fix: avoid unnecessary stringify in server attributes#18232
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Rich-Harris merged 2 commits intoMay 18, 2026
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🦋 Changeset detectedLatest commit: 5299073 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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Rich-Harris
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dummdidumm
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This PR was opened by the [Changesets release](https://github.com/changesets/action) GitHub action. When you're ready to do a release, you can merge this and the packages will be published to npm automatically. If you're not ready to do a release yet, that's fine, whenever you add more changesets to main, this PR will be updated. # Releases ## svelte@5.55.9 ### Patch Changes - fix: don't unset batch when calling `{#await ...}` promise ([#18243](#18243)) - fix: promise-ify `{#await await ...}` expressions on the server and correctly hydrate them on the client ([#18243](#18243)) - fix: deduplicate dependencies that are added outside the init/update cycle ([#18243](#18243)) - fix: avoid false-positive batch invariant error ([#18246](#18246)) - fix: inline primitive constants in attribute values during SSR ([#18232](#18232)) Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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Before submitting the PR, please make sure you do the following
$.stringifyon strings #10031.feat:,fix:,chore:, ordocs:.packages/svelte/src, add a changeset (npx changeset).What this changes
Server attribute template generation currently wraps each dynamic expression in
$.stringify, even when the compiler can prove the expression is a string or a known constant. This reuses the existing scope evaluation metadata so server output can avoid$.stringifyfor proven string/constant chunks while keeping it for possibly nullish unknown values.The updated snapshot covers a mixed attribute with a known string, mutable state,
null, numeric/undefined constants, a known string-producingtypeof, and an unknown prop value.Tests and linting
pnpm test snapshot -t nullish-coallescence-omittancepnpm test snapshotpnpm --filter svelte checkpnpm lintpnpm prettier --check .changeset/slow-bikes-serve.md