SpringBoot DynamicPropertySource doesn't correctly work with array properties

So, I have properties class

@Validated
@Data
@ConfigurationProperties("test-bug")
public class Properties {

    private List<Nested> nesteds;

    @Data
    public static class Nested {

        @NotBlank
        private String foo;

        @NotBlank
        private String bar;
    }
}

apllication-test.yml in test/resources folder

test-bug:
  nesteds:
    - foo: aaa

and test class

@ActiveProfiles("test") 
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
class TestAppTest {

    @DynamicPropertySource
    public static void init(DynamicPropertyRegistry registry) {

        registry.add("test-bug.nesteds[0].bar", () -> "bbb");
    }

    @Test
    void emptyTest() {

    }
}

After run test in Intellij Idea, i got the error

java.lang.IllegalStateException: Failed to load ApplicationContext

    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:132)
    at org.springframework.test.context.support.DefaultTestContext.getApplicationContext(DefaultTestContext.java:124)
    at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:118)
    at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:83)
    at org.springframework.boot.test.autoconfigure.SpringBootDependencyInjectionTestExecutionListener.prepareTestInstance(SpringBootDependencyInjectionTestExecutionListener.java:43)
    at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:244)
    at org.springframework.test.context.junit.jupiter.SpringExtension.postProcessTestInstance(SpringExtension.java:138)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$invokeTestInstancePostProcessors$6(ClassBasedTestDescriptor.java:350)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.executeAndMaskThrowable(ClassBasedTestDescriptor.java:355)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$invokeTestInstancePostProcessors$7(ClassBasedTestDescriptor.java:350)
    at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195)
    at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:177)
    at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1654)
    at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
    at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
    at java.base/java.util.stream.StreamSpliterators$WrappingSpliterator.forEachRemaining(StreamSpliterators.java:312)
    at java.base/java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:735)
    at java.base/java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:734)
    at java.base/java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:658)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.invokeTestInstancePostProcessors(ClassBasedTestDescriptor.java:349)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$instantiateAndPostProcessTestInstance$4(ClassBasedTestDescriptor.java:270)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.instantiateAndPostProcessTestInstance(ClassBasedTestDescriptor.java:269)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$testInstancesProvider$2(ClassBasedTestDescriptor.java:259)
    at java.base/java.util.Optional.orElseGet(Optional.java:369)
    at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$testInstancesProvider$3(ClassBasedTestDescriptor.java:258)
    at org.junit.jupiter.engine.execution.TestInstancesProvider.getTestInstances(TestInstancesProvider.java:31)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$prepare$0(TestMethodTestDescriptor.java:101)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.prepare(TestMethodTestDescriptor.java:100)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.prepare(TestMethodTestDescriptor.java:65)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$prepare$1(NodeTestTask.java:111)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.prepare(NodeTestTask.java:111)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:79)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1540)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1540)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:108)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:96)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:75)
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:220)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:53)
Caused by: org.springframework.boot.context.properties.ConfigurationPropertiesBindException: Error creating bean with name 'test-bug-com.example.Properties': Could not bind properties to 'Properties' : prefix=test-bug, ignoreInvalidFields=false, ignoreUnknownFields=true; nested exception is org.springframework.boot.context.properties.bind.BindException: Failed to bind properties under 'test-bug' to com.example.Properties
    at org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor.bind(ConfigurationPropertiesBindingPostProcessor.java:92)
    at org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor.postProcessBeforeInitialization(ConfigurationPropertiesBindingPostProcessor.java:78)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsBeforeInitialization(AbstractAutowireCapableBeanFactory.java:429)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1780)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:609)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:531)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:944)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:923)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:588)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:144)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:767)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:426)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:326)
