Improve error message when a Svelte config is not found (#3219)

* Improve an error message for MODULE_NOT_FOUND

* Add a changeset

* Update a changeset

Co-authored-by: Bjorn Lu <bjornlu.dev@gmail.com>

* Move some error messages

* Move some error messages again

* Update

* remove support for svelte.config.cjs

* tweak changeset

* simplify config error handling

* simplify further

* lint

* update test

Co-authored-by: Bjorn Lu <bjornlu.dev@gmail.com>
Co-authored-by: Rich Harris <hello@rich-harris.dev>

.changeset/neat-points-exercise.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+Improve error message when svelte.config.js is not found

packages/kit/package.json

@@ -39,6 +39,7 @@
 		"sirv": "^1.0.19",
 		"svelte": "^3.44.2",
 		"svelte-check": "^2.2.10",
+		"svelte-preprocess": "^4.9.8",
 		"svelte2tsx": "~0.4.10",
 		"tiny-glob": "^0.2.9",
 		"uvu": "^0.5.2"

packages/kit/src/cli.js

@@ -1,58 +1,22 @@
-import { existsSync } from 'fs';
 import sade from 'sade';
 import colors from 'kleur';
 import { relative } from 'path';
 import * as ports from 'port-authority';
 import { load_config } from './core/config/index.js';
 import { networkInterfaces, release } from 'os';
-import { coalesce_to_error, has_error_code } from './utils/error.js';
+import { coalesce_to_error } from './utils/error.js';
 
-async function get_config() {
-	// TODO this is temporary, for the benefit of early adopters
-	if (existsSync('svelte.config.cjs')) {
-		// prettier-ignore
-		console.error(colors.bold().red(
-			'svelte.config.cjs should be renamed to svelte.config.js and converted to an ES module. See https://kit.svelte.dev/docs#configuration for an example'
-		));
-	}
+/** @param {unknown} e */
+function handle_error(e) {
+	const error = coalesce_to_error(e);
 
-	if (existsSync('vite.config.js')) {
-		// prettier-ignore
-		console.error(colors.bold().red(
-			'Please remove vite.config.js and put Vite config in svelte.config.js: https://kit.svelte.dev/docs#configuration-vite'
-		));
-	}
+	if (error.name === 'SyntaxError') throw error;
 
-	try {
-		return await load_config();
-	} catch (err) {
-		const error = coalesce_to_error(err);
-		let message = error.message;
-
-		if (
-			has_error_code(error, 'MODULE_NOT_FOUND') &&
-			/Cannot find module svelte\.config\./.test(error.message)
-		) {
-			message = 'Missing svelte.config.js';
-		} else if (error.name === 'SyntaxError') {
-			message = 'Malformed svelte.config.js';
-		}
-
-		console.error(colors.bold().red(message));
-		if (error.stack) {
-			console.error(colors.grey(error.stack));
-		}
-		process.exit(1);
+	console.log(colors.bold().red(`> ${error.message}`));
+	if (error.stack) {
+		console.log(colors.gray(error.stack.split('\n').slice(1).join('\n')));
 	}
-}
 
-/** @param {unknown} error */
-function handle_error(error) {
-	const err = coalesce_to_error(error);
-	console.log(colors.bold().red(`> ${err.message}`));
-	if (err.stack) {
-		console.log(colors.gray(err.stack));
-	}
 	process.exit(1);
 }
 
@@ -85,12 +49,12 @@ prog
 	.option('-H, --https', 'Use self-signed HTTPS certificate')
 	.option('-o, --open', 'Open a browser tab')
 	.action(async ({ port, host, https, open }) => {
-		process.env.NODE_ENV = process.env.NODE_ENV || 'development';
-		const config = await get_config();
+		try {
+			process.env.NODE_ENV = process.env.NODE_ENV || 'development';
+			const config = await load_config();
 
-		const { dev } = await import('./core/dev/index.js');
+			const { dev } = await import('./core/dev/index.js');
 
-		try {
 			const cwd = process.cwd();
 
 			const { address_info, server_config } = await dev({
@@ -120,10 +84,10 @@ prog
 	.describe('Create a production build of your app')
 	.option('--verbose', 'Log more stuff', false)
 	.action(async ({ verbose }) => {
-		process.env.NODE_ENV = process.env.NODE_ENV || 'production';
-		const config = await get_config();
-
 		try {
+			process.env.NODE_ENV = process.env.NODE_ENV || 'production';
+			const config = await load_config();
+
 			const { build } = await import('./core/build/index.js');
 			const build_data = await build(config);
 
@@ -158,14 +122,14 @@ prog
 	.option('-H, --https', 'Use self-signed HTTPS certificate', false)
 	.option('-o, --open', 'Open a browser tab', false)
 	.action(async ({ port, host, https, open }) => {
-		await check_port(port);
+		try {
+			await check_port(port);
 
