refactor(router-core): getEnumerableOwnKeys fast path for 'no symbol key' common case, 6-11% faster replaceEqualDeep

[Sheraff]

This entire PR is basically just this one line: most objects going through replaceEqualDeep won't have symbols, so return early if that's the case:

if (symbols.length === 0) return names

Summary by CodeRabbit

• Refactor

  • Optimized internal key-enumeration to reduce memory allocations for plain objects and improve handling of symbol keys.

• Tests

  • Added comprehensive tests for key-enumeration covering symbol keys, non-enumerable properties, mixed scenarios, frozen/sealed objects, and typical router-state patterns.
  • Updated two test expectations to reflect a corrected update count during navigation.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

📝 Walkthrough

Walkthrough

Reworks internal key-enumeration in router-core: adds an isEnumerable helper and a symbol-aware fast-path in getEnumerableOwnKeys to avoid allocations when no symbol properties exist; behavior remains externally unchanged.

Changes

Cohort / File(s)	Summary
Core util change packages/router-core/src/utils.ts	Add isEnumerable bound to Object.prototype.propertyIsEnumerable; implement fast-path in getEnumerableOwnKeys to return string keys directly when no symbols exist and merge string/symbol accumulation only when needed to reduce allocations.
Tests added packages/router-core/tests/utils.test.ts	Add comprehensive tests covering string keys, symbol keys, mixed keys, non-enumerable/shadowed properties, prototype/inheritance edge cases, frozen/sealed/Object.create(null) objects, and router-like state scenarios.
Test expectation updates packages/react-router/tests/store-updates-during-navigation.test.tsx	Two test expectations adjusted from 7 → 8 to match changed behavior/observation counts during navigation tests.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• refactor(router-core): slightly faster deepEqual #5051 — Refactors deep-equality/key-iteration logic; touches related key enumeration areas in utils.ts.
• refactor(router-core): slightly faster replaceEqualDeep #5046 — Also modifies getEnumerableOwnKeys and symbol-aware enumeration/allocation logic.

Suggested labels

performance

Suggested reviewers

• schiller-manuel
• nlynzaad

Poem

🐰 I nibble through keys, both string and sign,

fast-path footsteps — light and fine.
Symbols hide? I skip the chore,
fewer arrays, and hops galore.
Tests clap paws — the change is mine! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main optimization: a fast path in getEnumerableOwnKeys for the common case without symbol keys, resulting in measurable performance improvements (6-11% faster replaceEqualDeep).
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

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[nx-cloud]

View your CI Pipeline Execution ↗ for commit a459a7a

Command	Status	Duration	Result
nx affected --targets=test:eslint,test:unit,tes...	✅ Succeeded	1m 55s	View ↗
nx run-many --target=build --exclude=examples/*...	✅ Succeeded	3s	View ↗

---

☁️ Nx Cloud last updated this comment at 2026-01-22 14:01:06 UTC

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commit: a459a7a