[java] UnusedPrivateField doesn't find annotated unused private fields anymore

[phoenix384]

Rule: UnusedPrivateField

With PMD 6.50 the rule UnusedPrivateField was changed to completely ignore any private field with an annotation (see #4100).
But what if the previous behaviour was totally ok? How to restore it? In my case I do want to find unused private fields even with annotation.

If you need a use case for that: Java Selenium Tests
There you annotate WebElements with the locator that points to the corresponding Element on the web page.

It looks like this:

@FindBy(id = "whateverID")
private WebElement myElement;

A class like this could have a bunch of WebElements and if some of them are unused, you don't see it.
If I don't use myElement, I want to remove it and I want PMD to find it.

Maybe at least a kind of whitelist could be added to configure PMD to find fields even if they have annotations that are on this list.

[adangel]

Thanks for sharing your use case.

As written already in the comment #4100 (comment):

I decided to deprecate the property "ignoreAnnotations". If there are good examples for false negatives, we might think of adding a new property to change the behavior, to deal with some annotations in a special way (e.g. "reportForAnnotations") or have a boolean flag (e.g. "reportRegardlessOfAnnotations"=true) which could be enabled if needed and would report all unused private fields whether annotated or not.

We can easily add either "reportForAnnotations" or "reportRegardlessOfAnnotations". What I want to avoid however is, that we start maintaining now a whitelist for Java frameworks in PMD (as we did before with the blacklist).

Would that work for you - given the rule has such a property - that you configure the rule to your needs?
Would you rather have a simple flag ("reportRegardlessOfAnnotations") or a more fine granular property ("reportForAnnotations") where you can list individual annotation classes?

[adangel]

I'll add a new property annotations (like in https://pmd.github.io/latest/pmd_rules_java_errorprone.html#missingstaticmethodinnoninstantiatableclass) which can be configured for this use case.
Maybe we can use org.openqa.selenium.support.FindBy as a default value.

[phoenix384]

Thank you. That works.