perf(router-core): hoist regex literals evaluated per built location by schiller-manuel · Pull Request #8425 · TanStack/router

schiller-manuel · 2026-09-14T17:27:57Z

🎯 Changes

A regex literal creates a new RegExp object every time it is evaluated
(measured: 56 B per evaluation, 0 once hoisted). decodePath and
encodePathLikeUrl run on every buildLocation, cleanPath on every href of a
basepath router, encodeParam on every splat and trimPathRight on every
trailing-slash path; parseLocation's fast-path test runs per navigation.
Their literals are now module constants. trimPathLeft (construction only)
and the cold branches of getUrlScheme are left as they were.

Allocation per buildLocation (sampling heap profiler over 160k builds against
the production dist, Node 24.8; on top of the previous commit):

relative destination 1309 -> 1197 B (-112)
search updater 1085 -> 969 B (-116)
static destination 955 -> 786 B (-169)

CPU (tests/build-location.bench.ts, two rounds, hz): within noise,
directionally +1-2%: search updater 41.6k/44.2k -> 43.5k/43.2k, relative
29.8k/30.2k -> 29.6k/30.3k, masked 20.5k/20.9k -> 20.8k/20.6k.

Bundle: react-router.minimal +18 gzip (derived from the composed measurements
86077 with, 86059 without these hoists).

Verification on `main`

router-core test:unit (3252 passed), test:types, test:eslint
Allocation numbers: sampling heap profiler over 160k buildLocation calls against the production dist/esm (56 B per regex-literal evaluation measured in isolation, 0 once hoisted); CPU numbers from the benchmark in test(router-core): add a Link-like buildLocation benchmark #8423.

Relationship to other PRs

Independent. Benchmark: #8423.

✅ 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

Performance
- Improved URL path processing efficiency during location parsing, encoding, and decoding.
- Optimized route matching and comparison operations.
- Existing URL matching and encoding behavior remains unchanged.
Bug Fixes
- Improved handling of undefined values during route comparisons for more consistent matching behavior.
Release
- Included in a patch release of the router core package.

coderabbitai · 2026-09-14T17:29:35Z

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: 09b17b36-51c8-44a6-8744-f5b5f087be89

📥 Commits

Reviewing files that changed from the base of the PR and between d31406c and 2ad9de3.

📒 Files selected for processing (2)

packages/router-core/src/router.ts
packages/router-core/src/utils.ts

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

📝 Walkthrough

Walkthrough

The change hoists regular expressions in router path, location, and URL utility code to module-level constants. It also changes the deepEqual signature and comparison handling. A patch changeset documents the update for @tanstack/router-core.

Changes

Router core optimization and comparison updates

Layer / File(s)	Summary
Path normalization and parameter encoding `packages/router-core/src/path.ts`, `.changeset/hoist-hot-regex.md`	`cleanPath`, `trimPathRight`, and `encodeParam` use module-level regex constants. The changeset declares a patch release.
Deep-equality comparison updates `packages/router-core/src/utils.ts`, `packages/router-core/src/router.ts`	`deepEqual` now accepts positional flags. Undefined-key handling, reference-equality handling, and object-key comparison changed. `matchRoute` passes the partial flag as `true`.
Location and URL utility regexes `packages/router-core/src/router.ts`, `packages/router-core/src/utils.ts`	`parseLocation`, `decodePath`, and `encodePathLikeUrl` use hoisted regex constants with the same matching patterns.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~15 minutes

Change: Refactor

Suggested reviewers: sheraff

Merge Risk: ⚪ Minimal · up to 2ad9d

The change is ready to merge; no concrete user-facing correctness or reliability risk remains.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 57.14% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the primary change: hoisting frequently evaluated regular expression literals in router-core.
Description check	✅ Passed	The description includes the required Changes, Checklist, and Release Impact sections. It explains the motivation, measured impact, verification, and changeset. One checklist item remains unchecked, b…
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.

