Exclude ReactorAutoConfiguration from global lazy init

This commits registers LazyInitializationExcludeFilter to exclude
`ReactorAutoConfiguration` from global lazy init when
'spring.reactor.context-propagation' is set to 'auto'.

Signed-off-by: Dmytro Nosan <dimanosan@gmail.com>

Author: nosan

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -18,10 +18,13 @@
 
 import reactor.core.publisher.Hooks;
 
+import org.springframework.boot.LazyInitializationExcludeFilter;
 import org.springframework.boot.autoconfigure.AutoConfiguration;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.context.annotation.Bean;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for Reactor.
@@ -31,6 +34,7 @@
  */
 @AutoConfiguration
 @ConditionalOnClass(Hooks.class)
+@ConditionalOnProperty(name = "spring.reactor.context-propagation", havingValue = "auto")
 @EnableConfigurationProperties(ReactorProperties.class)
 public class ReactorAutoConfiguration {
 
@@ -40,4 +44,9 @@ public class ReactorAutoConfiguration {
 		}
 	}
 
+	@Bean
+	static LazyInitializationExcludeFilter reactorLazyInitializationExcludeFilter() {
+		return LazyInitializationExcludeFilter.forBeanTypes(ReactorAutoConfiguration.class);
+	}
+
 }

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/reactor/ReactorAutoConfigurationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2025 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.
@@ -28,6 +28,8 @@
 import reactor.core.publisher.Mono;
 import reactor.util.context.Context;
 
+import org.springframework.boot.LazyInitializationBeanFactoryPostProcessor;
+import org.springframework.boot.LazyInitializationExcludeFilter;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
 
@@ -75,6 +77,7 @@ void shouldNotConfigurePropagationByDefault() {
 				.contextWrite(Context.of(THREADLOCAL_KEY, "updated"))
 				.block();
 			assertThat(threadLocalValue.get()).isEqualTo("initial");
+			assertThat(applicationContext).doesNotHaveBean(LazyInitializationExcludeFilter.class);
 		});
 	}
 
@@ -90,4 +93,19 @@ void shouldConfigurePropagationIfSetToAuto() {
 		});
 	}
 
+	@Test
+	void shouldConfigurePropagationIfSetToAutoAndLazyInitializationIsEnabled() {
+		AtomicReference<String> threadLocalValue = new AtomicReference<>();
+		this.contextRunner.withPropertyValues("spring.reactor.context-propagation=AUTO")
+			.withInitializer((applicationContext) -> applicationContext
+				.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor()))
+			.run((applicationContext) -> {
+				Mono.just("test")
+					.doOnNext((element) -> threadLocalValue.set(THREADLOCAL_VALUE.get()))
+					.contextWrite(Context.of(THREADLOCAL_KEY, "updated"))
+					.block();
+				assertThat(threadLocalValue.get()).isEqualTo("updated");
+			});
+	}
+
 }