fix deriving from rxjs observables (#4298)

src/runtime/internal/utils.ts

@@ -48,8 +48,8 @@ export function validate_store(store, name) {
 	}
 }
 
-export function subscribe(store, callback) {
+export function subscribe(store, ...args) {
-	const unsub = store.subscribe(callback);
+	const unsub = store.subscribe(...args);
 	return unsub.unsubscribe ? () => unsub.unsubscribe() : unsub;
 }
 

src/runtime/store/index.ts

@@ -1,4 +1,4 @@
-import { run_all, noop, safe_not_equal, is_function, get_store_value } from 'svelte/internal';
+import { run_all, subscribe, noop, safe_not_equal, is_function, get_store_value } from 'svelte/internal';
 
 /** Callback to inform of a value updates. */
 type Subscriber<T> = (value: T) => void;
@@ -173,7 +173,8 @@ export function derived<T>(stores: Stores, fn: Function, initial_value?: T): Rea
 			}
 		};
 
-		const unsubscribers = stores_array.map((store, i) => store.subscribe(
+		const unsubscribers = stores_array.map((store, i) => subscribe(
+			store,
 			(value) => {
 				values[i] = value;
 				pending &= ~(1 << i);