test(server): cover the feature flag regex helpers

[mariazuheros]

The helpers in server/src/services/featureFlags/regex.ts had no direct coverage, so I added tests for the whole module.

What is covered:

• validateFeatureFlagRegexPattern: an empty pattern, a pattern over the length limit, invalid syntax, a catastrophic backtracking pattern that safe-regex2 flags as too complex, and a safe pattern that returns null.
• precompileFeatureFlagRegexPattern and getCompiledFeatureFlagRegex: a valid pattern is compiled, cached, and returned on later lookups, the same instance comes back on a second call, and an invalid pattern returns undefined without being cached.
• precompileFeatureFlagRuleRegexes and precompileFeatureFlagConditionSetRegexes: regex rules are precompiled (including array values), non regex operators are skipped, and a missing list is a no-op.

The module keeps a process wide compile cache, so each test uses a unique pattern to stay independent. Run with cd server && npx vitest run src/services/featureFlags/regex.test.ts (14 tests pass).

Summary by CodeRabbit

• Tests
  • Added comprehensive coverage for feature-flag regular expression validation and compilation.
  • Verified handling of invalid, unsafe, empty, and overly long patterns.
  • Added tests for compilation caching, invalid-pattern handling, and regex processing across rules and condition sets.

[vercel]

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: b245e861-47a3-4ec7-8a1e-ff4d1c23bc83

📥 Commits

Reviewing files that changed from the base of the PR and between b7a8f86 and 468d48a.

📒 Files selected for processing (1)

• server/src/services/featureFlags/regex.test.ts

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📝 Walkthrough

Walkthrough

Adds Vitest tests covering feature-flag regex validation, compilation caching, invalid-pattern handling, and precompilation across rules and condition sets.

Changes

Feature flag regex tests

Layer / File(s)	Summary
Regex validation coverage server/src/services/featureFlags/regex.test.ts	Tests empty, oversized, invalid, overly complex, and valid regex patterns.
Regex compilation and caching server/src/services/featureFlags/regex.test.ts	Verifies RegExp compilation, cached instance reuse, and invalid-pattern cache behavior.
Rule and condition-set precompilation server/src/services/featureFlags/regex.test.ts	Covers regex rules, array-valued patterns, non-regex operators, condition sets, and undefined inputs.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the change: adding test coverage for feature-flag regex helpers in the server code.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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