add missing field to mongoose document (#39226)

types/mongoose/index.d.ts

@@ -1421,6 +1421,8 @@ declare module "mongoose" {
     isNew: boolean;
     /** The documents schema. */
     schema: Schema;
+    /** Empty object that you can use for storing properties on the document */
+    $locals: { [k: string]: any };
   }
 
   interface MongooseDocumentOptionals {

types/mongoose/mongoose-tests.ts

@@ -732,6 +732,7 @@ mongoose.plugin<PluginOption>(AwesomeLoggerPlugin, {modelName: 'Executive', time
  */
 var doc = <mongoose.MongooseDocument> {};
 doc.$isDefault('path').valueOf();
+doc.$locals.field = 'value';
 const docDotDepopulate: mongoose.MongooseDocument = doc.depopulate('path');
 doc.equals(doc).valueOf();
 doc.execPopulate().then(function (arg) {