feat(vercel): allow external redirects

.changeset/clean-cows-draw.md

@@ -0,0 +1,5 @@
+---
+'@astrojs/vercel': minor
+---
+
+Allow external redirects to be configured through Astro config

packages/vercel/src/lib/redirects.ts

@@ -86,17 +86,30 @@ function getReplacePattern(segments: RoutePart[][]) {
 }
 
 function getRedirectLocation(route: RouteData, config: AstroConfig): string {
+	let redirectPath: string;
+	let forceTrailingSlash = false;
+
 	if (route.redirectRoute) {
-		const pattern = getReplacePattern(route.redirectRoute.segments);
-		const path = config.trailingSlash === 'always' ? appendForwardSlash(pattern) : pattern;
-		return pathJoin(config.base, path);
+		redirectPath = getReplacePattern(route.redirectRoute.segments);
+		if (config.trailingSlash === 'always') forceTrailingSlash = true;
 		// biome-ignore lint/style/noUselessElse: <explanation>
 	} else if (typeof route.redirect === 'object') {
-		return pathJoin(config.base, route.redirect.destination);
+		redirectPath = route.redirect.destination;
 		// biome-ignore lint/style/noUselessElse: <explanation>
 	} else {
-		return pathJoin(config.base, route.redirect || '');
+		redirectPath = route.redirect || '';
+	}
+
+	// Is a full URL - do not transform
+	if (URL.canParse(redirectPath)) {
+		return redirectPath;
 	}
+
+	if (forceTrailingSlash) {
+		redirectPath = appendForwardSlash(redirectPath);
+	}
+
+	return pathJoin(config.base, redirectPath);
 }
 
 function getRedirectStatus(route: RouteData): number {

packages/vercel/test/redirects.test.js

@@ -18,6 +18,7 @@ describe('Redirects', () => {
 				},
 				'/blog/[...slug]': '/team/articles/[...slug]',
 				'/Basic/http-2-0.html': '/posts/http2',
+				'/google': 'https://google.com',
 			},
 			trailingSlash: 'always',
 		});
@@ -56,6 +57,14 @@ describe('Redirects', () => {
 		assert.equal(staticRoute.status, 301);
 	});
 
+	it('define external redirects', async () => {
+		const config = await getConfig();
+
+		const route = config.routes.find((r) => r.src === '/google');
+		assert.equal(route.headers.Location, 'https://google.com');
+		assert.equal(route.status, 301);
+	});
+
 	it('defines dynamic routes', async () => {
 		const config = await getConfig();