Fix inconsistent rendering of shadow routes on client/server-side

.changeset/curvy-experts-try.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+Make shadow endpoint `event.url` consistent between server and client navigation

packages/kit/src/runtime/client/renderer.js

@@ -754,7 +754,7 @@ export class Renderer {
 
 					if (has_shadow && i === a.length - 1) {
 						const res = await fetch(
-							`${url.pathname}${url.pathname.endsWith('/') ? '' : '/'}__data.json`,
+							`${url.pathname}${url.pathname.endsWith('/') ? '' : '/'}__data.json${url.search}`,
 							{
 								headers: {
 									'x-sveltekit-noredirect': 'true'

packages/kit/src/runtime/server/index.js

@@ -124,7 +124,17 @@ export async function respond(request, options, state = {}) {
 				}
 
 				const is_data_request = decoded.endsWith(DATA_SUFFIX);
-				if (is_data_request) decoded = decoded.slice(0, -DATA_SUFFIX.length) || '/';
+
+				if (is_data_request) {
+					decoded = decoded.slice(0, -DATA_SUFFIX.length) || '/';
+
+					const normalized = normalize_path(
+						url.pathname.slice(0, -DATA_SUFFIX.length),
+						options.trailing_slash
+					);
+
+					event.url = new URL(event.url.origin + normalized + event.url.search);
+				}
 
 				for (const route of options.manifest._.routes) {
 					const match = route.pattern.exec(decoded);

packages/kit/test/apps/basics/src/routes/shadowed/same-render-entry.svelte

@@ -0,0 +1 @@
+<a href="/shadowed/same-render?param1=value1">Click here to navigate</a>

packages/kit/test/apps/basics/src/routes/shadowed/same-render.js

@@ -0,0 +1,4 @@
+/** @type {import('@sveltejs/kit').RequestHandler} */
+export function get({ url }) {
+	return { body: { url: url.toString() } };
+}

packages/kit/test/apps/basics/src/routes/shadowed/same-render.svelte

@@ -0,0 +1,5 @@
+<script>
+    /** @type {string} */
+    export let url;
+</script>
+<h1>URL: {url}</h1>

packages/kit/test/apps/basics/test/test.js

@@ -432,6 +432,12 @@ test.describe.parallel('Shadowed pages', () => {
 		expect(await response.json()).toEqual({ answer: 42 });
 	});
 
+	test('Endpoint receives consistent URL', async ({ baseURL, page, clicknav }) => {
+		await page.goto('/shadowed/same-render-entry');
+		await clicknav('[href="/shadowed/same-render?param1=value1"]');
+		expect(await page.textContent('h1')).toBe(`URL: ${baseURL}/shadowed/same-render?param1=value1`);
+	});
+
 	test('responds to HEAD requests from endpoint', async ({ request }) => {
 		const url = '/shadowed/simple';