Spring @Configuration classes with Kotlin in native-image are broken

This happens only in a native image. I have this configuration:

@Configuration(proxyBeanMethods = false)
class MyConfiguration {
    @Bean
    fun a(): A {
        return A()
    }

    private fun b(): B {
        return B()
    }
}

class A

class B

Running the application works. Now rename the a() method to z_a() and it breaks:

java.lang.ClassNotFoundException: com.example.demo.B
        at java.base@17.0.5/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:52) ~[demo:na]
        at java.base@17.0.5/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188) ~[na:na]
        at java.base@17.0.5/java.lang.ClassLoader.loadClass(ClassLoader.java:132) ~[demo:na]
        at kotlin.reflect.jvm.internal.KDeclarationContainerImpl.parseType(KDeclarationContainerImpl.kt:273) ~[demo:1.7.21-release-272(1.7.21)]
        at kotlin.reflect.jvm.internal.KDeclarationContainerImpl.loadReturnType(KDeclarationContainerImpl.kt:288) ~[demo:1.7.21-release-272(1.7.21)]
        at kotlin.reflect.jvm.internal.KDeclarationContainerImpl.findMethodBySignature(KDeclarationContainerImpl.kt:198) ~[demo:1.7.21-release-272(1.7.21)]
        at kotlin.reflect.jvm.internal.KFunctionImpl$caller$2.invoke(KFunctionImpl.kt:68) ~[na:na]
        at kotlin.reflect.jvm.internal.KFunctionImpl$caller$2.invoke(KFunctionImpl.kt:61) ~[na:na]
        at kotlin.reflect.jvm.internal.ReflectProperties$LazyVal.invoke(ReflectProperties.java:63) ~[na:na]
        at kotlin.reflect.jvm.internal.ReflectProperties$Val.getValue(ReflectProperties.java:32) ~[demo:1.7.21-release-272(1.7.21)]
        at kotlin.reflect.jvm.internal.KFunctionImpl.getCaller(KFunctionImpl.kt:61) ~[na:na]
        at kotlin.reflect.jvm.ReflectJvmMapping.getJavaMethod(ReflectJvmMapping.kt:63) ~[na:na]
        at kotlin.reflect.jvm.ReflectJvmMapping.getKotlinFunction(ReflectJvmMapping.kt:136) ~[na:na]
        at org.springframework.core.MethodParameter$KotlinDelegate.getGenericReturnType(MethodParameter.java:914) ~[na:na]
        at org.springframework.core.MethodParameter.getGenericParameterType(MethodParameter.java:510) ~[na:na]
        at org.springframework.core.SerializableTypeWrapper$MethodParameterTypeProvider.getType(SerializableTypeWrapper.java:291) ~[na:na]
        at org.springframework.core.SerializableTypeWrapper.forTypeProvider(SerializableTypeWrapper.java:107) ~[na:na]
        at org.springframework.core.ResolvableType.forType(ResolvableType.java:1413) ~[demo:6.0.2]
        at org.springframework.core.ResolvableType.forMethodParameter(ResolvableType.java:1334) ~[demo:6.0.2]
        at org.springframework.core.ResolvableType.forMethodParameter(ResolvableType.java:1316) ~[demo:6.0.2]
        at org.springframework.core.ResolvableType.forMethodParameter(ResolvableType.java:1283) ~[demo:6.0.2]
        at org.springframework.core.ResolvableType.forMethodReturnType(ResolvableType.java:1228) ~[demo:6.0.2]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getTypeForFactoryMethod(AbstractAutowireCapableBeanFactory.java:814) ~[demo:6.0.2]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineTargetType(AbstractAutowireCapableBeanFactory.java:681) ~[demo:6.0.2]
Exception in thread "main" java.lang.reflect.UndeclaredThrowableException
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:652) ~[demo:6.0.2]
        at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1632) ~[demo:6.0.2]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.doGetBeanNamesForType(DefaultListableBeanFactory.java:559) ~[demo:6.0.2]
        at org.springframework.util.ReflectionUtils.rethrowRuntimeException(ReflectionUtils.java:147)
        at org.springframework.boot.SpringApplication.handleRunFailure(SpringApplication.java:794)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:321)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1302)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1291)
        at com.example.demo.DemoApplicationKt.main(DemoApplication.kt:13)
