fix: do not consider `style` literals inside `<script>` blocks

.changeset/modern-bats-work.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: do not consider `style` literals inside `<script>` blocks

packages/svelte/src/compiler/preprocess/index.js

@@ -251,7 +251,7 @@ function stringify_tag_attributes(attributes) {
 }
 
 const regex_style_tags =
-	/<!--[^]*?-->|<style((?:\s+[^=>'"/\s]+=(?:"[^"]*"|'[^']*'|[^>\s]+)|\s+[^=>'"/\s]+)*\s*)(?:\/>|>([\S\s]*?)<\/style>)/g;
+	/<!--[^]*?-->|<script[^]*?<\/script>|<style((?:\s+[^=>'"/\s]+=(?:"[^"]*"|'[^']*'|[^>\s]+)|\s+[^=>'"/\s]+)*\s*)(?:\/>|>([\S\s]*?)<\/style>)/g;
 const regex_script_tags =
 	/<!--[^]*?-->|<script((?:\s+[^=>'"/\s]+=(?:"[^"]*"|'[^']*'|[^>\s]+)|\s+[^=>'"/\s]+)*\s*)(?:\/>|>([\S\s]*?)<\/script>)/g;
 

packages/svelte/tests/preprocess/samples/style-tag-in-script/_config.js

@@ -0,0 +1,13 @@
+import * as assert from 'node:assert';
+import { test } from '../../test';
+
+export default test({
+	preprocess: {
+		style: ({ content }) => {
+			assert.equal(content, 'BEFORE');
+			return {
+				code: 'PROCESSED'
+			};
+		}
+	}
+});

packages/svelte/tests/preprocess/samples/style-tag-in-script/input.svelte

@@ -0,0 +1,5 @@
+<script>
+	const scope = (rules) => `<style>${rules.replaceAll('::highlight(a-', '::highlight(b-')}</style>`;
+</script>
+
+<style>BEFORE</style>

packages/svelte/tests/preprocess/samples/style-tag-in-script/output.svelte

@@ -0,0 +1,5 @@
+<script>
+	const scope = (rules) => `<style>${rules.replaceAll('::highlight(a-', '::highlight(b-')}</style>`;
+</script>
+
+<style>PROCESSED</style>