Merge branch '3.4.x' into 3.5.x

Closes gh-48123

Author: wilkinsona

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

@@ -461,11 +461,19 @@ private Map<String, BeanDefinition> getBeanDefinitions(ConfigurableListableBeanF
 }
 
 private List<String> getPrimaryBeans(Map<String, BeanDefinition> beanDefinitions) {
-return getMatchingBeans(beanDefinitions, BeanDefinition::isPrimary);
+return getMatchingBeans(beanDefinitions, this::isPrimary);
+}
+
+private boolean isPrimary(BeanDefinition beanDefinition) {
+return (beanDefinition != null) && beanDefinition.isPrimary();
 }
 
 private List<String> getNonFallbackBeans(Map<String, BeanDefinition> beanDefinitions) {
-return getMatchingBeans(beanDefinitions, Predicate.not(BeanDefinition::isFallback));
+return getMatchingBeans(beanDefinitions, this::isNotFallback);
+}
+
+private boolean isNotFallback(BeanDefinition beanDefinition) {
+return (beanDefinition == null) || !beanDefinition.isFallback();
 }
 
 private List<String> getMatchingBeans(Map<String, BeanDefinition> beanDefinitions, Predicate<BeanDefinition> test) {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/condition/ConditionalOnSingleCandidateTests.java

@@ -195,6 +195,16 @@ void singleCandidateMultipleCandidatesOneDefaultCandidate() {
 });
 }
 
+@Test
+void singleCandidateDoesNotMatchWhenMultipleRegisteredAsSingletonCandidates() {
+this.contextRunner.withInitializer((context) -> {
+context.getBeanFactory().registerSingleton("alpha", "alpha");
+context.getBeanFactory().registerSingleton("bravo", "bravo");
+})
+.withUserConfiguration(OnBeanSingleCandidateConfiguration.class)
+.run((context) -> assertThat(context).doesNotHaveBean("consumer"));
+}
+
 @Configuration(proxyBeanMethods = false)
 @ConditionalOnSingleCandidate(String.class)
 static class OnBeanSingleCandidateConfiguration {