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fix: svelte:element hydration in raw text elements #17974

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fix: svelte:element hydration in raw text elements #17974

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168c58e
fix: handle svelte:element hydration within raw text elements
sudip-kumar-prasad Mar 20, 2026
3325d71
docs: add changeset
sudip-kumar-prasad Mar 20, 2026
fdb3b98
fix: address review feedback (try-finally and test improvements)
sudip-kumar-prasad Mar 20, 2026
e738753
fix: resolve TS error in test _config.js
sudip-kumar-prasad Mar 20, 2026
7d08da0
fix: update expected html for script hydration test after comment rem…
sudip-kumar-prasad Mar 20, 2026
a2a5323
Merge branch 'main' into fix-svelte-element-hydration
sudip-kumar-prasad Mar 20, 2026
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5 changes: 5 additions & 0 deletions .changeset/fix-svelte-element-hydration.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'svelte': patch
---

fix: handle svelte:element hydration within raw text elements
10 changes: 9 additions & 1 deletion packages/svelte/src/internal/client/dom/blocks/svelte-element.js
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Expand Up @@ -88,9 +88,13 @@ export function element(node, get_tag, is_svg, render_fn, get_namespace, locatio
assign_nodes(element, element);

if (render_fn) {
/** @type {Comment | null} */
var comment = null;

if (hydrating && is_raw_text_element(next_tag)) {
// prevent hydration glitches
element.append(document.createComment(''));
comment = document.createComment('');
element.append(comment);
}

// If hydrating, use the existing ssr comment as the anchor so that the
Expand All @@ -115,6 +119,10 @@ export function element(node, get_tag, is_svg, render_fn, get_namespace, locatio
// and the DOM will be silently discarded
render_fn(element, child_anchor);

if (comment !== null) {
comment.remove();
}

set_animation_effect_override(null);
}

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4 changes: 4 additions & 0 deletions packages/svelte/tests/runtime-runes/samples/svelte-element-style-hydration/_config.js
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export default {
hydrate: true,
html: '<div><style>body { color: red; }</style></div>'
};
8 changes: 8 additions & 0 deletions packages/svelte/tests/runtime-runes/samples/svelte-element-style-hydration/main.svelte
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<script>
let { tag = 'style' } = $props();
const css = 'body { color: red; }';
</script>

<div>
<svelte:element this={tag}>{css}</svelte:element>
</div>