fix: improve ssr template literal generation (#10127)

.changeset/wicked-hairs-cheer.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: improve ssr template literal generation

packages/svelte/src/compiler/phases/3-transform/server/transform-server.js

@@ -705,7 +705,7 @@ function serialize_attribute_value(
 					/** @type {import('estree').Expression} */ (context.visit(node.expression))
 				)
 			);
-			if (i === attribute_value.length) {
+			if (i === attribute_value.length || attribute_value[i]?.type !== 'Text') {
 				quasis.push(b.quasi('', true));
 			}
 		}

packages/svelte/tests/runtime-runes/samples/attribute-parts/_config.js

@@ -0,0 +1,6 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	html: `<div class="123"></div><img src="12 hello, world 13">`
+});

packages/svelte/tests/runtime-runes/samples/attribute-parts/main.svelte

@@ -0,0 +1,9 @@
+<script>
+	let a = 1;
+	let b = 2;
+	let c = 3;
+</script>
+
+<div class="{a}{b}{c}" />
+
+<img src="{a}{b} hello, world {a}{c}" />