backport pull 13515

package.json

@@ -50,6 +50,7 @@
     "eslint-plugin-markdown": "^3.0.0",
     "eslint-plugin-mocha-no-only": "1.1.1",
     "express": "^4.18.1",
+    "fs-extra": "~11.1.1",
     "highlight.js": "11.7.0",
     "lodash.isequal": "4.5.0",
     "lodash.isequalwith": "4.4.0",
@@ -67,8 +68,7 @@
     "tsd": "0.25.0",
     "typescript": "4.9.5",
     "uuid": "9.0.0",
-    "webpack": "5.75.0",
-    "fs-extra": "~11.1.1"
+    "webpack": "5.75.0"
   },
   "directories": {
     "lib": "./lib/mongoose"

test/types/mongo.test.ts

@@ -0,0 +1,17 @@
+import * as mongoose from 'mongoose';
+import { expectType } from 'tsd';
+import * as bson from 'bson';
+
+function gh12537() {
+  const schema = new mongoose.Schema({ test: String });
+  const model = mongoose.model('Test', schema);
+
+  const doc = new model({});
+
+  const v = new bson.ObjectId('somehex');
+  expectType<string>(v._id.toHexString());
+
+  doc._id = new bson.ObjectId('somehex');
+}
+
+gh12537();

types/augmentations.d.ts

@@ -0,0 +1,9 @@
+// this import is required so that types get merged instead of completely overwritten
+import 'bson';
+
+declare module 'bson' {
+  interface ObjectId {
+    /** Mongoose automatically adds a conveniency "_id" getter on the base ObjectId class */
+    _id: this;
+  }
+}

types/index.d.ts

@@ -22,6 +22,7 @@
 /// <reference path="./validation.d.ts" />
 /// <reference path="./inferschematype.d.ts" />
 /// <reference path="./virtuals.d.ts" />
+/// <reference path="./augmentations.d.ts" />
 
 declare class NativeDate extends global.Date { }
 

types/types.d.ts

@@ -80,7 +80,7 @@ declare module 'mongoose' {
     }
 
     class ObjectId extends mongodb.ObjectId {
-      _id: this;
+
     }
 
     class Subdocument<IdType = any> extends Document<IdType> {