Random error when using refPath & strictPopulate on deep subdocs

[BobBatard]

Prerequisites

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

Mongoose version

8.7.1

Node.js version

20.7.0

MongoDB server version

8.0.1

Typescript version (if applicable)

No response

Description

Some context: I have a parent model, which contains a property child that stores an ObjectId pointing to either a childA or childB model, with the model being specified in a childType property. The value of childType is passed to the refPath of the child property.

childA has a property subChildA, and subChildA has a property grandChildA.
childB has no properties.

parent  > childA > subChildA > grandChildA
        > childB

When performing a find on parent and populating the entire chain of children, the populate function sometimes mixes up the models, resulting in an error indicating that child.subChildA.grandChildA is not in the schema.

/node_modules/mongoose/lib/helpers/populate/getModelsMapForPopulate.js:50
    return new StrictPopulate(options._fullPath || options.path);
           ^

StrictPopulateError: Cannot populate path `child.subChildA.grandChildA` because it is not in your schema. Set the `strictPopulate` option to false to override.
    at getModelsMapForPopulate (/Users/bob/Documents/work/inmemori/crm_api/node_modules/mongoose/lib/helpers/populate/getModelsMapForPopulate.js:50:12)
    at populate (/Users/bob/Documents/work/inmemori/crm_api/node_modules/mongoose/lib/model.js:4245:21)
    at _populate (/Users/bob/Documents/work/inmemori/crm_api/node_modules/mongoose/lib/model.js:4205:5)
    at /Users/bob/Documents/work/inmemori/crm_api/node_modules/mongoose/lib/model.js:4177:5
    at new Promise (<anonymous>)
    at Function.populate (/Users/bob/Documents/work/inmemori/crm_api/node_modules/mongoose/lib/model.js:4176:10)
    at populate (/Users/bob/Documents/work/inmemori/crm_api/node_modules/mongoose/lib/model.js:4335:13)
    at _populate (/Users/bob/Documents/work/inmemori/crm_api/node_modules/mongoose/lib/model.js:4205:5)
    at /Users/bob/Documents/work/inmemori/crm_api/node_modules/mongoose/lib/model.js:4177:5
    at new Promise (<anonymous>) {
  path: 'child.subChildA.grandChildA'

Here’s what I observed in the code of the getModelsMapForPopulate.js file:

In getModelsMapForPopulate, adding
console.log(model, options.path)

just before line 50:
return new StrictPopulate(options._fullPath || options.path)

outputs Model { childB } subChildA.grandChildA.

Adding options = _.cloneDeep(options) at the beginning of this function resolves the issue.

In the addModelNamesToMap function, replacing line 526
utils.merge(currentOptions, options)
with
utils.merge(currentOptions, _.cloneDeep(options))

also resolves the issue.

It appears, then, that the problem is caused by a mutation of the options object passed as a parameter to the function, associated with a concurrency issue, given the random nature of the bug.

Steps to Reproduce

import mongoose from 'mongoose'

(async () => {
	await mongoose.connect('mongodb://localhost:27017/test')
	await mongoose.connection.dropDatabase()

	const { ObjectId } = mongoose.Types

	const Parent = new mongoose.Schema({
		child: { type: ObjectId, refPath: 'childType' },
		childType: { type: String, enum: ['childA', 'childB'] }
	})

	const ChildA = new mongoose.Schema({
		subChildA: { type: ObjectId, ref: 'subChildA' }
	})

	const SubChildA = new mongoose.Schema({
		grandChildA: { type: ObjectId, ref: 'grandChildA' }
	})

	const GrandChildA = new mongoose.Schema()

	const ChildB = new mongoose.Schema()

	const parentModel = mongoose.model('parent', Parent)
	const childAModel = mongoose.model('childA', ChildA)
	const subChildAModel = mongoose.model('subChildA', SubChildA)
	const grandChildAModel = mongoose.model('grandChildA', GrandChildA)
	const childBModel = mongoose.model('childB', ChildB)

	const grandChildA = await grandChildAModel.create({})
	const subChildA = await subChildAModel.create({ grandChildA })
	const childA = await childAModel.create({ subChildA })
	const childB = await childBModel.create({})

	await parentModel.create([
		{ child: childA, childType: 'childA' },
		{ child: childB, childType: 'childB' }
	])

	const getParents = () => parentModel
		.find()
		.populate({
			path: 'child',
			populate: {
				path: 'subChildA',
				strictPopulate: false,
				populate: {
					path: 'grandChildA',
					strictPopulate: true
				}
			}
		})

	// you may have to duplicate these lines to trigger the bug
	// on my computer, the problem doesn't occur when disabling the second line
	// the problem doesn't occur either when increasing the size of the arrays to 1000 😮
	// as a last resort, rerunning the script several times should be enough to trigger the bug
	// for i in {1..100}; do node strictPopulate.mjs; done
	await Promise.all(new Array(100).fill().map(getParents))
	await Promise.all(new Array(100).fill().map(getParents))

	process.exit()
})()

Expected Behavior

well, it shouldn't throw :)
thanks for your help, and this wonderful project !