spring-data-commons changed AuditorAware from 1.x to 2.x

[Jenson3210]

What problem are you trying to solve?

Migrating between Spring boot 1 and 2, the implementation of AuditorAware changed.

Describe the situation before applying the recipe

see the code

public class AuditorAwareImpl implements AuditorAware<String> {
    public String getCurrentAuditor() {
        return "Some code here";
    }
}

Describe the situation after applying the recipe

see the code

public class AuditorAwareImpl implements AuditorAware<String> {
    public Optional<String> getCurrentAuditor() {
        return Optional.ofNullable("Some code here");
    }
}

Are you interested in contributing this recipe to OpenRewrite?

This should be an easy one. Will see, if no one picks it up sooner.

[timtebeek]

Indeed looks fairly straightforward; thanks for calling this out! Best to start with tests, and then introduce a visitor that

1. overrides visitMethodDeclaration
2. uses a MethodMatcher to see if it's getCurrentAuditor
3. if the return type is already an Optional, return early
4. otherwise change the method return type
5. and wrap any returned expression in an Optional.ofNullable method invocation
6. hook the recipe into the Spring Boot 2.0 migration