fix: recommend safe include patterns in tsconfig warning

.changeset/safe-configs-smile.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: recommend safe include and exclude patterns in tsconfig warning

packages/kit/src/core/sync/write_tsconfig/index.js

@@ -54,7 +54,9 @@ export function write_tsconfig(kit, root) {
 		types,
 		exclusions: [kit.files.serviceWorker],
 		example: {
-			extends: '$app/tsconfig'
+			extends: '$app/tsconfig',
+			include: ['src', 'test', '*'],
+			exclude: ['src/service-worker']
 		}
 	});
 

packages/kit/src/core/sync/write_tsconfig/index.spec.js

@@ -0,0 +1,46 @@
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+import { afterEach, expect, test, vi } from 'vitest';
+import { process_config, validate_config } from '../../config/index.js';
+import { write_tsconfig } from './index.js';
+
+/** @type {string[]} */
+const dirs = [];
+
+afterEach(() => {
+	vi.restoreAllMocks();
+
+	for (const dir of dirs) {
+		fs.rmSync(dir, { recursive: true, force: true });
+	}
+
+	dirs.length = 0;
+});
+
+test('warns with a safe root tsconfig', () => {
+	const root = fs.mkdtempSync(path.join(os.tmpdir(), 'svelte-kit-tsconfig-'));
+	dirs.push(root);
+
+	fs.writeFileSync(
+		path.join(root, 'tsconfig.json'),
+		JSON.stringify({ extends: './.svelte-kit/tsconfig.json' })
+	);
+
+	const warn = vi.spyOn(console, 'warn').mockImplementation(() => {});
+	const config = process_config(validate_config({}), root);
+	write_tsconfig(config, root);
+
+	expect(warn).toHaveBeenNthCalledWith(
+		2,
+		JSON.stringify(
+			{
+				extends: '$app/tsconfig',
+				include: ['src', 'test', '*'],
+				exclude: ['src/service-worker']
+			},
+			null,
+			'  '
+		)
+	);
+});