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fix: allow optional remote form schema fields under {exactOptionalPropertyTypes: true} #15866

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fix: allow optional remote form schema fields under {exactOptionalPropertyTypes: true} #15866

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9f333a8
silence needless eslint errors
echocrow May 22, 2026
0a8f4ba
relocate test line
echocrow May 22, 2026
3dd0e17
add failing tests
echocrow May 22, 2026
af9bbd8
pass failing tests due to exactOptionalPropertyTypes
echocrow May 22, 2026
7a2d1b3
fix new type error
echocrow May 22, 2026
6d6a58e
add changeset
echocrow May 22, 2026
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5 changes: 5 additions & 0 deletions .changeset/nice-mugs-mate.md
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@@ -0,0 +1,5 @@
---
'@sveltejs/kit': patch
---

fix: support `exactOptionalPropertyTypes` for optional form schema fields
2 changes: 1 addition & 1 deletion packages/kit/src/exports/public.d.ts
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Expand Up @@ -2090,7 +2090,7 @@ type RecursiveFormFields = RemoteFormFieldContainer<any> & {
type MaybeArray<T> = T | T[];

export interface RemoteFormInput {
[key: string]: MaybeArray<string | number | boolean | File | RemoteFormInput>;
[key: string]: MaybeArray<string | number | boolean | File | RemoteFormInput> | undefined;
}

export interface RemoteFormIssue {
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42 changes: 26 additions & 16 deletions packages/kit/src/runtime/client/client.js
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Expand Up @@ -514,7 +514,14 @@ function persist_state() {

/**
* @param {string | URL} url
* @param {{ replaceState?: boolean; noScroll?: boolean; keepFocus?: boolean; invalidateAll?: boolean; invalidate?: Array<string | URL | ((url: URL) => boolean)>; state?: Record<string, any> }} options
* @param {{
* replaceState?: boolean | undefined;
* noScroll?: boolean | undefined;
* keepFocus?: boolean | undefined;
* invalidateAll?: boolean | undefined;
* invalidate?: Array<string | URL | ((url: URL) => boolean)> | undefined;
* state?: Record<string, any> | undefined;
* }} options
* @param {number} redirect_count
* @param {{}} [nav_token]
*/
Expand Down Expand Up @@ -697,7 +704,7 @@ async function initialize(result, target, hydrate) {
page.status = rendering_error.status;
return error;
}
: undefined
: /** @type {never} */ (undefined)
});

// Wait for a microtask in case svelte experimental async is enabled,
Expand Down Expand Up @@ -731,11 +738,11 @@ async function initialize(result, target, hydrate) {
* url: URL;
* params: Record<string, string>;
* branch: Array<import('./types.js').BranchNode | undefined>;
* errors?: Array<import('types').CSRPageNodeLoader | undefined>;
* errors?: Array<import('types').CSRPageNodeLoader | undefined> | undefined;
* status: number;
* error: App.Error | null;
* route: import('types').CSRRoute | null;
* form?: Record<string, any> | null;
* form?: Record<string, any> | null | undefined;
* }} opts
*/
async function get_navigation_result_from_branch({
Expand Down Expand Up @@ -962,7 +969,7 @@ async function load_node({ loader, parent, url, params, route, server_data_node
// implement streaming request bodies and/or the body getter
body:
resource.method === 'GET' || resource.method === 'HEAD'
? undefined
? /** @type {never} */ (undefined)
: await resource.blob(),
cache: resource.cache,
credentials: resource.credentials,
Expand All @@ -971,7 +978,10 @@ async function load_node({ loader, parent, url, params, route, server_data_node
// To keep the two values in sync, we explicitly set the headers to `undefined`.
// Also, not sure why, but sometimes 0 is evaluated as truthy so we need to
// explicitly compare the headers length to a number here
headers: [...resource.headers].length > 0 ? resource?.headers : undefined,
headers:
[...resource.headers].length > 0
? resource?.headers
: /** @type {never} */ (undefined),
integrity: resource.integrity,
keepalive: resource.keepalive,
method: resource.method,
Expand Down Expand Up @@ -1650,16 +1660,16 @@ function _before_navigate({ url, type, intent, delta, event, scroll }) {
* state: Record<string, any>;
* scroll: { x: number, y: number };
* delta: number;
* };
* keepfocus?: boolean;
* noscroll?: boolean;
* replace_state?: boolean;
* state?: Record<string, any>;
* redirect_count?: number;
* nav_token?: {};
* accept?: () => void;
* block?: () => void;
* event?: Event
* } | undefined;
* keepfocus?: boolean | undefined;
* noscroll?: boolean | undefined;
* replace_state?: boolean | undefined;
* state?: Record<string, any> | undefined;
* redirect_count?: number | undefined;
* nav_token?: {} | undefined;
* accept?: (() => void) | undefined;
* block?: (() => void) | undefined;
* event?: Event | undefined;
* }} opts
*/
async function navigate({
Expand Down
4 changes: 2 additions & 2 deletions packages/kit/src/runtime/client/types.d.ts
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Expand Up @@ -100,14 +100,14 @@ export type BranchNode = {
server: DataNode | null;
universal: DataNode | null;
data: Record<string, any> | null;
slash?: TrailingSlash;
slash?: TrailingSlash | undefined;
};

