Data loss pushing items to list when sorting list and saving multiple times

[johnpeb]

Prerequisites

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

Mongoose version

6.7.0

Node.js version

16.13.1

MongoDB server version

4.2.8

Typescript version (if applicable)

4.8.4

Description

The provided test case shows data loss pushing items to list/subcollection when sorting the subcollection AND saving multiple times.

If the orderBy() lines are omitted, the result is correct OR if the first doc.save() is omitted, the result is correct.

This test case shows data loss, but a similar flow causes duplicate items to be inserted into the array on the 2nd save.

Steps to Reproduce

import * as assert from 'assert'
import { orderBy } from 'lodash'
import { Schema } from 'mongoose'
import * as mongoose from 'mongoose'

run().catch(err => console.log(err))

/**
 * npx ts-node scripts/mongoose.ts
 */
async function run (): Promise<void> {
  await mongoose.connect('mongodb://localhost:27017/test-mongoose', {})
  await mongoose.connection.dropDatabase()
  mongoose.set('debug', true)

  const Test = mongoose.model('Test', new Schema({
    list: [{
      // _id: false,
      a: Number
    }]
  }))

  await Test.create({ list: [{ a: 1, b: 11 }] })

  let doc = await Test.findOne()
  doc.list.push({ a: 2 })
  doc.list = orderBy(doc.list, 'a', 'asc') // Same behavior if line replaced with: doc.list = [...doc.list]
  await doc.save()

  doc.list.push({ a: 3 })
  doc.list = orderBy(doc.list, 'a', 'asc') // Same behavior if line replaced with: doc.list = [...doc.list]
  await doc.save()

  doc = await Test.findOne()
  assert(doc.list.length === 3, `Got ${JSON.stringify(
    // @ts-expect-error toObject() not typed
    doc.list.toObject()
  )}`)

  process.exit()
}

Actual output. Note that the {a: 3} element is missing. If the first doc.save() is omitted the output is correct.

% npx ts-node scripts/mongoose.ts
Mongoose: tests.insertOne({ list: [ { a: 1, _id: new ObjectId("6365530081dd159228ce5c94") } ], _id: new ObjectId("6365530081dd159228ce5c93"), __v: 0}, { session: null })
Mongoose: tests.findOne({}, { projection: {} })
Mongoose: tests.updateOne({ _id: new ObjectId("6365530081dd159228ce5c93") }, { '$push': { list: { '$each': [ { a: 2, _id: new ObjectId("6365530081dd159228ce5c98") } ] } }, '$inc': { __v: 1 }}, { session: null })
Mongoose: tests.findOne({ _id: new ObjectId("6365530081dd159228ce5c93") }, { session: null, projection: { _id: 1 } })
Mongoose: tests.findOne({}, { projection: {} })
AssertionError [ERR_ASSERTION]: Got [{"a":1,"_id":"6365530081dd159228ce5c94"},{"a":2,"_id":"6365530081dd159228ce5c98"}]
    at /Users/johnpeberdy/Documents/Code/phenix/scripts/mongoose.ts:47:3
    at Generator.next (<anonymous>)
    at fulfilled (/Users/johnpeberdy/Documents/Code/phenix/scripts/mongoose.ts:5:58)
    at processTicksAndRejections (node:internal/process/task_queues:96:5) {
  generatedMessage: false,
  code: 'ERR_ASSERTION',
  actual: false,
  expected: true,
  operator: '=='
}

Expected Behavior

The result should not change if the first doc.save() is omitted. If this use case is not supported, then it should fail loudly.

[johnpeb]

Workaround: replace doc.list.push(x) with doc.list = [...doc.list, x]

[johnpeb]

Thanks @vkarpov15 !