Detection of “unused” annotations

[yrodiere]

E.g. if a JPA/Hibernate annotation is in ClassDetails, but its descriptor has never been accessed, then there is probably a problem. We could report it as an error or warning?

We have a similar feature for unused/misspelled configuration properties in Hibernate Search: https://docs.jboss.org/hibernate/stable/search/reference/en-US/html_single/#configuration-property-tracking

(Creating this issue to track an idea we had during earlier discussions -- I'm certainly not saying it's the top priority :) )

[sebersole]

You mean to detect cases like this?

@ManyToOne
class MyEntity {
    ...
}

I have a few concerns with this ;)

The main technical one is what constitues "never been accessed"? I think what you are really wanting is that the descriptor is never accessed from the expected place(s). E.g. using the MyEntity example, ORM is never going to ask ClassDetails for a @ManyToOne annotation.

But the only feasible way I can see to support that in models itself would be to add an additional Map to the various AnnotationTarget impls to track which were accessed. I'm definitely concerned about the overhead of that.

[yrodiere]

That, but also more common mistakes like this:

class MyEntity {


    @Column
    String foo() {
        ...
    }

}

It never can be 100% fool-proof, but could help.

And BTW it can be opt-in; Quarkus would likely enable it if we manage to move annotation processing to build time.

[yrodiere]

Actually, no, your example cannot happen, since @ManyToOne cannot target a class. I'm mainly talking about places that don't get scanned for whatever reason (here JavaBean property accessor naming).

[sebersole]

Actually, no, your example cannot happen, since @ManyToOne cannot target a class. I'm mainly talking about places that don't get scanned for whatever reason (here JavaBean property accessor naming).

I mean clearly it was just an example 🙄

[sebersole]

I'm against adding this in models itself per-se. But I'll think about a hook for consumers to achieve this.