Unable to override/set nested ConfigurationProperties by passing as a system property

[coduinix]

When using nested classes in @ConfigurationProperties annotated classes, it's normally possible to override that value by passing a system property.
Now with 3.5.0-RC1 it does not work anymore.

System properties for the non-nested properties are being picked up normally, the issue seems to be only with nested properties.

@Getter
@Setter
@ConfigurationProperties(prefix="demo.greeting")
public class GreetingProperties {
    private String message = "Default Message";

    private GreetingDetailsProperties details = new GreetingDetailsProperties();

    @Setter
    @Getter
    static class GreetingDetailsProperties {
        String salutation = "Default Salutation";
    }
}

When the system property demo.greeting.details.salutation is passed with some custom value, it's not being picked up and the "salutation" will always be "Default Salutation".

A small and isolated reproduction case can be found in this repository:
https://github.com/coduinix/gh-45639-repro-configuration-properties-issue

[coduinix]

Looking at the git history, it might be related to commit d9d206a

[wilkinsona]

Thanks for the report and the reproducer. Interestingly the problem only occurs in servlet-based web applications. WebFlux and non-web apps are not affected.

[nosan]

With the changes from main...nosan:spring-boot:45639 applied, everything appears to be working correctly, but honestly, I am not sure; this area is quite complex.

[philwebb]

Thanks for looking @nosan, that helped me track down the problem. I've gone for a slightly different fix because I remember that I was worried we shouldn't reuse previously cached descendants.

[nosan]

Happy to help, @philwebb!

I've gone for a slightly different fix...

//recalculation
for (String propertyName : propertyNames) {
addParents(descendants, reverseMappings.get(propertyName));
}

This seems equivalent to:

Set<ConfigurationPropertyName> descendants = (!this.captureDescendants) ? null : cloneOrCreate((data != null) ? data.descendants() : null, size);

At least, I couldn't spot any meaningful difference between the two.

Did I overlook something?

[philwebb]

I think the data.descendants() value might have stale entries in it, ones that were previously in the property source but have since been removed. Using for (String propertyName : propertyNames) should (I hope) mean we get only descendants for the current property names.