fix: deep partial .value() and .set(...) types for forms

.changeset/nice-chairs-switch.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: deep partial `.value()` and `.set(...)` types for forms

packages/kit/src/exports/public.d.ts

@@ -15,7 +15,8 @@ import {
 	PrerenderUnseenRoutesHandlerValue,
 	PrerenderOption,
 	RequestOptions,
-	RouteSegment
+	RouteSegment,
+	DeepPartial
 } from '../types/private.js';
 import { BuildData, SSRNodeLoader, SSRRoute, ValidatedConfig } from 'types';
 import { SvelteConfig } from '@sveltejs/vite-plugin-svelte';
@@ -1875,9 +1876,9 @@ type InputElementProps<T extends keyof InputTypeMap> = T extends 'checkbox' | 'r
 
 type RemoteFormFieldMethods<T> = {
 	/** The values that will be submitted */
-	value(): T;
+	value(): DeepPartial<T>;
 	/** Set the values that will be submitted */
-	set(input: T): T;
+	set(input: DeepPartial<T>): DeepPartial<T>;
 	/** Validation issues, if any */
 	issues(): RemoteFormIssue[] | undefined;
 };

packages/kit/src/types/private.d.ts

@@ -241,3 +241,11 @@ export interface RouteSegment {
 }
 
 export type TrailingSlash = 'never' | 'always' | 'ignore';
+
+export type DeepPartial<T> = T extends Record<PropertyKey, unknown> | unknown[]
+	? {
+			[K in keyof T]?: T[K] extends Record<PropertyKey, unknown> | unknown[]
+				? DeepPartial<T[K]>
+				: T[K];
+		}
+	: T | undefined;

packages/kit/types/index.d.ts

@@ -1851,9 +1851,9 @@ declare module '@sveltejs/kit' {
 
 	type RemoteFormFieldMethods<T> = {
 		/** The values that will be submitted */
-		value(): T;
+		value(): DeepPartial<T>;
 		/** Set the values that will be submitted */
-		set(input: T): T;
+		set(input: DeepPartial<T>): DeepPartial<T>;
 		/** Validation issues, if any */
 		issues(): RemoteFormIssue[] | undefined;
 	};
@@ -2375,6 +2375,14 @@ declare module '@sveltejs/kit' {
 	}
 
 	type TrailingSlash = 'never' | 'always' | 'ignore';
+
+	type DeepPartial<T> = T extends Record<PropertyKey, unknown> | unknown[]
+		? {
+				[K in keyof T]?: T[K] extends Record<PropertyKey, unknown> | unknown[]
+					? DeepPartial<T[K]>
+					: T[K];
+			}
+		: T | undefined;
 	interface Asset {
 		file: string;
 		size: number;