance, Tag.class)).isEmpty();
 
-		assertThat(AnnotationSupport.findAnnotatedFieldValues(instance, FieldMarker.class))//
+		Assertions.<Object> assertThat(AnnotationSupport.findAnnotatedFieldValues(instance, FieldMarker.class))//
 				.containsExactlyInAnyOrder("i1", "i2");
 	}
 
 	@Test
 	void findAnnotatedFieldValuesForStaticFields() {
 		assertThat(AnnotationSupport.findAnnotatedFieldValues(Fields.class, Tag.class)).isEmpty();
 
-		assertThat(AnnotationSupport.findAnnotatedFieldValues(Fields.class, FieldMarker.class))//
+		Assertions.<Object> assertThat(AnnotationSupport.findAnnotatedFieldValues(Fields.class, FieldMarker.class))//
 				.containsExactlyInAnyOrder("s1", "s2");
 	}
 

platform-tests/src/test/java/org/junit/platform/commons/util/ReflectionUtilsTests.java

@@ -60,6 +60,7 @@
 import java.util.stream.IntStream;
 import java.util.stream.Stream;
 
+import org.assertj.core.api.Assertions;
 import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
@@ -1953,7 +1954,8 @@ void readFieldValuesFromInstance() {
 
 			var values = readFieldValues(fields, new ClassWithFields());
 
-			assertThat(values).containsExactly("enigma", 3.14, "text", 2.5, null, 42, "constant", 99);
+			Assertions.<Object> assertThat(values).containsExactly("enigma", 3.14, "text", 2.5, null, 42, "constant",
+				99);
 		}
 
 		@Test
@@ -1962,7 +1964,7 @@ void readFieldValuesFromClass() {
 
 			var values = readFieldValues(fields, null);
 
-			assertThat(values).containsExactly(2.5, "constant", 99);
+			Assertions.<Object> assertThat(values).containsExactly(2.5, "constant", 99);
 		}
 
 		/**
@@ -1973,15 +1975,15 @@ void readFieldValuesFromClass() {
 		void readFieldValuesFromInterfacesAndClassesInTypeHierarchy() {
 			var fields = findFields(InterfaceWithField.class, ReflectionUtils::isStatic, TOP_DOWN);
 			var values = readFieldValues(fields, null);
-			assertThat(values).containsOnly("ifc");
+			Assertions.<Object> assertThat(values).containsOnly("ifc");
 
 			fields = findFields(SuperclassWithFieldAndFieldFromInterface.class, ReflectionUtils::isStatic, TOP_DOWN);
 			values = readFieldValues(fields, null);
-			assertThat(values).containsExactly("ifc", "super");
+			Assertions.<Object> assertThat(values).containsExactly("ifc", "super");
 
 			fields = findFields(SubclassWithFieldAndFieldFromInterface.class, ReflectionUtils::isStatic, TOP_DOWN);
 			values = readFieldValues(fields, null);
-			assertThat(values).containsExactly("ifc", "super", "sub");
+			Assertions.<Object> assertThat(values).containsExactly("ifc", "super", "sub");
 		}
 
 		@Test
@@ -1990,7 +1992,7 @@ void readFieldValuesFromInstanceWithTypeFilterForString() {
 
 			var values = readFieldValues(fields, new ClassWithFields(), isA(String.class));
 
-			assertThat(values).containsExactly("enigma", "text", null, "constant");
+			Assertions.<Object> assertThat(values).containsExactly("enigma", "text", null, "constant");
 		}
 
 		@Test
@@ -1999,7 +2001,7 @@ void readFieldValuesFromClassWithTypeFilterForString() {
 
 			var values = readFieldValues(fields, null, isA(String.class));
 
-			assertThat(values).containsExactly("constant");
+			Assertions.<Object> assertThat(values).containsExactly("constant");
 		}
 
 		@Test
@@ -2008,7 +2010,7 @@ void readFieldValuesFromInstanceWithTypeFilterForInteger() {
 
 			var values = readFieldValues(fields, new ClassWithFields(), isA(int.class));
 
-			assertThat(values).containsExactly(42);
+			Assertions.<Object> assertThat(values).containsExactly(42);
 		}
 
 		@Test
@@ -2017,7 +2019,7 @@ void readFieldValuesFromClassWithTypeFilterForInteger() {
 
 			var values = readFieldValues(fields, null, isA(Integer.class));
 
-			assertThat(values).containsExactly(99);
+			Assertions.<Object> assertThat(values).containsExactly(99);
 		}
 
 		@Test
@@ -2026,7 +2028,7 @@ void readFieldValuesFromInstanceWithTypeFilterForDouble() {
 
 			var values = readFieldValues(fields, new ClassWithFields(), isA(double.class));
 
-			assertThat(values).containsExactly(3.14);
+			Assertions.<Object> assertThat(values).containsExactly(3.14);
 		}
 
 		@Test
@@ -2035,7 +2037,7 @@ void readFieldValuesFromClassWithTypeFilterForDouble() {
 
 			var values = readFieldValues(fields, null, isA(Double.class));
 
-			assertThat(values).containsExactly(2.5);
+			Assertions.<Object> assertThat(values).containsExactly(2.5);
 		}
 
 		private static Predicate<Field> isA(Class<?> type) {