fix(signals): skip UNSTABLE_MEMO_OUTPUT for merge()'s function-source memo (#4256) by ryansolid · Pull Request #4260 · solidjs/solid

ryansolid · 2026-10-25T01:05:27Z

Before: a component spread whose expression isn't a plain object, such as <Child {...(on() ? { tone: "info" } : {})} />, compiles to mergeProps(() => …). merge() wraps that function in a memo with no options. The idiom returns a fresh key bag on every run, so after four runs the attribution engine reports UNSTABLE_MEMO_OUTPUT for memo "computed" and says to pass equals. Nobody wrote that memo, so nobody can pass it options.

After: observe builds create that memo with the name merge and a new CONFIG_KEY_BAG bit. The unstable-output check skips any memo carrying that bit. Production output is unchanged: the prod branch is still createMemo(s).

How: merge() passes { name: "merge", _extraConfig: CONFIG_KEY_BAG } behind __OBSERVE__, using the existing _extraConfig route. checkUnstableOutput returns early for that bit. This follows the existing exemptions (CONFIG_WIDE, CONFIG_SUPERSEDES).

The issue also proposed a shallow equals on the merge memo. I left that out because it would add bytes to every app that spreads into a component.

Fixes #4256

How did you test this change?

New packages/signals/tests/attribution-unstable-merge-4256.test.ts uses the issue's repro shape with merge(() => …) and a reader of props.tone, run eight times. It fails on next (one UNSTABLE_MEMO_OUTPUT) and passes with this change.
The existing attribution-unstable-memo.test.ts still passes, so user memos still warn.
signals: 5,577 passed (2 expected fail, 2 skipped). The build's type check is clean, and dist/prod/store/utils.js still emits createMemo(o).

Generated by Claude Code

… memo (#4256) A component spread whose expression is not a plain object compiles to merge(fn), and merge() wraps the function in a memo with no options. The idiom returns a fresh key bag every run, so the attribution engine reported UNSTABLE_MEMO_OUTPUT for memo "computed" with advice (`equals`) nobody can apply. Observe builds now create that memo as `merge` with a new CONFIG_KEY_BAG bit, and the unstable-output check skips it. Production creates the memo exactly as before. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_015hPxMkC3jg3Uivh65gvaf2

changeset-bot · 2026-10-25T01:05:33Z

🦋 Changeset detected

Latest commit: 78dab45

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

This PR includes changesets to release 15 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
board-example	Patch
canvas-example	Patch
server-dbmon-example	Patch
todos-server-example	Patch

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github-actions · 2026-10-25T01:08:20Z

