From 641d7d588d2d77f519201e583f0275db4260575c Mon Sep 17 00:00:00 2001
From: Matt Kane <m@mk.gg>
Date: Thu, 23 Jan 2025 14:30:03 +0000
Subject: [PATCH] fix(vercel): update middleware esbuild settings (#519)

* fix(vercel): update middleware esbuild settings

* Update target
---
 .changeset/grumpy-phones-explode.md                       | 5 +++++
 packages/vercel/src/serverless/middleware.ts              | 8 ++++++--
 .../fixtures/middleware-with-edge-file/src/middleware.js  | 5 +++++
 3 files changed, 16 insertions(+), 2 deletions(-)
 create mode 100644 .changeset/grumpy-phones-explode.md

diff --git a/.changeset/grumpy-phones-explode.md b/.changeset/grumpy-phones-explode.md
new file mode 100644
index 000000000..db2db6cef
--- /dev/null
+++ b/.changeset/grumpy-phones-explode.md
@@ -0,0 +1,5 @@
+---
+'@astrojs/vercel': patch
+---
+
+Updates edge middleware to support esnext syntax
diff --git a/packages/vercel/src/serverless/middleware.ts b/packages/vercel/src/serverless/middleware.ts
index 6663731b7..c175b36bb 100644
--- a/packages/vercel/src/serverless/middleware.ts
+++ b/packages/vercel/src/serverless/middleware.ts
@@ -42,10 +42,14 @@ export async function generateEdgeMiddleware(
 			contents: code,
 			resolveDir: fileURLToPath(root),
 		},
-		target: 'es2020',
+		// Vercel Edge runtime targets ESNext, because Cloudflare Workers update v8 weekly
+		// https://github.com/vercel/vercel/blob/1006f2ae9d67ea4b3cbb1073e79d14d063d42436/packages/next/scripts/build-edge-function-template.js
+		target: 'esnext',
 		platform: 'browser',
+		// esbuild automatically adds the browser, import and default conditions
+		// https://esbuild.github.io/api/#conditions
 		// https://runtime-keys.proposal.wintercg.org/#edge-light
-		conditions: ['edge-light', 'worker', 'browser'],
+		conditions: ['edge-light', 'workerd', 'worker'],
 		outfile: bundledFilePath,
 		allowOverwrite: true,
 		format: 'esm',
diff --git a/packages/vercel/test/fixtures/middleware-with-edge-file/src/middleware.js b/packages/vercel/test/fixtures/middleware-with-edge-file/src/middleware.js
index b1a67f550..cf085321c 100644
--- a/packages/vercel/test/fixtures/middleware-with-edge-file/src/middleware.js
+++ b/packages/vercel/test/fixtures/middleware-with-edge-file/src/middleware.js
@@ -1,3 +1,7 @@
+export const hello = async () => 'hello world';
+
+const message = await hello();
+
 /**
  * @type {import("astro").MiddlewareResponseHandler}
  */
@@ -5,5 +9,6 @@ export const onRequest = async (context, next) => {
 	const test = 'something';
 	context.cookies.set('foo', 'bar');
 	const response = await next();
+	response.headers.set('x-message', message);	
 	return response;
 };