Prerendered server redirects

.changeset/gorgeous-snakes-pretend.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+Generate `__data.json` files for server-side redirects when prerendering

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

@@ -95,6 +95,9 @@ export async function render_page(event, route, options, state, resolve_opts) {
 			}
 		}
 
+		const should_prerender_data = nodes.some((node) => node?.server);
+		const data_pathname = `${event.url.pathname.replace(/\/$/, '')}/__data.json`;
+
 		if (!resolve_opts.ssr) {
 			return await render_response({
 				branch: [],
@@ -214,6 +217,16 @@ export async function render_page(event, route, options, state, resolve_opts) {
 					const error = normalize_error(e);
 
 					if (error instanceof Redirect) {
+						if (state.prerendering && should_prerender_data) {
+							state.prerendering.dependencies.set(data_pathname, {
+								response: new Response(undefined),
+								body: JSON.stringify({
+									type: 'redirect',
+									location: error.location
+								})
+							});
+						}
+
 						return redirect_response(error.status, error.location);
 					}
 
@@ -267,19 +280,14 @@ export async function render_page(event, route, options, state, resolve_opts) {
 			}
 		}
 
-		// generate __data.json files when prerendering
-		if (state.prerendering && nodes.some((node) => node?.server)) {
-			const pathname = `${event.url.pathname.replace(/\/$/, '')}/__data.json`;
-
-			const dependency = {
+		if (state.prerendering && should_prerender_data) {
+			state.prerendering.dependencies.set(data_pathname, {
 				response: new Response(undefined),
 				body: JSON.stringify({
 					type: 'data',
 					nodes: branch.map((branch_node) => ({ data: branch_node?.server_data }))
 				})
-			};
-
-			state.prerendering.dependencies.set(pathname, dependency);
+			});
 		}
 
 		// TODO use validation_errors

packages/kit/test/prerendering/basics/src/routes/redirect-server/+page.server.js

@@ -0,0 +1,6 @@
+import { redirect } from '@sveltejs/kit';
+
+/** @type {import('@sveltejs/kit').Load} */
+export function load() {
+	throw redirect(301, 'https://example.com/redirected');
+}

packages/kit/test/prerendering/basics/test/test.js

@@ -21,6 +21,20 @@ test('renders a redirect', () => {
 	);
 });
 
+test('renders a server-side redirect', () => {
+	const html = read('redirect-server.html');
+	assert.equal(html, '<meta http-equiv="refresh" content="0;url=https://example.com/redirected">');
+
+	const json = read('redirect-server/__data.json');
+	assert.equal(
+		json,
+		JSON.stringify({
+			type: 'redirect',
+			location: 'https://example.com/redirected'
+		})
+	);
+});
+
 test('does not double-encode redirect locations', () => {
 	const content = read('redirect-encoded.html');
 	assert.equal(