fix(vercel): Switch to node 18 when local version is not supported

.changeset/gorgeous-ads-develop.md

@@ -0,0 +1,5 @@
+---
+'@astrojs/vercel': patch
+---
+
+The vercel adapter now Warns when using a deprecated version of Node, and switches to 18 when using an unsupported version.

packages/integrations/vercel/src/serverless/adapter.ts

@@ -19,6 +19,13 @@ const PACKAGE_NAME = '@astrojs/vercel/serverless';
 export const ASTRO_LOCALS_HEADER = 'x-astro-locals';
 export const VERCEL_EDGE_MIDDLEWARE_FILE = 'vercel-edge-middleware';
 
+// https://vercel.com/docs/concepts/functions/serverless-functions/runtimes/node-js#node.js-version
+const SUPPORTED_NODE_VERSIONS: Record<string, { status: 'current' } | { status: 'deprecated', removal: Date }> = {
+	14: { status: 'deprecated', removal: new Date('August 15 2023')  },
+	16: { status: 'deprecated', removal: new Date('February 6 2024') },
+	18: { status: 'current' }
+}
+
 function getAdapter(): AstroAdapter {
 	return {
 		name: PACKAGE_NAME,
@@ -193,5 +200,17 @@ export default function vercelServerless({
 function getRuntime() {
 	const version = process.version.slice(1); // 'v16.5.0' --> '16.5.0'
 	const major = version.split('.')[0]; // '16.5.0' --> '16'
+	const support = SUPPORTED_NODE_VERSIONS[major]
+	if (support === undefined) {
+		console.warn(`[${PACKAGE_NAME}] The local Node.js version (${major}) is not supported by Vercel Serverless Functions.`)
+		console.warn(`[${PACKAGE_NAME}] Your project will use Node.js 18 as the runtime instead.`)
+		console.warn(`[${PACKAGE_NAME}] Consider switching your local version to 18.`)
+		return 'nodejs18.x';
+	}
+	if (support.status === 'deprecated') {
+		console.warn(`[${PACKAGE_NAME}] Your project is being built for Node.js ${major} as the runtime.`)
+		console.warn(`[${PACKAGE_NAME}] This version is deprecated by Vercel Serverless Functions, and scheduled to be disabled on ${new Intl.DateTimeFormat(undefined, { dateStyle: "long" }).format(support.removal)}.`)
+		console.warn(`[${PACKAGE_NAME}] Consider upgrading your local version to 18.`)
+	}
 	return `nodejs${major}.x`;
 }