fix(solid): SSR boundaries resolve children in a scope mirroring the client's flatten computed (#3414)

[ryansolid]

Closes #3414

Problem

A server-rendered <Errored> fallback hydrates dead: the HTML is right, but the fallback's button never fires and its signals never update the DOM. Reported shape (from the @solidjs/vite-plugin start entry): DefaultErrorBoundary > Document > DefaultErrorBoundary > App, where App renders <Errored fallback={() => <Fallback />}><SyncFailure /></Errored>.

It is a hydration id mismatch, not an event or reactivity problem. Errored with a zero-arg fallback hands the thunk back unresolved on both sides, and the consumer of the boundary's output unwraps it. When that consumer is another boundary, the two sides allocate ids for the unwrapped content in different places:

• client createCollectionBoundary — two computeds under the boundary owner: c = computed(fn) (…0) and boundaryComputed(() => flatten(read(c))) (…1); flatten calls the thunk inside …1, so the fallback's <main> gets …10
• server createErrorBoundary.resolve — one owner for fn (…0), then ctx.resolve(...) inline under the boundary owner, so <main> got …1

For the reported document: server <main _hk=00101>, client expected 001010 → "Hydration key miss", a detached fallback, dead button. The same misalignment hits Loading as the consumer, fragment children, and Show's fallback thunk. An element hole in between (compiled scope() on the server ↔ transparent insert effect on the client) is already aligned, which is why simpler repros pass.

Fix

The server Errored and Loading boundaries resolve their children's result in a virtual id scope mirroring the client's second computed — ssrScope's technique: the owner keeps its identity and only its id/_childCount are rewritten for the duration of the resolve; retry pulls resume the surviving holes in the same scope with the counter continuing where the discovery pass left it.

Why virtual and not a real createOwner(): retry wraps (buildAsyncWrap) capture the owner and read the current pull's ErrorContext handler off it. A real child owner snapshots the handler of the pull that created it; on the retry pass the stale handler rendered the fallback once, then the current pull rendered it again (double render, error serialized twice, ids off by two) — ssr-stream.spec.tsx's "Loading wrapping Errored" test caught this.

The error record is now serialized at the boundary's own id, read once (boundaryId), since owner.id is rewritten while the error lands mid-resolve.

Tests

Five parity-harness scenarios (SSR artifact → hydrate, both compilers): errored-thunk-fallback-under-errored, -under-loading, -in-fragment, -in-element (control), show-thunk-fallback-under-errored. Four failed before the fix (key miss / dead update); all pass with matching owner chains on both sides. Full web dom/server/hydrate and solid suites green.

Not verified against the reporter's Vite app (it pins rc.8 from npm); the jsdom repro reproduces its exact markup and ids (001000 record, 001010 fallback root on both sides).

[changeset-bot]

🦋 Changeset detected

Latest commit: f100afa

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

This PR includes changesets to release 11 packages

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

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[coveralls]

Coverage Report for CI Build 34860340383

Coverage remained the same at 71.842%

Details

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

Relevant Lines:	1007
Covered Lines:	772
Line Coverage:	76.66%
Relevant Branches:	790
Covered Branches:	519
Branch Coverage:	65.7%
Branches in Coverage %:	Yes
Coverage Strength:	15.02 hits per line

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[codspeed]

Merging this PR will not alter performance

✅ 160 untouched benchmarks

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_{Comparing fix/ssr-boundary-resolve-scope-3414 (f100afa) with next (1643d2a)}