Do not validate value object bean definion when singleton present

Prior to this commit constructor bound configuration properties could
not be mocked because it would fail validation from
ConfigurationPropertiesBeanDefinitionValidator. The MockitoPostProcessor
registers the mocked bean as a singleton and validation can be skipped if a
singleton for the type is found in the bean factory.

Fixes gh-18652

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/ConfigurationPropertiesBeanDefinitionValidator.java

@@ -40,13 +40,17 @@ class ConfigurationPropertiesBeanDefinitionValidator implements BeanFactoryPostP
 	@Override
 	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
 		for (String beanName : beanFactory.getBeanDefinitionNames()) {
-			BeanDefinition definition = beanFactory.getBeanDefinition(beanName);
-			if (!(definition instanceof ConfigurationPropertiesValueObjectBeanDefinition)) {
+			if (!(beanFactory.containsSingleton(beanName) || isValueObjectBeanDefinition(beanFactory, beanName))) {
 				validate(beanFactory, beanName);
 			}
 		}
 	}
 
+	private boolean isValueObjectBeanDefinition(ConfigurableListableBeanFactory beanFactory, String beanName) {
+		BeanDefinition definition = beanFactory.getBeanDefinition(beanName);
+		return (definition instanceof ConfigurationPropertiesValueObjectBeanDefinition);
+	}
+
 	@Override
 	public int getOrder() {
 		return Ordered.LOWEST_PRECEDENCE;

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/ConfigurationPropertiesTests.java

@@ -44,8 +44,11 @@ import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.beans.factory.support.AbstractBeanDefinition;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
 import org.springframework.beans.factory.support.GenericBeanDefinition;
+import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.boot.context.properties.bind.BindException;
 import org.springframework.boot.context.properties.bind.DefaultValue;
 import org.springframework.boot.context.properties.bind.validation.BindValidationException;
@@ -895,6 +898,15 @@ class ConfigurationPropertiesTests {
 		assertThat(bean.getNested().getAge()).isEqualTo(10);
 	}
 
+	@Test // gh-18652
+	void loadWhenBeanFactoryContainsSingletonForConstructorBindingTypeShouldNotFail() {
+		ConfigurableListableBeanFactory beanFactory = this.context.getBeanFactory();
+		((BeanDefinitionRegistry) beanFactory).registerBeanDefinition("test",
+				new RootBeanDefinition(ConstructorParameterProperties.class));
+		beanFactory.registerSingleton("test", new ConstructorParameterProperties("bar", 5));
+		load(TestConfiguration.class);
+	}
+
 	private AnnotationConfigApplicationContext load(Class<?> configuration, String... inlinedProperties) {
 		return load(new Class<?>[] { configuration }, inlinedProperties);
 	}
@@ -921,6 +933,12 @@ class ConfigurationPropertiesTests {
 		this.context = new AnnotationConfigApplicationContext();
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@EnableConfigurationProperties
+	static class TestConfiguration {
+
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	@EnableConfigurationProperties(BasicProperties.class)
 	static class BasicConfiguration {

spring-boot-project/spring-boot/src/test/kotlin/org/springframework/boot/context/properties/KotlinConfigurationPropertiesTests.kt

@@ -0,0 +1,40 @@
+package org.springframework.boot.context.properties
+
+import org.junit.jupiter.api.Test
+import org.springframework.beans.factory.support.BeanDefinitionRegistry
+import org.springframework.beans.factory.support.RootBeanDefinition
+import org.springframework.context.annotation.AnnotationConfigApplicationContext
+import org.springframework.context.annotation.Configuration
+
+/**
+ * Tests for {@link ConfigurationProperties @ConfigurationProperties}-annotated beans.
+ *
+ * @author Madhura Bhave
+ */
+class KotlinConfigurationPropertiesTests {
+
+	private var context = AnnotationConfigApplicationContext()
+
+	@Test //gh-18652
+	fun `type with constructor binding and existing singleton should not fail`() {
+		val beanFactory = this.context.beanFactory
+		(beanFactory as BeanDefinitionRegistry).registerBeanDefinition("foo",
+				RootBeanDefinition(BingProperties::class.java))
+		beanFactory.registerSingleton("foo", BingProperties(""))
+		this.context.register(TestConfig::class.java)
+		this.context.refresh();
+	}
+
+	@ConfigurationProperties(prefix = "foo")
+	@ConstructorBinding
+	class BingProperties(@Suppress("UNUSED_PARAMETER") bar: String) {
+
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	@EnableConfigurationProperties
+	internal open class TestConfig {
+
+	}
+
+}