ApplicationContextRunner does not work correctly when AutoConfiguration class has not @Configuration

[filiphr]

This is most definitely my error that I forgot to add an @Configuration to my custom auto configuration.

The problem occurs when an auto configuration class (e.g. MyCustomAutoConfiguration) has a nested configuration class with @EnableConfigurationProperties is missing a @Configuration (the root class) then the Spring Boot application works correctly. However, when using the ApplicationContextRunner the behaviour is not the same.

See this repository for a reproducing example. In the example repo if you move the @EnableConfigurationProperties then tests that were failing before will pass.

If you think that there is nothing that Boot can do about this, feel free to close it. I was just confused why it was working in one instance, but not in the other

[wilkinsona]

Thanks for the sample.

The difference in behaviour is due to a difference in how MyCustomAutoConfiguration is registered with the application context. When you use @SpringBootTest it's registered via the import selector for auto-configuration and is processed as a configuration class. When you use ApplicationContextRunner it's registered via a call to org.springframework.context.annotation.AnnotationConfigRegistry.register(Class<?>...) and isn't processed in the same way. Critically, it isn't processed by ConfigurationClassParser and doesn't go through its processMemberClasses method. It's there that the nested configuration class is found when using @SpringBootTest.

[filiphr]

Thanks a lot analysis and looking into it

[wilkinsona]

I believe this is a Spring Framework bug so I have opened SPR-16839. If the Framework team disagree we can re-open this issue and look for a workaround.