The function .transform of .findOne gets called twice

[stantanasi]

Prerequisites

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

Mongoose version

8.0.3

Node.js version

20.10.0

MongoDB server version

5.0.4

Typescript version (if applicable)

5.3.3

Description

The .transform function when using .findOne is executed twice instead of once.

Steps to Reproduce

const UserSchema = new Schema({
  name: String,
})

const User = model('User', UserSchema)

const user = new User({
  name: "John Doe"
})

await user.save()

let i = 1
console.log("-------- FIND ONE --------")
await User.findById(user._id)
  .transform((doc) => {
    console.log("Transform executed:", i++)
    return doc
  })
/**
 * -------- FIND ONE --------
 * Transform executed: 1
 * Transform executed: 2 // <- WRONG
 */

i = 1
console.log("-------- FIND --------")
await User.find()
  .transform((doc) => {
    console.log("Transform executed:", i++)
    return doc
  })
/**
 * -------- FIND --------
 * Transform executed: 1
 */

Expected Behavior

The .transform function should be executed only once.

Example of error occured:

const name = await User.findById(user._id)
  .transform((doc) => {
    return doc!.name
  })
console.log(name) // Should display user's name but it's undefined (= user.name.name)