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Create PR with unit tests
Commit unit tests in branch codex/hoist-hot-regex

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nx-cloud · 2026-09-14T17:48:57Z

View your CI Pipeline Execution ↗ for commit 2ad9de3

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`nx affected --targets=test:eslint,test:unit,tes...`	✅ Succeeded	12m 51s	View ↗
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☁️ Nx Cloud last updated this comment at 2026-09-15 21:13:43 UTC

pkg-pr-new · 2026-09-14T17:50:01Z

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commit: 2ad9de3

github-actions · 2026-09-14T17:54:06Z

🚀 Changeset Version Preview

4 package(s) bumped directly, 19 bumped as dependents.

🟩 Patch bumps

Package	Version	Reason
`@tanstack/react-router`	1.170.36 → 1.170.37	Changeset
`@tanstack/router-core`	1.171.30 → 1.171.31	Changeset
`@tanstack/solid-router`	1.170.34 → 1.170.35	Changeset
`@tanstack/vue-router`	1.170.33 → 1.170.34	Changeset
`@tanstack/react-start`	1.168.54 → 1.168.55	Dependent
`@tanstack/react-start-client`	1.168.34 → 1.168.35	Dependent
`@tanstack/react-start-rsc`	0.1.53 → 0.1.54	Dependent
`@tanstack/react-start-server`	1.167.41 → 1.167.42	Dependent
`@tanstack/router-cli`	1.167.36 → 1.167.37	Dependent
`@tanstack/router-generator`	1.167.36 → 1.167.37	Dependent
`@tanstack/router-plugin`	1.168.38 → 1.168.39	Dependent
`@tanstack/router-vite-plugin`	1.167.38 → 1.167.39	Dependent
`@tanstack/solid-start`	1.168.52 → 1.168.53	Dependent
`@tanstack/solid-start-client`	1.168.33 → 1.168.34	Dependent
`@tanstack/solid-start-server`	1.167.40 → 1.167.41	Dependent
`@tanstack/start-client-core`	1.170.30 → 1.170.31	Dependent
`@tanstack/start-plugin-core`	1.171.44 → 1.171.45	Dependent
`@tanstack/start-server-core`	1.169.35 → 1.169.36	Dependent
`@tanstack/start-static-server-functions`	1.167.35 → 1.167.36	Dependent
`@tanstack/start-storage-context`	1.167.32 → 1.167.33	Dependent
`@tanstack/vue-start`	1.168.51 → 1.168.52	Dependent
`@tanstack/vue-start-client`	1.167.36 → 1.167.37	Dependent
`@tanstack/vue-start-server`	1.167.40 → 1.167.41	Dependent

