fix: support Node.js 26 in adapter-vercel (2.x)

.changeset/quiet-nodes-twenty-six.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-vercel': patch
+---
+
+fix: support Node.js 26 (`nodejs26.x`) and future even Node.js versions

documentation/docs/25-build-and-deploy/90-adapter-vercel.md

@@ -42,7 +42,7 @@ export const config = {
 
 The following options apply to all functions:
 
-- `runtime`: `'edge'`, `'nodejs20.x'` or `'nodejs22.x'`. By default, the adapter will select the `'nodejs<version>.x'` corresponding to the Node version your project is configured to use on the Vercel dashboard
+- `runtime`: `'edge'`, or an even Node version (for example `'nodejs20.x'`, `'nodejs22.x'`, `'nodejs24.x'`, `'nodejs26.x'`). By default, the adapter will select the `'nodejs<version>.x'` corresponding to the Node version your project is configured to use on the Vercel dashboard
   > [!NOTE] This option is deprecated and will be removed in a future version, at which point all your functions will use whichever Node version is specified in the project configuration on Vercel
 - `regions`: an array of [edge network regions](https://vercel.com/docs/concepts/edge-network/regions) (defaulting to `["iad1"]` for serverless functions) or `'all'` if `runtime` is `edge` (its default). Note that multiple regions for serverless functions are only supported on Enterprise plans
 - `split`: if `true`, causes a route to be deployed as an individual function. If `split` is set to `true` at the adapter level, all routes will be deployed as individual functions

packages/adapter-vercel/index.d.ts

@@ -6,7 +6,7 @@ export default function plugin(config?: Config): Adapter;
 
 export interface ServerlessConfig {
 	/**
-	 * Whether to use [Edge Functions](https://vercel.com/docs/concepts/functions/edge-functions) (`'edge'`) or [Serverless Functions](https://vercel.com/docs/concepts/functions/serverless-functions) (`'nodejs22.x'`, `'nodejs24.x'` etc).
+	 * Whether to use [Edge Functions](https://vercel.com/docs/concepts/functions/edge-functions) (`'edge'`) or [Serverless Functions](https://vercel.com/docs/concepts/functions/serverless-functions) (`'nodejs22.x'`, `'nodejs24.x'`, `'nodejs26.x'` etc).
 	 * @default Same as the build environment
 	 */
 	runtime?: Exclude<RuntimeConfigKey, 'edge'>;
@@ -78,7 +78,7 @@ type ImagesConfig = {
 /** @deprecated */
 export interface EdgeConfig {
 	/**
-	 * Whether to use [Edge Functions](https://vercel.com/docs/concepts/functions/edge-functions) (`'edge'`) or [Serverless Functions](https://vercel.com/docs/concepts/functions/serverless-functions) (`'nodejs22.x'`, `'nodejs24.x'` etc).
+	 * Whether to use [Edge Functions](https://vercel.com/docs/concepts/functions/edge-functions) (`'edge'`) or [Serverless Functions](https://vercel.com/docs/concepts/functions/serverless-functions) (`'nodejs22.x'`, `'nodejs24.x'`, `'nodejs26.x'` etc).
 	 */
 	runtime?: 'edge';
 	/**

packages/adapter-vercel/test/utils.spec.js

@@ -1,3 +1,4 @@
+import process from 'node:process';
 import { assert, test, describe } from 'vitest';
 import { get_pathname, parse_isr_expiration, pattern_to_src, resolve_runtime } from '../utils.js';
 
@@ -185,7 +186,69 @@ describe('resolve_runtime', () => {
 		assert.equal(result, 'bun1.x');
 	});
 
-	test('throws an error when resolving to an invalid runtime', () => {
-		assert.throws(() => resolve_runtime('node18.x', undefined), /Unsupported runtime: node18.x/);
+	test.each(['node18.x', 'nodejs028.x', 'nodejs18.x', 'nodejs33.x', 'nodejs100.x', 'nodejs2,.x'])(
+		'throws an error when resolving to an invalid runtime (%s)',
+		(runtime) => {
+			assert.throws(() => resolve_runtime(runtime), /Unsupported runtime/);
+		}
+	);
+
+	test.each(['nodejs20.x', 'nodejs22.x', 'nodejs24.x', 'nodejs26.x', 'nodejs96.x', 'nodejs98.x'])(
+		'accepts %s',
+		(runtime) => {
+			assert.equal(resolve_runtime(runtime), runtime);
+		}
+	);
+
+	test.each(['bun1.x', 'edge'])('accepts %s', (runtime) => {
+		assert.equal(resolve_runtime(runtime), runtime);
 	});
 });
+
+describe('resolve_runtime with node detected', () => {
+	/**
+	 * @param {string} node_version
+	 * @param {() => void} fn
+	 */
+	function with_node(node_version, fn) {
+		const version = Object.getOwnPropertyDescriptor(process, 'version');
+		Object.defineProperty(process, 'version', { value: `v${node_version}`, configurable: true });
+		try {
+			fn();
+		} finally {
+			if (version) Object.defineProperty(process, 'version', version);
+		}
+	}
+
+	test.each([
+		['20.0.0', 'nodejs20.x'],
+		['22.0.0', 'nodejs22.x'],
+		['24.1.0', 'nodejs24.x'],
+		['26.0.0', 'nodejs26.x'],
+		['28.0.0', 'nodejs28.x'],
+		['96.1.0', 'nodejs96.x'],
+		['98.0.0', 'nodejs98.x']
+	])('detects Node %s', (version, runtime) => {
+		with_node(version, () => {
+			assert.equal(resolve_runtime(undefined, undefined), runtime);
+		});
+	});
+
+	test('an explicit nodejs26.x override wins over the detected version', () => {
+		with_node('24.0.0', () => {
+			assert.equal(resolve_runtime(undefined, 'nodejs26.x'), 'nodejs26.x');
+		});
+	});
+
+	test.each(['18.0.0', '25.0.0', '27.0.0'])(
+		'throws for an unsupported Node major (%s)',
+		(version) => {
+			with_node(version, () => {
+				assert.throws(
+					() => resolve_runtime(undefined, undefined),
+					/Unsupported Node\.js version.*Please use an even Node version to build your project/
+				);
+			});
+		}
+	);
+});

packages/adapter-vercel/utils.js

@@ -118,44 +118,44 @@ export function resolve_runtime(default_key, override_key) {
 	return key;
 }
 
-const valid_node_versions = [20, 22, 24];
-const formatter = new Intl.ListFormat('en', { type: 'disjunction' });
+const valid_node_version_regex = /^nodejs[2-9][02468]\.x$/;
 
 /** @returns {RuntimeKey} */
 function get_default_runtime() {
 	// TODO may someday need to auto-detect Bun, but this will be complicated because you may want to run your build
 	// with Bun but not have your serverless runtime be in Bun. Vercel will likely have to attach something to `globalThis` or similar
 	// to tell us what the bun configuration is.
 	const major = Number(process.version.slice(1).split('.')[0]);
+	const version_key = /** @type {const} */ (`nodejs${major}.x`);
 
-	if (!valid_node_versions.includes(major)) {
+	if (!valid_node_version_regex.test(version_key)) {
 		throw new Error(
-			`Unsupported Node.js version: ${process.version}. Please use Node ${formatter.format(valid_node_versions.map((v) => `${v}`))} to build your project, or explicitly specify a runtime in your adapter configuration.`
+			`Unsupported Node.js version: ${process.version}. Please use an even Node version to build your project, or explicitly specify a runtime in your adapter configuration.`
 		);
 	}
 
-	return `nodejs${/** @type {20 | 22 | 24} */ (major)}.x`;
+	return version_key;
 }
 
-const valid_runtimes = /** @type {const} */ ([
-	'nodejs20.x',
-	'nodejs22.x',
-	'nodejs24.x',
-	'bun1.x',
-	'edge'
-]);
+const valid_non_node_runtimes = /** @type {const} */ (['bun1.x', 'edge']);
 
 /**
  * @param {string} key
  * @returns {asserts key is RuntimeKey}
  */
 function assert_is_valid_runtime(key) {
-	if (!valid_runtimes.includes(/** @type {RuntimeKey} */ (key))) {
+	if (
+		!valid_non_node_runtimes.includes(
+			/** @type {typeof valid_non_node_runtimes[number]} */ (key)
+		) &&
+		!valid_node_version_regex.test(key)
+	) {
 		throw new Error(
-			`Unsupported runtime: ${key}. Supported runtimes are: ${valid_runtimes.join(', ')}. See the Node.js Version section in your Vercel project settings for info on the currently supported versions.`
+			`Unsupported runtime: ${key}. Supported runtimes are: ${valid_non_node_runtimes.join(', ')}, and even Node versions. See the Node.js Version section in your Vercel project settings for info on the currently supported versions.`
 		);
 	}
 }
 
 /** @typedef {Exclude<RuntimeKey, 'bun1.x'> | 'experimental_bun1.x'} RuntimeConfigKey */
-/** @typedef {typeof valid_runtimes[number]} RuntimeKey */
+// this is what to update when Vercel adds a new Node runtime or deprecates an old one! leave the rest of the code alone
+/** @typedef {typeof valid_non_node_runtimes[number] | 'nodejs20.x' | 'nodejs22.x' | 'nodejs24.x' | 'nodejs26.x' | ({} & `nodejs${number}.x`)} RuntimeKey */