From edad51b2fafc022c1cc0a7578731f92fc1cd2559 Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Sat, 20 May 2023 14:51:13 -0400
Subject: [PATCH] fix(array): track correct changes when setting nested array
 of primitives

Fix #13372
---
 lib/schema/array.js      |  6 +++++-
 test/schema.test.js      |  2 +-
 test/types.array.test.js | 14 ++++++++++++++
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/lib/schema/array.js b/lib/schema/array.js
index a33b4e497cb..5a621ba6aac 100644
--- a/lib/schema/array.js
+++ b/lib/schema/array.js
@@ -359,7 +359,11 @@ SchemaArray.prototype.cast = function(value, doc, init, prev, options) {
     options = options || emptyOpts;
 
     let rawValue = utils.isMongooseArray(value) ? value.__array : value;
-    value = MongooseArray(rawValue, options.path || this._arrayPath || this.path, doc, this);
+    let path = options.path || this.path;
+    if (options.arrayPathIndex != null) {
+      path += '.' + options.arrayPathIndex;
+    }
+    value = MongooseArray(rawValue, path, doc, this);
     rawValue = value.__array;
 
     if (init && doc != null && doc.$__ != null && doc.$populated(this.path)) {
diff --git a/test/schema.test.js b/test/schema.test.js
index af085121c59..8752374b866 100644
--- a/test/schema.test.js
+++ b/test/schema.test.js
@@ -2562,7 +2562,7 @@ describe('schema', function() {
     });
 
     const casted = schema.path('ids').cast([[]]);
-    assert.equal(casted[0].$path(), 'ids.$');
+    assert.equal(casted[0].$path(), 'ids.0');
   });
 
   describe('cast option (gh-8407)', function() {
diff --git a/test/types.array.test.js b/test/types.array.test.js
index 5c7381ca203..219d2df01ed 100644
--- a/test/types.array.test.js
+++ b/test/types.array.test.js
@@ -1899,4 +1899,18 @@ describe('types array', function() {
 
     m.Schema.Types.Array.options.castNonArrays = true;
   });
+
+  it('supports setting nested arrays directly (gh-13372)', async function() {
+    const Test = db.model('Test', new Schema({ intArr: [[Number]] }));
+
+    const intArr = [[1, 2], [3, 4]];
+    const doc = Test.hydrate({ intArr });
+
+    doc.intArr[1][1] = 5;
+    assert.deepStrictEqual(doc.getChanges(), {
+      $set: {
+        'intArr.1.1': 5
+      }
+    });
+  });
 });