Add "required" flag to discriminator model's nested property

[fardolieri]

Do you want to request a feature or report a bug?

Potential bug

My Problem

I want my discriminated model to have a required flag on name.firstName, but my base model should not.

What is the current behavior?

Given the following code snippet:

const nameSchema = new Schema({
  firstName: { type: 'String' },
  lastName: { type: 'String' },
});

const personSchema = new Schema(
  {
    name: { type: nameSchema, default: {} },
    kind: { type: 'String', enum: ['normal', 'vip'], required: true },
  },
  { discriminatorKey: 'kind' },
);

const Person = mongoose.model('Person', personSchema);

const vipSchema = new Schema({
  name: {
    type: new Schema({
      firstName: { type: 'String', required: true },
      title: { type: 'String', required: true },
    }),
  },
});

const Vip = Person.discriminator('vip', vipSchema);


new Vip({ name: { firstName: 'John', title: 'Dr' } }).validateSync(); // does not throw, as expected
new Vip({ name: { firstName: 'John' } }).validateSync(); // does throw, as expected ('name.title' is required and missing)
new Vip({ name: { title: 'Dr' } }).validateSync(); // !? does NOT throw, but I would expect it to ('name.firstName' should be required and is missing)

What are the versions of Node.js, Mongoose and MongoDB you are using?
Node 15.14.0, mongoose 5.12.3, MongoDB 4.4.4 Community

---

It looks like the title's required flag in my vipSchema is working just fine, but on firstName it is somehow ignored. Im wondering if this is the expected behaviour of mongoose and if so, how else am I supposed to add the required flag to my discriminator model?

[IslandRhythms]

const mongoose = require('mongoose');
const {Schema} = mongoose;

const nameSchema = new Schema({
    firstName: { type: 'String' },
    lastName: { type: 'String' },
  });
  
  const personSchema = new Schema(
    {
      name: { type: nameSchema, default: {} },
      kind: { type: 'String', enum: ['normal', 'vip'], required: true },
    },
    { discriminatorKey: 'kind' },
  );
  
  const Person = mongoose.model('Person', personSchema);
  
  const vipSchema = new Schema({
    name: {
      type: new Schema({
        firstName: { type: 'String', required: true },
        title: { type: 'String', required: true },
      }),
    },
  });
  
  async function test() {
    await mongoose.connect('mongodb://localhost:27017/test', {
        useNewUrlParser: true,
        useUnifiedTopology: true
      });
    
      await mongoose.connection.dropDatabase();

      const entry = await Person.create({name: {firstName: 'John', lastName: 'Does'}, kind: 'vip'})
      await entry.save();
      const Vip = Person.discriminator('vip', vipSchema);
  
  
      console.log('1', new Vip({ name: { firstName: 'John', title: 'Dr' } }).validateSync()); // does not throw, as expected
      console.log('2', new Vip({ name: { firstName: 'John' } }).validateSync()); // does throw, as expected ('name.title' is required and missing)
      console.log('3', new Vip({ name: { title: 'Dr' } }).validateSync()); // !? does NOT throw, but I would expect it to ('name.firstName' should be required and is missing)
  }
test();

[vkarpov15]

I've been digging into this and confirmed this is a bug. It looks like it is due to the discriminator() function overwriting vipSchema's name.firstName with personSchema's name.firstName for some reason. Will look into this more tomorrow.

[fardolieri]

Wow I didn't expect a fix so soon. Thank you for your hard work! 🥇