Cannot define discriminator options on a Schema

[forivall]

Prerequisites

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

Mongoose version

7.x.x, 8.x.x

Node.js version

20.x

MongoDB server version

7.2.2

Typescript version (if applicable)

No response

Description

While the options for a discriminator can be defined on a Model, SchemaSubdocument or SchemaDocumentArray, they cannot be defined on a general Schema.

Steps to Reproduce

const clickedEventSchema = new mongoose.Schema({ element: String }, { discriminatorKey: 'kind' });
eventSchema.discriminator('ClickedEvent', clickedEventSchema, { value: 'click' });
//                                                            ^ this will not be used
const Event = mongoose.model('Event', eventSchema);
const doc = await Event.create({ kind: 'clicked', element: '#hero' });
doc.element; // '#hero'
doc instanceof ClickedModel; // this should be `true`, this will currently be `false`

Expected Behavior

Potential fix: master...forivall:mongoose:schema-discriminator-options

[IslandRhythms]

const mongoose = require('mongoose');

const eventSchema = new mongoose.Schema({
  name: String
});
const clickedEventSchema = new mongoose.Schema({ element: String }, { discriminatorKey: 'kind' });
eventSchema.discriminator('ClickedEvent', clickedEventSchema, { value: 'click' });
//                                                            ^ this will not be used
const Event = mongoose.model('Event', eventSchema);

const ClickedModel = mongoose.model('Clicked', clickedEventSchema);


async function run() {
  await mongoose.connect('mongodb://localhost:27017');
  await mongoose.connection.dropDatabase();
  const doc = await Event.create({ kind: 'clicked', element: '#hero' });
  doc.element; // '#hero'
  console.log(doc instanceof ClickedModel); // this should be `true`, this will currently be `false`
  console.log('done');
}

run();