github-actions · 2026-09-14T18:37:47Z

Bundle Size Benchmarks

Commit: 4fc006a89dae
Measured at: 2026-09-15T20:59:33.205Z
Baseline source: history:83895f127216
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 +44 B	83.9 KiB +44 B	261.7 KiB +56 B	73.3 KiB +82 B	▂▂▂▇▇▇▇▁▁▁▁█
`react-router.full`	87.5 KiB +55 B	87.4 KiB +53 B	273.3 KiB +54 B	76.3 KiB +125 B	▄▄▃████▂▁▁▁█
`solid-router.minimal`	33.5 KiB +44 B	33.3 KiB +44 B	95.9 KiB +59 B	30.3 KiB +122 B	▆▆▅▃▃▃▃▁▁▁▁█
`solid-router.full`	38.3 KiB +47 B	38.2 KiB +46 B	110.6 KiB +59 B	34.5 KiB +35 B	▄▄▃▃▃▃▃▁▁▁▁█
`vue-router.minimal`	49.5 KiB +46 B	49.4 KiB +45 B	137.1 KiB +59 B	44.9 KiB +48 B	███▃▃▃▃▁▁▁▁▄
`vue-router.full`	55.1 KiB +53 B	55.0 KiB +51 B	155.3 KiB +59 B	49.7 KiB +31 B	███▃▃▃▃▁▁▁▁▄
`react-start.minimal`	96.9 KiB +37 B	96.8 KiB +37 B	303.9 KiB +36 B	84.0 KiB +14 B	▂▂▁████▄▄▄▄▇
`react-start.query-integration`	104.3 KiB +37 B	104.2 KiB +40 B	330.4 KiB +57 B	90.5 KiB +42 B	▂▂▁████▄▄▄▄█
`react-start.deferred-hydration`	97.7 KiB +36 B	96.8 KiB +36 B	305.2 KiB +36 B	84.6 KiB +20 B	▁▁▁████▃▃▃▃▆
`react-start.full`	100.1 KiB +50 B	100.0 KiB +48 B	313.6 KiB +58 B	86.8 KiB -1 B	▁▁▁▇▇▇▇▃▃▃▃█
`react-start.rsbuild.minimal`	100.2 KiB +45 B	100.1 KiB +45 B	314.3 KiB +50 B	86.5 KiB +53 B	▁▁▁▇▇▇▇▆▆▆▆█
`react-start.rsbuild.minimal-iife`	100.7 KiB +43 B	100.5 KiB +43 B	315.3 KiB +50 B	86.9 KiB -1 B	▁▁▁▇▇▇▇▆▆▆▆█
`react-start.rsbuild.full`	103.5 KiB +35 B	103.3 KiB +35 B	324.4 KiB +50 B	89.3 KiB +119 B	▁▁▁████▅▅▅▅▇
`solid-start.minimal`	46.4 KiB +37 B	46.3 KiB +40 B	137.1 KiB +59 B	41.2 KiB -31 B	▂▂▁▆▆▆▆▃▃▃▃█
`solid-start.deferred-hydration`	49.5 KiB +47 B	46.3 KiB +49 B	144.4 KiB +59 B	44.0 KiB +41 B	▁▁▂▅▅▅▅▂▂▂▂█
`solid-start.full`	51.5 KiB +56 B	51.3 KiB +58 B	152.4 KiB +59 B	45.6 KiB +10 B	▁▁▁▅▅▅▅▃▃▃▃█
`vue-start.minimal`	65.7 KiB +46 B	65.5 KiB +45 B	187.9 KiB +59 B	58.6 KiB +45 B	███▃▃▃▃▁▁▁▁▄
`vue-start.full`	69.5 KiB +51 B	69.4 KiB +49 B	200.3 KiB +59 B	61.9 KiB +150 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.

codspeed · 2026-09-14T18:50:28Z

Merging this PR will degrade performance by 5.03%

⚠️

Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 1 regressed benchmark
✅ 179 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
❌	Memory	`mem client unique-location-churn (vue)`	2 MB	2.1 MB	-5.03%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

_{Comparing codex/hoist-hot-regex (2ad9de3) with main (83895f1)}

A regex literal creates a new RegExp object every time it is evaluated (measured: 56 B per evaluation, 0 once hoisted). decodePath and encodePathLikeUrl run on every buildLocation, cleanPath on every href of a basepath router, encodeParam on every splat and trimPathRight on every trailing-slash path; parseLocation's fast-path test runs per navigation. Their literals are now module constants. trimPathLeft (construction only) and the cold branches of getUrlScheme are left as they were. Allocation per buildLocation (sampling heap profiler over 160k builds against the production dist, Node 24.8; on top of the previous commit): relative destination 1309 -> 1197 B (-112) search updater 1085 -> 969 B (-116) static destination 955 -> 786 B (-169) CPU (tests/build-location.bench.ts, two rounds, hz): within noise, directionally +1-2%: search updater 41.6k/44.2k -> 43.5k/43.2k, relative 29.8k/30.2k -> 29.6k/30.3k, masked 20.5k/20.9k -> 20.8k/20.6k. Bundle: react-router.minimal +18 gzip (derived from the composed measurements 86077 with, 86059 without these hoists). Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> (cherry picked from commit 72b093cad28641112858bfbc9140175eb2c1a3da)

schiller-manuel requested a review from Sheraff September 14, 2026 17:48

github-actions Bot added the package: router-core label Sep 14, 2026

Sheraff approved these changes Sep 14, 2026

View reviewed changes

schiller-manuel force-pushed the codex/hoist-hot-regex branch from d31406c to 2ad9de3 Compare September 15, 2026 20:56

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perf(router-core): hoist regex literals evaluated per built location - #8425

perf(router-core): hoist regex literals evaluated per built location#8425
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