From 500acb3c117070ee5838a8b567e9bdcf68703227 Mon Sep 17 00:00:00 2001
From: Matthew Phillips <matthew@skypack.dev>
Date: Tue, 18 Oct 2022 13:09:38 -0700
Subject: [PATCH] Throw when using Response.redirect from SSG site (#5116)

* Throw when using Response.redirect from SSG site

* Adding a changeset
---
 .changeset/tall-trainers-do.md                     |  5 +++++
 .../astro/src/vite-plugin-astro-server/index.ts    | 14 +++++++++++++-
 packages/astro/test/dev-routing.test.js            |  6 +++++-
 .../without-site-config/src/pages/redirect.astro   |  4 ++++
 4 files changed, 27 insertions(+), 2 deletions(-)
 create mode 100644 .changeset/tall-trainers-do.md
 create mode 100644 packages/astro/test/fixtures/without-site-config/src/pages/redirect.astro

diff --git a/.changeset/tall-trainers-do.md b/.changeset/tall-trainers-do.md
new file mode 100644
index 0000000000..7d67768a36
--- /dev/null
+++ b/.changeset/tall-trainers-do.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Throws when using Response.redirect in SSG mode
diff --git a/packages/astro/src/vite-plugin-astro-server/index.ts b/packages/astro/src/vite-plugin-astro-server/index.ts
index 34707b084d..b3af040b04 100644
--- a/packages/astro/src/vite-plugin-astro-server/index.ts
+++ b/packages/astro/src/vite-plugin-astro-server/index.ts
@@ -1,7 +1,7 @@
 import type http from 'http';
 import mime from 'mime';
 import type * as vite from 'vite';
-import type { AstroSettings, ManifestData } from '../@types/astro';
+import type { AstroConfig, AstroSettings, ManifestData } from '../@types/astro';
 import { DevelopmentEnvironment, SSROptions } from '../core/render/dev/index';
 
 import { Readable } from 'stream';
@@ -296,6 +296,16 @@ async function handleRequest(
 	}
 }
 
+function isRedirect(statusCode: number) {
+	return statusCode >= 300 && statusCode < 400;
+}
+
+function throwIfRedirectNotAllowed(response: Response, config: AstroConfig) {
+	if(config.output !== 'server' && isRedirect(response.status)) {
+		throw new Error(`Redirects are only available when using output: 'server'. Update your Astro config if you need SSR features.`);
+	}
+}
+
 async function handleRoute(
 	matchedRoute: AsyncReturnType<typeof matchRoute>,
 	url: URL,
@@ -367,6 +377,7 @@ async function handleRoute(
 					res
 				);
 			}
+			throwIfRedirectNotAllowed(result.response, config);
 			await writeWebResponse(res, result.response);
 		} else {
 			let contentType = 'text/plain';
@@ -389,6 +400,7 @@ async function handleRoute(
 		}
 	} else {
 		const result = await renderPage(options);
+		throwIfRedirectNotAllowed(result, config);
 		return await writeSSRResult(result, res);
 	}
 }
diff --git a/packages/astro/test/dev-routing.test.js b/packages/astro/test/dev-routing.test.js
index 255d8d2498..7188e1ff0c 100644
--- a/packages/astro/test/dev-routing.test.js
+++ b/packages/astro/test/dev-routing.test.js
@@ -1,5 +1,4 @@
 import { expect } from 'chai';
-import * as cheerio from 'cheerio';
 import { loadFixture } from './test-utils.js';
 
 describe('Development Routing', () => {
@@ -42,6 +41,11 @@ describe('Development Routing', () => {
 			const response = await fixture.fetch('/2');
 			expect(response.status).to.equal(404);
 		});
+
+		it('500 when redirecting in SSG mode', async () => {
+			const response = await fixture.fetch('/redirect');
+			expect(response.status).to.equal(500);
+		});
 	});
 
 	describe('No subpath used', () => {
diff --git a/packages/astro/test/fixtures/without-site-config/src/pages/redirect.astro b/packages/astro/test/fixtures/without-site-config/src/pages/redirect.astro
new file mode 100644
index 0000000000..4b640e5b5d
--- /dev/null
+++ b/packages/astro/test/fixtures/without-site-config/src/pages/redirect.astro
@@ -0,0 +1,4 @@
+---
+const anotherURL = new URL('./another/', Astro.url);
+return Response.redirect(anotherURL.toString());
+---