replaceEqualDeep optimization by schiller-manuel · Pull Request #7462 · TanStack/router

schiller-manuel · 2026-05-21T20:21:52Z

replaceEqualDeep Bundle Optimization

Bundle Size

Target scenario baseline:

react-router.minimal: gzip 89179, initial 89039, raw 279330, brotli 77564

Target scenario final:

react-router.minimal: gzip 89159, initial 89020, raw 279298, brotli 77583
Delta: gzip -20, initial -19, raw -32, brotli +19

Full benchmark final deltas:

react-router.minimal: gzip -20, initial -19, raw -32, brotli +19
react-router.full: gzip -20, initial -21, raw -32, brotli -76
solid-router.minimal: gzip -28, initial -29, raw -32, brotli -53
solid-router.full: gzip -25, initial -23, raw -32, brotli -43
vue-router.minimal: gzip -27, initial -27, raw -32, brotli +4
vue-router.full: gzip -30, initial -29, raw -32, brotli -65
react-start.minimal: gzip -26, initial -21, raw -32, brotli -78
react-start.deferred-hydration: gzip -21, initial -20, raw -32, brotli -156
react-start.full: gzip -24, initial -22, raw -32, brotli +19
react-start.rsbuild.minimal: gzip -17, initial -17, raw -28, brotli -98
react-start.rsbuild.full: gzip -17, initial -17, raw -28, brotli -6
solid-start.minimal: gzip -29, initial -31, raw -32, brotli +32
solid-start.deferred-hydration: gzip -17, initial -17, raw -32, brotli +45
solid-start.full: gzip -23, initial -22, raw -32, brotli -39

Perf

Focused bench: @tanstack/router-core:test:perf -- tests/replace-equal-deep.bench.ts

Mixed router state: baseline 19.53 hz, current 20.74 hz
Plain object equal: baseline 4191.32 hz, current 4493.67 hz
Array matches equal: baseline 2249.29 hz, current 2350.51 hz
Long matches mixed: baseline 22.80 hz, current 23.05 hz
Primitive mismatch: baseline 9470.48 hz, current 9493.51 hz
Null search: baseline 599.22 hz, current 609.79 hz

Validation

@tanstack/router-core:test:unit: pass
@tanstack/router-core:test:types: pass
@tanstack/router-core:test:eslint: pass with existing warnings
tanstack-router-e2e-react-basic-file-based:test:e2e: 157 passed
git diff --check: pass

Attribution

Kept overload/alias removal: gzip -2 vs final without it.
Kept array equality count simplification: gzip -6 vs final without it.
Kept object recursion branch inversion: gzip -6 vs final without it.
Rejected Reflect.ownKeys: gzip win but slower on focused bench.
Rejected inline isPlainArray: only gzip -1 and worse raw/brotli.
Rejected merged fast-path branch: neutral after attribution.

Summary by CodeRabbit

Bug Fixes
- Improved handling of undefined values in object and array comparisons within router core.
Tests
- Added comprehensive benchmark suite for deep equality operations.
- Enhanced test coverage for edge cases including symbol keys and null-prototype objects.
Refactor
- Optimized internal comparison logic for better referential equality preservation.

coderabbitai · 2026-05-21T20:22:07Z

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: 6aeb676c-141b-45da-908a-26404f55e104

📥 Commits

Reviewing files that changed from the base of the PR and between e2896b5 and 21dab5b.

📒 Files selected for processing (3)

packages/router-core/src/utils.ts
packages/router-core/tests/replace-equal-deep.bench.ts
packages/router-core/tests/utils.test.ts

📝 Walkthrough

Walkthrough

This PR optimizes replaceEqualDeep by renaming the _next parameter to next, consolidating deep-recursion conditions, and refactoring equality-counting logic. getEnumerableOwnKeys is restructured with explicit early-return blocks. A new nullReplaceEqualDeep variant is introduced. Test coverage expands to handle undefined-value edge cases and null-prototype objects. A comprehensive benchmark suite validates the optimization against a baseline implementation.

Changes

replaceEqualDeep optimization and testing

Layer / File(s)	Summary
replaceEqualDeep and getEnumerableOwnKeys refactoring `packages/router-core/src/utils.ts`	Parameter signature changed from `_next` to `next` in both overloads and implementation. Loop logic consolidated with combined `p && n && typeof p === 'object' && typeof n === 'object'` condition for deep recursion; equality counting now conditional on referential equality of recursive result. `getEnumerableOwnKeys` refactored into explicit early-return blocks for string property and symbol enumerability checks.
Unit test coverage for undefined-handling and nullReplaceEqualDeep `packages/router-core/tests/utils.test.ts`	Extended `replaceEqualDeep` tests for undefined appending/removal in arrays, undefined key removal in objects, symbol-key existence tracking, and reuse of equal nested values. New test section validates `nullReplaceEqualDeep` behavior on null-prototype objects and nested value reuse.
Benchmark suite with baseline implementation and assertions `packages/router-core/tests/replace-equal-deep.bench.ts`	New Vitest benchmark file with baseline deep-replacement logic, enumerable-key enumeration, and recursive reuse patterns. Constructs router-state fixtures (arrays, symbols, non-enumerable properties, null-prototype objects). Asserts optimized implementations match baseline outputs and preserve object identity. Runs benchmarks across mixed, array, long-array, primitive, and null-prototype scenarios.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐰 A rabbit hops through deep-replacement trees,
Where next now dances where _next did please,
With null-prototype cousins and benchmark cheer,
The optimization bounds through undefined's frontier!
Equal and swift, referential and clear! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 16.67% 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
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title 'replaceEqualDeep optimization' directly and clearly describes the main change: optimizing the replaceEqualDeep function. It is concise, specific, and summarizes the primary purpose of the changeset.
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.

