fix: generate correct external redirects (#13480)

3 files changed, 21 insertions, 4 deletions

diff --git a/.changeset/little-doors-tickle.md b/.changeset/little-doors-tickle.md
new file mode 100644
index 000000000..ec74adbe4
--- /dev/null
+++ b/.changeset/little-doors-tickle.md
@@ -0,0 +1,5 @@
+---
+'@astrojs/vercel': patch
+---
+
+Fixes a bug that caused external redirects to fail
diff --git a/packages/integrations/vercel/src/lib/redirects.ts b/packages/integrations/vercel/src/lib/redirects.ts
index 23a4dc11f..612c8e917 100644
--- a/packages/integrations/vercel/src/lib/redirects.ts
+++ b/packages/integrations/vercel/src/lib/redirects.ts
@@ -1,5 +1,5 @@
 import nodePath from 'node:path';
-import { removeLeadingForwardSlash } from '@astrojs/internal-helpers/path';
+import { isRemotePath, removeLeadingForwardSlash } from '@astrojs/internal-helpers/path';
 import type { AstroConfig, IntegrationResolvedRoute, RoutePart } from 'astro';
 
 import type { Redirect } from '@vercel/routing-utils';
@@ -92,10 +92,14 @@ function getRedirectLocation(route: IntegrationResolvedRoute, config: AstroConfi
 		return pathJoin(config.base, pattern);
 	}
 
-	if (typeof route.redirect === 'object') {
-		return pathJoin(config.base, route.redirect.destination);
+	const destination =
+		typeof route.redirect === 'object' ? route.redirect.destination : (route.redirect ?? '');
+
+	if (isRemotePath(destination)) {
+		return destination;
 	}
-	return pathJoin(config.base, route.redirect || '');
+
+	return pathJoin(config.base, destination);
 }
 
 function getRedirectStatus(route: IntegrationResolvedRoute): number {
diff --git a/packages/integrations/vercel/test/redirects.test.js b/packages/integrations/vercel/test/redirects.test.js
index ec28b7b6f..a76ff6ad9 100644
--- a/packages/integrations/vercel/test/redirects.test.js
+++ b/packages/integrations/vercel/test/redirects.test.js
@@ -16,6 +16,10 @@ describe('Redirects', () => {
 					status: 302,
 					destination: '/',
 				},
+				'/four': {
+					status: 302,
+					destination: 'http://example.com',
+				},
 				'/blog/[...slug]': '/team/articles/[...slug]',
 				'/Basic/http-2-0.html': '/posts/http2',
 			},
@@ -43,6 +47,10 @@ describe('Redirects', () => {
 		const threeRoute = config.routes.find((r) => r.src === '^/three$');
 		assert.equal(threeRoute.headers.Location, '/');
 		assert.equal(threeRoute.status, 302);
+
+		const fourRoute = config.routes.find((r) => r.src === '^/four$');
+		assert.equal(fourRoute.headers.Location, 'http://example.com');
+		assert.equal(fourRoute.status, 302);
 	});
 
 	it('define redirects for static files', async () => {