Spring ConfigurationProperties issue reproduction

Reproduction case for issue: spring-projects/spring-boot#45639

The GreetingProperties is a @ConfigurationProperties annotated class. It contains a nested properties object GreetingDetails.

When the application is ran without specifying any system properties it runs as expected:

./mvnw spring-boot:run

A call to the hello endpoint will return the default salutation and default message:

$ curl http://localhost:8080/hello
Default Salutation, Default Message

All good, so far. Now Stop the application

Now when you try to override the demo.greeting.message and demo.greeting.details.salutation properties using System properties, something odd is going on.

./mvnw spring-boot:run \
  -Dspring-boot.run.jvmArguments='-Ddemo.greeting.message="Custom Message" -Ddemo.greeting.details.salutation="Custom Salutation"'

When the endpoint is called again with:

curl http://localhost:8080/hello

When the application is ran with 3.5.0-M3 the curl command returns:

Custom Salutation, Custom Message

But when the application is ran with 3.5.0-RC1 the curl command returns:

Default Salutation, Custom Message

NOTE The salutation should have been Custom, but it's returning Default

The system property does not seem to affect the nested GreetingDetails property.