From 811382aefd7d36857f66291727f399b3470ad90d Mon Sep 17 00:00:00 2001
From: Samuel Denis-D'Ortun <sam@sddproductions.com>
Date: Wed, 17 Feb 2021 16:19:36 -0500
Subject: [PATCH 1/2] When traversing fields, ensure we create them as we go to
 avoid accessing undefined object

---
 src/ObjectStateMutations.js                |  6 +++++-
 src/__tests__/ObjectStateMutations-test.js | 15 ++++++++++++++-
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/ObjectStateMutations.js b/src/ObjectStateMutations.js
index f9911847e..bcac048a0 100644
--- a/src/ObjectStateMutations.js
+++ b/src/ObjectStateMutations.js
@@ -138,7 +138,11 @@ export function estimateAttributes(
           data[first] = { ...serverData[first] };
           let object = { ...data };
           for (let i = 0; i < fields.length - 1; i++) {
-            object = object[fields[i]];
+            const key = fields[i];
+            if (!(key in object)) {
+              object[key] = {};
+            }
+            object = object[key];
           }
           object[last] = pendingOps[i][attr].applyTo(object[last]);
         } else {
diff --git a/src/__tests__/ObjectStateMutations-test.js b/src/__tests__/ObjectStateMutations-test.js
index 08c750719..82ca13055 100644
--- a/src/__tests__/ObjectStateMutations-test.js
+++ b/src/__tests__/ObjectStateMutations-test.js
@@ -163,7 +163,7 @@ describe('ObjectStateMutations', () => {
   });
 
   it('can estimate attributes for nested documents', () => {
-    const serverData = { objectField: { counter: 10, letter: 'a' } };
+    let serverData = { objectField: { counter: 10, letter: 'a' } };
     let pendingOps = [{ 'objectField.counter': new ParseOps.IncrementOp(2) }];
     expect(
       ObjectStateMutations.estimateAttributes(serverData, pendingOps, 'someClass', 'someId')
@@ -182,6 +182,19 @@ describe('ObjectStateMutations', () => {
         letter: 'a',
       },
     });
+    serverData = {};
+    pendingOps = [{ 'objectField.subField.subField.counter': new ParseOps.IncrementOp(20) }];
+    expect(
+      ObjectStateMutations.estimateAttributes(serverData, pendingOps, 'someClass', 'someId')
+    ).toEqual({
+      objectField: {
+        subField: {
+          subField: {
+            counter: 20,
+          },
+        },
+      },
+    });
   });
 
   it('can commit changes from the server', () => {

From ff88610930c6fc313e077905194b7cdf267d933d Mon Sep 17 00:00:00 2001
From: Samuel Denis-D'Ortun <sam@sddproductions.com>
Date: Tue, 23 Feb 2021 05:10:39 -0500
Subject: [PATCH 2/2] Add integration test

---
 integration/test/ParseObjectTest.js | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/integration/test/ParseObjectTest.js b/integration/test/ParseObjectTest.js
index 3c94ad360..45304dfc8 100644
--- a/integration/test/ParseObjectTest.js
+++ b/integration/test/ParseObjectTest.js
@@ -278,6 +278,20 @@ describe('Parse Object', () => {
     assert.equal(result.get('objectField').number, 20);
   });
 
+  it('can increment nested four levels', async () => {
+    const obj = new TestObject({ a: { b: { c: { d: 1 } } } });
+    await obj.save();
+    obj.increment('a.b.c.d');
+    assert.strictEqual(obj.get('a').b.c.d, 2);
+
+    await obj.save();
+    assert.strictEqual(obj.get('a').b.c.d, 2);
+
+    const query = new Parse.Query(TestObject);
+    const result = await query.get(obj.id);
+    assert.strictEqual(result.get('a').b.c.d, 2);
+  });
+
   it('can increment nested field and retain full object', async () => {
     const obj = new Parse.Object('TestIncrementObject');
     obj.set('objectField', { number: 5, letter: 'a' });