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2.0.0-rc.3 | projection leaks after flush while in transition #3074
Description
Describe the bug
A projection of count() leaks the set value after a flush while still being in the transition
while count() still shows the uncommitted value.
logs
[log] action:start
[log] p.a 0
[log] count 0
[log] p.a 5 <--- leak
[log] count 0 <-- no leak
[log] action:done
Your Example Website or App
Steps to Reproduce the Bug or Issue
playground
Expected behavior
expecting the expected. no leak
Screenshots or Videos
Platform
.
Additional context
import { render, untrack } from '@solidjs/web';
import { createSignal, createProjection, action, flush } from 'solid-js';
export default function App() {
const [count, setCount] = createSignal(0);
const p = createProjection(() => {
return { a: count() }
}, {})
const act = action(function* () {
console.log("action:start")
yield new Promise(r => setTimeout(r, 3000))
console.log("action:done")
})
setTimeout(() => {
untrack(() => {
act() // holds transition for 3s
setCount(v => v + 5)
console.log("p.a", p.a) // 0
console.log("count", count()) // 0
flush()
console.log("p.a", p.a) // 5
console.log("count", count()) // 0
})
})
return (
<div class="p-2">
Projection leak after flush, see logs
</div>
);
}
if (typeof document !== 'undefined') {
render(() => <App />, document.getElementById('root')!);
}
Activity
[-]2.0.0.rc3 | projection acts[/-][+]2.0.0.rc3 | projection leaks after flush while in transition [/+][-]2.0.0.rc3 | projection leaks after flush while in transition [/-][+]2.0.0-rc.3 | projection leaks after flush while in transition [/+]fix(signals): projection transition isolation and latest() parity (#3074
ryansolid commentedon Aug 27, 2026
Fixed in 0e37f90 — thanks for the tight repro, and for filing #3075 alongside it: they turned out to be the two halves of the same isolation gap, in opposite directions.
What was happening: a projection recompute commits its output through the store's adoption channel, which swaps the committed backing eagerly by contract (that's what makes reconcile immediately visible outside transitions). Node-level notifications ride core
setSignaland park correctly under the transition — which is why subscribed effects were properly held — but an untracked read serves the backing directly, sop.ashowed the speculative value afterflush()whilecount()(whose write parked in the signal's pending slot) correctly stayed committed.The fix stages a held view: when a projection adoption lands under a live transition, the pre-hold committed backing stays servable, and committed-visibility readers (untracked reads included) keep seeing it until the transition commits. Speculative readers — the derive's own draft, computeds recomputing inside the transaction, and
latest()— see the adopted backing, so the transaction still observes itself consistently.Your repro's log sequence now reads
p.a 0 / count 0after the flush, and both flip to 5 when the action's transition lands.Tier-1 creation-cost benches (stage-3 fence) (#3083)
fix: restore next work reverted by the stage-2 replay (pre-merge sweep)
fix: restore next work reverted by the stage-2 replay (pre-merge sweep)
Stage 2: store patch channel + patch-mode list driver (dormant by def…