When saving a model with bulkSave, the values in the discriminator schema are not updated.

[0skgc]

Prerequisites

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

Mongoose version

7.5.3

Node.js version

18.16.0

MongoDB server version

6.0.10

Typescript version (if applicable)

5.2.2

Description

When saving a model with bulkSave, the properties of the discriminator schema are not updated.
When I try the same update with model.prototype.save, it is updated, so is this a bug with bulkSave?

I followed the internal process of bulkSave in the debugger, and it looks like updates to paths that are not in the base schema (updates to the discriminator schema) are deleted in the walkUpdatePath function in castUpdate.js.

Steps to Reproduce

Test code that can reproduce the problem

import mongoose from "mongoose"
import { beforeEach, test, expect } from "vitest"

const schema = new mongoose.Schema({ value: String }, { discriminatorKey: "type" })
const typeASchema = new mongoose.Schema({ aValue: String })
schema.discriminator("A", typeASchema)

type IBaseTest = mongoose.InferSchemaType<typeof schema>
type ITypeATest = IBaseTest & { type: "A" } & mongoose.InferSchemaType<typeof typeASchema>
type ITest = ITypeATest

const TestModel = mongoose.model<ITest>("Test", schema)

describe("mongoose buksSave test", () => {
  beforeEach(async () => {
    await TestModel.deleteMany({})
  })

  const testData: ITypeATest = { value: "initValue", type: "A", aValue: "initAValue" }

  test("bulkSave", async () => {
    // Arrange
    const doc = await TestModel.create<ITypeATest>(testData)

    // Act
    doc.value = "updatedValue1"
    doc.aValue = "updatedValue2"
    await TestModel.bulkSave([doc])

    // Assert (!!!aValue is not updated)
    const findDoc = await TestModel.findById(doc._id)
    expect(findDoc).toMatchInlineSnapshot(`
      {
        "__v": 0,
        "_id": "${doc._id.toString()}",
        "aValue": "initAValue",
        "type": "A",
        "value": "updatedValue1",
      }
    `)
  })

  test("save", async () => {
    // Arrange
    const doc = await TestModel.create<ITypeATest>(testData)

    // Act
    doc.value = "updatedValue1"
    doc.aValue = "updatedValue2"
    await doc.save()

    // Assert (both value and aValue are updated)
    const findDoc = await TestModel.findById(doc._id)
    expect(findDoc).toMatchInlineSnapshot(`
      {
        "__v": 0,
        "_id": "${doc._id.toString()}",
        "aValue": "updatedValue2",
        "type": "A",
        "value": "updatedValue1",
      }
    `)
  })
})

Expected Behavior

bulkSave also updates the properties of the discriminator in the same way as save.

[IslandRhythms]

const schema = new mongoose.Schema({ value: String }, { discriminatorKey: "type" })
const typeASchema = new mongoose.Schema({ aValue: String })
schema.discriminator("A", typeASchema)

const TestModel = mongoose.model("Test", schema);


async function run() {
  await mongoose.connect('mongodb://127.0.0.1:27017');
  await mongoose.connection.dropDatabase();

  const testData = { value: "initValue", type: "A", aValue: "initAValue" }
    // Arrange
    const doc = await TestModel.create(testData)

    // Act
    doc.value = "updatedValue1"
    doc.aValue = "updatedValue2"
    await TestModel.bulkSave([doc])

    // Assert (!!!aValue is not updated)
    const findDoc = await TestModel.findById(doc._id)
    /*
      {
        "__v": 0,
        "_id": "${doc._id.toString()}",
        "aValue": "initAValue",
        "type": "A",
        "value": "updatedValue1",
      }
    */
    console.log('what is findDoc', findDoc);

    const doc2 = await TestModel.create(testData);
    doc2.value = "updatedValue1"
    doc2.aValue = "updatedValue2"
    await doc2.save()
    /*
      {
        "__v": 0,
        "_id": "${doc._id.toString()}",
        "aValue": "updatedValue2",
        "type": "A",
        "value": "updatedValue1",
      }
    */
    const findDoc2 = await TestModel.findById(doc2._id);
    console.log('what is findDoc2', findDoc2);
}

run();