fix: RecursiveFormFields type for recursive or unknown schemas (#14734)

* fix: `RecursiveFormFields` type for recursive or unknown schemas

* fix: better recursive unknown fields

* simplify type

Author: sillvva

.changeset/upset-hotels-mix.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: `RecursiveFormFields` type for recursive or unknown schemas

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

@@ -1914,22 +1914,46 @@ type RemoteFormFieldContainer<Value> = RemoteFormFieldMethods<Value> & {
 	allIssues(): RemoteFormIssue[] | undefined;
 };
 
+type UnknownField<Value> = RemoteFormFieldMethods<Value> & {
+	/** Validation issues belonging to this or any of the fields that belong to it, if any */
+	allIssues(): RemoteFormIssue[] | undefined;
+	/**
+	 * Returns an object that can be spread onto an input element with the correct type attribute,
+	 * aria-invalid attribute if the field is invalid, and appropriate value/checked property getters/setters.
+	 * @example
+	 * ```svelte
+	 * <input {...myForm.fields.myString.as('text')} />
+	 * <input {...myForm.fields.myNumber.as('number')} />
+	 * <input {...myForm.fields.myBoolean.as('checkbox')} />
+	 * ```
+	 */
+	as<T extends RemoteFormFieldType<Value>>(...args: AsArgs<T, Value>): InputElementProps<T>;
+} & {
+	[key: string | number]: UnknownField<any>;
+};
+
 /**
  * Recursive type to build form fields structure with proxy access
  */
-type RemoteFormFields<T> =
+export type RemoteFormFields<T> =
 	WillRecurseIndefinitely<T> extends true
 		? RecursiveFormFields
 		: NonNullable<T> extends string | number | boolean | File
 			? RemoteFormField<NonNullable<T>>
 			: T extends string[] | File[]
 				? RemoteFormField<T> & { [K in number]: RemoteFormField<T[number]> }
 				: T extends Array<infer U>
-					? RemoteFormFieldContainer<T> & { [K in number]: RemoteFormFields<U> }
-					: RemoteFormFieldContainer<T> & { [K in keyof T]-?: RemoteFormFields<T[K]> };
+					? RemoteFormFieldContainer<T> & {
+							[K in number]: RemoteFormFields<U>;
+						}
+					: RemoteFormFieldContainer<T> & {
+							[K in keyof T]-?: RemoteFormFields<T[K]>;
+						};
 
 // By breaking this out into its own type, we avoid the TS recursion depth limit
-type RecursiveFormFields = RemoteFormField<any> & { [key: string | number]: RecursiveFormFields };
+type RecursiveFormFields = RemoteFormFieldContainer<any> & {
+	[key: string | number]: UnknownField<any>;
+};
 
 type MaybeArray<T> = T | T[];
 

packages/kit/types/index.d.ts

@@ -1890,22 +1890,46 @@ declare module '@sveltejs/kit' {
 		allIssues(): RemoteFormIssue[] | undefined;
 	};
 
+	type UnknownField<Value> = RemoteFormFieldMethods<Value> & {
+		/** Validation issues belonging to this or any of the fields that belong to it, if any */
+		allIssues(): RemoteFormIssue[] | undefined;
+		/**
+		 * Returns an object that can be spread onto an input element with the correct type attribute,
+		 * aria-invalid attribute if the field is invalid, and appropriate value/checked property getters/setters.
+		 * @example
+		 * ```svelte
+		 * <input {...myForm.fields.myString.as('text')} />
+		 * <input {...myForm.fields.myNumber.as('number')} />
+		 * <input {...myForm.fields.myBoolean.as('checkbox')} />
+		 * ```
+		 */
+		as<T extends RemoteFormFieldType<Value>>(...args: AsArgs<T, Value>): InputElementProps<T>;
+	} & {
+		[key: string | number]: UnknownField<any>;
+	};
+
 	/**
 	 * Recursive type to build form fields structure with proxy access
 	 */
-	type RemoteFormFields<T> =
+	export type RemoteFormFields<T> =
 		WillRecurseIndefinitely<T> extends true
 			? RecursiveFormFields
 			: NonNullable<T> extends string | number | boolean | File
 				? RemoteFormField<NonNullable<T>>
 				: T extends string[] | File[]
 					? RemoteFormField<T> & { [K in number]: RemoteFormField<T[number]> }
 					: T extends Array<infer U>
-						? RemoteFormFieldContainer<T> & { [K in number]: RemoteFormFields<U> }
-						: RemoteFormFieldContainer<T> & { [K in keyof T]-?: RemoteFormFields<T[K]> };
+						? RemoteFormFieldContainer<T> & {
+								[K in number]: RemoteFormFields<U>;
+							}
+						: RemoteFormFieldContainer<T> & {
+								[K in keyof T]-?: RemoteFormFields<T[K]>;
+							};
 
 	// By breaking this out into its own type, we avoid the TS recursion depth limit
-	type RecursiveFormFields = RemoteFormField<any> & { [key: string | number]: RecursiveFormFields };
+	type RecursiveFormFields = RemoteFormFieldContainer<any> & {
+		[key: string | number]: UnknownField<any>;
+	};
 
 	type MaybeArray<T> = T | T[];