update readable signature to match writable - fixes #2296

store.mjs

@@ -1,8 +1,9 @@
 import { run_all, noop, get_store_value, safe_not_equal } from './internal';
 
-export function readable(start, value) {
-	const { set, subscribe } = writable(value, () => start(set));
-	return { subscribe };
+export function readable(value, start) {
+	return {
+		subscribe: writable(value, start).subscribe
+	};
 }
 
 export function writable(value, start = noop) {
@@ -25,7 +26,7 @@ export function writable(value, start = noop) {
 	function subscribe(run, invalidate = noop) {
 		const subscriber = [run, invalidate];
 		subscribers.push(subscriber);
-		if (subscribers.length === 1) stop = start() || noop;
+		if (subscribers.length === 1) stop = start(set) || noop;
 		run(value);
 
 		return () => {
@@ -45,7 +46,7 @@ export function derive(stores, fn) {
 	const auto = fn.length < 2;
 	let value = {};
 
-	return readable(set => {
+	return readable(undefined, set => {
 		let inited = false;
 		const values = [];
 

test/store/index.js

@@ -66,7 +66,7 @@ describe('store', () => {
 			let running;
 			let tick;
 
-			const store = readable(set => {
+			const store = readable(undefined, set => {
 				tick = set;
 				running = true;
 
@@ -192,7 +192,7 @@ describe('store', () => {
 
 	describe('get', () => {
 		it('gets the current value of a store', () => {
-			const store = readable(() => {}, 42);
+			const store = readable(42, () => {});
 			assert.equal(get(store), 42);
 		});
 	});