perf: skip unmodifiableMap wrapper when hookHints is empty

[tobias-ibounig-dt]

This PR

• Skips the Collections.unmodifiableMap() wrapper when hookHints is empty (the common case)

Related Issues

None

Notes

hookHints is resolved once per flag evaluation. Previously it was always wrapped in an unmodifiable view, even when empty. This PR avoids that allocation by returning Collections.emptyMap() directly when there are
no hints.

Allocation impact is negligible, but reduces on totalAllocatedInstances can be seen.

Metric	main (baseline)	PR 2	Delta
run:+totalAllocatedBytes	124,265,984	124,268,232	~0 (noise)
run:+totalAllocatedInstances	2,723,316	2,691,291	−32,025 (−1.2%)

Follow-up Tasks

• More PRs with memory improvements
• Update benchmark.txt after all are applied

[gemini-code-assist]

Code Review

This pull request optimizes the initialization of hookSupportData.hints in OpenFeatureClient.java by using Collections.emptyMap() when the hook hints are empty. A review comment points out that getHookHints() could return null, which would cause a NullPointerException when calling isEmpty(), and suggests adding a null check to handle this case safely.

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[gemini-code-assist]

If flagOptions.getHookHints() returns null (which can happen if hookHints is explicitly set to null via the builder in FlagEvaluationOptions), calling hookHints.isEmpty() will throw a NullPointerException.

To ensure robust defensive programming, we should handle the null case gracefully by defaulting to Collections.emptyMap().

Suggested change

	var hookHints = flagOptions.getHookHints();
	hookSupportData.hints = hookHints.isEmpty() ? Collections.emptyMap() : Collections.unmodifiableMap(hookHints);
	var hookHints = flagOptions.getHookHints();
	hookSupportData.hints = hookHints == null || hookHints.isEmpty() ? Collections.emptyMap() : Collections.unmodifiableMap(hookHints);

[chrfwow]

I think this is something that should be handled in the builder, but idk if we can modify this, since I assume it will be a lombok builder. Can we add a test to make sure we won't have a NPE?

[tobias-ibounig-dt]

ensured in builder that it can't be null

[toddbaert]

Same codecov-action issue as #1955 (comment) - rebasing this PR onto main should fix it. cc @chrfwow

[tobias-ibounig-dt]

Realized another thing in FlagEvaluationOptions. Builder Default is currently new HashMap<>();, would it make sense to change this to Collections.emptyMap()?
Didn't do it yet, as it could theoretically break someone doing something like getHookHints().put(...).
Any preference from your side?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.28%. Comparing base (58091f3) to head (aad8866).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1953      +/-   ##
============================================
+ Coverage     92.27%   93.28%   +1.01%     
- Complexity      653      658       +5     
============================================
  Files            59       59              
  Lines          1592     1594       +2     
  Branches        179      181       +2     
============================================
+ Hits           1469     1487      +18     
+ Misses           76       62      -14     
+ Partials         47       45       -2     

Flag	Coverage Δ
unittests	93.28% <100.00%> (+1.01%)	⬆️

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[chrfwow]

The current build issue can be fixed by running spotless:apply

[tobias-ibounig-dt]

The current build issue can be fixed by running spotless:apply

Oh sorry, I thought I made sure to run it every time.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud