fix: correctly type form remote functions that do not accept data (#14573)

* fix

* changeset

* generate types

* test

Author: teemingc

.changeset/lucky-humans-make.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: correctly type the `result` of `form` remote functions that do not accept data

packages/kit/src/runtime/app/server/remote/form.js

@@ -13,7 +13,7 @@ import { convert_formdata, flatten_issues } from '../../../utils.js';
  *
  * @template Output
  * @overload
- * @param {() => Output} fn
+ * @param {() => MaybePromise<Output>} fn
  * @returns {RemoteForm<void, Output>}
  * @since 2.27
  */

packages/kit/test/types/remote.test.ts

@@ -301,6 +301,11 @@ function form_tests() {
 	f6.input!['array[0].array[]'] = [''];
 	// @ts-expect-error
 	f6.input!['array[0].prop'] = 123;
+
+	// doesn't use data
+	// eslint-disable-next-line @typescript-eslint/require-await --- we are testing that the async function does not cause `result` to be typed as a Promise
+	const f7 = form(async () => ({ success: true }));
+	f7.result?.success === true;
 }
 form_tests();
 

packages/kit/types/index.d.ts

@@ -3061,7 +3061,7 @@ declare module '$app/server' {
 	 *
 	 * @since 2.27
 	 */
-	export function form<Output>(fn: () => Output): RemoteForm<void, Output>;
+	export function form<Output>(fn: () => MaybePromise<Output>): RemoteForm<void, Output>;
 	/**
 	 * Creates a form object that can be spread onto a `<form>` element.
 	 *