Support ConfigurationClassPostProcessor supplier

Update `SharedMetadataReaderFactoryContextInitializer` to optionally
support a `ConfigurationClassPostProcessor` provided via an instance
`Supplier`.

If the instance supplier is available then we can use that to set the
`MetadataReaderFactory` non-reflectively, instead of using a
`PropertyValue` (and the `BeanWrapper` eventually).

The previous behavior is left as a  fallback and without a change in
Spring Framework will continue to be the default for most applications.

See gh-22858

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/SharedMetadataReaderFactoryContextInitializer.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.autoconfigure;
 
+import java.util.function.Supplier;
+
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanClassLoaderAware;
 import org.springframework.beans.factory.FactoryBean;
@@ -23,6 +25,7 @@ import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.beans.factory.config.RuntimeBeanReference;
+import org.springframework.beans.factory.support.AbstractBeanDefinition;
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
 import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
@@ -53,7 +56,7 @@ class SharedMetadataReaderFactoryContextInitializer
 
 	@Override
 	public void initialize(ConfigurableApplicationContext applicationContext) {
-		applicationContext.addBeanFactoryPostProcessor(new CachingMetadataReaderFactoryPostProcessor());
+		applicationContext.addBeanFactoryPostProcessor(new CachingMetadataReaderFactoryPostProcessor(applicationContext));
 	}
 
 	@Override
@@ -69,6 +72,12 @@ class SharedMetadataReaderFactoryContextInitializer
 	private static class CachingMetadataReaderFactoryPostProcessor
 			implements BeanDefinitionRegistryPostProcessor, PriorityOrdered {
 
+		private ConfigurableApplicationContext context;
+
+		CachingMetadataReaderFactoryPostProcessor(ConfigurableApplicationContext context) {
+			this.context = context;
+		}
+
 		@Override
 		public int getOrder() {
 			// Must happen before the ConfigurationClassPostProcessor is created
@@ -96,12 +105,28 @@ class SharedMetadataReaderFactoryContextInitializer
 			try {
 				BeanDefinition definition = registry
 						.getBeanDefinition(AnnotationConfigUtils.CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME);
+				if (definition instanceof AbstractBeanDefinition) {
+					AbstractBeanDefinition bean = (AbstractBeanDefinition) definition;
+					if (bean.getInstanceSupplier() != null) {
+						Supplier<?> supplier = bean.getInstanceSupplier();
+						bean.setInstanceSupplier(() -> modify(supplier));
+						return;
+					}
+				}
 				definition.getPropertyValues().add("metadataReaderFactory", new RuntimeBeanReference(BEAN_NAME));
 			}
 			catch (NoSuchBeanDefinitionException ex) {
 			}
 		}
 
+		private Object modify(Supplier<?> supplier) {
+			Object object = supplier.get();
+			if (object instanceof ConfigurationClassPostProcessor) {
+				((ConfigurationClassPostProcessor) object).setMetadataReaderFactory(this.context.getBean(BEAN_NAME, MetadataReaderFactory.class));
+			}
+			return object;
+		}
+
 	}
 
 	/**