Check for package-visible constructor in case of ClassLoader mismatch

Closes gh-34950

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

@@ -16,6 +16,7 @@
 
 package org.springframework.context.annotation;
 
+import java.lang.reflect.Constructor;
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
@@ -139,14 +140,20 @@ class ConfigurationClassEnhancer {
 	}
 
 	/**
-	 * Checks whether the given config class relies on package visibility,
+	 * Checks whether the given config class relies on package visibility, either for
-	 * either for the class itself or for any of its {@code @Bean} methods.
+	 * the class and any of its constructors 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 (Constructor<?> ctor : configSuperClass.getDeclaredConstructors()) {
+			mod = ctor.getModifiers();
+			if (!Modifier.isPublic(mod) && !Modifier.isProtected(mod)) {
+				return true;
+			}
+		}
 		for (Method method : ReflectionUtils.getDeclaredMethods(configSuperClass)) {
 			if (BeanAnnotationHelper.isBeanAnnotated(method)) {
 				mod = method.getModifiers();

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

@@ -104,6 +104,31 @@ class ConfigurationClassEnhancerTests {
 		assertThat(enhancedClass.getClassLoader()).isEqualTo(classLoader.getParent());
 	}
 
+	@Test
+	void withNonPublicConstructor() {
+		ConfigurationClassEnhancer configurationClassEnhancer = new ConfigurationClassEnhancer();
+
+		ClassLoader classLoader = new URLClassLoader(new URL[0], getClass().getClassLoader());
+		Class<?> enhancedClass = configurationClassEnhancer.enhance(MyConfigWithNonPublicConstructor.class, classLoader);
+		assertThat(MyConfigWithNonPublicConstructor.class).isAssignableFrom(enhancedClass);
+		assertThat(enhancedClass.getClassLoader()).isEqualTo(classLoader.getParent());
+
+		classLoader = new OverridingClassLoader(getClass().getClassLoader());
+		enhancedClass = configurationClassEnhancer.enhance(MyConfigWithNonPublicConstructor.class, classLoader);
+		assertThat(MyConfigWithNonPublicConstructor.class).isAssignableFrom(enhancedClass);
+		assertThat(enhancedClass.getClassLoader()).isEqualTo(classLoader.getParent());
+
+		classLoader = new CustomSmartClassLoader(getClass().getClassLoader());
+		enhancedClass = configurationClassEnhancer.enhance(MyConfigWithNonPublicConstructor.class, classLoader);
+		assertThat(MyConfigWithNonPublicConstructor.class).isAssignableFrom(enhancedClass);
+		assertThat(enhancedClass.getClassLoader()).isEqualTo(classLoader.getParent());
+
+		classLoader = new BasicSmartClassLoader(getClass().getClassLoader());
+		enhancedClass = configurationClassEnhancer.enhance(MyConfigWithNonPublicConstructor.class, classLoader);
+		assertThat(MyConfigWithNonPublicConstructor.class).isAssignableFrom(enhancedClass);
+		assertThat(enhancedClass.getClassLoader()).isEqualTo(classLoader.getParent());
+	}
+
 	@Test
 	void withNonPublicMethod() {
 		ConfigurationClassEnhancer configurationClassEnhancer = new ConfigurationClassEnhancer();
@@ -160,6 +185,19 @@ class ConfigurationClassEnhancerTests {
 	}
 
 
+	@Configuration
+	public static class MyConfigWithNonPublicConstructor {
+
+		MyConfigWithNonPublicConstructor() {
+		}
+
+		@Bean
+		public String myBean() {
+			return "bean";
+		}
+	}
+
+
 	@Configuration
 	public static class MyConfigWithNonPublicMethod {