Preserve Set.of immutability in UseEnumSetOf

[martinfrancois]

Suggested review order: 7 of 52 (Score: 8)
Review first: openrewrite/rewrite#8447

What's changed?

Wraps generated EnumSet values with Collections.unmodifiableSet(...) so UseEnumSetOf preserves the mutation contract of Set.of(...). When source names prevent both safe spellings of Collections, the recipe leaves the original expression unchanged.

What's your motivation?

Recipe: org.openrewrite.java.migrate.util.UseEnumSetOf.

I found this by running org.openrewrite.java.migrate.util.UseEnumSetOf from org.openrewrite.recipe:rewrite-migrate-java:3.40.0 on WorkflowConfigEditor.java in Symphony-Trello at a8013f27. I reproduced the same result with the latest released recipe artifact, org.openrewrite.recipe:rewrite-migrate-java:3.42.0.

Before

private static final Set<PosixFilePermission> POSIX_WRITE_PERMISSIONS =
        Set.of(PosixFilePermission.OWNER_WRITE, PosixFilePermission.GROUP_WRITE, PosixFilePermission.OTHERS_WRITE);

Actual after the recipe

private static final Set<PosixFilePermission> POSIX_WRITE_PERMISSIONS =
        EnumSet.of(PosixFilePermission.OWNER_WRITE, PosixFilePermission.GROUP_WRITE, PosixFilePermission.OTHERS_WRITE);

Expected after the recipe

private static final Set<PosixFilePermission> POSIX_WRITE_PERMISSIONS =
        Collections.unmodifiableSet(EnumSet.of(
                PosixFilePermission.OWNER_WRITE,
                PosixFilePermission.GROUP_WRITE,
                PosixFilePermission.OTHERS_WRITE));

Set.of returns an unmodifiable set, while EnumSet.of returns a mutable set. The recipe changes an observable contract of the static constant even though the declared type remains Set.

Confirmed real-world execution

• Project: Symphony-Trello.
• Location: WorkflowConfigEditor.java at a8013f27.
• Discovery checkout: martinfrancois/symphony-trello@a8013f27.

Anything in particular you'd like reviewers to focus on?

Please review the decision to retain the intended EnumSet representation while preserving the source set's mutation contract and the conservative no-change result when neither Collections spelling is safe.

Have you considered any alternatives or workarounds?

Leaving every Set.of(...) expression unchanged preserves behavior but removes the standalone recipe's intended conversion. The unmodifiable wrapper retains both properties.

Any additional context

Pre-existing tests changed: UseEnumSetOfTest.java.changeDeclaration (updated), UseEnumSetOfTest.java.changeAssignment (updated), UseEnumSetOfTest.java.dontHaveArgs (updated).

• Target commit: martinfrancois/symphony-trello@a8013f27
• Discovery release: org.openrewrite.recipe:rewrite-migrate-java:3.40.0
• Latest verification release: org.openrewrite.recipe:rewrite-migrate-java:3.42.0
• Focused tests: UseEnumSetOfTest
• Existing issue: UseEnumSetOf is too opinionated for Spring Boot / Java upgrades #958

This change was prepared with AI assistance. I reviewed the target execution evidence, implementation, tests, generated metadata, and contribution text.

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've run ./gradlew build locally, and committed any resulting changes to recipes.csv
• I've formatted the lines I changed, without reformatting code I didn't touch