-		process.env.NODE_ENV = process.env.NODE_ENV || 'production';
-		const config = await get_config();
+			process.env.NODE_ENV = process.env.NODE_ENV || 'production';
+			const config = await load_config();
 
-		const { preview } = await import('./core/preview/index.js');
+			const { preview } = await import('./core/preview/index.js');
 
-		try {
 			await preview({ port, host, config, https });
 
 			welcome({ port, host, https, open });
@@ -179,11 +143,11 @@ prog
 	.describe('Create a package')
 	.option('-d, --dir', 'Destination directory', 'package')
 	.action(async () => {
-		const config = await get_config();
+		try {
+			const config = await load_config();
 
-		const { make_package } = await import('./packaging/index.js');
+			const { make_package } = await import('./packaging/index.js');
 
-		try {
 			await make_package(config);
 		} catch (error) {
 			handle_error(error);

packages/kit/src/core/config/index.js

@@ -28,10 +28,14 @@ export function load_template(cwd, config) {
 }
 
 export async function load_config({ cwd = process.cwd() } = {}) {
-	const config_file_esm = path.join(cwd, 'svelte.config.js');
-	const config_file = fs.existsSync(config_file_esm)
-		? config_file_esm
-		: path.join(cwd, 'svelte.config.cjs');
+	const config_file = path.join(cwd, 'svelte.config.js');
+
+	if (!fs.existsSync(config_file)) {
+		throw new Error(
+			'You need to create a svelte.config.js file. See https://kit.svelte.dev/docs#configuration'
+		);
+	}
+
 	const config = await import(url.pathToFileURL(config_file).href);
 
 	const validated = validate_config(config.default);
@@ -51,17 +55,9 @@ export async function load_config({ cwd = process.cwd() } = {}) {
  * @returns {import('types/config').ValidatedConfig}
  */
 export function validate_config(config) {
-	const type = typeof config;
-
-	if (type === 'undefined') {
-		throw new Error(
-			'Your config is missing default exports. Make sure to include "export default config;"'
-		);
-	}
-
-	if (type !== 'object') {
+	if (typeof config !== 'object') {
 		throw new Error(
-			`Unexpected config type "${type}", make sure your default export is an object.`
+			'svelte.config.js must have a configuration object as its default export. See https://kit.svelte.dev/docs#configuration'
 		);
 	}
 

packages/kit/src/core/config/test/index.js

@@ -10,11 +10,8 @@ import { load_config } from '../index.js';
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = join(__filename, '..');
 
-/**
- * @param {string} path
- */
-async function testLoadDefaultConfig(path) {
-	const cwd = join(__dirname, 'fixtures', path);
+test('load default config (esm)', async () => {
+	const cwd = join(__dirname, 'fixtures/default');
 
 	const config = await load_config({ cwd });
 	remove_keys(config, ([, v]) => typeof v === 'function');
@@ -64,28 +61,21 @@ async function testLoadDefaultConfig(path) {
 			trailingSlash: 'never'
 		}
 	});
-}
-
-test('load default config (cjs)', async () => {
-	await testLoadDefaultConfig('default-cjs');
-});
-
-test('load default config (esm)', async () => {
-	await testLoadDefaultConfig('default-esm');
 });
 
 test('errors on loading config with incorrect default export', async () => {
-	let errorMessage = null;
+	let message = null;
+
 	try {
 		const cwd = join(__dirname, 'fixtures', 'export-string');
 		await load_config({ cwd });
 	} catch (/** @type {any} */ e) {
-		errorMessage = e.message;
+		message = e.message;
 	}
 
 	assert.equal(
-		errorMessage,
-		'Unexpected config type "string", make sure your default export is an object.'
+		message,
+		'svelte.config.js must have a configuration object as its default export. See https://kit.svelte.dev/docs#configuration'
 	);
 });
 

packages/kit/src/packaging/test/fixtures/resolve-alias/package.json

@@ -1,5 +1,6 @@
 {
 	"name": "resolve-alias",
 	"version": "1.0.0",
-	"description": "package using $lib alias"
+	"description": "package using $lib alias",
+	"type": "module"
 }

packages/kit/src/packaging/test/fixtures/resolve-alias/svelte.config.js

@@ -0,0 +1,5 @@
+import preprocess from 'svelte-preprocess';
+
+export default {
+	preprocess: preprocess()
+};

packages/kit/src/packaging/test/fixtures/typescript/package.json

@@ -1,5 +1,6 @@
 {
 	"name": "typescript",
 	"version": "1.0.0",
-	"description": "standard typescript package"
+	"description": "standard typescript package",
+	"type": "module"
 }

packages/kit/src/packaging/test/fixtures/typescript/svelte.config.js

@@ -0,0 +1,5 @@
+import preprocess from 'svelte-preprocess';
+
+export default {
+	preprocess: preprocess()
+};