chore: re-use current active effect for toStore if it already exists

[trueadm]

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🦋 Changeset detected

Latest commit: d950577

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

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-svelte-15437-svelte.vercel.app/

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Playground

pnpm add https://pkg.pr.new/svelte@15437

[paoloricciuti]

I wonder if this is all we need to do tho: if we execute the teardown of the root before the component unmount it should still work even with the current code (we can still add this)...I'll look into it later

[trueadm]

I wonder if this is all we need to do tho: if we execute the teardown of the root before the component unmount it should still work even with the current code (we can still add this)...I'll look into it later

The issue is that when we schedule work on an effect and they're in different roots, you'll have race conditions where one root will happen entirely before the other. So if one root is trying to manage the other root, then the timing of teardown is not going to be consistent.

[trueadm]

A better fix #15439.