fix: align the SSR environment config with @cloudflare/vite-plugin

.changeset/workerd-ssr-environment.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-cloudflare': patch
+---
+
+fix: build the server with the environment config from `@cloudflare/vite-plugin` so that CommonJS `require` calls of Node builtins work in workerd

packages/adapter-cloudflare/config.js

@@ -0,0 +1,81 @@
+/** @import { Plugin } from 'vite' */
+import { fileURLToPath } from 'node:url';
+import { cloudflare } from '@cloudflare/vite-plugin';
+
+const useful_cloudflare_plugins = new Set([
+	// resolves the plugin config that the other plugins read
+	'vite-plugin-cloudflare',
+	// alias Node.js builtins to the polyfills workerd uses and leave the rest as imports
+	'vite-plugin-cloudflare:nodejs-als',
+	'vite-plugin-cloudflare:nodejs-compat',
+	'vite-plugin-cloudflare:nodejs-compat-warnings'
+]);
+
+/**
+ * Applies the Worker environment config that `@cloudflare/vite-plugin` generates
+ * so that the server output suits workerd
+ * @param {string | undefined} config_path
+ * @returns {Plugin[]}
+ */
+export function plugin_config(config_path) {
+	const plugins = cloudflare({
+		configPath: config_path,
+		viteEnvironment: { name: 'ssr' },
+		config(config) {
+			// the plugin requires `main` to exist but our Worker entrypoint is generated after the build
+			config.main = fileURLToPath(new URL('./files/worker.js', import.meta.url));
+		}
+	});
+
+	const cloudflare_config_hook = plugins.find(
+		(plugin) => plugin.name === 'vite-plugin-cloudflare:config'
+	)?.config;
+
+	if (typeof cloudflare_config_hook !== 'function') {
+		throw new Error(
+			"Failed to find the vite-plugin-cloudflare:config plugin's config hook. This should not happen."
+		);
+	}
+
+	return [
+		...plugins
+			.filter((plugin) => useful_cloudflare_plugins.has(plugin.name))
+			.map((plugin) => /** @satisfies {Plugin} */ ({ ...plugin, apply: 'build' })),
+		{
+			name: 'vite-plugin-sveltekit-adapter-cloudflare-environment',
+			apply: 'build',
+			async config(user_config, env) {
+				const ssr = (await cloudflare_config_hook.call(this, user_config, env))?.environments?.ssr;
+
+				if (ssr === undefined) {
+					throw new Error(
+						'Failed to get the SSR environment config from @cloudflare/vite-plugin. This should not happen.'
+					);
+				}
+
+				return {
+					environments: {
+						ssr: {
+							keepProcessEnv: ssr.keepProcessEnv,
+							define: ssr.define,
+							resolve: {
+								noExternal: ssr.resolve?.noExternal,
+								// `browser` would resolve `esm-env` to `BROWSER = true` and similar
+								conditions: ssr.resolve?.conditions?.filter((condition) => condition !== 'browser'),
+								// we resolve `cloudflare:workers` to a stub that runs in Node
+								builtins: ssr.resolve?.builtins?.filter((id) => id !== 'cloudflare:workers')
+							},
+							build: {
+								target: ssr.build?.target,
+								rolldownOptions: {
+									platform: ssr.build?.rolldownOptions?.platform,
+									resolve: ssr.build?.rolldownOptions?.resolve
+								}
+							}
+						}
+					}
+				};
+			}
+		}
+	];
+}

packages/adapter-cloudflare/index.js

@@ -1,20 +1,20 @@
 /** @import { Plugin, PreviewServer, ViteDevServer } from 'vite' */
 /** @import { GetPlatformProxyOptions } from 'wrangler' */
-
 import fs from 'node:fs';
 import path from 'node:path';
 import process from 'node:process';
 import { fileURLToPath } from 'node:url';
 import { getPlatformProxy, unstable_readConfig } from 'wrangler';
+import { exactRegex } from '@rolldown/pluginutils';
+import { getRequest } from '@sveltejs/kit/node';
+import { plugin_config } from './config.js';
 import {
 	is_building_for_cloudflare_pages,
 	validate_worker_settings,
 	get_routes_json,
 	parse_redirects,
 	append_headers
 } from './utils.js';
-import { exactRegex } from '@rolldown/pluginutils';
-import { getRequest } from '@sveltejs/kit/node';
 
 const name = '@sveltejs/adapter-cloudflare';
 