export interface DataNode {
type: 'data';
data: Record<string, any> | null;
uses: Uses;
slash?: TrailingSlash;
slash?: TrailingSlash | undefined;
}

export interface NavigationState {
Expand Down
4 changes: 2 additions & 2 deletions packages/kit/src/types/internal.d.ts
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Expand Up @@ -673,8 +673,8 @@ export interface RemoteFormInternals extends BaseRemoteInternals {
export interface RemotePrerenderInternals extends BaseRemoteInternals {
type: 'prerender';
has_arg: boolean;
dynamic?: boolean;
inputs?: RemotePrerenderInputsGenerator;
dynamic?: boolean | undefined;
inputs?: RemotePrerenderInputsGenerator | undefined;
}

export type RemoteAnyQueryInternals =
Expand Down
44 changes: 42 additions & 2 deletions packages/kit/test/types/remote.test.ts
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Expand Up @@ -10,6 +10,9 @@ import {
invalid
} from '@sveltejs/kit';

/* eslint-disable @typescript-eslint/require-await */
/* eslint-disable @typescript-eslint/no-floating-promises */

const schema: StandardSchemaV1<string> = null as any;
const schema2: StandardSchemaV1<string, number> = null as any;
const schema3: StandardSchemaV1<string | undefined, number> = null as any;
Expand Down Expand Up @@ -58,6 +61,23 @@ function query_tests() {
}
void query_with_optional_arg();

async function query_with_optional_undefined_arg() {
const q = query(
null as any as StandardSchemaV1<{ a?: string | undefined }>,
() => 'Hello world'
);
// @ts-expect-error
void q();
void q({});
void q({ a: 'hi' });
void q({ a: undefined });
// @ts-expect-error
void q({ a: null });
// @ts-expect-error
void q(1);
}
void query_with_optional_undefined_arg();

async function query_unsafe() {
const q = query('unchecked', (a: number) => a);
const result: number = await q(1);
Expand Down Expand Up @@ -515,6 +535,8 @@ function form_tests() {
f6.fields.array[0].array.value();
// @ts-expect-error
f6.fields.array[0].array.as('text');
// @ts-expect-error
f6.input!['array[0].prop'] = 123;

// any
const f7 = form(null as any, (data, issue) => {
Expand All @@ -540,8 +562,6 @@ function form_tests() {
f8.fields.allIssues();
// @ts-expect-error
f8.fields.x;
// @ts-expect-error
f6.input!['array[0].prop'] = 123;

// schema with optional array fields (e.g. Zod's `.default([])` produces an input
// type where the property is optional, so its value type is `string[] | undefined`).
Expand Down Expand Up @@ -578,6 +598,26 @@ function form_tests() {
// @ts-expect-error
f_optional_arrays.fields.files.as('text');

// schema with optional & value-undefined fields. (e.g. Valibot's `.optional()`
// produces an input type that accepts `undefined` as value, which under
// `exactOptionalPropertyTypes` is treated distinctly from an omitted property.)
const f_optional_undefined_prop = form(
null as any as StandardSchemaV1<{
strings?: string[] | undefined;
}>,
(data) => {
data.strings?.[0] === 'a';
return { success: true };
}
);
// `.as()` should be available on optional|undefined fields
f_optional_undefined_prop.fields.strings.as('checkbox', 'value');
f_optional_undefined_prop.fields.strings.as('select multiple');
// indexed access gives back a typed field
f_optional_undefined_prop.fields.strings[0].as('text');
// @ts-expect-error
f_optional_undefined_prop.fields.strings.as('number');

// doesn't use data
const f9 = form(() => Promise.resolve({ success: true }));
f9.result?.success === true;
Expand Down
4 changes: 3 additions & 1 deletion packages/kit/test/types/tsconfig.json
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@@ -1,7 +1,9 @@
{
"extends": "../../tsconfig.json",
"compilerOptions": {
"noEmit": true
"exactOptionalPropertyTypes": true,
"noEmit": true,
"skipLibCheck": true
},
"include": ["**/*.test.ts", "../../src/types/*.d.ts"]
}
2 changes: 1 addition & 1 deletion packages/kit/types/index.d.ts
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Expand Up @@ -2064,7 +2064,7 @@ declare module '@sveltejs/kit' {
type MaybeArray<T> = T | T[];

export interface RemoteFormInput {
[key: string]: MaybeArray<string | number | boolean | File | RemoteFormInput>;
[key: string]: MaybeArray<string | number | boolean | File | RemoteFormInput> | undefined;
}

export interface RemoteFormIssue {
Expand Down
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