I'm writing to notify everyone about an important change in our codebase that will be coming in PR #24239: https://github.com/apache/pulsar/pull/24239
We are currently using multiple nullness annotation libraries. Many JDK, tool and library vendors (https://jspecify.dev/about/) have standardized on JSpecify nullness annotations so that each vendor doesn't introduce its own classes for this purpose. We should migrate too. In addition, one additional motivation is that recent Google Guava versions no longer contain a transitive dependency on the checker-qual library (https://github.com/google/guava/commit/2cc8c5eddb587db3ac12dacdd5563e79a4681ec4). Pulsar modules use checker-qual as a transitive dependency coming from Guava, so Pulsar builds would no longer need modifications when we upgrade Guava once we have migrated off checker-qual. PR changes: Migrate these to org.jspecify.annotations.NonNull: - org.checkerframework.checker.nullness.qual.NonNull - javax.annotation.Nonnull - org.jetbrains.annotations.NotNull Migrate these to org.jspecify.annotations.Nullable: - org.checkerframework.checker.nullness.qual.Nullable - javax.annotation.Nullable - org.jetbrains.annotations.Nullable In addition, there was code that was using javax.validation annotations for nullness information. That's invalid since those annotations are used for user input validation and not static code analysis. Add checkstyle rules: - to prevent introducing the replaced deprecated annotations - to prevent introducing javax.validation annotations These changes should help standardize our codebase and align with industry practices for nullness annotations. The PR is currently under review and targeted for milestone 4.1.0, with backports planned for releases 3.0.12, 3.3.7, and 4.0.5. Please review the PR https://github.com/apache/pulsar/pull/24239 if you have time. Your feedback is appreciated. Thanks, Lari
