feat: implement prototype of safe server stores

packages/kit/package.json

@@ -28,7 +28,7 @@
 		"@playwright/test": "^1.41.0",
 		"@sveltejs/vite-plugin-svelte": "^3.0.1",
 		"@types/connect": "^3.4.38",
-		"@types/node": "^18.19.3",
+		"@types/node": "^18.19.33",
 		"@types/sade": "^1.7.8",
 		"@types/set-cookie-parser": "^2.4.7",
 		"dts-buddy": "0.4.6",

packages/kit/src/runtime/app/stores.js

@@ -92,3 +92,83 @@ function get_store(name) {
 		);
 	}
 }
+
+/**
+ * @template {keyof Stores}
+ */
+class ClientStores {
+	constructor() {
+		this.store = {}
+	}
+
+	getStore() {
+		return this.store
+	}
+}
+
+
+/** @typedef {Record<string, any>} Stores */
+
+const local_stores = new ClientStores();
+
+/** @type {{ getStore: () => Stores }}} */
+// eslint-disable-next-line prefer-const
+export const stores_object = {
+	getStore() {
+		return local_stores.getStore()
+	}
+}
+
+let store_counter = 0;
+
+/**
+ * @param {any} initialValue
+ */
+export const unshared_writable = (initialValue) => {
+	console.log('unshared_writable');
+	store_counter++;
+
+	/** @param {any} newValue */
+	function set(newValue) {
+		const stores = stores_object.getStore();
+		if (!stores) throw new Error('AsyncLocalStorage is not available');
+
+		stores[store_counter] ??= { value: initialValue, subscribers: [] };
+		stores[store_counter].value = newValue;
+
+		for (const fn of stores[store_counter].subscribers) {
+			fn(newValue);
+		}
+	}
+
+	/** @param {(value: any) => any} fn */
+	async function update(fn) {
+		const store = stores_object.getStore();
+		if (!store) throw new Error('AsyncLocalStorage is not available');
+		store[store_counter] ??= { value: initialValue, subscribers: [] };
+		set(fn(store[store_counter].value));
+	}
+
+	/** @param {(value: any) => void} fn */
+	function subscribe(fn) {
+		const stores = stores_object.getStore();
+		if (!stores) throw new Error('AsyncLocalStorage is not available');
+		stores[store_counter] ??= { value: initialValue, subscribers: [] };
+		stores[store_counter].subscribers.push(fn);
+
+		fn(stores[store_counter].value);
+
+		return () => {
+			const index = stores[store_counter].subscribers.indexOf(fn);
+			if (index !== -1) {
+				stores[store_counter].subscribers.splice(index, 1);
+			}
+		};
+	}
+
+	return {
+		subscribe,
+		set,
+		update
+	};
+}

packages/kit/src/runtime/server/index.js

@@ -5,6 +5,10 @@ import { DEV } from 'esm-env';
 import { filter_private_env, filter_public_env } from '../../utils/env.js';
 import { prerendering } from '__sveltekit/environment';
 import { set_read_implementation, set_manifest } from '__sveltekit/server';
+import { AsyncLocalStorage } from 'node:async_hooks';
+import { stores_object } from '../app/stores.js';
+
+const local_stores = new AsyncLocalStorage();
 
 /** @type {ProxyHandler<{ type: 'public' | 'private' }>} */
 const prerender_env_handler = {
@@ -95,10 +99,14 @@ export class Server {
 	 * @param {import('types').RequestOptions} options
 	 */
 	async respond(request, options) {
-		return respond(request, this.#options, this.#manifest, {
-			...options,
-			error: false,
-			depth: 0
+		return local_stores.run({}, async () => {
+			stores_object.getStore = () => local_stores.getStore()
+
+			return respond(request, this.#options, this.#manifest, {
+				...options,
+				error: false,
+				depth: 0
+			});
 		});
 	}
 }

packages/kit/types/index.d.ts

@@ -1828,7 +1828,7 @@ declare module '@sveltejs/kit' {
 	export type NumericRange<TStart extends number, TEnd extends number> = Exclude<TEnd | LessThan<TEnd>, LessThan<TStart>>;
 	export const VERSION: string;
 	class HttpError_1 {
-		
+
 		constructor(status: number, body: {
 			message: string;
 		} extends App.Error ? (App.Error | string | undefined) : App.Error);
@@ -1837,7 +1837,7 @@ declare module '@sveltejs/kit' {
 		toString(): string;
 	}
 	class Redirect_1 {
-		
+
 		constructor(status: 300 | 301 | 302 | 303 | 304 | 305 | 306 | 307 | 308, location: string);
 		status: 301 | 302 | 303 | 307 | 308 | 300 | 304 | 305 | 306;
 		location: string;
@@ -2180,11 +2180,11 @@ declare module '$app/server' {
 
 declare module '$app/stores' {
 	export function getStores(): {
-		
+
 		page: typeof page;
-		
+
 		navigating: typeof navigating;
-		
+
 		updated: typeof updated;
 	};
 	/**
@@ -2210,6 +2210,8 @@ declare module '$app/stores' {
 	export const updated: import('svelte/store').Readable<boolean> & {
 		check(): Promise<boolean>;
 	};
+
+	export const unshared_writable: (initialValue: any) => import('svelte/store').Writable<any>;
 }/**
  * It's possible to tell SvelteKit how to type objects inside your app by declaring the `App` namespace. By default, a new project will have a file called `src/app.d.ts` containing the following:
  *

playgrounds/basic/src/lib/global_store.js

@@ -0,0 +1,5 @@
+// import { writable } from 'svelte/store';
+
+import { unshared_writable } from '$app/stores';
+
+export const global_counter = unshared_writable(0);

playgrounds/basic/src/routes/+page.svelte

@@ -1,2 +1,10 @@
-<h1>Welcome to SvelteKit</h1>
-<p>Visit <a href="https://kit.svelte.dev">kit.svelte.dev</a> to read the documentation</p>
+<script>
+import { global_counter } from '$lib/global_store';
+
+global_counter.subscribe(count => console.log("counter updated", count));
+
+</script>
+<h1>{$global_counter}</h1>
+
+<button on:click={() => global_counter.set(1)}>set</button>
+<button on:click={() => global_counter.update((count) => count + 1)}>update</button>

playgrounds/basic/src/routes/+page.ts

@@ -0,0 +1,6 @@
+import { global_counter } from '$lib/global_store';
+
+export async function load() {
+    // increment the counter on every page load, but it will always stay at 1 because requests are isolated
+    global_counter.update((count) => count + 1);
+}