Virtuals not serialized after v8.5

[alko89]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Mongoose version

8.5.2

Node.js version

v22.5.1

MongoDB server version

7.0.12

Typescript version (if applicable)

5.5.4

Description

I have a nested schema, that contains calculated (virtual) props based on level. After updating from 8.4.5 to 8.5.2, the virtuals are no longer serialized. I'm using Mongoose with @nestjs/mongoose if that matters, it hasn't been updated since.

enum EProduct {
  TOYS = "Toys",
}

const labs: Record<EProduct, Lab> = {
  [EProduct.TOYS]: {
    baseCapacity: 100,
    baseProduction: 10,
  },
}


@Schema({ _id: false })
export class UserLab {
  @Prop({ required: true })
  product: EProduct;

  @Prop({ required: true, default: 1 })
  capacityLevel: number;

  @Prop({ required: true, default: 1 })
  productionLevel: number;

  @Prop({ required: true, default: new Date() })
  collectTime: Date;

  @Prop({
    virtual: true,
    get: function () {
      const lab = labs[this.product];
      return this.capacityLevel * lab.baseCapacity;
    },
  })
  capacity?: number;

  @Prop({
    virtual: true,
    get: function () {
      const lab = labs[this.product];
      return this.productionLevel * lab.baseProduction;
    },
  })
  production?: number;

  @Prop({
    virtual: true,
    get: function () {
      const now = new Date();
      const diff = getUnixTime(now) - getUnixTime(this.collectTime);
      const productionPerSecond = this.production / 3600;
      const produced = Math.floor(productionPerSecond * diff);
      return produced < this.capacity ? produced : this.capacity;
    },
  })
  produced?: number;
}

@Schema({ _id: false })
export class LabPlot {
  @Prop({ required: true })
  plotId: number;

  @Prop({ type: UserLab, required: false })
  lab?: UserLab;
}

@Schema({
  toObject: {
    getters: true,
  },
  toJSON: {
    getters: true,
  },
})
export class User extends Document {
  @Prop({ required: true, unique: true })
  id: number;

  @Prop({ required: true })
  username: string;

  @Prop({ type: [LabPlot], default: [{ plotId: 0 }] })
  labPlots: LabPlot[];
}

v8.4.5

{
    "_id": "66a9f217839a26bca6511464",
    "id": 475680949,
    "username": "alko89",
    "labPlots": [
        {
            "plotId": 0,
            "lab": {
                "product": "Toys",
                "capacityLevel": 1,
                "productionLevel": 1,
                "collectTime": "2024-07-31T08:14:37.829Z",
                "produced": 65,
                "production": 10,
                "capacity": 100
            }
        }
    ],
    "__v": 0
}

v8.5.2

{
    "_id": "66a9f217839a26bca6511464",
    "id": 475680949,
    "username": "alko89",
    "labPlots": [
        {
            "plotId": 0,
            "lab": {
                "product": "Toys",
                "capacityLevel": 1,
                "productionLevel": 1,
                "collectTime": "2024-07-31T08:14:37.829Z"
            }
        }
    ],
    "__v": 0
}

Steps to Reproduce

Update to v8.5.2

Expected Behavior

Virtuals should be serialized.

[vkarpov15]

Mongoose playground link

Repro script:

'use strict';

const mongoose = require('mongoose');

const userLabSchema = new mongoose.Schema({
  capacityLevel: Number
});

userLabSchema.virtual('capacityLevelCeil').get(function() {
  return Math.ceil(this.capacityLevel);
});

const labPlotSchema = new mongoose.Schema({
  plotId: Number,
  lab: userLabSchema
});

const userSchema = new mongoose.Schema({
  username: String,
  labPlots: [labPlotSchema]
}, { toObject: { virtuals: true } });

const User = mongoose.model('User', userSchema);

const doc = new User({
  username: 'test',
  labPlots: [{
    plotId: 1,
    lab: { capacityLevel: 3.14 }
  }]
});
console.log(doc.toObject().labPlots[0]);

Output:

{
  plotId: 1,
  lab: {
    capacityLevel: 3.14,
    _id: new ObjectId('66abad45f09d38ae5c9bcd30')
  },
  _id: new ObjectId('66abad45f09d38ae5c9bcd2f')
}

[vkarpov15]

It looks like, in older versions of Mongoose, schema-level virtual default applied to subdocuments, but not in Mongoose 8.5. We'll revert to the old behavior for backwards compatibility. As a workaround, please add the following to your UserLab class:

@Schema({
  toObject: {
    getters: true,
  },
  toJSON: {
    getters: true,
  },
})

With toObject option set on the user lab schema, the repro script works fine:

const userLabSchema = new mongoose.Schema({
  capacityLevel: Number
}, { toObject: { virtuals: true } }); // <-- added `virtuals: true` here

userLabSchema.virtual('capacityLevelCeil').get(function() {
  return Math.ceil(this.capacityLevel);
});

[alko89]

Thanks @vkarpov15 🙌 that makes sense, not sure why I didn't try if that would fix the issue.