fix: Address issues when evaluating the context in the InMemoryProvider

[kylejuliandev]

This PR

Fixes a couple of issues when the InMemoryProvider cannot evaluate the variant. First when the variant does not exist, we should fallback to the default variant configured in the flags. Second when the ContextEvaluator throws an exception. Instead of throwing an error we can fallback to the default variant. This is the behaviour in the Java SDK, as well as behaviour described in the gherkin tests. Specifically, the Null context values scenario and the Empty evaluation context scenario.

Related Issues

Fixes #603

Notes

Follow-up Tasks

How to test

[kylejuliandev]

/gemini review

[gemini-code-assist]

Summary of Changes

Hello @kylejuliandev, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the robustness of the InMemoryProvider by implementing more resilient variant evaluation logic. It addresses cases where the context evaluator fails or returns a non-existent variant, ensuring that the system gracefully falls back to the default variant as per the OpenFeature specification and other SDK implementations. This change prevents unexpected exceptions and provides a more stable feature flagging experience.

Highlights

• Robust Variant Evaluation: The InMemoryProvider now gracefully handles scenarios where the evaluated variant does not exist or when the context evaluator throws an exception. Instead of throwing errors, it now falls back to the configured default variant.
• Specification Alignment: This change aligns the provider's behavior with the OpenFeature specification, specifically the 'Null context values' and 'Empty evaluation context' scenarios, and mirrors the behavior found in the Java SDK.
• Code Refactoring: A new private helper method, EvaluateDefaultVariant, has been introduced to centralize the logic for resolving and returning the default variant, improving code readability and maintainability.
• Enhanced Test Coverage: New and updated unit tests have been added to validate the new fallback behaviors, ensuring that the provider correctly returns the default variant when an evaluated variant is missing or when the context evaluator encounters an error.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.89%. Comparing base (c987b58) to head (054f7ae).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #615      +/-   ##
==========================================
+ Coverage   89.84%   89.89%   +0.04%     
==========================================
  Files          77       77              
  Lines        3162     3167       +5     
  Branches      364      364              
==========================================
+ Hits         2841     2847       +6     
  Misses        251      251              
+ Partials       70       69       -1     

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[gemini-code-assist]

Code Review

This pull request correctly addresses issues in the InMemoryProvider by falling back to the default variant when context evaluation fails or returns a non-existent variant. The logic is sound and aligns with the behavior of other OpenFeature SDKs. The changes are accompanied by relevant tests. I've included a few suggestions to enhance code readability and improve the completeness of the tests.

[gemini-code-assist]

Code Review

This pull request correctly addresses issues in the InMemoryProvider's context evaluation. When the context evaluator throws an exception or when an evaluated variant doesn't exist, the provider now falls back to the default variant, which aligns with the OpenFeature specification. The changes are logical, and the addition of new tests ensures the new behavior is covered. I have one minor suggestion to improve code readability.