perf(history): avoid generating unused location keys by LadyBluenotes · Pull Request #8349 · TanStack/router

LadyBluenotes · 2026-09-11T02:20:01Z

🎯 Changes

Generate a fallback history key in parseHref only when no state is supplied. Parsing a location with existing state no longer creates and discards a random key.

Performance

Local Node.js 24.12.0 microbenchmark comparing 6494e75362 with 9eeb94f921. Nine alternating baseline/candidate rounds per case, with 100,000 warmup calls and 2,000,000 timed calls per sample. The URL is /items/123?tab=details#top; times below are medians.

Case	Before	After	Change
`parseHref` with existing state	375.41 ms	115.24 ms	About 69% less elapsed time
`parseHref` without state	382.24 ms	382.98 ms	About +0.2%; within observed run variation
Minimal React Router bundle, gzip	85,993 bytes	85,996 bytes	+3 bytes

Existing-state parsing removes one discarded key-generation operation per call. These are isolated runtime results, not an end-to-end navigation speedup or a retained-heap measurement.

✅ Checklist

I have followed the steps in the Contributing guide.
I have tested code changes locally with the relevant test commands, or tests do not apply to this pull request.
I fully understand the code in this pull request, including any code generated with AI assistance.

🚀 Release Impact

This change affects published code, and I have generated a changeset.
This change is docs/CI/dev-only (no release).

Summary by CodeRabbit

Bug Fixes
- Existing location state is now preserved without generating an unnecessary history key.
- Locations created without state continue to receive independent initial state, including a unique key and index.
Tests
- Added coverage for preserving supplied state and isolating automatically generated location state.

coderabbitai · 2026-09-11T02:20:23Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Advanced

Run ID: 4a2f714b-2348-4553-a958-f69a81dd9cb3

📥 Commits

Reviewing files that changed from the base of the PR and between 6494e75 and 9eeb94f.

📒 Files selected for processing (3)

.changeset/lazy-locations-listen.md
packages/history/src/index.ts
packages/history/tests/parseHref.test.ts

Included review availability: Your plan provides up to 10 included reviews per hour; 8 remain after this review.

📝 Walkthrough

Walkthrough

parseHref now creates a default history state only when no state is supplied. Tests verify supplied state identity and independent generated states. A patch changeset documents the fix for @tanstack/history.

Changes

History state preservation

Layer / File(s)	Summary
Conditional history state creation `packages/history/src/index.ts`, `.changeset/lazy-locations-listen.md`	`parseHref` preserves supplied state and creates a keyed default state only when state is absent. The changeset records a patch release.
State preservation tests `packages/history/tests/parseHref.test.ts`	Tests verify exact preservation of supplied frozen state and independence of generated default states.

Priority: ⬇️ Low

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

Suggested reviewers: sheraff

Merge Risk: ⚪ Minimal · up to 9eeb9

The change avoids unnecessary key generation while preserving existing history-state behavior. No actionable merge risk remains.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files. (1 skipped: 1 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description explains the change and motivation. It includes all required template sections, completed checklist items, testing confirmation, and changeset information.
Title check	✅ Passed	The title clearly and concisely describes the main change: avoiding generation of unused location keys in history parsing.
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.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files. (1 skipped: 1 unsupported.)

Fix all pre-merge checks with AI

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

Create stacked PR
Commit on current branch

🧪 Generate unit tests (beta)

Create PR with unit tests
Commit unit tests in branch perf/history-lazy-location-key

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nx-cloud · 2026-09-11T02:20:28Z

View your CI Pipeline Execution ↗ for commit 9eeb94f

Command	Status	Duration	Result
`nx affected --targets=test:eslint,test:unit,tes...`	❌ Failed	12m 11s	View ↗
`nx run-many --target=build --exclude=examples/*...`	✅ Succeeded	2m 11s	View ↗

☁️ Nx Cloud last updated this comment at 2026-09-11 02:33:53 UTC

github-actions · 2026-09-11T02:21:27Z

🚀 Changeset Version Preview

1 package(s) bumped directly, 23 bumped as dependents.

🟩 Patch bumps

Package	Version	Reason
`@tanstack/history`	1.162.3 → 1.162.4	Changeset
`@tanstack/react-router`	1.170.35 → 1.170.36	Dependent
`@tanstack/react-start`	1.168.52 → 1.168.53	Dependent
`@tanstack/react-start-client`	1.168.33 → 1.168.34	Dependent
`@tanstack/react-start-rsc`	0.1.51 → 0.1.52	Dependent
`@tanstack/react-start-server`	1.167.40 → 1.167.41	Dependent
`@tanstack/router-cli`	1.167.35 → 1.167.36	Dependent
`@tanstack/router-core`	1.171.29 → 1.171.30	Dependent
`@tanstack/router-generator`	1.167.35 → 1.167.36	Dependent
`@tanstack/router-plugin`	1.168.37 → 1.168.38	Dependent
`@tanstack/router-vite-plugin`	1.167.37 → 1.167.38	Dependent
`@tanstack/solid-router`	1.170.33 → 1.170.34	Dependent
`@tanstack/solid-start`	1.168.50 → 1.168.51	Dependent
`@tanstack/solid-start-client`	1.168.32 → 1.168.33	Dependent
`@tanstack/solid-start-server`	1.167.39 → 1.167.40	Dependent
`@tanstack/start-client-core`	1.170.29 → 1.170.30	Dependent
`@tanstack/start-plugin-core`	1.171.42 → 1.171.43	Dependent
`@tanstack/start-server-core`	1.169.34 → 1.169.35	Dependent
`@tanstack/start-static-server-functions`	1.167.34 → 1.167.35	Dependent
`@tanstack/start-storage-context`	1.167.31 → 1.167.32	Dependent
`@tanstack/vue-router`	1.170.32 → 1.170.33	Dependent
`@tanstack/vue-start`	1.168.49 → 1.168.50	Dependent
`@tanstack/vue-start-client`	1.167.35 → 1.167.36	Dependent
`@tanstack/vue-start-server`	1.167.39 → 1.167.40	Dependent

github-actions · 2026-09-11T02:23:11Z

Bundle Size Benchmarks

Commit: 1d2719acf09e
Measured at: 2026-09-11T02:22:32.709Z
Baseline source: history:6494e75362ff
Dashboard: bundle-size history

