fix: decode URI when previewing prerendered pages (#12874)

fixes #12865

The issue only affected the preview server as we weren't decoding the URI before checking if the prerendered file existed or not

Author: eltigerchino

.changeset/eleven-turkeys-jump.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: decode non-latin characters when previewing prerendered pages

packages/kit/src/exports/vite/preview/index.js

@@ -131,6 +131,13 @@ export async function preview(vite, vite_config, svelte_config) {
 				let filename = normalizePath(
 					join(svelte_config.kit.outDir, 'output/prerendered/pages' + pathname)
 				);
+
+				try {
+					filename = decodeURI(filename);
+				} catch {
+					// malformed URI
+				}
+
 				let prerendered = is_file(filename);
 
 				if (!prerendered) {

packages/kit/test/apps/basics/src/routes/prerendering/中文/+page.svelte

@@ -0,0 +1 @@
+export const prerender = true;

packages/kit/test/apps/basics/src/routes/prerendering/中文/+page.ts

@@ -630,6 +630,11 @@ test.describe('Miscellaneous', () => {
 		expect(response.status()).toBe(200);
 		expect(await response.text()).toBe('foo');
 	});
+
+	test('serves prerendered non-latin pages', async ({ request }) => {
+		const response = await request.get('/prerendering/中文');
+		expect(response.status()).toBe(200);
+	});
 });
 
 test.describe('reroute', () => {