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)	7.43 KB	0 B	0 B	−79 B	7.44 KB	✅
signals: + createStore	14.97 KB	0 B	0 B	−930 B	15.04 KB	✅
signals: + isPending/latest	10.30 KB	0 B	0 B	−83 B	10.30 KB	✅
signals: + until/refresh (truth readers, no optimism)	8.06 KB	0 B	0 B	−85 B	8.05 KB	⚠️ over by 5.9999999999990905 B, 105 B minified headroom
app: render + one signal (the simple-app floor)	9.79 KB	0 B	0 B	−84 B	9.75 KB	⚠️ over by 35 B, 104 B minified headroom
app: hydrating (no stores) with Show/For/Loading/Errored/lazy	18.43 KB	0 B	0 B	−93 B	18.38 KB	⚠️ over by 45 B, 113 B minified headroom	lazy-page.js 0.04 KB
app: hydrating + every store primitive family	30.68 KB	0 B	0 B	−949 B	30.66 KB	⚠️ over by 21 B, 969 B minified headroom	lazy-page.js 0.04 KB
app: CSR with Show/For/Loading/Errored/lazy	13.38 KB	0 B	0 B	−78 B	13.33 KB	⚠️ over by 51 B, 98 B minified headroom	lazy-page.js 0.04 KB
app: CSR, observe tier (same app on the `observe` artifacts)	15.10 KB	+7 B (+0.0%)	0 B	−79 B	15.08 KB	⚠️ over by 19 B, 99 B minified headroom	lazy-page.js 0.04 KB
app: CSR, observe tier + attribution engine enabled	29.68 KB	+1 B (+0.0%)	+15 B	−60 B	29.64 KB	⚠️ over by 41 B, 80 B minified headroom	lazy-page.js 0.04 KB
app: compiled floor (one template, one text hole, one delegated click)	9.96 KB	0 B	0 B	−83 B	9.93 KB	⚠️ over by 32 B, 103 B minified headroom
app: compiled CSR (JSX todo app: spread/merge/omit, events, class/style, keyed For, Show, Loading + lazy, store)	26.24 KB	0 B	0 B	−923 B	26.23 KB	⚠️ over by 6 B, 943 B minified headroom	stats.js 0.18 KB
app: compiled hydrating (the same JSX todo app through hydrate(), compiled hydratable)	32.23 KB	0 B	0 B	−946 B	32.23 KB	✅	stats.js 0.20 KB
frames: eager client consumer (frames client + transport, lazy codec)	11.75 KB	0 B	0 B	0 B	11.76 KB	✅
page: base server components (hydrating + dynamic + frames + sf reference)	33.33 KB	0 B	0 B	−83 B	33.27 KB	⚠️ over by 56 B, 103 B minified headroom	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)	37.58 KB	0 B	0 B	−93 B	37.64 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)	35.33 KB	0 B	0 B	−87 B	35.30 KB	⚠️ over by 29 B, 107 B minified headroom	assets.js 0.78 KB, decode.js 7.09 KB, regions.js 1.06 KB, sc-comments.js 0.20 KB, trace.js 9.08 KB, wire.js 3.47 KB
page: compiled live server components (the compiled base page + live/GET + action + isPending/latest)	41.49 KB	0 B	0 B	−91 B	41.47 KB	⚠️ over by 21 B, 111 B minified headroom	eager (counted): web.js 22.12 KB; assets.js 0.78 KB, decode.js 7.09 KB, regions.js 1.06 KB, sc-comments.js 0.19 KB, trace.js 9.08 KB, wire.js 3.47 KB
page: base + router (base page + @solidjs/router: createRouter, two routes, preload, useNavigate)	40.81 KB	0 B	0 B	−89 B	40.78 KB	⚠️ over by 29 B, 109 B minified headroom	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 3.58 KB, trace.js 9.09 KB, wire.js 3.48 KB
page: live + router (live page + @solidjs/router: createRouter, two routes, preload, useNavigate)	47.00 KB	0 B	0 B	−99 B	47.01 KB	✅	eager (counted): client.js 27.16 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 3.32 KB, trace.js 9.09 KB, wire.js 3.49 KB
server: floor (getRequestEvent + isServer)	1.27 KB	0 B	0 B	−69 B	1.34 KB	✅
server: renderToString (the server-render floor)	22.79 KB	0 B	0 B	0 B	22.80 KB	✅

⚠️ Over the brotli cap within the minified allowance (passes)

