Fix bug in TYPE_HIERARCHY_AND_ENCLOSING_CLASSES strategy

Prior to this commit, the new `TYPE_HIERARCHY_AND_ENCLOSING_CLASSES`
annotation search strategy failed to find annotations on enclosing
classes if the source class was a nested class that itself had no
annotations present.

This commit fixes this by adding special logic to AnnotationsScanner's
isWithoutHierarchy() method to properly support nested classes.

Closes gh-23378

spring-core/src/main/java/org/springframework/core/annotation/AnnotationsScanner.java

@@ -39,6 +39,7 @@
  * {@link AnnotatedElement}.
  *
  * @author Phillip Webb
+ * @author Sam Brannen
  * @since 5.2
  * @see AnnotationsProcessor
  */
@@ -121,7 +122,7 @@ private static <C, R> R processClass(C context, Class<?> source,
 			case DIRECT:
 				return processElement(context, source, processor, classFilter);
 			case INHERITED_ANNOTATIONS:
-				return processClassInheritedAnnotations(context, source, processor, classFilter);
+				return processClassInheritedAnnotations(context, source, searchStrategy, processor, classFilter);
 			case SUPERCLASS:
 				return processClassHierarchy(context, source, processor, classFilter, false, false);
 			case EXHAUSTIVE:
@@ -135,9 +136,9 @@ private static <C, R> R processClass(C context, Class<?> source,
 
 	@Nullable
 	private static <C, R> R processClassInheritedAnnotations(C context, Class<?> source,
-			AnnotationsProcessor<C, R> processor, @Nullable BiPredicate<C, Class<?>> classFilter) {
+			SearchStrategy searchStrategy, AnnotationsProcessor<C, R> processor, @Nullable BiPredicate<C, Class<?>> classFilter) {
 
-		if (isWithoutHierarchy(source)) {
+		if (isWithoutHierarchy(source, searchStrategy)) {
 			return processElement(context, source, processor, classFilter);
 		}
 		Annotation[] relevant = null;
@@ -505,7 +506,7 @@ static boolean isKnownEmpty(AnnotatedElement source, SearchStrategy searchStrate
 		if (hasPlainJavaAnnotationsOnly(source)) {
 			return true;
 		}
-		if (searchStrategy == SearchStrategy.DIRECT || isWithoutHierarchy(source)) {
+		if (searchStrategy == SearchStrategy.DIRECT || isWithoutHierarchy(source, searchStrategy)) {
 			if (source instanceof Method && ((Method) source).isBridge()) {
 				return false;
 			}
@@ -530,19 +531,21 @@ static boolean hasPlainJavaAnnotationsOnly(Class<?> type) {
 		return (type.getName().startsWith("java.") || type == Ordered.class);
 	}
 
-	private static boolean isWithoutHierarchy(AnnotatedElement source) {
+	private static boolean isWithoutHierarchy(AnnotatedElement source, SearchStrategy searchStrategy) {
 		if (source == Object.class) {
 			return true;
 		}
 		if (source instanceof Class) {
 			Class<?> sourceClass = (Class<?>) source;
-			return (sourceClass.getSuperclass() == Object.class &&
+			boolean noSuperTypes = (sourceClass.getSuperclass() == Object.class &&
 					sourceClass.getInterfaces().length == 0);
+			return (searchStrategy == SearchStrategy.TYPE_HIERARCHY_AND_ENCLOSING_CLASSES ? noSuperTypes &&
+					sourceClass.getEnclosingClass() == null : noSuperTypes);
 		}
 		if (source instanceof Method) {
 			Method sourceMethod = (Method) source;
 			return (Modifier.isPrivate(sourceMethod.getModifiers()) ||
-					isWithoutHierarchy(sourceMethod.getDeclaringClass()));
+					isWithoutHierarchy(sourceMethod.getDeclaringClass(), searchStrategy));
 		}
 		return true;
 	}

spring-core/src/test/java/org/springframework/core/annotation/MergedAnnotationsTests.java

@@ -692,6 +692,19 @@ public void streamTypeHierarchyFromClassWithInterface() throws Exception {
 				Transactional.class)).hasSize(1);
 	}
 
+	@Test
+	public void streamTypeHierarchyAndEnclosingClassesFromNonAnnotatedInnerClassWithAnnotatedEnclosingClass() {
+		Stream<Class<?>> classes = MergedAnnotations.from(AnnotatedClass.NonAnnotatedInnerClass.class,
+			SearchStrategy.TYPE_HIERARCHY_AND_ENCLOSING_CLASSES).stream().map(MergedAnnotation::getType);
+		assertThat(classes).containsExactly(Component.class, Indexed.class);
+	}
+
+	@Test
+	public void streamTypeHierarchyAndEnclosingClassesFromNonAnnotatedStaticNestedClassWithAnnotatedEnclosingClass() {
+		Stream<Class<?>> classes = MergedAnnotations.from(AnnotatedClass.NonAnnotatedStaticNestedClass.class,
+			SearchStrategy.TYPE_HIERARCHY_AND_ENCLOSING_CLASSES).stream().map(MergedAnnotation::getType);
+		assertThat(classes).containsExactly(Component.class, Indexed.class);
+	}
 	@Test
 	public void getFromMethodWithMethodAnnotationOnLeaf() throws Exception {
 		Method method = Leaf.class.getMethod("annotatedOnLeaf");
@@ -2112,6 +2125,16 @@ public void asAnnotationAttributesReturnsPopulatedAnnotationAttributes() {
 	static class NonAnnotatedClass {
 	}
 
+	@Component
+	static class AnnotatedClass {
+
+		class NonAnnotatedInnerClass {
+		}
+
+		static class NonAnnotatedStaticNestedClass {
+		}
+	}
+
 	static interface NonAnnotatedInterface {
 	}
 
@@ -2839,6 +2862,7 @@ public interface InterfaceWithGenericAnnotatedMethod<T> {
 	public static class ImplementsInterfaceWithGenericAnnotatedMethod
 			implements InterfaceWithGenericAnnotatedMethod<String> {
 
+		@Override
 		public void foo(String t) {
 		}
 	}
@@ -2852,6 +2876,7 @@ public static abstract class BaseClassWithGenericAnnotatedMethod<T> {
 	public static class ExtendsBaseClassWithGenericAnnotatedMethod
 			extends BaseClassWithGenericAnnotatedMethod<String> {
 
+		@Override
 		public void foo(String t) {
 		}
 	}