fix(signals): a projection's synchronous throw reaches its readers (#3956)

[ryansolid]

Fixes #3956

What was wrong: when a createProjection re-ran and threw synchronously (e.g. the entry it reads has since failed), the error stayed on the projection's internal derive. Readers of the projection's fields subscribe to the leaves, not to the derive, so nothing woke them: the screen kept showing the last good value and no <Errored> caught anything. The catch only woke the leaves' readers for NotReadyError (a flight going up).

Fix: in the pass's catch, any other error wakes the family's readers too (errorFamily), so they re-derive and meet the error. One line in store/projection.ts.

Test: tests/store/projection-sync-throw-3956.test.ts. A projection reads entry(key()) and throws when the entry is errored, under Errored(Loading(...)). setKey("bad") now shows ERRORED; on next it stayed row-good.

Size: +6 B minified on "hydrating + every store primitive family"; the core, isPending/latest, render and CSR scenarios are unchanged. Full signals suite: 5156 passed, 22 expected fail.

🤖 Generated with Claude Code

https://claude.ai/code/session_01LVm3wseHt9wRTY8LfPiHmQ

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Generated by Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: 4b711c3

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 12 packages

Name	Type
@solidjs/signals	Patch
test-integration	Patch
@solidjs/web	Patch
@solidjs/babel-plugin	Patch
@solidjs/compiler	Patch
@solidjs/diagnostics	Patch
@solidjs/element	Patch
@solidjs/h	Patch
@solidjs/html	Patch
solid-js	Patch
@solidjs/universal	Patch
todos-server-example	Patch

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[github-actions]

Size (brotli, eager entry chunk)

scenario	head	vs base	minified vs base	minified vs recorded	cap		lazy chunks (not counted)
signals: core floor (createSignal/Memo/Effect/Root/flush)	7.44 KB	0 B	0 B	+32 B	7.45 KB	✅
signals: + createStore	14.70 KB	+5 B (+0.0%)	+6 B	+10 B	14.71 KB	✅
signals: + isPending/latest	9.71 KB	0 B	0 B	−42 B	9.73 KB	✅
app: render + one signal (the simple-app floor)	9.92 KB	0 B	0 B	−38 B	9.94 KB	✅
app: hydrating (no stores) with Show/For/Loading/Errored/lazy	17.69 KB	0 B	0 B	−649 B	17.93 KB	✅	lazy-page.js 0.04 KB
app: hydrating + every store primitive family	29.07 KB	−49 B (−0.2%)	+6 B	−518 B	29.27 KB	✅	lazy-page.js 0.04 KB
app: CSR with Show/For/Loading/Errored/lazy	12.95 KB	0 B	0 B	−46 B	12.98 KB	✅	lazy-page.js 0.04 KB
app: CSR, observe tier (same app on the observe artifacts)	14.55 KB	0 B	0 B	−30 B	14.56 KB	✅	lazy-page.js 0.04 KB
app: CSR, observe tier + attribution engine enabled	28.84 KB	0 B	0 B	+26 B	28.89 KB	✅	lazy-page.js 0.04 KB
app: compiled floor (one template, one text hole, one delegated click)	10.12 KB	0 B	0 B	−56 B	10.13 KB	✅
app: compiled CSR (JSX todo app: spread/merge/omit, events, class/style, keyed For, Show, Loading + lazy, store)	25.42 KB	−21 B (−0.1%)	+8 B	−33 B	25.46 KB	✅	stats.js 0.18 KB
app: compiled hydrating (the same JSX todo app through hydrate(), compiled hydratable)	31.13 KB	−7 B (−0.0%)	+6 B	−655 B	31.39 KB	✅	stats.js 0.20 KB
frames: eager client consumer (frames client + transport, lazy codec)	11.43 KB	0 B	0 B	0 B	11.43 KB	✅
page: base server components (hydrating + dynamic + frames + sf reference)	33.85 KB	0 B	0 B	−2310 B	34.33 KB	✅	assets.js 0.78 KB, bind.js 1.83 KB, decode.js 6.23 KB, lazy-page.js 0.04 KB, regions.js 0.80 KB, trace.js 8.78 KB, wire.js 0.93 KB
page: live server components (base + live/GET + action + isPending/latest)	37.62 KB	0 B	0 B	−2382 B	38.15 KB	✅	assets.js 0.78 KB, bind.js 1.83 KB, decode.js 6.23 KB, lazy-page.js 0.04 KB, regions.js 0.80 KB, trace.js 8.77 KB, wire.js 0.93 KB
page: compiled base server components (the base page as JSX: templates with class/style/attributes/events, For/Show; no spread)	34.75 KB	0 B	0 B	−3475 B	35.66 KB	✅	assets.js 0.78 KB, bind.js 1.82 KB, decode.js 6.23 KB, regions.js 0.80 KB, sc-comments.js 0.20 KB, trace.js 8.74 KB, wire.js 0.93 KB
page: compiled live server components (the compiled base page + live/GET + action + isPending/latest)	40.29 KB	0 B	0 B	−3488 B	41.21 KB	✅	eager (counted): web.js 21.23 KB; assets.js 0.78 KB, bind.js 1.83 KB, decode.js 6.23 KB, regions.js 0.79 KB, sc-comments.js 0.19 KB, trace.js 8.73 KB, wire.js 0.93 KB
page: base + router (base page + @solidjs/router: createRouter, two routes, preload, useNavigate)	41.25 KB	0 B	0 B	−2316 B	41.79 KB	✅	assets.js 0.78 KB, bind.js 1.84 KB, decode.js 6.23 KB, lazy-page.js 0.04 KB, regions.js 0.80 KB, server.js 1.02 KB, serverForms.js 3.59 KB, trace.js 8.79 KB, wire.js 0.94 KB
page: live + router (live page + @solidjs/router: createRouter, two routes, preload, useNavigate)	47.02 KB	0 B	0 B	−2327 B	47.49 KB	✅	eager (counted): client.js 27.48 KB; assets.js 0.78 KB, bind.js 1.85 KB, decode.js 6.23 KB, lazy-page.js 0.04 KB, regions.js 0.81 KB, server.js 1.02 KB, serverForms.js 3.30 KB, trace.js 8.75 KB, wire.js 0.94 KB
server: floor (getRequestEvent + isServer)	1.33 KB	0 B	0 B	0 B	1.34 KB	✅
server: renderToString (the server-render floor)	20.40 KB	0 B	0 B	+4 B	20.42 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]

