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fix: flush eager effects in production#18107

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Rich-Harris merged 2 commits into
mainfrom
eager-production-fix
Apr 29, 2026
Merged

fix: flush eager effects in production#18107
Rich-Harris merged 2 commits into
mainfrom
eager-production-fix

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@dummdidumm

@dummdidumm dummdidumm commented Apr 13, 2026

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While working on #18106 I noticed that we're not adding eager effects inside mark_reactions when DEV is false. As a result production build could have $state.eager or $state.pending not working correctly.

No test because I can't get Vitest to not run with DEV being true. added a test

While working on #18106 I noticed that we're not adding eager effects inside `mark_reactions` when `DEV` is `false`. As a result production build could have `$state.eager` or `$state.pending` not working correctly.

No test because I can't get Vitest to not run with `DEV` being `true`.
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changeset-bot Bot commented Apr 13, 2026

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🦋 Changeset detected

Latest commit: 8c22b5a

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

This PR includes changesets to release 1 package
Name Type
svelte Patch

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Playground

pnpm add https://pkg.pr.new/svelte@18107

@7nik

7nik commented Apr 13, 2026

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No test because I can't get Vitest to not run with DEV being true.

We have runtime-production suit for it

@dummdidumm

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TIL, thank you!

@dummdidumm

dummdidumm commented Apr 16, 2026

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I played around locally with not adding eager_effect to the effect tree, because it doesn't make sense to traverse it as part of #traverse. The problem is then to destroy it at the right time. For $inspect that's easy because we can use the sibling render_effect. But for $state.eager in combination with #18108 (which we need to get in) it could mean leaks. In fact this may hint at #18108 leaking in a few very specific situations where $state.eager does not have a parent effect and therefore is not connected to the effect tree.
So now I'm wondering if we should go the other way and require $state.eager to be placed in an active effect context so we can properly clean it up - and which could also open up refactoring this towards not having flush_eager_effects for $state.eager, instead this becomes a dev-time only thing for $inspect effects.
Update: I was not able to prove any memory leaks. $state.eager is cleaned up even when not being connected to the graph.

@Rich-Harris Rich-Harris merged commit 90a70cb into main Apr 29, 2026
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@Rich-Harris Rich-Harris deleted the eager-production-fix branch April 29, 2026 22:18
@github-actions github-actions Bot mentioned this pull request Apr 29, 2026
Rich-Harris pushed a commit that referenced this pull request May 14, 2026
This PR was opened by the [Changesets
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# Releases
## svelte@5.55.6

### Patch Changes

- fix: leave stale promises to wait for a later resolution, instead of
rejecting ([#18180](#18180))

- fix: keep dependencies of `$state.eager/pending`
([#18218](#18218))

- fix: reapply context after transforming error during SSR
([#18099](#18099))

- fix: don't rebase just-created batches
([#18117](#18117))

- chore: allow `null` for `pending` in typings
([#18201](#18201))

- fix: flush eager effects in production
([#18107](#18107))

- fix: rethrow error of failed iterable after calling `return()`
([#18169](#18169))

- fix: account for proxified instance when updating `bind:this`
([#18147](#18147))

- fix: ensure scheduled batch is flushed if not obsolete
([#18131](#18131))

- fix: resolve stale deriveds with latest value
([#18167](#18167))

- chore: remove unnecessary `increment_pending` calls
([#18183](#18183))

- fix: correctly compile component member expressions for SSR
([#18192](#18192))

- fix: reset `source.updated` stack traces after `flush`
([#18196](#18196))

- fix: replacing async 'blocking' strategy with 'merging'
([#18205](#18205))

- fix: allow `@debug` tags to reference awaited variables
([#18138](#18138))

- fix: re-run fallback props if dependencies update
([#18146](#18146))

- fix: abort running obsolete async branches
([#18118](#18118))

- fix: ignore comments when reading CSS values
([#18153](#18153))

- fix: wrap `Promise.all` in `save` during SSR
([#18178](#18178))

- fix: ignore false-positive errors of `$inspect` dependencies
([#18106](#18106))

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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3 participants