Caused by: java.lang.ClassNotFoundException: com.example.demo.B
        at java.base@17.0.5/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:52)
        at java.base@17.0.5/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
        at java.base@17.0.5/java.lang.ClassLoader.loadClass(ClassLoader.java:132)
        at kotlin.reflect.jvm.internal.KDeclarationContainerImpl.parseType(KDeclarationContainerImpl.kt:273)
        at kotlin.reflect.jvm.internal.KDeclarationContainerImpl.loadReturnType(KDeclarationContainerImpl.kt:288)
        at kotlin.reflect.jvm.internal.KDeclarationContainerImpl.findMethodBySignature(KDeclarationContainerImpl.kt:198)
        at kotlin.reflect.jvm.internal.KFunctionImpl$caller$2.invoke(KFunctionImpl.kt:68)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanNamesForType(DefaultListableBeanFactory.java:531) ~[demo:6.0.2]
        at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:106) ~[na:na]
        at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:745) ~[demo:6.0.2]
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:565) ~[demo:6.0.2]
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:730) ~[demo:3.0.0]
        at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:432) ~[demo:3.0.0]
        at kotlin.reflect.jvm.internal.KFunctionImpl$caller$2.invoke(KFunctionImpl.kt:61)
        at kotlin.reflect.jvm.internal.ReflectProperties$LazyVal.invoke(ReflectProperties.java:63)
        at kotlin.reflect.jvm.internal.ReflectProperties$Val.getValue(ReflectProperties.java:32)
        at kotlin.reflect.jvm.internal.KFunctionImpl.getCaller(KFunctionImpl.kt:61)
        at kotlin.reflect.jvm.ReflectJvmMapping.getJavaMethod(ReflectJvmMapping.kt:63)
        at kotlin.reflect.jvm.ReflectJvmMapping.getKotlinFunction(ReflectJvmMapping.kt:136)
        at org.springframework.core.MethodParameter$KotlinDelegate.getGenericReturnType(MethodParameter.java:914)
        at org.springframework.core.MethodParameter.getGenericParameterType(MethodParameter.java:510)
        at org.springframework.core.SerializableTypeWrapper$MethodParameterTypeProvider.getType(SerializableTypeWrapper.java:291)
        at org.springframework.core.SerializableTypeWrapper.forTypeProvider(SerializableTypeWrapper.java:107)
        at org.springframework.core.ResolvableType.forType(ResolvableType.java:1413)
        at org.springframework.core.ResolvableType.forMethodParameter(ResolvableType.java:1334)
        at org.springframework.core.ResolvableType.forMethodParameter(ResolvableType.java:1316)
        at org.springframework.core.ResolvableType.forMethodParameter(ResolvableType.java:1283)
        at org.springframework.core.ResolvableType.forMethodReturnType(ResolvableType.java:1228)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getTypeForFactoryMethod(AbstractAutowireCapableBeanFactory.java:814)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineTargetType(AbstractAutowireCapableBeanFactory.java:681)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:652)
        at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1632)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.doGetBeanNamesForType(DefaultListableBeanFactory.java:559)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanNamesForType(DefaultListableBeanFactory.java:531)
        at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:106)
        at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:745)
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:565)
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:730)
        at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:432)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:308)
        ... 3 more
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:308) ~[demo:3.0.0]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1302) ~[demo:3.0.0]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1291) ~[demo:3.0.0]
        at com.example.demo.DemoApplicationKt.main(DemoApplication.kt:13) ~[demo:na]

