Improve condition message produced by @ConditionalOnSingleCandidate

Closes gh-30073

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2022 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.
@@ -130,13 +130,25 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 			if (!matchResult.isAllMatched()) {
 				return ConditionOutcome.noMatch(spec.message().didNotFind("any beans").atAll());
 			}
-			else if (!hasSingleAutowireCandidate(context.getBeanFactory(), matchResult.getNamesOfAllMatches(),
-					spec.getStrategy() == SearchStrategy.ALL)) {
-				return ConditionOutcome.noMatch(spec.message().didNotFind("a primary bean from beans")
-						.items(Style.QUOTE, matchResult.getNamesOfAllMatches()));
+			Set<String> allBeans = matchResult.getNamesOfAllMatches();
+			if (allBeans.size() == 1) {
+				matchMessage = spec.message(matchMessage).found("a single bean").items(Style.QUOTE, allBeans);
+			}
+			else {
+				List<String> primaryBeans = getPrimaryBeans(context.getBeanFactory(), allBeans,
+						spec.getStrategy() == SearchStrategy.ALL);
+				if (primaryBeans.isEmpty()) {
+					return ConditionOutcome.noMatch(
+							spec.message().didNotFind("a primary bean from beans").items(Style.QUOTE, allBeans));
+				}
+				if (primaryBeans.size() > 1) {
+					return ConditionOutcome
+							.noMatch(spec.message().found("multiple primary beans").items(Style.QUOTE, primaryBeans));
+				}
+				matchMessage = spec.message(matchMessage)
+						.found("a single primary bean '" + primaryBeans.get(0) + "' from beans")
+						.items(Style.QUOTE, allBeans);
 			}
-			matchMessage = spec.message(matchMessage).found("a primary bean from beans").items(Style.QUOTE,
-					matchResult.getNamesOfAllMatches());
 		}
 		if (metadata.isAnnotated(ConditionalOnMissingBean.class.getName())) {
 			Spec<ConditionalOnMissingBean> spec = new Spec<>(context, metadata, annotations,
@@ -341,11 +353,6 @@ class OnBeanCondition extends FilteringSpringBootCondition implements Configurat
 		}
 	}
 
-	private boolean hasSingleAutowireCandidate(ConfigurableListableBeanFactory beanFactory, Set<String> beanNames,
-			boolean considerHierarchy) {
-		return (beanNames.size() == 1 || getPrimaryBeans(beanFactory, beanNames, considerHierarchy).size() == 1);
-	}
-
 	private List<String> getPrimaryBeans(ConfigurableListableBeanFactory beanFactory, Set<String> beanNames,
 			boolean considerHierarchy) {
 		List<String> primaryBeans = new ArrayList<>();