From 4e87fdcdfef860a303042e7806e110a0de84b195 Mon Sep 17 00:00:00 2001
From: "J. Ryan Stinnett" <jryans@gmail.com>
Date: Wed, 24 Feb 2021 13:40:22 +0000
Subject: [PATCH] Fix object diffing when objects have different keys

The object diff optimisation in 32cca0534c5ff7c7a86d854e6a00a4764652d20b is not
correct for the case where `b` has some keys that are not in `a`.

By ensuring their key arrays are same length, we can preserve optimisation and
be correct as well.

Fixes https://github.com/vector-im/element-web/issues/16514
---
 src/utils/objects.ts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/utils/objects.ts b/src/utils/objects.ts
index 166c31c4c3..e7f4f0f907 100644
--- a/src/utils/objects.ts
+++ b/src/utils/objects.ts
@@ -89,6 +89,7 @@ export function objectHasDiff<O extends {}>(a: O, b: O): boolean {
     if (a === b) return false;
     const aKeys = Object.keys(a);
     const bKeys = Object.keys(b);
+    if (aKeys.length !== bKeys.length) return true;
     const possibleChanges = arrayUnion(aKeys, bKeys);
     // if the amalgamation of both sets of keys has the a different length to the inputs then there must be a change
     if (possibleChanges.length !== aKeys.length) return true;