micrometer-metrics/micrometer

Remove @NullUnmarked workaround for NullAway bug on generic types

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#6404 opened on Jun 14, 2025

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help wantednullabilitypolishtype: task

Description

It seems <T extends @Nullable Object> does not work well in some situations, see https://github.com/uber/NullAway/issues/1075.

Because of this bug in NullAway, we need to use @NullUnmarked and "invert" the contract unnecessarily, see here and here.

Contributor guide

Tech stack
java
Domain
tooling
Issue type
refactor
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
JavaNullAwayGenerics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
Examine the referenced PR #6385 and the specific lines where @NullUnmarked is used (see diff links in issue). Monitor the NullAway issue #1075 for the upstream fix. Once the NullAway bug is resolved, remove the @NullUnmarked annotations and revert the inverted contract. Update any relevant tests to ensure correctness without the workaround.