Explicitly use original ClassLoader in case of package visibility

Closes gh-34684

Author: jhoeller

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassEnhancer.java

@@ -116,6 +116,12 @@ public Class<?> enhance(Class<?> configClass, @Nullable ClassLoader classLoader)
 			boolean classLoaderMismatch = (classLoader != null && classLoader != configClass.getClassLoader());
 			if (classLoaderMismatch && classLoader instanceof SmartClassLoader smartClassLoader) {
 				classLoader = smartClassLoader.getOriginalClassLoader();
+				classLoaderMismatch = (classLoader != configClass.getClassLoader());
+			}
+			// Use original ClassLoader if config class relies on package visibility
+			if (classLoaderMismatch && reliesOnPackageVisibility(configClass)) {
+				classLoader = configClass.getClassLoader();
+				classLoaderMismatch = false;
 			}
 			Enhancer enhancer = newEnhancer(configClass, classLoader);
 			Class<?> enhancedClass = createClass(enhancer, classLoaderMismatch);
@@ -132,6 +138,26 @@ public Class<?> enhance(Class<?> configClass, @Nullable ClassLoader classLoader)
 		}
 	}
 
+	/**
+	 * Checks whether the given config class relies on package visibility,
+	 * either for the class itself or for any of its {@code @Bean} methods.
+	 */
+	private boolean reliesOnPackageVisibility(Class<?> configSuperClass) {
+		int mod = configSuperClass.getModifiers();
+		if (!Modifier.isPublic(mod) && !Modifier.isProtected(mod)) {
+			return true;
+		}
+		for (Method method : ReflectionUtils.getDeclaredMethods(configSuperClass)) {
+			if (BeanAnnotationHelper.isBeanAnnotated(method)) {
+				mod = method.getModifiers();
+				if (!Modifier.isPublic(mod) && !Modifier.isProtected(mod)) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
 	/**
 	 * Creates a new CGLIB {@link Enhancer} instance.
 	 */

spring-context/src/test/java/org/springframework/context/annotation/ConfigurationClassEnhancerTests.java

@@ -111,7 +111,7 @@ void withNonPublicMethod() {
 		ClassLoader classLoader = new URLClassLoader(new URL[0], getClass().getClassLoader());
 		Class<?> enhancedClass = configurationClassEnhancer.enhance(MyConfigWithNonPublicMethod.class, classLoader);
 		assertThat(MyConfigWithNonPublicMethod.class).isAssignableFrom(enhancedClass);
-		assertThat(enhancedClass.getClassLoader()).isEqualTo(classLoader);
+		assertThat(enhancedClass.getClassLoader()).isEqualTo(classLoader.getParent());
 
 		classLoader = new OverridingClassLoader(getClass().getClassLoader());
 		enhancedClass = configurationClassEnhancer.enhance(MyConfigWithNonPublicMethod.class, classLoader);
@@ -126,7 +126,7 @@ void withNonPublicMethod() {
 		classLoader = new BasicSmartClassLoader(getClass().getClassLoader());
 		enhancedClass = configurationClassEnhancer.enhance(MyConfigWithNonPublicMethod.class, classLoader);
 		assertThat(MyConfigWithNonPublicMethod.class).isAssignableFrom(enhancedClass);
-		assertThat(enhancedClass.getClassLoader()).isEqualTo(classLoader);
+		assertThat(enhancedClass.getClassLoader()).isEqualTo(classLoader.getParent());
 	}