test(signals): pin the 3540 keyed-Show park re-derive at its target [1,2,2] as a known bug (#4417) by ryansolid · Pull Request #4419 · solidjs/solid

ryansolid · 2026-10-29T15:48:30Z

What changed

Tests only — no source, no changeset.

packages/signals/tests/boundary-not-born-held-3540.test.ts: the static over latest and callback over latest matrix rows now assert the target mount counts [1, 2, 2] and run as test.fails. The other rows (on over latest, all committed rows) are unchanged and still pass.
packages/web/test/loading-on-keyed-boundary-3540.spec.tsx: the same for show-static-latest and show-callback-latest.

The mid-flight/landed snapshot assertions in those rows are untouched; the only thing failing is the mount count ([1, 3, 3] received vs [1, 2, 2] expected), so the test.fails guards exactly the bug.

Known bug: #4417 — a keyed Show on latest() of a staged write mounts its child twice when the flush parks (regressed by #4393).

Why `it.fails` at `[1, 2, 2]` instead of pinning `[1, 3, 3]`

[1, 3, 3] is the wrong number per the maintainer ruling on #4417: the park re-derive (D-2) says nothing about discarding the provisional pass's output, and latest() serves the staging on both runs, so the key is identical and one child should mount once. Pinning [1, 3, 3] would guard the bug. With test.fails at the target, the pin turns red-to-green when the in-place park re-derive lands (reader-seat rebuild S1, #4395) and alerts us if the number drifts anywhere else.

Both files run as N passed | 2 expected fail locally.

Public API changes

None.

…1,2,2] as a known bug (#4417) Co-authored-by: Cursor <[email protected]>

changeset-bot · 2026-10-29T15:48:37Z

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Latest commit: cfd33ea

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github-actions · 2026-10-29T15:51:37Z

Size (brotli, eager entry chunk)

scenario	head	cap		lazy chunks (not counted)
signals: core floor (createSignal/Memo/Effect/Root/flush)	7.51 KB	7.53 KB	✅
signals: + createStore	15.04 KB	15.06 KB	✅
signals: + isPending/latest	11.02 KB	11.03 KB	✅
signals: + until/refresh (truth readers, no optimism)	8.14 KB	8.16 KB	✅
app: render + one signal (the simple-app floor)	9.87 KB	9.88 KB	✅
app: hydrating (no stores) with Show/For/Loading/Errored/lazy	18.79 KB	18.80 KB	✅	lazy-page.js 0.04 KB
app: hydrating + every store primitive family	32.41 KB	32.42 KB	✅	lazy-page.js 0.04 KB
app: CSR with Show/For/Loading/Errored/lazy	13.52 KB	13.53 KB	✅	lazy-page.js 0.04 KB
app: CSR, observe tier (same app on the `observe` artifacts)	15.28 KB	15.29 KB	✅	lazy-page.js 0.04 KB
app: CSR, observe tier + attribution engine enabled	29.84 KB	29.85 KB	✅	lazy-page.js 0.04 KB
app: compiled floor (one template, one text hole, one delegated click)	10.06 KB	10.07 KB	✅
app: compiled CSR (JSX todo app: spread/merge/omit, events, class/style, keyed For, Show, Loading + lazy, store)	26.38 KB	26.40 KB	✅	stats.js 0.18 KB
app: compiled hydrating (the same JSX todo app through hydrate(), compiled hydratable)	32.57 KB	32.58 KB	✅	stats.js 0.20 KB
frames: eager client consumer (frames client + transport, lazy codec)	11.75 KB	11.77 KB	✅
page: base server components (hydrating + dynamic + frames + sf reference)	33.77 KB	33.78 KB	✅	assets.js 0.78 KB, decode.js 7.09 KB, lazy-page.js 0.04 KB, regions.js 1.06 KB, trace.js 9.03 KB, wire.js 3.47 KB
page: live server components (base + live/GET + action + isPending/latest)	38.66 KB	38.67 KB	✅	assets.js 0.78 KB, decode.js 7.09 KB, lazy-page.js 0.04 KB, regions.js 1.06 KB, trace.js 9.04 KB, wire.js 3.47 KB
page: compiled base server components (the base page as JSX: templates with class/style/attributes/events, For/Show; no spread)	35.68 KB	35.69 KB	✅	assets.js 0.78 KB, decode.js 7.09 KB, regions.js 1.06 KB, sc-comments.js 0.20 KB, trace.js 8.99 KB, wire.js 3.47 KB
page: compiled live server components (the compiled base page + live/GET + action + isPending/latest)	42.59 KB	42.61 KB	✅	eager (counted): web.js 22.69 KB; assets.js 0.78 KB, decode.js 7.09 KB, regions.js 1.07 KB, sc-comments.js 0.19 KB, trace.js 9.05 KB, wire.js 3.47 KB
page: base + router (base page + @solidjs/router: createRouter, two routes, preload, useNavigate)	41.30 KB	41.32 KB	✅	assets.js 0.78 KB, decode.js 7.09 KB, lazy-page.js 0.04 KB, regions.js 1.06 KB, server.js 1.03 KB, serverForms.js 3.57 KB, trace.js 9.01 KB, wire.js 3.48 KB
page: live + router (live page + @solidjs/router: createRouter, two routes, preload, useNavigate)	48.27 KB	48.29 KB	✅	eager (counted): client.js 27.86 KB; assets.js 0.78 KB, decode.js 7.09 KB, lazy-page.js 0.04 KB, regions.js 1.07 KB, server.js 1.03 KB, serverForms.js 3.30 KB, trace.js 9.00 KB, wire.js 3.49 KB
server: floor (getRequestEvent + isServer)	1.27 KB	1.34 KB	✅
server: renderToString (the server-render floor)	22.79 KB	22.80 KB	✅

