From 4a946ffb9a3e37efa46603b60c05a9782cf16e74 Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Tue, 23 Aug 2022 15:13:51 -0400
Subject: [PATCH] fix(schema): make ArraySubdocuments apply `_id` defaults on
 init

Fix #12264
---
 lib/schema/documentarray.js      |  2 +-
 test/types.documentarray.test.js | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/lib/schema/documentarray.js b/lib/schema/documentarray.js
index 0c552453fbc..0bb64d779cf 100644
--- a/lib/schema/documentarray.js
+++ b/lib/schema/documentarray.js
@@ -392,7 +392,7 @@ DocumentArrayPath.prototype.getDefault = function(scope, init, options) {
 };
 
 const _toObjectOptions = Object.freeze({ transform: false, virtuals: false });
-const initDocumentOptions = Object.freeze({ skipId: true, willInit: true });
+const initDocumentOptions = Object.freeze({ skipId: false, willInit: true });
 
 /**
  * Casts contents
diff --git a/test/types.documentarray.test.js b/test/types.documentarray.test.js
index 6ee188f9eb4..c5b0c5221c8 100644
--- a/test/types.documentarray.test.js
+++ b/test/types.documentarray.test.js
@@ -748,4 +748,18 @@ describe('types.documentarray', function() {
     doc.arr.push(subdoc);
     await doc.validate();
   });
+
+  it('applies _id default (gh-12264)', function() {
+    mongoose.deleteModel(/Test/);
+    const nestedArraySchema = Schema({
+      subDocArray: [{ name: String }]
+    });
+
+    const Model = db.model('Test', nestedArraySchema);
+    const doc = new Model().init({
+      subDocArray: [{ name: 'foo' }]
+    });
+
+    assert.ok(doc.subDocArray[0]._id instanceof mongoose.Types.ObjectId);
+  });
 });