Avoid enhancement of configuration class in case of existing instance

Closes gh-25738

Author: jhoeller

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -507,14 +507,18 @@ public void enhanceConfigurationClasses(ConfigurableListableBeanFactory beanFact
 					throw new BeanDefinitionStoreException("Cannot enhance @Configuration bean definition '" +
 							beanName + "' since it is not stored in an AbstractBeanDefinition subclass");
 				}
-				else if (logger.isWarnEnabled() && beanFactory.containsSingleton(beanName)) {
-					logger.warn("Cannot enhance @Configuration bean definition '" + beanName +
-							"' since its singleton instance has been created too early. The typical cause " +
-							"is a non-static @Bean method with a BeanDefinitionRegistryPostProcessor " +
-							"return type: Consider declaring such methods as 'static' and/or marking the " +
-							"containing configuration class as 'proxyBeanMethods=false'.");
+				else if (beanFactory.containsSingleton(beanName)) {
+					if (logger.isWarnEnabled()) {
+						logger.warn("Cannot enhance @Configuration bean definition '" + beanName +
+								"' since its singleton instance has been created too early. The typical cause " +
+								"is a non-static @Bean method with a BeanDefinitionRegistryPostProcessor " +
+								"return type: Consider declaring such methods as 'static' and/or marking the " +
+								"containing configuration class as 'proxyBeanMethods=false'.");
+					}
+				}
+				else {
+					configBeanDefs.put(beanName, abd);
 				}
-				configBeanDefs.put(beanName, abd);
 			}
 		}
 		if (configBeanDefs.isEmpty()) {
@@ -647,9 +651,9 @@ private Map<String, String> buildImportAwareMappings() {
 			}
 			return mappings;
 		}
-
 	}
 
+
 	private static class PropertySourcesAotContribution implements BeanFactoryInitializationAotContribution {
 
 		private static final String ENVIRONMENT_VARIABLE = "environment";
@@ -761,17 +765,18 @@ private CodeBlock handleNull(@Nullable Object value, Supplier<CodeBlock> nonNull
 				return nonNull.get();
 			}
 		}
-
 	}
 
+
 	private static class ConfigurationClassProxyBeanRegistrationCodeFragments extends BeanRegistrationCodeFragmentsDecorator {
 
 		private final RegisteredBean registeredBean;
 
 		private final Class<?> proxyClass;
 
-		public ConfigurationClassProxyBeanRegistrationCodeFragments(BeanRegistrationCodeFragments codeFragments,
-				RegisteredBean registeredBean) {
+		public ConfigurationClassProxyBeanRegistrationCodeFragments(
+				BeanRegistrationCodeFragments codeFragments, RegisteredBean registeredBean) {
+
 			super(codeFragments);
 			this.registeredBean = registeredBean;
 			this.proxyClass = registeredBean.getBeanType().toClass();
@@ -780,6 +785,7 @@ public ConfigurationClassProxyBeanRegistrationCodeFragments(BeanRegistrationCode
 		@Override
 		public CodeBlock generateSetBeanDefinitionPropertiesCode(GenerationContext generationContext,
 				BeanRegistrationCode beanRegistrationCode, RootBeanDefinition beanDefinition, Predicate<String> attributeFilter) {
+
 			CodeBlock.Builder code = CodeBlock.builder();
 			code.add(super.generateSetBeanDefinitionPropertiesCode(generationContext,
 					beanRegistrationCode, beanDefinition, attributeFilter));
@@ -790,8 +796,7 @@ public CodeBlock generateSetBeanDefinitionPropertiesCode(GenerationContext gener
 
 		@Override
 		public CodeBlock generateInstanceSupplierCode(GenerationContext generationContext,
-				BeanRegistrationCode beanRegistrationCode,
-				boolean allowDirectSupplierShortcut) {
+				BeanRegistrationCode beanRegistrationCode, boolean allowDirectSupplierShortcut) {
 
 			Executable executableToUse = proxyExecutable(generationContext.getRuntimeHints(),
 					this.registeredBean.resolveConstructorOrFactoryMethod());
@@ -812,7 +817,6 @@ private Executable proxyExecutable(RuntimeHints runtimeHints, Executable userExe
 			}
 			return userExecutable;
 		}
-
 	}
 
 }