Pre 'findOneAndUpdate' hooks not working for array of child schemas

[jcnmsg]

Prerequisites

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

Mongoose version

6.7.2

Node.js version

14.16.1

MongoDB server version

4.11.0

Typescript version (if applicable)

No response

Description

Having a childSchema and using it inside an array on the mainSchema and then calling findOneAndUpdate on the model fires the findOneAndUpdate pre-hook on the mainSchema but not on the childSchema.

Steps to Reproduce

const childSchema = new mongoose.Schema({
   name: String
});

const mainSchema = new mongoose.Schema({
   child: [childSchema]
});

mainSchema.pre('findOneAndUpdate', function () {
    console.log('fired.2') // Works
});

childSchema.pre('findOneAndUpdate', function () {
    console.log('fired.1') // Doesn't work
});

const Model = mongoose.model('Model', mainSchema);
const test = new Model();

test.findOneAndUpdate({ _id: id }, {...data}, {}, (err, res) => {})

Expected Behavior

I would expect the console to log fired.1 and fired.2 but the pre-hook is only firing on the mainSchema. Also tried save, update and updateOne pre-hooks on childSchema without luck. Is this intended behavior or a bug?

[IslandRhythms]

const mongoose = require('mongoose');

const childSchema = new mongoose.Schema({
  name: String
});

const mainSchema = new mongoose.Schema({
  child: [childSchema]
});

mainSchema.pre('findOneAndUpdate', function () {
   console.log('fired.2') // Works
});

childSchema.pre('findOneAndUpdate', function () {
   console.log('fired.1') // Doesn't work
});

const Test = mongoose.model('Test', mainSchema);

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

  const entry = await Test.create({
    child: [{ name: 'Test' }]
  });

  await Test.findOneAndUpdate({_id: entry._id}, {child: [{name: 'Testerson'}, {name: 'Testserson'}]})

run();

[vkarpov15]

This is intentional behavior. We do not fire query middleware on subdocuments. We will add a note about this to the docs.