From a7265f65e3ad2ea0d8d02343f5a9e5aca1b36873 Mon Sep 17 00:00:00 2001
From: Richard Harris <richard.a.harris@gmail.com>
Date: Mon, 6 May 2019 06:26:38 -0400
Subject: [PATCH] use safe_not_equal logic for derived stores - fixes #2644

---
 store.mjs           |  2 +-
 test/store/index.js | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/store.mjs b/store.mjs
index 9f8cdf0c48..bc9bc46ed1 100644
--- a/store.mjs
+++ b/store.mjs
@@ -55,7 +55,7 @@ export function derived(stores, fn, initial_value) {
 		const sync = () => {
 			if (pending) return;
 			const result = fn(single ? values[0] : values, set);
-			if (auto && (value !== (value = result))) set(result);
+			if (auto) set(result);
 		};
 
 		const unsubscribers = stores.map((store, i) => store.subscribe(
diff --git a/test/store/index.js b/test/store/index.js
index d7c1e76668..44617d6d00 100644
--- a/test/store/index.js
+++ b/test/store/index.js
@@ -188,6 +188,29 @@ describe('store', () => {
 
 			unsubscribe();
 		});
+
+		it('is updated with safe_not_equal logic', () => {
+			const arr = [0];
+
+			const number = writable(1);
+			const numbers = derived(number, $number => {
+				arr[0] = $number;
+				return arr;
+			});
+
+			const concatenated = [];
+
+			const unsubscribe = numbers.subscribe(value => {
+				concatenated.push(...value);
+			});
+
+			number.set(2);
+			number.set(3);
+
+			assert.deepEqual(concatenated, [1, 2, 3]);
+
+			unsubscribe();
+		});
 	});
 
 	describe('get', () => {