@@ -204,6 +204,7 @@ export default function (options = {}) {
 				return request;
 			},
 			plugins: [
+				...plugin_config(options.config),
 				virtual_workers_module(
 					{
 						configPath: options.config,
@@ -216,6 +217,8 @@ export default function (options = {}) {
 	};
 }
 
+// TODO: move the Vite plugin stuff into their own file
+
 /**
  * Sets a new platform proxy and disposes the old one if it exists
  * @param {GetPlatformProxyOptions} options

packages/adapter-cloudflare/package.json

@@ -31,6 +31,7 @@
 		"files/worker.js",
 		"index.js",
 		"utils.js",
+		"config.js",
 		"index.d.ts"
 	],
 	"scripts": {
@@ -43,6 +44,7 @@
 		"tsc-native": "node node_modules/@typescript/native/bin/tsc"
 	},
 	"dependencies": {
+		"@cloudflare/vite-plugin": "^1.64.0",
 		"@cloudflare/workers-types": "^5.20260925.1",
 		"@rolldown/pluginutils": "^1.0.1"
 	},
@@ -56,6 +58,6 @@
 	},
 	"peerDependencies": {
 		"@sveltejs/kit": "^3.0.0-next.0",
-		"wrangler": "^4.118.0"
+		"wrangler": "^4.151.0"
 	}
 }

packages/adapter-cloudflare/test/apps/workers/cjs-dep/index.cjs

@@ -0,0 +1,6 @@
+// A CommonJS module that require()s a Node builtin, like node-forge does.
+// Bundling this must not emit `createRequire(import.meta.url)` because
+// `import.meta.url` is undefined in workerd https://github.com/sveltejs/kit/issues/15960
+const crypto = require('node:crypto');
+
+module.exports.token = () => crypto.randomBytes(8).toString('hex');

packages/adapter-cloudflare/test/apps/workers/cjs-dep/package.json

@@ -0,0 +1,5 @@
+{
+	"name": "cjs-dep",
+	"version": "0.0.1",
+	"main": "./index.cjs"
+}

packages/adapter-cloudflare/test/apps/workers/config/wrangler.jsonc

@@ -3,7 +3,7 @@
 {
 	"$schema": "../node_modules/wrangler/config-schema.json",
 	"main": "../dist/index.js",
-	"compatibility_date": "2026-06-24",
+	"compatibility_date": "2026-09-01",
 	"assets": {
 		"directory": "../dist/public",
 		"binding": "ASSETS"

packages/adapter-cloudflare/test/apps/workers/package.json

@@ -15,6 +15,7 @@
 		"@sveltejs/adapter-cloudflare": "workspace:*",
 		"@sveltejs/kit": "workspace:^",
 		"@sveltejs/vite-plugin-svelte": "catalog:",
+		"cjs-dep": "file:cjs-dep",
 		"server-side-dep": "file:server-side-dep",
 		"svelte": "catalog:",
 		"vite": "catalog:",

packages/adapter-cloudflare/test/apps/workers/src/routes/cjs-node-builtin/+server.js

@@ -0,0 +1,5 @@
+import { token } from 'cjs-dep';
+
+export function GET() {
+	return new Response(token());
+}

packages/adapter-cloudflare/test/apps/workers/test/test.js

@@ -32,3 +32,8 @@ test('prerendering throws', async ({ request }) => {
 	const res = await request.get('/prerender');
 	expect(await res.text()).toContain('Cannot access cloudflare:workers in a prerenderable route');
 });
+
+test('CommonJS dependencies can require Node builtins', async ({ request }) => {
+	const res = await request.get('/cjs-node-builtin');
+	expect(await res.text()).toMatch(/^[0-9a-f]{16}$/);
+});

packages/adapter-cloudflare/tsconfig.json

@@ -22,6 +22,7 @@
 		"utils.js",
 		"utils.spec.js",
 		"vitest.config.js",
+		"config.js",
 		"globals.d.ts",
 		"test/utils.js"
 	]