feat: use edge-light condition when building for Vercel Edge Runtime (#13720)

* feat: use edge-light condition when building for Vercel Edge Runtime

* fmt

* Update packages/adapter-vercel/index.js

* Update packages/adapter-vercel/index.js

* changeset

---------

Co-authored-by: Tee Ming <[email protected]>
Co-authored-by: Chew Tee Ming <[email protected]>

Author: blaine-arcjet

.changeset/silly-ears-visit.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-vercel': patch
+---
+
+fix: include the `edge-light` bundling condition when building edge functions

packages/adapter-vercel/index.js

@@ -137,9 +137,19 @@ const plugin = function (defaults = {}) {
 					const result = await esbuild.build({
 						entryPoints: [`${tmp}/edge.js`],
 						outfile: `${dirs.functions}/${name}.func/index.js`,
-						target: 'es2020', // TODO verify what the edge runtime supports
+						// minimum Node.js version supported is v14.6.0 that is mapped to ES2019
+						// https://edge-runtime.vercel.app/features/polyfills
+						// TODO verify the latest ES version the edge runtime supports
+						target: 'es2020',
 						bundle: true,
 						platform: 'browser',
+						conditions: [
+							// Vercel's Edge runtime key https://runtime-keys.proposal.wintercg.org/#edge-light
+							'edge-light',
+							// re-include these since they are included by default when no conditions are specified
+							// https://esbuild.github.io/api/#conditions
+							'module'
+						],
 						format: 'esm',
 						external: [
 							...compatible_node_modules,