fix: flush batches whenever an async value resolves #16912
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🦋 Changeset detectedLatest commit: ec721bb The changes in this PR will be included in the next version bump. This PR includes changesets to release 1 package
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dummdidumm
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Oct 8, 2025
Test for #16912 Also some explanation what the bug was: 1. async batch kicks off 2. outer async work succeeds, still something pending, so doesn't do anything for now 3. something unrelated writes to a signal (in the remote functions case it's the query writing to loading, raw etc), which creates a new batch 4. new batch executes. since there are multiple batches it takes the previous value which means if block is still alive. commits that, since no async work from the perspective of this branch 5. inner async work succeeds. now the batch has zero pending async work so it can flush. But the if block is no longer dirty since it was done by the other batch already -> never undos the other work #16912 fixes it by still traversing the tree which means the if block deletion is scheduled to commit later, which it then does
dummdidumm
added a commit
that referenced
this pull request
Oct 8, 2025
Test for #16912 Also some explanation what the bug was: 1. async batch kicks off 2. outer async work succeeds, still something pending, so doesn't do anything for now 3. something unrelated writes to a signal (in the remote functions case it's the query writing to loading, raw etc), which creates a new batch 4. new batch executes. since there are multiple batches it takes the previous value which means if block is still alive. commits that, since no async work from the perspective of this branch 5. inner async work succeeds. now the batch has zero pending async work so it can flush. But the if block is no longer dirty since it was done by the other batch already -> never undos the other work #16912 fixes it by still traversing the tree which means the if block deletion is scheduled to commit later, which it then does
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This fixes a tricky bug that occurs with remote functions. I struggled to make a narrow repro, but the change is one that makes sense on the face of it: whenever an async value resolves, we update the batch, flushing the change through the effect tree. This has the effect of destroying anything inside blocks that would otherwise keep them alive.
It feels like we might actually need to go even further than this, and deactivate async work inside skipped branches, but I'm not immediately sure how to tackle that, so just making this change for now.
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feat:,fix:,chore:, ordocs:.packages/svelte/src, add a changeset (npx changeset).Tests and linting
pnpm testand lint the project withpnpm lint