From 9a2462c81f6fe74d8e3a05a28f5e9fd7227ea48e Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Mon, 29 Jul 2024 13:54:25 -0400
Subject: [PATCH] fix: allow setting document array default to `null`

Fix #6691
Re: #14717
---
 lib/schema/documentArray.js | 2 +-
 test/document.test.js       | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/lib/schema/documentArray.js b/lib/schema/documentArray.js
index a10d2ec76b1..aa0c0d7984a 100644
--- a/lib/schema/documentArray.js
+++ b/lib/schema/documentArray.js
@@ -69,7 +69,7 @@ function SchemaDocumentArray(key, schema, options, schemaOptions) {
 
   const fn = this.defaultValue;
 
-  if (!('defaultValue' in this) || fn !== void 0) {
+  if (!('defaultValue' in this) || fn != null) {
     this.default(function() {
       let arr = fn.call(this);
       if (arr != null && !Array.isArray(arr)) {
diff --git a/test/document.test.js b/test/document.test.js
index c11f72753ee..5957556a867 100644
--- a/test/document.test.js
+++ b/test/document.test.js
@@ -3203,16 +3203,22 @@ describe('document', function() {
         names: {
           type: [String],
           default: null
+        },
+        tags: {
+          type: [{ tag: String }],
+          default: null
         }
       });
 
       const Model = db.model('Test', schema);
       const m = new Model();
       assert.strictEqual(m.names, null);
+      assert.strictEqual(m.tags, null);
       await m.save();
 
       const doc = await Model.collection.findOne({ _id: m._id });
       assert.strictEqual(doc.names, null);
+      assert.strictEqual(doc.tags, null);
     });
 
     it('validation works when setting array index (gh-3816)', async function() {