add a SvelteKit namespace for app-level types (#3569)

packages/kit/test/apps/basics/src/app.d.ts

@@ -0,0 +1,15 @@
+declare namespace SvelteKit {
+	interface Session {
+		answer: number;
+		calls: number;
+	}
+
+	interface Stuff {
+		message: string;
+		error: string;
+		page: string;
+		value: number;
+		x: string;
+		y: string;
+	}
+}

packages/kit/test/apps/basics/src/routes/store/index.svelte

@@ -7,12 +7,18 @@
 	let calls = 0;
 
 	onMount(() => {
-		session.set(calls);
+		session.update(($session) => ({
+			...$session,
+			calls
+		}));
 	});
 
 	const unsubscribe = page.subscribe(() => {
 		calls++;
-		session.set(calls);
+		session.update(($session) => ({
+			...$session,
+			calls
+		}));
 	});
 
 	onDestroy(unsubscribe);

packages/kit/test/apps/basics/src/routes/store/result.svelte

@@ -8,9 +8,9 @@
 	let calls = 0;
 
 	onMount(() => {
-		calls = get(session);
+		({ calls } = get(session));
 	});
 </script>
 
 <h1>Result</h1>
-<h2>Calls: {calls}</h2>
+<h2>Calls: {calls}</h2>

packages/kit/types/ambient-modules.d.ts

@@ -1,5 +1,12 @@
 /* eslint-disable import/no-duplicates */
 
+declare namespace SvelteKit {
+	interface Locals {}
+	interface Platform {}
+	interface Session {}
+	interface Stuff {}
+}
+
 declare module '$app/env' {
 	/**
 	 * Whether or not app is in AMP mode.
@@ -106,10 +113,10 @@ declare module '$app/stores' {
 	 * A convenience function around `getContext` that returns `{ navigating, page, session }`.
 	 * Most of the time, you won't need to use it.
 	 */
-	export function getStores<Session = any>(): {
+	export function getStores(): {
 		navigating: typeof navigating;
 		page: typeof page;
-		session: Writable<Session>;
+		session: Writable<SvelteKit.Session>;
 		updated: typeof updated;
 	};
 	/**
@@ -132,7 +139,7 @@ declare module '$app/stores' {
 	 * A writable store whose initial value is whatever was returned from `getSession`.
 	 * It can be written to, but this will not cause changes to persist on the server — this is something you must implement yourself.
 	 */
-	export const session: Writable<any>;
+	export const session: Writable<SvelteKit.Session>;
 	/**
 	 * A writable store indicating if the site was updated since the store was created.
 	 * It can be written to when custom logic is required to detect updates.

packages/kit/types/helper.d.ts

@@ -16,9 +16,6 @@ export type ResponseHeaders = Record<string, string | string[]>;
 type Only<T, U> = { [P in keyof T]: T[P] } & { [P in Exclude<keyof U, keyof T>]?: never };
 
 export type Either<T, U> = Only<T, U> | Only<U, T>;
-export type InferValue<T, Key extends keyof T, Default> = T extends Record<Key, infer Val>
-	? Val
-	: Default;
 export type MaybePromise<T> = T | Promise<T>;
 export type RecursiveRequired<T> = {
 	// Recursive implementation of TypeScript's Required utility type.

packages/kit/types/page.d.ts

@@ -1,85 +1,40 @@
 import { Fallthrough } from './endpoint';
-import { Either, InferValue, MaybePromise } from './helper';
+import { Either, MaybePromise } from './helper';
 
-export interface LoadInput<
-	PageParams extends Record<string, string> = Record<string, string>,
-	Stuff extends Record<string, any> = Record<string, any>,
-	Session = any
-> {
+export interface LoadInput<Params = Record<string, string>> {
 	url: URL;
-	params: PageParams;
+	params: Params;
 	fetch(info: RequestInfo, init?: RequestInit): Promise<Response>;
-	session: Session;
-	stuff: Stuff;
+	session: SvelteKit.Session;
+	stuff: Partial<SvelteKit.Stuff>;
 }
 
-export interface ErrorLoadInput<
-	PageParams extends Record<string, string> = Record<string, string>,
-	Stuff extends Record<string, any> = Record<string, any>,
-	Session = any
-> extends LoadInput<PageParams, Stuff, Session> {
+export interface ErrorLoadInput<Params = Record<string, string>> extends LoadInput<Params> {
 	status?: number;
 	error?: Error;
 }
 
-export interface LoadOutput<
-	Props extends Record<string, any> = Record<string, any>,
-	Stuff extends Record<string, any> = Record<string, any>
-> {
+export interface LoadOutput<Props = Record<string, any>> {
 	status?: number;
 	error?: string | Error;
 	redirect?: string;
 	props?: Props;
-	stuff?: Stuff;
+	stuff?: Partial<SvelteKit.Stuff>;
 	maxage?: number;
 }
 
 interface LoadInputExtends {
-	stuff?: Record<string, any>;
-	pageParams?: Record<string, string>;
-	session?: any;
+	params?: Record<string, string>;
 }
 
 interface LoadOutputExtends {
-	stuff?: Record<string, any>;
 	props?: Record<string, any>;
 }
 
-export interface Load<
-	Input extends LoadInputExtends = Required<LoadInputExtends>,
-	Output extends LoadOutputExtends = Required<LoadOutputExtends>
-> {
-	(
-		input: LoadInput<
-			InferValue<Input, 'pageParams', Record<string, string>>,
-			InferValue<Input, 'stuff', Record<string, any>>,
-			InferValue<Input, 'session', any>
-		>
-	): MaybePromise<
-		Either<
-			Fallthrough,
-			LoadOutput<
-				InferValue<Output, 'props', Record<string, any>>,
-				InferValue<Output, 'stuff', Record<string, any>>
-			>
-		>
-	>;
+export interface Load<Params = Record<string, string>, Props = Record<string, any>> {
+	(input: LoadInput<Params>): MaybePromise<Either<Fallthrough, LoadOutput<Props>>>;
 }
 
-export interface ErrorLoad<
-	Input extends LoadInputExtends = Required<LoadInputExtends>,
-	Output extends LoadOutputExtends = Required<LoadOutputExtends>
-> {
-	(
-		input: ErrorLoadInput<
-			InferValue<Input, 'pageParams', Record<string, string>>,
-			InferValue<Input, 'stuff', Record<string, any>>,
-			InferValue<Input, 'session', any>
-		>
-	): MaybePromise<
-		LoadOutput<
-			InferValue<Output, 'props', Record<string, any>>,
-			InferValue<Output, 'stuff', Record<string, any>>
-		>
-	>;
+export interface ErrorLoad<Params = Record<string, string>, Props = Record<string, any>> {
+	(input: ErrorLoadInput<Params>): MaybePromise<LoadOutput<Props>>;
 }