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

✨ Finishing Touches

📝 Generate docstrings

Create stacked PR
Commit on current branch

🧪 Generate unit tests (beta)

Create PR with unit tests
Commit unit tests in branch perf-replaceEqualDeep

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nx-cloud · 2026-05-21T20:23:22Z

View your CI Pipeline Execution ↗ for commit 21dab5b

Command	Status	Duration	Result
`nx affected --targets=test:eslint,test:unit,tes...`	❌ Failed	9m 34s	View ↗
`nx run-many --target=build --exclude=examples/*...`	✅ Succeeded	2m 18s	View ↗

☁️ Nx Cloud last updated this comment at 2026-05-21 20:33:36 UTC

github-actions · 2026-05-21T20:24:15Z

🚀 Changeset Version Preview

No changeset entries found. Merging this PR will not cause a version bump for any packages.

pkg-pr-new · 2026-05-21T20:27:16Z

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commit: 21dab5b

github-actions · 2026-05-21T20:33:45Z

Bundle Size Benchmarks

Commit: c72f338b7846
Measured at: 2026-05-21T20:24:22.666Z
Baseline source: history:65b4abe65bc2
Dashboard: bundle-size history

Scenario	Current (gzip)	Delta vs baseline	Initial gzip	Raw	Brotli	Trend
`react-router.minimal`	87.28 KiB	-22 B (-0.02%)	87.14 KiB	273.98 KiB	75.94 KiB	███████▄▄▄▄▁
`react-router.full`	90.81 KiB	-11 B (-0.01%)	90.67 KiB	285.48 KiB	78.83 KiB	▇▇▇▇▇▇█▂▂▂▂▁
`solid-router.minimal`	35.51 KiB	-17 B (-0.05%)	35.39 KiB	106.29 KiB	31.95 KiB	▆▆▆████▃▃▃▃▁
`solid-router.full`	40.25 KiB	-17 B (-0.04%)	40.13 KiB	120.49 KiB	36.16 KiB	▆▆▆▆▆▆▇████▁
`vue-router.minimal`	53.30 KiB	-19 B (-0.03%)	53.18 KiB	151.43 KiB	47.86 KiB	██████▅▇▇▇▇▁
`vue-router.full`	58.43 KiB	-19 B (-0.03%)	58.30 KiB	167.59 KiB	52.42 KiB	██████▇████▁
`react-start.minimal`	102.00 KiB	-18 B (-0.02%)	101.87 KiB	322.44 KiB	88.24 KiB	▃▃▃▆▆▆▅████▁
`react-start.deferred-hydration`	103.05 KiB	-18 B (-0.02%)	102.18 KiB	324.08 KiB	89.18 KiB	████▆▆▆▆▁
`react-start.full`	105.41 KiB	-15 B (-0.01%)	105.27 KiB	332.75 KiB	91.07 KiB	▇▇▇████▃▃▃▃▁
`react-start.rsbuild.minimal`	99.62 KiB	-18 B (-0.02%)	99.45 KiB	316.90 KiB	85.71 KiB	▇▇▇▇▇▇▅████▁
`react-start.rsbuild.full`	102.91 KiB	-18 B (-0.02%)	102.74 KiB	327.31 KiB	88.46 KiB	██████▇▇▇▇▇▁
`solid-start.minimal`	49.65 KiB	-24 B (-0.05%)	49.52 KiB	152.42 KiB	43.87 KiB	▃▃▃███▇▅▅▅▅▁
`solid-start.deferred-hydration`	53.73 KiB	-12 B (-0.02%)	50.38 KiB	160.96 KiB	47.74 KiB	███▇▂▂▂▂▁
`solid-start.full`	55.44 KiB	-20 B (-0.04%)	55.30 KiB	169.31 KiB	48.73 KiB	▂▂▂███▆▇▇▇▇▁

Current gzip tracks all emitted client JS chunks. Initial gzip tracks only the entry/import graph. Trend sparkline is historical current gzip ending with this PR measurement; lower is better.

nx-cloud

Nx Cloud has identified a possible root cause for your failed CI:

We classified this failure as an environment issue rather than a code change. The failing test (preserves scroll position after a force reload on a visible boundary) lives outside the touched project and failed due to a 5-second polling timeout on a scroll position assertion — a transient condition consistent with a slow CI environment. The replaceEqualDeep optimization is behavior-neutral and no direct link to scroll restoration logic was found.

No code changes were suggested for this issue.

Trigger a rerun:

View detailed reasoning on Nx Cloud ↗

_{🎓 Learn more about Self-Healing CI on nx.dev}

codspeed-hq · 2026-05-21T20:40:26Z

Merging this PR will not alter performance

✅ 5 untouched benchmarks
⏩ 1 skipped benchmark¹

_{Comparing perf-replaceEqualDeep (21dab5b) with main (65b4abe)²}

1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩
No successful run was found on main (e2896b5) during the generation of this report, so 65b4abe was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

replaceEqualDeep optimization

21dab5b

github-actions Bot added the package: router-core label May 21, 2026

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replaceEqualDeep optimization#7462

replaceEqualDeep optimization#7462
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replaceEqualDeep Bundle Optimization

Bundle Size

Perf

Validation

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Summary by CodeRabbit

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Merging this PR will not alter performance

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