micrometer-metrics/micrometer

Remove @NullUnmarked workaround for NullAway bug on generic types

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#6,404 opened on Jun 14, 2025

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help wantednullabilitypolishtype: task

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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

Research direction
Investigate the NullAway bug report mentioned in the issue to understand the root cause and verify that the fix is available in the version used by Micrometer. Then locate the @NullUnmarked workaround in the codebase and remove it, ensuring no new NullAway warnings are introduced.
Tech stack
java
Domain
build systemdeveloper experience
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
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.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Needs investigation
Prerequisites
JavaNullAway
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30