fix: avoid deleting root route types and metadata cache during sync cleanup

.changeset/fix-sync-root-types-and-metadata-cache.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: retain root route types and metadata cache across sync runs

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

@@ -64,11 +64,15 @@ export function write_all_types(config, manifest_data, root) {
 		posixify(path.relative(root, config.files.routes))
 	);
 	const expected_directories = new Set(
-		manifest_data.routes.map((route) => path.posix.join(routes_dir, route.id))
+		manifest_data.routes.map((route) => {
+			const dir = path.posix.join(routes_dir, route.id);
+			return dir.endsWith('/') && dir !== '/' ? dir.slice(0, -1) : dir;
+		})
 	);
 
 	if (fs.existsSync(types_dir)) {
 		for (const file of walk(types_dir)) {
+			if (file === 'route_meta_data.json') continue;
 			const dir = path.posix.dirname(file);
 			if (!expected_directories.has(dir)) {
 				fs.rmSync(path.join(types_dir, file), { force: true, recursive: true });

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

@@ -402,3 +402,41 @@ test('prunes stale entries from route_meta_data.json when routes are deleted', (
 		fs.rmSync(tmp, { force: true, recursive: true });
 	}
 });
+
+test('preserves root route $types.d.ts and route_meta_data.json on repeated sync runs', () => {
+	const tmp = fs.mkdtempSync(path.join(os.tmpdir(), 'sveltekit-sync-cache-test-'));
+	try {
+		const config = validate_config({});
+		config.files.assets = path.resolve(cwd, 'static');
+		const routes_dir = path.resolve(tmp, 'src', 'routes');
+		fs.mkdirSync(routes_dir, { recursive: true });
+		fs.writeFileSync(path.join(routes_dir, '+page.svelte'), '<h1>Home</h1>');
+
+		config.files.params = path.resolve(tmp, 'src', 'params');
+		config.files.routes = routes_dir;
+		config.outDir = path.resolve(tmp, '.svelte-kit');
+
+		const manifest = create_manifest_data(config, tmp);
+
+		// First sync run: generates types and route_meta_data.json
+		write_all_types(config, manifest, tmp);
+
+		const root_types_file = path.join(config.outDir, 'types', 'src', 'routes', '$types.d.ts');
+		const meta_data_file = path.join(config.outDir, 'types', 'route_meta_data.json');
+
+		expect(fs.existsSync(root_types_file)).toBe(true);
+		expect(fs.existsSync(meta_data_file)).toBe(true);
+
+		// Append a marker comment to verify the root type file and cache are retained
+		fs.appendFileSync(root_types_file, '\n// marker-test-sync-cache');
+
+		// Second sync run: should not wipe root types or route_meta_data.json
+		write_all_types(config, manifest, tmp);
+
+		expect(fs.existsSync(root_types_file)).toBe(true);
+		expect(fs.existsSync(meta_data_file)).toBe(true);
+		expect(fs.readFileSync(root_types_file, 'utf-8')).toContain('// marker-test-sync-cache');
+	} finally {
+		fs.rmSync(tmp, { force: true, recursive: true });
+	}
+});