[feat] adapter-node entryPoint option (#2414)

Author: benmccann

.changeset/young-cougars-poke.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-node': patch
+---
+
+[feat] add entryPoint option for custom servers

packages/adapter-node/README.md

@@ -27,6 +27,10 @@ export default {
 
 ## Options
 
+### entryPoint
+
+The server entry point. Allows you to provide a [custom server implementation](#middleware). Defaults to the provided reference server.
+
 ### out
 
 The directory to build the server to. It defaults to `build` — i.e. `node build` would start the server locally after it has been created.
@@ -49,28 +53,29 @@ You can specify different environment variables if necessary using the `env` opt
 
 The adapter exports a middleware `(req, res, next) => {}` that's compatible with [Express](https://github.com/expressjs/expressjs.com) / [Connect](https://github.com/senchalabs/connect) / [Polka](https://github.com/lukeed/polka). Additionally, it also exports a reference server implementation using this middleware with a plain Node HTTP server.
 
-But you can use your favorite server framework to combine it with other middleware and server logic. You can import `kitMiddleware`, your ready-to-use SvelteKit bundle as middleware, from `./build/middlewares.js`.
+But you can use your favorite server framework to combine it with other middleware and server logic. You can import `kitMiddleware`, your ready-to-use SvelteKit middleware from the `build` directory. You can use [the `entryPoint` option](#entryPoint) to bundle your custom server entry point.
 
-```
-import { assetsMiddleware, prerenderedMiddleware, kitMiddleware } from './build/middlewares.js';
+```js
+// src/server.js
+import { assetsMiddleware, prerenderedMiddleware, kitMiddleware } from '../build/middlewares.js';
 import polka from 'polka';
 
 const app = polka();
 
-const myMiddleware = function(req, res, next) {
-  console.log('Hello world!');
-  next();
+const myMiddleware = function (req, res, next) {
+	console.log('Hello world!');
+	next();
 };
 
 app.use(myMiddleware);
 
 app.get('/no-svelte', (req, res) => {
-  res.end('This is not Svelte!')
+	res.end('This is not Svelte!');
 });
 
 app.use(assetsMiddleware, prerenderedMiddleware, kitMiddleware);
 
-app.listen(3000)
+app.listen(3000);
 ```
 
 For using middleware in dev mode, [see the FAQ](https://kit.svelte.dev/faq#how-do-i-use-x-with-sveltekit-how-do-i-use-middleware).

packages/adapter-node/index.d.ts

@@ -2,6 +2,7 @@ import { Adapter } from '@sveltejs/kit';
 import { BuildOptions } from 'esbuild';
 
 interface AdapterOptions {
+	entryPoint?: string;
 	out?: string;
 	precompress?: boolean;
 	env?: {

packages/adapter-node/index.js

@@ -22,6 +22,7 @@ const pipe = promisify(pipeline);
 
 /** @type {import('.')} */
 export default function ({
+	entryPoint = '.svelte-kit/node/index.js',
 	out = 'build',
 	precompress,
 	env: { path: path_env = 'SOCKET_PATH', host: host_env = 'HOST', port: port_env = 'PORT' } = {},
@@ -74,10 +75,10 @@ export default function ({
 			const build_options = esbuild_config ? await esbuild_config(defaultOptions) : defaultOptions;
 			await esbuild.build(build_options);
 
-			utils.log.minor('Building SvelteKit reference server');
+			utils.log.minor('Building SvelteKit server');
 			/** @type {BuildOptions} */
 			const default_options_ref_server = {
-				entryPoints: ['.svelte-kit/node/index.js'],
+				entryPoints: [entryPoint],
 				outfile: join(out, 'index.js'),
 				bundle: true,
 				external: ['./middlewares.js'], // does not work, eslint does not exclude middlewares from target