[fix] Handle throw error/redirect in +server.js (#6028)

Fixes #5993

.changeset/honest-parrots-compare.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+Handle `throw error/redirect` in `+server.js`

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

@@ -1,3 +1,4 @@
+import { HttpError, Redirect } from '../../index/private.js';
 import { check_method_names, method_not_allowed } from './utils.js';
 
 /**
@@ -29,16 +30,29 @@ export async function render_endpoint(event, route) {
 		return method_not_allowed(mod, method);
 	}
 
-	const response = await handler(
-		/** @type {import('types').RequestEvent<Record<string, any>>} */ (event)
-	);
-
-	if (!(response instanceof Response)) {
-		return new Response(
-			`Invalid response from route ${event.url.pathname}: handler should return a Response object`,
-			{ status: 500 }
+	try {
+		const response = await handler(
+			/** @type {import('types').RequestEvent<Record<string, any>>} */ (event)
 		);
-	}
 
-	return response;
+		if (!(response instanceof Response)) {
+			return new Response(
+				`Invalid response from route ${event.url.pathname}: handler should return a Response object`,
+				{ status: 500 }
+			);
+		}
+
+		return response;
+	} catch (error) {
+		if (error instanceof HttpError) {
+			return new Response(error.message, { status: error.status });
+		} else if (error instanceof Redirect) {
+			return new Response(undefined, {
+				status: error.status,
+				headers: { Location: error.location }
+			});
+		} else {
+			throw error;
+		}
+	}
 }

packages/kit/test/apps/basics/src/routes/errors/endpoint-throw-error/+server.js

@@ -0,0 +1,5 @@
+import { error } from '@sveltejs/kit';
+
+export function GET() {
+	throw error(401, 'You shall not pass');
+}

packages/kit/test/apps/basics/src/routes/errors/endpoint-throw-redirect/+server.js

@@ -0,0 +1,5 @@
+import { redirect } from '@sveltejs/kit';
+
+export function GET() {
+	throw redirect(302, '/');
+}

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

@@ -147,6 +147,26 @@ test.describe('Errors', () => {
 			'This is your custom error page saying: "Cannot read properties of undefined (reading \'toUpperCase\')"'
 		);
 	});
+
+	test('throw error(..) in endpoint', async ({ page, read_errors }) => {
+		const res = await page.goto('/errors/endpoint-throw-error');
+
+		const error = read_errors('/errors/endpoint-throw-error');
+		expect(error).toBe(undefined);
+
+		expect(await res?.text()).toBe('You shall not pass');
+		expect(res?.status()).toBe(401);
+	});
+
+	test('throw redirect(..) in endpoint', async ({ page, read_errors }) => {
+		const res = await page.goto('/errors/endpoint-throw-redirect');
+		expect(res?.status()).toBe(200); // redirects are opaque to the browser
+
+		const error = read_errors('/errors/endpoint-throw-redirect');
+		expect(error).toBe(undefined);
+
+		expect(await page.textContent('h1')).toBe('the answer is 42');
+	});
 });
 
 test.describe('Load', () => {