fix: html tag hydration: regard empty claimed_nodes array as content mismatch (#9184)

fixes #6832

Author: kelvinsjk

.changeset/spicy-shrimps-divide.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: more robust hydration of html tag

packages/svelte/src/runtime/internal/dom.js

@@ -807,6 +807,9 @@ export function claim_html_tag(nodes, is_svg) {
 	detach(html_tag_nodes[0]);
 	detach(html_tag_nodes[html_tag_nodes.length - 1]);
 	const claimed_nodes = html_tag_nodes.slice(1, html_tag_nodes.length - 1);
+	if (claimed_nodes.length === 0) {
+		return new HtmlTagHydration(is_svg);
+	}
 	for (const n of claimed_nodes) {
 		n.claim_order = nodes.claim_info.total_claimed;
 		nodes.claim_info.total_claimed += 1;

packages/svelte/test/hydration/samples/html-tag-hydration/_after.html

@@ -0,0 +1 @@
+1 2 3

packages/svelte/test/hydration/samples/html-tag-hydration/_before.html

@@ -0,0 +1,3 @@
+ 1
+<!-- HTML_TAG_START -->2<!-- HTML_TAG_END -->
+3

packages/svelte/test/hydration/samples/html-tag-hydration/main.svelte

@@ -0,0 +1,5 @@
+<script>
+	const a = 1, b=2, c=3;
+</script>
+
+{a} {@html b} {c}