Unable to use `$pull` on nested array within discriminated union

[rpmccarter]

Prerequisites

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

Mongoose version

8.4.3

Node.js version

20.10.0

MongoDB server version

6.0.14

Typescript version (if applicable)

5.4.5

Description

It is not possible to perform a $pull on a nested discriminator field using Model.findOneAndUpdate()

Steps to Reproduce

I have created an MRE repo at rpmccarter/mongoose-discriminator-pull-bug-repro that demonstrates the bug. Here is some of the relevant code, taken from index.ts:

const LoginSchema = new Schema({}, { discriminatorKey: 'type', _id: false });
const UserSchema = new Schema({
  name: String,
  login: LoginSchema,
});

UserSchema.path<Schema.Types.Subdocument>('login').discriminator(
  'ssh-key',
  new Schema(
    {
      keys: {
        type: [{
          id: { type: String, required: true },
          publicKey: { type: String, required: true }
        }],
        default: [],
      }
    },
    { _id: false }
  )
);

const User = mongoose.model<User>('User', UserSchema, 'users');

const id = '123-456';

// does not work
await User.findOneAndUpdate(
  { _id: user._id, 'login.type': 'ssh-key' },
  { $pull: { 'login.keys': { id } } },
  { new: true }
);

Expected Behavior

$pull should work on nested array fields when the discriminator is specified.