    at org.springframework.boot.test.context.SpringBootContextLoader.loadContext(SpringBootContextLoader.java:123)
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:99)
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:124)
    ... 68 more
Caused by: org.springframework.boot.context.properties.bind.BindException: Failed to bind properties under 'test-bug' to com.example.Properties
    at org.springframework.boot.context.properties.bind.Binder.handleBindError(Binder.java:363)
    at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:323)
    at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:308)
    at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:238)
    at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:225)
    at org.springframework.boot.context.properties.ConfigurationPropertiesBinder.bind(ConfigurationPropertiesBinder.java:91)
    at org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor.bind(ConfigurationPropertiesBindingPostProcessor.java:89)
    ... 88 more
Caused by: org.springframework.boot.context.properties.bind.validation.BindValidationException: Binding validation errors on test-bug.nesteds[0]
   - Field error in object 'test-bug.nesteds[0]' on field 'foo': rejected value [null]; codes [NotBlank.test-bug.nesteds[0].foo,NotBlank.foo,NotBlank.java.lang.String,NotBlank]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [test-bug.nesteds[0].foo,foo]; arguments []; default message [foo]]; default message [не должно быть пустым]
    at org.springframework.boot.context.properties.bind.validation.ValidationBindHandler.validateAndPush(ValidationBindHandler.java:139)
    at org.springframework.boot.context.properties.bind.validation.ValidationBindHandler.validate(ValidationBindHandler.java:112)
    at org.springframework.boot.context.properties.bind.validation.ValidationBindHandler.onFinish(ValidationBindHandler.java:103)
    at org.springframework.boot.context.properties.bind.Binder.handleBindResult(Binder.java:339)
    at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:320)
    at org.springframework.boot.context.properties.bind.Binder.lambda$null$1(Binder.java:411)
    at org.springframework.boot.context.properties.bind.Binder$Context.withSource(Binder.java:547)
    at org.springframework.boot.context.properties.bind.Binder$Context.access$800(Binder.java:512)
    at org.springframework.boot.context.properties.bind.Binder.lambda$bindAggregate$2(Binder.java:412)
    at org.springframework.boot.context.properties.bind.IndexedElementsBinder.bindIndexed(IndexedElementsBinder.java:107)
    at org.springframework.boot.context.properties.bind.IndexedElementsBinder.bindIndexed(IndexedElementsBinder.java:87)
    at org.springframework.boot.context.properties.bind.IndexedElementsBinder.bindIndexed(IndexedElementsBinder.java:71)
    at org.springframework.boot.context.properties.bind.CollectionBinder.bindAggregate(CollectionBinder.java:49)
    at org.springframework.boot.context.properties.bind.AggregateBinder.bind(AggregateBinder.java:56)
    at org.springframework.boot.context.properties.bind.Binder.lambda$bindAggregate$3(Binder.java:414)
    at org.springframework.boot.context.properties.bind.Binder$Context.withIncreasedDepth(Binder.java:571)
    at org.springframework.boot.context.properties.bind.Binder$Context.access$100(Binder.java:512)
    at org.springframework.boot.context.properties.bind.Binder.bindAggregate(Binder.java:414)
    at org.springframework.boot.context.properties.bind.Binder.bindObject(Binder.java:375)
    at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:319)
    at org.springframework.boot.context.properties.bind.Binder.lambda$bindDataObject$4(Binder.java:447)
    at org.springframework.boot.context.properties.bind.JavaBeanBinder.bind(JavaBeanBinder.java:95)
    at org.springframework.boot.context.properties.bind.JavaBeanBinder.bind(JavaBeanBinder.java:83)
    at org.springframework.boot.context.properties.bind.JavaBeanBinder.bind(JavaBeanBinder.java:59)
    at org.springframework.boot.context.properties.bind.Binder.lambda$bindDataObject$5(Binder.java:451)
    at org.springframework.boot.context.properties.bind.Binder$Context.withIncreasedDepth(Binder.java:571)
    at org.springframework.boot.context.properties.bind.Binder$Context.withDataObject(Binder.java:557)
    at org.springframework.boot.context.properties.bind.Binder$Context.access$300(Binder.java:512)
    at org.springframework.boot.context.properties.bind.Binder.bindDataObject(Binder.java:449)
    at org.springframework.boot.context.properties.bind.Binder.bindObject(Binder.java:390)
    at org.springframework.boot.context.properties.bind.Binder.bind(Binder.java:319)
    ... 93 more

My value test-bug.nesteds[0].foo from apllication-test.yml was overwrited to null. When i comment registry.add("test-bug.nesteds[0].bar", () -> "bbb"); then the property value from application-test.yml remains in place, but bug.nesteds[0].bar stay null (obviously). But I think both propeties must be set to Properties fields, from application-test.yml and from DynamicPropertySource method.

I use Spring Boot and dependencies from

 <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.2</version>
  </parent>

Run on OpenJDK 11.0.2

Comment From: snicoll

Unfortunately, that's not how merging complex types works, see the reference documentation for more details.

Comment From: FoKas90

I got it, thks!