_{Bundled with Rolldown (what Vite ships), brotli q11, decimal KB. A scenario fails only when it is over its brotli cap and its minified size is more than 20 B over the minified recorded with the cap; over the cap within that allowance is brotli layout noise and passes with a warning. Caps and their recorded minified in scripts/size/scenarios.js; the floor and page caps in floor-caps.json are frozen (lower only, or Size-Exception: in the PR body). npm run ratchet lowers caps per RC; it never raises one (scripts/size/README.md).}

coveralls · 2026-10-29T15:56:46Z

Coverage Report for CI Build 40905288483

Coverage remained the same at 78.516%

Details

Coverage remained the same as the base build.
Patch coverage: No coverable lines changed in this PR.
No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

Coverage Stats


Relevant Lines:	1355
Covered Lines:	1125
Line Coverage:	83.03%
Relevant Branches:	1084
Covered Branches:	790
Branch Coverage:	72.88%
Branches in Coverage %:	Yes
Coverage Strength:	29.81 hits per line

💛 - Coveralls

codspeed · 2026-10-29T16:13:22Z

Merging this PR will degrade performance by 11.08%

2 warnings

⚠️ 2 benchmarks are dominated by system calls

System calls cannot be simulated consistently and are left out of the measure. The reported value understates the real cost. Switch to the Walltime instrument to measure them.

Learn more about system calls

See affected benchmarks

⚠️ Base and head ran on different runner types

Some benchmarks with significant performance changes were compared across different runner types, so the changes might not come from the code. Run base and head on the same runner type, or use CodSpeed Macro Runners for more stable results.

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❌ 1 regressed benchmark
✅ 199 untouched benchmarks
⏩ 5 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	`BASE`	`HEAD`	Efficiency
❌	`arrow in template`	11 ms	12.4 ms	-11.08%

Tip

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

_{Comparing fix/pin-3540-double-mount (cfd33ea) with next (9545058)}

5 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

test(signals): pin the 3540 keyed-Show park re-derive at its target […

cfd33ea

…1,2,2] as a known bug (#4417) Co-authored-by: Cursor <[email protected]>

ryansolid merged commit 4e1a83a into next Oct 29, 2026
8 of 9 checks passed

ryansolid mentioned this pull request Oct 29, 2026

refactor(signals): reader seat — S1 swap (deciders → seat + slot table; lanes.ts split) #4430

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test(signals): pin the 3540 keyed-Show park re-derive at its target [1,2,2] as a known bug (#4417) - #4419

test(signals): pin the 3540 keyed-Show park re-derive at its target [1,2,2] as a known bug (#4417)#4419
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fix/pin-3540-double-mount

ryansolid commented Oct 29, 2026

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ryansolid commented Oct 29, 2026

What changed

Why it.fails at [1, 2, 2] instead of pinning [1, 3, 3]

Public API changes

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changeset-bot Bot commented Oct 29, 2026

⚠️ No Changeset found

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github-actions Bot commented Oct 29, 2026

Size (brotli, eager entry chunk)

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coveralls commented Oct 29, 2026

Coverage Report for CI Build 40905288483

Coverage remained the same at 78.516%

Details

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Coverage Stats

💛 - Coveralls

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codspeed Bot commented Oct 29, 2026

Merging this PR will degrade performance by 11.08%

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Why `it.fails` at `[1, 2, 2]` instead of pinning `[1, 3, 3]`