Merge branch '3.5.x'

The issue had already been fixed in 4.0 as part of the nullability work. As such, this commit doesn't fix anything. It does, however, merge forward a test and makes some stylistic changes to the code so that it's aligned with the same code in 3.5.x and 3.4.x

Author: wilkinsona

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

@@ -472,13 +472,19 @@ private void appendMessageForMatches(StringBuilder reason, Map<String, Collectio
 }
 
 private List<String> getPrimaryBeans(Map<String, @Nullable BeanDefinition> beanDefinitions) {
-return getMatchingBeans(beanDefinitions,
-(beanDefinition) -> beanDefinition != null && beanDefinition.isPrimary());
+return getMatchingBeans(beanDefinitions, this::isPrimary);
+}
+
+private boolean isPrimary(@Nullable BeanDefinition beanDefinition) {
+return (beanDefinition != null) && beanDefinition.isPrimary();
 }
 
 private List<String> getNonFallbackBeans(Map<String, @Nullable BeanDefinition> beanDefinitions) {
-return getMatchingBeans(beanDefinitions,
-Predicate.not((beanDefinition) -> beanDefinition != null && beanDefinition.isFallback()));
+return getMatchingBeans(beanDefinitions, this::isNotFallback);
+}
+
+private boolean isNotFallback(@Nullable BeanDefinition beanDefinition) {
+return (beanDefinition == null) || !beanDefinition.isFallback();
 }
 
 private List<String> getMatchingBeans(Map<String, @Nullable BeanDefinition> beanDefinitions,

core/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 {