From 4afb8dde75a411c054b8dd9aa8f9af87259888a3 Mon Sep 17 00:00:00 2001
From: Nicolas DUBIEN <github@dubien.org>
Date: Tue, 19 Feb 2019 23:37:08 +0100
Subject: [PATCH] Suggestion of fix for #7937

---
 packages/expect/src/__tests__/matchers.test.js | 4 ++++
 packages/expect/src/utils.js                   | 5 ++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/packages/expect/src/__tests__/matchers.test.js b/packages/expect/src/__tests__/matchers.test.js
index bff61b7edc12..ad70c847e934 100644
--- a/packages/expect/src/__tests__/matchers.test.js
+++ b/packages/expect/src/__tests__/matchers.test.js
@@ -281,6 +281,10 @@ describe('.toStrictEqual()', () => {
     }).not.toStrictEqual({b: 2});
   });
 
+  it('does not ignore keys with undefined values inside an array', () => {
+    expect([{a: undefined}]).not.toStrictEqual([{}]);
+  });
+
   it('passes when comparing same type', () => {
     expect({
       test: new TestClassA(1, 2),
diff --git a/packages/expect/src/utils.js b/packages/expect/src/utils.js
index 680c5faa0c1b..3551cdcc1564 100644
--- a/packages/expect/src/utils.js
+++ b/packages/expect/src/utils.js
@@ -251,7 +251,10 @@ export const sparseArrayEquality = (a: any, b: any) => {
   // A sparse array [, , 1] will have keys ["2"] whereas [undefined, undefined, 1] will have keys ["0", "1", "2"]
   const aKeys = Object.keys(a);
   const bKeys = Object.keys(b);
-  return equals(a, b) && equals(aKeys, bKeys);
+  return (
+    equals(a, b, [iterableEquality, typeEquality], true) &&
+    equals(aKeys, bKeys)
+  );
 };
 
 export const partition = <T>(