Vercel externals

.changeset/eight-birds-run.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-vercel': patch
+---
+
+Expose external option

packages/adapter-vercel/README.md

@@ -14,11 +14,17 @@ import vercel from '@sveltejs/adapter-vercel';
 export default {
  kit: {
  ...
- adapter: vercel()
+ adapter: vercel(options)
  }
 };
 ```
 
+## Options
+
+You can pass an `options` argument, if necessary, with the following:
+
+- `external` — an array of dependencies that [esbuild](https://esbuild.github.io/api/#external) should treat as external
+
 ## Changelog
 
 [The Changelog for this package is available on GitHub](https://github.com/sveltejs/kit/blob/master/packages/adapter-vercel/CHANGELOG.md).

packages/adapter-vercel/index.d.ts

@@ -1,4 +1,8 @@
 import { Adapter } from '@sveltejs/kit';
 
-declare function plugin(): Adapter;
+type Options = {
+ external?: string[];
+};
+
+declare function plugin(options?: Options): Adapter;
 export = plugin;

packages/adapter-vercel/index.js

@@ -6,7 +6,7 @@ import esbuild from 'esbuild';
 const dir = '.vercel_build_output';
 
 /** @type {import('.')} **/
-export default function () {
+export default function ({ external = [] } = {}) {
  return {
  name: '@sveltejs/adapter-vercel',
 
@@ -52,7 +52,8 @@ export default function () {
  outfile: `${dirs.lambda}/index.js`,
  target: 'node14',
  bundle: true,
- platform: 'node'
+ platform: 'node',
+ external
  });
 
  writeFileSync(`${dirs.lambda}/package.json`, JSON.stringify({ type: 'commonjs' }));