2022-12-08T17:30:40.001+01:00  WARN 179946 --- [           main] o.s.boot.SpringApplication               : Unable to close ApplicationContext

java.lang.ClassNotFoundException: com.example.demo.B
        at java.base@17.0.5/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:52) ~[demo:na]
        at java.base@17.0.5/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188) ~[na:na]
        at java.base@17.0.5/java.lang.ClassLoader.loadClass(ClassLoader.java:132) ~[demo:na]
        at kotlin.reflect.jvm.internal.KDeclarationContainerImpl.parseType(KDeclarationContainerImpl.kt:273) ~[demo:1.7.21-release-272(1.7.21)]
        at kotlin.reflect.jvm.internal.KDeclarationContainerImpl.loadReturnType(KDeclarationContainerImpl.kt:288) ~[demo:1.7.21-release-272(1.7.21)]
        at kotlin.reflect.jvm.internal.KDeclarationContainerImpl.findMethodBySignature(KDeclarationContainerImpl.kt:198) ~[demo:1.7.21-release-272(1.7.21)]
        at kotlin.reflect.jvm.internal.KFunctionImpl$caller$2.invoke(KFunctionImpl.kt:68) ~[na:na]
        at kotlin.reflect.jvm.internal.KFunctionImpl$caller$2.invoke(KFunctionImpl.kt:61) ~[na:na]
        at kotlin.reflect.jvm.internal.ReflectProperties$LazyVal.invoke(ReflectProperties.java:63) ~[na:na]
        at kotlin.reflect.jvm.internal.ReflectProperties$Val.getValue(ReflectProperties.java:32) ~[demo:1.7.21-release-272(1.7.21)]
        at kotlin.reflect.jvm.internal.KFunctionImpl.getCaller(KFunctionImpl.kt:61) ~[na:na]
        at kotlin.reflect.jvm.ReflectJvmMapping.getJavaMethod(ReflectJvmMapping.kt:63) ~[na:na]
        at kotlin.reflect.jvm.ReflectJvmMapping.getKotlinFunction(ReflectJvmMapping.kt:136) ~[na:na]
        at org.springframework.core.MethodParameter$KotlinDelegate.getGenericReturnType(MethodParameter.java:914) ~[na:na]
        at org.springframework.core.MethodParameter.getGenericParameterType(MethodParameter.java:510) ~[na:na]
        at org.springframework.core.SerializableTypeWrapper$MethodParameterTypeProvider.getType(SerializableTypeWrapper.java:291) ~[na:na]
        at org.springframework.core.SerializableTypeWrapper.forTypeProvider(SerializableTypeWrapper.java:107) ~[na:na]
        at org.springframework.core.ResolvableType.forType(ResolvableType.java:1413) ~[demo:6.0.2]
        at org.springframework.core.ResolvableType.forMethodParameter(ResolvableType.java:1334) ~[demo:6.0.2]
        at org.springframework.core.ResolvableType.forMethodParameter(ResolvableType.java:1316) ~[demo:6.0.2]
        at org.springframework.core.ResolvableType.forMethodParameter(ResolvableType.java:1283) ~[demo:6.0.2]
        at org.springframework.core.ResolvableType.forMethodReturnType(ResolvableType.java:1228) ~[demo:6.0.2]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getTypeForFactoryMethod(AbstractAutowireCapableBeanFactory.java:814) ~[demo:6.0.2]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.determineTargetType(AbstractAutowireCapableBeanFactory.java:681) ~[demo:6.0.2]
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.predictBeanType(AbstractAutowireCapableBeanFactory.java:652) ~[demo:6.0.2]
        at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:1632) ~[demo:6.0.2]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.doGetBeanNamesForType(DefaultListableBeanFactory.java:559) ~[demo:6.0.2]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanNamesForType(DefaultListableBeanFactory.java:531) ~[demo:6.0.2]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeansOfType(DefaultListableBeanFactory.java:658) ~[demo:6.0.2]
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeansOfType(DefaultListableBeanFactory.java:650) ~[demo:6.0.2]
        at org.springframework.context.support.AbstractApplicationContext.getBeansOfType(AbstractApplicationContext.java:1276) ~[demo:6.0.2]
        at org.springframework.boot.SpringApplication.getExitCodeFromMappedException(SpringApplication.java:863) ~[demo:3.0.0]
        at org.springframework.boot.SpringApplication.getExitCodeFromException(SpringApplication.java:851) ~[demo:3.0.0]
        at org.springframework.boot.SpringApplication.handleExitCode(SpringApplication.java:838) ~[demo:3.0.0]
        at org.springframework.boot.SpringApplication.handleRunFailure(SpringApplication.java:778) ~[demo:3.0.0]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:321) ~[demo:3.0.0]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1302) ~[demo:3.0.0]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1291) ~[demo:3.0.0]
        at com.example.demo.DemoApplicationKt.main(DemoApplication.kt:13) ~[demo:na]

Demo project here: demo.zip

I debugged that to a behaviour in Kotlin reflection. Essentially you need reflection metadata for ALL methods (not only for the @Bean methods like it's at the moment) if you use ResolvableType.forMethodReturnType(method). It depends on the iteration order of the methods. You can read more here: https://github.com/mhalbritter/kotlin-graalvm-reflection

Comment From: sdeleuze

Confirmed, I have bring this behavior to the attention of the Kotlin team and will share their feedback here. Worst case scenario, I guess we could configure introspect medadata for all functions of Kotlin classes.

Comment From: sdeleuze

Feedback from Kotlin team:

The implementation can be optimized somewhat, but in the worst case we still have to iterate over all methods in a class, because the rules of correspondence between KFunction <-> java.lang.reflect.Method are not trivial and even their names don't match sometimes (e.g. because of @JvmName, default parameters, inline classes, etc).

So let's configure introspection on all functions for Kotlin classes.