Extending existing rules

[jsmolinski-vivint]

Hi all,

I'm working on updating our Detekt configuration to be more friendly for Compose. One issue that our developers are running into is the LongParameterList rule. I've reviewed the guidance and suggestions here, but was wondering if there was a way we could actually extend the LongParameterList class (and potentially others) and provide an alternate check (or omit the check) for Compose-annotated functions.

I tried creating a custom rule and extending the LongParameterList rule, but it's closed/final. I'm able to hack around it by creating an "outer-rule" and selectively passing findings from LongParameterList as an "inner-rule", but it's pretty convoluted.

So I have two questions:

1. Would it be possible to open the built-in rules for developers to extend and customize their behavior?
2. If not, is there another way to extend existing rules without re-implementing them or creating this strange "outer-rule" and "inner-rule" relationship?

Thank you!

[schalkms]

I don't understand what you mean by outer- and inner-rule.

Nevertheless, the suggested approach is to copy the source code of LongParameterList as it is to a custom rule and modify the needed parts.

Just setting classes of built-in rules to open doesn't provide a remedy, because you also need to provide hooks for all possible parts needing to be customized. I don't think it's worth the effort.

[jsmolinski-vivint]

Sure, that makes sense. Thanks for your reply!

[cortinico]

Nevertheless, the suggested approach is to copy the source code of LongParameterList as it is to a custom rule and modify the needed parts.

That's the suggested approach.

If there is a snippet of code that is frequently re-used to manipulate the PSI, we can consider exposing it as a public API (i.e. see the detekt-utils artifact).

But we don't offer an easy way to 'extend' rules as you're suggesting as that will make our API surface explode