signals: + until/refresh (truth readers, no optimism): over brotli cap by 5.9999999999990905 B; minified 21,861 B vs 21,946 B recorded with the cap (−85 B) — 105 B of the 20 B minified allowance left; +0 B minified over this PR's base
app: render + one signal (the simple-app floor): over brotli cap by 35 B; minified 26,945 B vs 27,029 B recorded with the cap (−84 B) — 104 B of the 20 B minified allowance left; +0 B minified over this PR's base
app: hydrating (no stores) with Show/For/Loading/Errored/lazy: over brotli cap by 45 B; minified 53,505 B vs 53,598 B recorded with the cap (−93 B) — 113 B of the 20 B minified allowance left; +0 B minified over this PR's base
app: hydrating + every store primitive family: over brotli cap by 21 B; minified 94,888 B vs 95,837 B recorded with the cap (−949 B) — 969 B of the 20 B minified allowance left; +0 B minified over this PR's base
app: CSR with Show/For/Loading/Errored/lazy: over brotli cap by 51 B; minified 37,174 B vs 37,252 B recorded with the cap (−78 B) — 98 B of the 20 B minified allowance left; +0 B minified over this PR's base
app: CSR, observe tier (same app on the observe artifacts): over brotli cap by 19 B; minified 42,130 B vs 42,209 B recorded with the cap (−79 B) — 99 B of the 20 B minified allowance left; +0 B minified over this PR's base
app: CSR, observe tier + attribution engine enabled: over brotli cap by 41 B; minified 88,467 B vs 88,527 B recorded with the cap (−60 B) — 80 B of the 20 B minified allowance left; +15 B minified over this PR's base
app: compiled floor (one template, one text hole, one delegated click): over brotli cap by 32 B; minified 27,477 B vs 27,560 B recorded with the cap (−83 B) — 103 B of the 20 B minified allowance left; +0 B minified over this PR's base
app: compiled CSR (JSX todo app: spread/merge/omit, events, class/style, keyed For, Show, Loading + lazy, store): over brotli cap by 6 B; minified 80,404 B vs 81,327 B recorded with the cap (−923 B) — 943 B of the 20 B minified allowance left; +0 B minified over this PR's base
page: base server components (hydrating + dynamic + frames + sf reference): over brotli cap by 56 B; minified 101,443 B vs 101,526 B recorded with the cap (−83 B) — 103 B of the 20 B minified allowance left; +0 B minified over this PR's base
page: compiled base server components (the base page as JSX: templates with class/style/attributes/events, For/Show; no spread): over brotli cap by 29 B; minified 107,789 B vs 107,876 B recorded with the cap (−87 B) — 107 B of the 20 B minified allowance left; +0 B minified over this PR's base
page: compiled live server components (the compiled base page + live/GET + action + isPending/latest): over brotli cap by 21 B; minified 123,029 B vs 123,120 B recorded with the cap (−91 B) — 111 B of the 20 B minified allowance left; +0 B minified over this PR's base
page: base + router (base page + @solidjs/router: createRouter, two routes, preload, useNavigate): over brotli cap by 29 B; minified 125,275 B vs 125,364 B recorded with the cap (−89 B) — 109 B of the 20 B minified allowance left; +0 B minified over this PR's base

_{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 · 2026-10-25T01:16:27Z

Coverage Report for CI Build 40149257064

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No base build found for commit 2a0da2f on next.
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If a base build is processing, this comment will update automatically when it completes.

Coverage: 77.764%

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Patch coverage: No coverable lines changed in this PR.

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Coverage Stats


Relevant Lines:	1358
Covered Lines:	1114
Line Coverage:	82.03%
Relevant Branches:	1066
Covered Branches:	771
Branch Coverage:	72.33%
Branches in Coverage %:	Yes
Coverage Strength:	27.72 hits per line

💛 - Coveralls

codspeed · 2026-10-25T01:19:45Z

Merging this PR will degrade performance by 13.38%

2 warnings

⚠️ 4 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.

Learn more about Macro Runners

Open the report in CodSpeed to investigate

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

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	`BASE`	`HEAD`	Efficiency
❌	`memo + sync render effect only (reference)`	29.6 ms	34.1 ms	-13.38%

Tip

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

_{Comparing claude/project-thread-x1ore2-4256 (78dab45) with next (2a0da2f)}

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. ↩

ryansolid · 2026-10-25T01:20:04Z

CodSpeed flags one benchmark: the mount-rows "memo + sync render effect only (reference)" bench, 29.6 → 34.3 ms. The benches run the prod tier, and this PR leaves that tier's merge() call as createMemo(s), the same as base. The size report also shows 0 B change on every prod scenario. CodSpeed says base and head ran on different runner types. This reference bench flips by about the same amount between runner types: #4250 and #4251 went 34.2 → 29.6 ms against an earlier base. I'm treating it as runner noise and re-running CodSpeed once.

Generated by Claude Code

ryansolid marked this pull request as ready for review October 25, 2026 01:20

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fix(signals): skip UNSTABLE_MEMO_OUTPUT for merge()'s function-source memo (#4256) - #4260

fix(signals): skip UNSTABLE_MEMO_OUTPUT for merge()'s function-source memo (#4256)#4260
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ryansolid commented Oct 25, 2026

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Size (brotli, eager entry chunk)

⚠️ Over the brotli cap within the minified allowance (passes)

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coveralls commented Oct 25, 2026

Coverage Report for CI Build 40149257064

Coverage: 77.764%

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Merging this PR will degrade performance by 13.38%

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