Merge pull request #12321 from Automattic/vkarpov15/gh-12264

Make ArraySubdocuments apply `_id` defaults on init

Author: vkarpov15

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

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);
+  });
 });