Coverage Report for CI Build 38124404564

Coverage remained the same at 77.429%

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.

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Coverage Stats

Relevant Lines:	1321
Covered Lines:	1079
Line Coverage:	81.68%
Relevant Branches:	1036
Covered Branches:	746
Branch Coverage:	72.01%
Branches in Coverage %:	Yes
Coverage Strength:	27.15 hits per line

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💛 - Coveralls

[ryansolid]

Review at 4b711c35, compared against next (c51c5c95). Good to merge; no findings.

Checked by running the sync-throw shape beside its rejected-promise twin (which already worked on next). With this PR the two agree everywhere I tried:

shape	next, sync throw	this PR, sync throw	rejected-promise twin
good → bad, plain reader	stays row-good	ERRORED	ERRORED
reader that also calls isPending	stays row-good	ERRORED	ERRORED
two Errored boundaries over the same projection	both stay	both ERRORED	both ERRORED
reader through a memo	stays	ERRORED	ERRORED
key change held by an open action	stays after release	row-good while held, ERRORED at release	same
createStore(fn) instead of createProjection	stays	ERRORED	ERRORED

• No extra runs. The projection runs the same number of times as the twin for the change (+2) and not at all while idle afterwards, so waking the family on a sync throw doesn't start a retry loop, including with the isPending reader that [2.0 rc.14 / next] Errored derived store re-fetches in an endless loop when a row binding also reads isPending() #3945 was about.
• Recovery matches the twin. setKey("good"), a new key, and reset() after the entry is fixed all leave the fallback.
• Starting on the failing key already reached ERRORED on next and still does.
• Signals suite passes locally (5156 passed, 22 expected fail); required checks are green.

One thing for the issue, not this PR: #3956 also reports a "Potential Infinite Loop Detected" with a mutation's isPending and a refetched list on one spread. It has no repro and nothing here touches it, so it will be lost when #3956 is closed unless it gets its own issue.

— Claude via Claude Code

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Generated by Claude Code

[codspeed]

Merging this PR will improve performance by 12.68%

⚠️ 2 benchmarks spent significant time in system calls

System calls cannot be consistently instrumented, so they are not included in the measure, which understates the real cost. Please switch to the Walltime instrument to accurately measure system calls.

Measurement and system calls

• readAllowed
• propagation:diamond

⚠️ 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 improved benchmark
✅ 194 untouched benchmarks

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	createStore setter: delete + set one root key (#3044 overlay)	2.1 ms	1.8 ms	+12.68%

Tip

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

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_{Comparing fix/projection-sync-throw-3956 (4b711c3) with next (c51c5c9)}