Change mutable public collections to immutable versions: ref issue #2413

[MoritzCSchmidt]

What's changed?

Added new recipe to wrap modifiable lists to be unmodifiable.

What's your motivation?

Closes openrewrite/rewrite-static-analysis#125

Any additional context

Thanks for your work! I hope we can support with our small improvements.

Checklist

• I've added unit tests to cover both positive and negative cases
• I've added the license header to any new files through ./gradlew licenseFormat
• I've used the IntelliJ auto-formatter on affected files
• I've updated the documentation (if applicable)

[timtebeek]

Thank you for starting this implementation! It's looking quite good already.
I've added two small polishing commits, and will add some review comments.

[timtebeek]

Perhaps this is more of an issue with the original feature request rather than the recipe implementation, but I have some doubts if this recipe could do harm in certain situations. More details here: https://github.com/openrewrite/rewrite/issues/2413#issuecomment-1586767731

[JLLeitschuh]

IIRC, Arrays.asList already returns a list that is unmodifiable.

[JLLeitschuh]

Ah, I'm wrong, you can't append to it, but you can replace existing values.

[timtebeek]

Indeed; more details discussed in this thread; I like your suggestion of using data flow to make this recipe safe to execute. I've not used data flow myself before, but would be good to explore here.

[JLLeitschuh]

To use data flow, this recipe would need to be moved to the cleanup package in rewrite-static-analysis repository

[timtebeek]

That's indeed perhaps a better place for this recipe; sorry about that @marynasavchenko . Would you mind targeting https://github.com/openrewrite/rewrite-static-analysis/tree/main/src/main/java/org/openrewrite/staticanalysis for these files?
As seen above that's necessary to use data flow, which we need to be sure we can safely apply this recipe.

[timtebeek]

Closed pending a move to rewrite-static-analysis, which we need for the data flow analysis to determine if it's safe to do this replacement: we can't replace when list elements or order is modified. Great start, looking forward to the full implementation.