fix: prevent component pre-mounting in async boundaries#16633
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harshmandan wants to merge 2 commits into
Closed
fix: prevent component pre-mounting in async boundaries#16633harshmandan wants to merge 2 commits into
harshmandan wants to merge 2 commits into
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🦋 Changeset detectedLatest commit: eebadcd 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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The test passes locally. Not sure why the CI run failed. 
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This was referenced Aug 18, 2025
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As far as I can tell (there was no test included in this PR, so I'm deducing from the playground links above) this was fixed at some point, so I'll close this |
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Note: Follows up #16624.
failing test case w/ 16624 | The same test case with this PR
Description:
This PR changes how deferred components and their effects are mounted. Earlier components inside svelte:boundary with await were being mounted immediately as offscreen fragments and then replaced/swapped after the promises resolved, triggering effects immediately.
In this PR mounting is deferred until promise is resolved (no offscreen fragment is created. Not sure if this has any implications 🤞).
So, this solves the original issue of changed lifecycle order and the component unmounting is also kept deferred.
Tests and linting
pnpm testand lint the project withpnpm lint