The following scenarios have bundle-size changes compared with the baseline:

Scenario	Current (gzip)	Initial (gzip)	Raw	Brotli	Trend
`react-router.minimal`	84.0 KiB +3 B	83.8 KiB -1 B	262.3 KiB +12 B	73.2 KiB -25 B	▁▁███████▄▄▄
`react-router.full`	87.5 KiB +2 B	87.3 KiB +3 B	274.0 KiB +12 B	76.2 KiB -92 B	▁▁███████▅▅▅
`solid-router.minimal`	33.5 KiB -2 B	33.3 KiB +2 B	96.8 KiB +12 B	30.3 KiB +15 B	▁▁██████████
`solid-router.full`	38.3 KiB -1 B	38.2 KiB 0 B	111.4 KiB +12 B	34.4 KiB -56 B	▁▁██████████
`vue-router.minimal`	49.6 KiB -1 B	49.5 KiB +2 B	138.3 KiB +12 B	44.9 KiB +14 B	▁▂███████▁▁▁
`vue-router.full`	55.2 KiB +1 B	55.1 KiB +1 B	156.5 KiB +12 B	49.8 KiB -19 B	▂▂███████▁▁▁
`react-start.minimal`	96.9 KiB -1 B	96.8 KiB -1 B	304.6 KiB +12 B	84.1 KiB -33 B	▁▁███████▄▄▄
`react-start.query-integration`	104.2 KiB -3 B	104.1 KiB +1 B	331.1 KiB +12 B	90.4 KiB +69 B	▁▁███████▅▅▅
`react-start.deferred-hydration`	97.6 KiB +3 B	96.8 KiB +2 B	306.0 KiB +12 B	84.8 KiB +75 B	▁▁███████▄▄▄
`react-start.full`	100.1 KiB +4 B	99.9 KiB +1 B	314.3 KiB +12 B	86.7 KiB +9 B	▁▁███████▄▄▄
`react-start.rsbuild.minimal`	100.1 KiB +1 B	100.0 KiB +1 B	314.9 KiB +12 B	86.4 KiB -16 B	▁▁███████▃▃▃
`react-start.rsbuild.minimal-iife`	100.5 KiB +1 B	100.4 KiB +1 B	315.8 KiB +12 B	86.7 KiB -149 B	▁▁███████▃▃▃
`react-start.rsbuild.full`	103.4 KiB +3 B	103.2 KiB +3 B	325.0 KiB +12 B	89.2 KiB +24 B	▁▁███████▂▂▂
`solid-start.minimal`	46.3 KiB -1 B	46.2 KiB -2 B	137.9 KiB +12 B	41.2 KiB -19 B	▁▁██████████
`solid-start.deferred-hydration`	49.4 KiB +1 B	46.3 KiB +1 B	145.3 KiB +12 B	44.0 KiB -26 B	▁▁██▇███████
`solid-start.full`	51.4 KiB +1 B	51.3 KiB 0 B	153.3 KiB +12 B	45.5 KiB -69 B	▁▁██████████
`vue-start.minimal`	65.7 KiB -2 B	65.6 KiB -2 B	189.2 KiB +12 B	58.5 KiB -57 B	▂▂███████▁▁▁
`vue-start.full`	69.6 KiB -1 B	69.5 KiB 0 B	201.5 KiB +12 B	61.8 KiB +35 B	▁▁███████▁▁▁

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.

pkg-pr-new · 2026-09-11T02:25:31Z

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commit: 9eeb94f

nx-cloud

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

We determined these E2E failures are environment-related and not caused by this PR. The parseHref change is a functionally identical performance optimization, and neither failing project is in the set of projects touched by the diff. The React test shows explicit ECONNRESET network errors from the test server, and the Solid test is a router-idle timeout — both pointing to infrastructure instability rather than a logic regression.

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 · 2026-09-11T02:38:31Z

Merging this PR will improve performance by 5.91%

⚡ 1 improved benchmark
✅ 179 untouched benchmarks

Performance Changes

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
⚡	Simulation	`ssr server-route (vue)`	155.2 ms	146.5 ms	+5.91%

Tip

Curious why performance improved? Comment @codspeedbot explain why performance improved on this PR, or directly use the CodSpeed MCP with your agent.

_{Comparing perf/history-lazy-location-key (9eeb94f) with main (6494e75)}

perf(history): avoid generating unused location keys

9eeb94f

github-actions Bot added the package: history label Sep 11, 2026

LadyBluenotes requested a review from schiller-manuel September 11, 2026 02:30

nx-cloud Bot reviewed Sep 11, 2026

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perf(history): avoid generating unused location keys - #8349

perf(history): avoid generating unused location keys#8349
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Merging this PR will improve performance by 5.91%

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