[fix] prerender in subprocess

.changeset/witty-avocados-admire.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+prerender in a subprocess

packages/kit/rollup.config.js

@@ -61,9 +61,10 @@ export default [
 	{
 		input: {
 			cli: 'src/cli.js',
+			hooks: 'src/hooks.js',
 			node: 'src/node/index.js',
 			'node/polyfills': 'src/node/polyfills.js',
-			hooks: 'src/hooks.js',
+			prerender: 'src/core/prerender/prerender.js',
 			vite: 'src/vite/index.js'
 		},
 		output: {

packages/kit/src/core/prerender/prerender.js

@@ -7,12 +7,18 @@ import { is_root_relative, resolve } from '../../utils/url.js';
 import { queue } from './queue.js';
 import { crawl } from './crawl.js';
 import { escape_html_attr } from '../../utils/escape.js';
+import { logger } from '../utils.js';
+import { load_config } from '../config/index.js';
 
 /**
  * @typedef {import('types').PrerenderErrorHandler} PrerenderErrorHandler
  * @typedef {import('types').Logger} Logger
  */
 
+const [, , client_out_dir, results_path, manifest_path, verbose] = process.argv;
+
+prerender();
+
 /**
  * @param {Parameters<PrerenderErrorHandler>[0]} details
  * @param {import('types').ValidatedKitConfig} config
@@ -50,14 +56,19 @@ const OK = 2;
 const REDIRECT = 3;
 
 /**
- * @param {{
- *   config: import('types').ValidatedKitConfig;
- *   client_out_dir: string;
- *   manifest_path: string;
- *   log: Logger;
- * }} opts
+ * @param {import('types').Prerendered} prerendered
  */
-export async function prerender({ config, client_out_dir, manifest_path, log }) {
+const output_and_exit = (prerendered) => {
+	writeFileSync(
+		results_path,
+		JSON.stringify(prerendered, (_key, value) =>
+			value instanceof Map ? Array.from(value.entries()) : value
+		)
+	);
+	process.exit(0);
+};
+
+export async function prerender() {
 	/** @type {import('types').Prerendered} */
 	const prerendered = {
 		pages: new Map(),
@@ -66,10 +77,19 @@ export async function prerender({ config, client_out_dir, manifest_path, log })
 		paths: []
 	};
 
+	/** @type {import('types').ValidatedKitConfig} */
+	const config = (await load_config()).kit;
+
 	if (!config.prerender.enabled) {
-		return prerendered;
+		output_and_exit(prerendered);
+		return;
 	}
 
+	/** @type {import('types').Logger} */
+	const log = logger({
+		verbose: verbose === 'true'
+	});
+
 	installPolyfills();
 	const { fetch } = globalThis;
 	globalThis.fetch = async (info, init) => {
@@ -349,7 +369,7 @@ export async function prerender({ config, client_out_dir, manifest_path, log })
 	mkdirp(dirname(file));
 	writeFileSync(file, await rendered.text());
 
-	return prerendered;
+	output_and_exit(prerendered);
 }
 
 /** @return {string} */

packages/kit/src/vite/index.js

@@ -1,20 +1,21 @@
-import fs from 'fs';
-import path from 'path';
+import { fork } from 'node:child_process';
+import fs, { existsSync } from 'node:fs';
+import path from 'node:path';
 import colors from 'kleur';
 import { svelte } from '@sveltejs/vite-plugin-svelte';
 import * as vite from 'vite';
 import { mkdirp, posixify, rimraf } from '../utils/filesystem.js';
 import * as sync from '../core/sync/sync.js';
 import { build_server } from './build/build_server.js';
 import { build_service_worker } from './build/build_service_worker.js';
-import { prerender } from '../core/prerender/prerender.js';
 import { load_config } from '../core/config/index.js';
 import { dev } from './dev/index.js';
 import { generate_manifest } from '../core/generate_manifest/index.js';
 import { get_runtime_directory, logger } from '../core/utils.js';
 import { find_deps, get_default_config as get_default_build_config } from './build/utils.js';
 import { preview } from './preview/index.js';
 import { get_aliases, resolve_entry } from './utils.js';
+import { fileURLToPath } from 'node:url';
 
 const cwd = process.cwd();
 
@@ -273,9 +274,8 @@ function kit() {
 		 * then use this hook to kick off builds for the server and service worker.
 		 */
 		async writeBundle(_options, bundle) {
-			log = logger({
-				verbose: vite_config.logLevel === 'info'
-			});
+			const verbose = vite_config.logLevel === 'info';
+			log = logger({ verbose });
 
 			fs.writeFileSync(
 				`${paths.client_out_dir}/${svelte_config.kit.appDir}/version.json`,
@@ -318,14 +318,39 @@ function kit() {
 				})};\n`
 			);
 
-			process.env.SVELTEKIT_SERVER_BUILD_COMPLETED = 'true';
 			log.info('Prerendering');
+			await new Promise((fulfil, reject) => {
+				const results_path = `${svelte_config.kit.outDir}/generated/prerendered.json`;
+
+				// do prerendering in a subprocess so any dangling stuff gets killed upon completion
+				const script = fileURLToPath(
+					new URL(
+						process.env.BUNDLED ? './prerender.js' : '../core/prerender/prerender.js',
+						import.meta.url
+					)
+				);
 
-			prerendered = await prerender({
-				config: svelte_config.kit,
-				client_out_dir: vite_config.build.outDir,
-				manifest_path,
-				log
+				const child = fork(
+					script,
+					[vite_config.build.outDir, results_path, manifest_path, '' + verbose],
+					{
+						stdio: 'inherit'
+					}
+				);
+
+				child.on('exit', (code) => {
+					if (code) {
+						reject(new Error(`Prerendering failed with code ${code}`));
+					} else {
+						prerendered = JSON.parse(fs.readFileSync(results_path, 'utf8'), (key, value) => {
+							if (key === 'pages' || key === 'assets' || key === 'redirects') {
+								return new Map(value);
+							}
+							return value;
+						});
+						fulfil(undefined);
+					}
+				});
 			});
 
 			if (options.service_worker_entry_file) {
@@ -365,13 +390,6 @@ function kit() {
 					`See ${colors.bold().cyan('https://kit.svelte.dev/docs/adapters')} to learn how to configure your app to run on the platform of your choosing`
 				);
 			}
-
-			if (svelte_config.kit.prerender.enabled) {
-				// this is necessary to close any open db connections, etc.
-				// TODO: prerender in a subprocess so we can exit in isolation and then remove this
-				// https://github.com/sveltejs/kit/issues/5306
-				process.exit(0);
-			}
 		},
 
 		/**