Enforce backwards compatibility for null bean in shortcut code path

Closes gh-34929

Author: jhoeller

spring-beans/src/main/java/org/springframework/beans/factory/support/DefaultListableBeanFactory.java

@@ -1679,7 +1679,12 @@ public Object doResolveDependency(DependencyDescriptor descriptor, @Nullable Str
 						if (autowiredBeanNames != null) {
 							autowiredBeanNames.add(dependencyName);
 						}
+						boolean preExisting = containsSingleton(dependencyName);
 						Object dependencyBean = getBean(dependencyName);
+						if (preExisting && dependencyBean instanceof NullBean) {
+							// for backwards compatibility with addCandidateEntry in the regular code path
+							dependencyBean = null;
+						}
 						return resolveInstance(dependencyBean, descriptor, type, dependencyName);
 					}
 				}
@@ -1760,7 +1765,6 @@ private Object resolveInstance(Object candidate, DependencyDescriptor descriptor
 			throw new BeanNotOfRequiredTypeException(name, type, candidate.getClass());
 		}
 		return result;
-
 	}
 
 	@Nullable

spring-beans/src/test/java/org/springframework/beans/factory/annotation/AutowiredAnnotationBeanPostProcessorTests.java

@@ -960,11 +960,34 @@ void constructorResourceInjectionWithMultipleCandidates() {
 	@Test
 	void constructorResourceInjectionWithNoCandidatesAndNoFallback() {
 		bf.registerBeanDefinition("annotatedBean", new RootBeanDefinition(ConstructorWithoutFallbackBean.class));
+
 		assertThatExceptionOfType(UnsatisfiedDependencyException.class)
 				.isThrownBy(() -> bf.getBean("annotatedBean"))
 				.satisfies(methodParameterDeclaredOn(ConstructorWithoutFallbackBean.class));
 	}
 
+	@Test
+	void constructorResourceInjectionWithCandidateAndNoFallback() {
+		bf.registerBeanDefinition("annotatedBean", new RootBeanDefinition(ConstructorWithoutFallbackBean.class));
+		RootBeanDefinition tb = new RootBeanDefinition(NullFactoryMethods.class);
+		tb.setFactoryMethodName("createTestBean");
+		bf.registerBeanDefinition("testBean", tb);
+
+		bf.getBean("testBean");
+		assertThat(bf.getBean("annotatedBean", ConstructorWithoutFallbackBean.class).getTestBean3()).isNull();
+	}
+
+	@Test
+	void constructorResourceInjectionWithNameMatchingCandidateAndNoFallback() {
+		bf.registerBeanDefinition("annotatedBean", new RootBeanDefinition(ConstructorWithoutFallbackBean.class));
+		RootBeanDefinition tb = new RootBeanDefinition(NullFactoryMethods.class);
+		tb.setFactoryMethodName("createTestBean");
+		bf.registerBeanDefinition("testBean3", tb);
+
+		bf.getBean("testBean3");
+		assertThat(bf.getBean("annotatedBean", ConstructorWithoutFallbackBean.class).getTestBean3()).isNull();
+	}
+
 	@Test
 	void constructorResourceInjectionWithSometimesNullBeanEarly() {
 		RootBeanDefinition bd = new RootBeanDefinition(ConstructorWithNullableArgument.class);
@@ -1193,6 +1216,7 @@ void singleConstructorInjectionWithEmptyCollectionAsNull() {
 	@Test
 	void singleConstructorInjectionWithMissingDependency() {
 		bf.registerBeanDefinition("annotatedBean", new RootBeanDefinition(SingleConstructorOptionalCollectionBean.class));
+
 		assertThatExceptionOfType(UnsatisfiedDependencyException.class)
 				.isThrownBy(() -> bf.getBean("annotatedBean"));
 	}
@@ -1203,6 +1227,7 @@ void singleConstructorInjectionWithNullDependency() {
 		RootBeanDefinition tb = new RootBeanDefinition(NullFactoryMethods.class);
 		tb.setFactoryMethodName("createTestBean");
 		bf.registerBeanDefinition("testBean", tb);
+
 		assertThatExceptionOfType(UnsatisfiedDependencyException.class)
 				.isThrownBy(() -> bf.getBean("annotatedBean"));
 	}
@@ -3060,7 +3085,6 @@ public static class ConstructorWithoutFallbackBean {
 
 		protected ITestBean testBean3;
 
-		@Autowired(required = false)
 		public ConstructorWithoutFallbackBean(ITestBean testBean3) {
 			this.testBean3 = testBean3;
 		}
@@ -3075,7 +3099,6 @@ public static class ConstructorWithNullableArgument {
 
 		protected ITestBean testBean3;
 
-		@Autowired(required = false)
 		public ConstructorWithNullableArgument(@Nullable ITestBean testBean3) {
 			this.testBean3 = testBean3;
 		}