在猫鼬中填充嵌套数组不起作用

Question

所需的输出应该是被引用的产品，但是我只得到产品的_id

router.get('/',async (req,res)=>{
     try {
          const ordersGet =await OrderModel.find({}).populate("orders.product").exec()

          console.log(ordersGet[0].orders[0])
           //this outputs { _id: 5f88e552794e0b1bb0a4b99d, quantity: 1 }
           // { _id: 5f88e552794e0b1bb0a4b99d, quantity: 1 }
           //I want to get something like this { product: {referenced product doc}, quantity: 1 }


          if(ordersGet[0] == undefined) throw new Error('no orders')
          res.json(ordersGet)
     } catch (error) {
       res.sendStatus(400).send('no orders')
     }
})

这是我的订单模型

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

const OrderSchema = new Schema(
    {
        orders:[
           {
               product :{
                type: Schema.Types.ObjectId, 
                ref: 'Product'
               },
               quantity:Number,
           }
        ],
        clientId : {
            type: Schema.Types.ObjectId, 
            ref: 'User'
        },
        date:Date,
        cost:Number,
        billing_details:{}

    }
)
module.exports = mongoose.model('Order', OrderSchema);