perf: return ImmutableContext.EMPTY when merging two empty contexts

[tobias-ibounig-dt]

This PR

• ImmutableContext.merge() returns ImmutableContext.EMPTY when both this and the overriding context are empty

Related Issues

None

Notes

When merging two empty contexts the previous code still allocated a new ImmutableContext (via this.asUnmodifiableMap()). The result is always semantically equivalent to EMPTY, so we can return the existing singleton directly.

This path is not exercised by the current benchmark workload, so no allocation numbers are provided.

Follow-up Tasks

• More PRs with memory improvements

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 02802ded-1d75-4873-a416-c0d8da448921

📥 Commits

Reviewing files that changed from the base of the PR and between c7ea4db and 1d4609c.

📒 Files selected for processing (2)

• src/main/java/dev/openfeature/sdk/ImmutableContext.java
• src/test/java/dev/openfeature/sdk/ImmutableContextTest.java

🚧 Files skipped from review as they are similar to previous changes (2)

• src/main/java/dev/openfeature/sdk/ImmutableContext.java
• src/test/java/dev/openfeature/sdk/ImmutableContextTest.java

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📝 Walkthrough

Walkthrough

ImmutableContext.merge() is updated to return the EMPTY singleton instead of constructing a new instance when both the current context and the overriding context are empty. New tests cover constructor branch behavior for null/empty inputs and verify the EMPTY singleton short-circuit semantics.

Changes

ImmutableContext EMPTY singleton short-circuit

Layer / File(s)	Summary
merge() short-circuit and comprehensive test coverage src/main/java/dev/openfeature/sdk/ImmutableContext.java, src/test/java/dev/openfeature/sdk/ImmutableContextTest.java	merge() now returns ImmutableContext.EMPTY when this.isEmpty() and the overriding context is null or empty, avoiding unnecessary allocation. New nested test classes assert EMPTY singleton identity for all empty-context merge combinations, verify non-empty contexts do not return EMPTY, and cover constructor branches for null/empty targeting key and attributes.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• open-feature/java-sdk#1972: Both PRs modify ImmutableContext empty-context handling around the shared ImmutableContext.EMPTY singleton—main PR changes ImmutableContext.merge(...) to short-circuit to EMPTY for empty/null overrides, while retrieved PR alters ImmutableContext constructors/empty structure to reduce allocations and support consistent empty-singleton behavior.

Suggested reviewers

• toddbaert

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 11.11% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: returning ImmutableContext.EMPTY when merging two empty contexts, which is the core optimization in this PR.
Description check	✅ Passed	The description clearly explains the optimization, the rationale, and acknowledges that the code path is not exercised by current benchmarks.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.20%. Comparing base (62fda56) to head (1d4609c).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1973      +/-   ##
============================================
+ Coverage     92.21%   93.20%   +0.98%     
- Complexity      666      670       +4     
============================================
  Files            59       59              
  Lines          1631     1633       +2     
  Branches        185      186       +1     
============================================
+ Hits           1504     1522      +18     
+ Misses           80       66      -14     
+ Partials         47       45       -2     

Flag	Coverage Δ
unittests	93.20% <100.00%> (+0.98%)	⬆️

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
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