perf(start-client-core): avoid unused middleware array by LadyBluenotes · Pull Request #8353 · TanStack/router

LadyBluenotes · 2026-09-11T03:58:10Z

🎯 Changes

Use an indexed loop instead of map when registering server-function middleware. This avoids the unused result array and the iteration callback. Composition order, factory expansion, and sparse-array handling stay unchanged. The loop captures the initial array length, so entries appended during registration are not visited. Request execution is untouched.

✅ 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
- Improved server-function middleware registration for consistent ordering and reliable handling of nested, frozen, empty, and sparse middleware lists.
- Middleware added during registration is no longer unexpectedly included.
Tests
- Added coverage for middleware concatenation, input preservation, and edge-case array behavior.

coderabbitai · 2026-09-11T03:58:29Z

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packages/start-client-core/src/createServerFn.ts

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📝 Walkthrough

Walkthrough

The middleware builder now uses forEach to flatten middleware arrays without retaining an unused array. Tests cover ordering, input preservation, frozen arrays, empty arrays, sparse arrays, and middleware appended during iteration. A patch changeset records the update.

Changes

Middleware registration

Layer / File(s)	Summary
Middleware flattening and validation `packages/start-client-core/src/createServerFn.ts`, `packages/start-client-core/tests/createServerFn.test.ts`, `.changeset/start-middleware-registration.md`	The builder uses `forEach`, skips sparse-array holes, ignores items appended during iteration, and preserves middleware flattening behavior. Tests cover array handling and input preservation. A patch changeset records the update.

Priority: ⬇️ Low

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

Change: Refactor

Merge Risk: ⚪ Minimal · up to 81414

This is a localized performance cleanup with no remaining actionable merge risk.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the performance change: avoiding the unused middleware array in start-client-core.
Description check	✅ Passed	The description includes all required sections, completed checklist items, testing information, and changeset information. It inaccurately says the implementation uses an indexed loop; the change uses…
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…
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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Commit unit tests in branch perf/server-function-middleware-iteration

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nx-cloud · 2026-09-11T03:58:47Z

View your CI Pipeline Execution ↗ for commit 81414d8

Command	Status	Duration	Result
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☁️ Nx Cloud last updated this comment at 2026-09-12 00:53:25 UTC

github-actions · 2026-09-11T03:59:38Z

🚀 Changeset Version Preview

4 package(s) bumped directly, 20 bumped as dependents.

🟩 Patch bumps

Package	Version	Reason
`@tanstack/history`	1.162.3 → 1.162.4	Changeset
`@tanstack/router-core`	1.171.29 → 1.171.30	Changeset
`@tanstack/start-client-core`	1.170.29 → 1.170.30	Changeset
`@tanstack/start-server-core`	1.169.34 → 1.169.35	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-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-plugin-core`	1.171.42 → 1.171.43	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 · 2026-09-11T04:03:24Z

Bundle Size Benchmarks

Commit: 52cb70f718f1
Measured at: 2026-09-12T00:52:54.399Z
Baseline source: history:f021f6d1c6dc
Dashboard: bundle-size history

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

Scenario	Current (gzip)	Initial (gzip)	Raw	Brotli	Trend
`react-start.full`	100.0 KiB 0 B	99.9 KiB -2 B	314.3 KiB +4 B	86.7 KiB +36 B	███████▁▁▁▁
`react-start.rsbuild.full`	103.4 KiB 0 B	103.2 KiB 0 B	324.9 KiB +4 B	89.2 KiB +31 B	███████▁▁▁▁
`solid-start.full`	51.4 KiB +4 B	51.3 KiB +2 B	153.3 KiB +4 B	45.6 KiB +40 B	▆▆▅▁▁▁▁▁▁▁▁█
`vue-start.full`	69.6 KiB -1 B	69.5 KiB +1 B	201.5 KiB +4 B	61.8 KiB +27 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 · 2026-09-11T04:03:37Z

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commit: 81414d8

codspeed-hq · 2026-09-11T04:14:10Z

Merging this PR will not alter performance

✅ 180 untouched benchmarks

_{Comparing perf/server-function-middleware-iteration (ec6bd76) with main (dbf0bd9)¹}

No successful run was found on main (05422da) during the generation of this report, so dbf0bd9 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

nx-cloud

Nx Cloud has identified a flaky task in your failed CI:

🔂 Since the failure was identified as flaky, we triggered a CI rerun by adding an empty commit to this branch.

View detailed reasoning in Nx Cloud ↗

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

Sheraff · 2026-09-11T08:43:33Z

would a for loop be even better than using array methods?

LadyBluenotes · 2026-09-11T15:01:03Z

would a for loop be even better than using array methods?

yeah youre right. ill update

forEach keeps the hole-skipping and length-snapshot semantics the tests cover without the extra `in` check and length hoist, and it avoids the result array that map allocated. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

github-actions Bot added the package: start-client-core label Sep 11, 2026

nx-cloud Bot reviewed Sep 11, 2026

View reviewed changes

LadyBluenotes force-pushed the perf/server-function-middleware-iteration branch 2 times, most recently from ce7bb7b to 50a4560 Compare September 11, 2026 20:38

LadyBluenotes added 2 commits September 11, 2026 16:46

perf(start-client-core): avoid unused middleware array

240d7b7

perf(start-client-core): use indexed middleware iteration

ec6bd76

LadyBluenotes force-pushed the perf/server-function-middleware-iteration branch from 50a4560 to ec6bd76 Compare September 11, 2026 23:46

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