solidjs / solid / 40735678941

78%

main: 89%

push

github

fix(signals): a derived store over latest() never serves its seed after it first resolves (#4355) (#4369)

A derived store whose derive reads an async memo through `latest()`
resolved, but a memo reading it saw the seed for one pass: a render effect
behind that memo committed `undefined`, then the value. A render effect
reading the store directly saw only the value.

Cause: the derive reads `latest()`, so it is a verdict reader, and a memo
that reads it through the store's status pull becomes one too (F-6, #4050).
In the landing flush the derive's first write is a staging and the derive is
still uninitialized. Core serves a verdict reader the screen for a staged
signal (A10, `stagedScreen`), and a store leaf's screen is the committed
backing, which is the seed. The seed is never observable (A25, D-30). A
memo born staged has the same guard in core `serve`, but store leaves take
the signal fast path, which has no status to check.

Fix: the store's `nodeValue` serves the leaf's unheld staging while the
family's derive has never committed (STATUS_UNINITIALIZED), as it already
does for a handler read. Store engine only: +19 B minified on the four
store scenarios, every floor unchanged.

Tests: packages/signals/tests/derived-store-latest-seed-4355.test.ts (memo,
second derived store and direct readers, latest and plain derives) and
packages/web/test/derived-store-latest-seed-4355.spec.tsx (a hole through a
memo and a direct hole). Size ledger lines added; RULES-INDEX regenerated.


Claude-Session: https://claude.ai/code/session_015hPxMkC3jg3Uivh65gvaf2

Co-authored-by: Claude <noreply@anthropic.com>

790 of 1079 branches covered (73.22%)

Branch coverage included in aggregate %.

1122 of 1352 relevant lines covered (82.99%)

28.73 hits per line