Build order for Classes to Schemas is changed to bottom-up

[j-d-carmichael]

https://github.com/typegoose/typegoose/blob/master/CHANGELOG.md#-breaking-changes

"Build order for Classes to Schemas is changed to bottom-up, which can affect some environments"

We are on version 8 across all services right now, do you have any more info on what is meant by bottom-up in this context?

[hasezoey]

i hope the following example explains what is affected:

on 8.3.0:

// NodeJS: 16.11.0
// MongoDB: 4.2-bionic (Docker)
import { getModelForClass, prop } from '@typegoose/typegoose'; // @typegoose/typegoose@8.3.0
import { assertion } from '@typegoose/typegoose/lib/internal/utils';
import * as mongoose from 'mongoose'; // mongoose@5.13.13

class Animal {
  @prop({ default: 'AnimalType' })
  public type?: string;

  public getName(): string {
    return 'AnimalGetName';
  }
}

class Cat extends Animal {
  @prop({ default: 'CatType' })
  public type?: string;

  @prop({ default: 'unknownSubType' })
  public subtype?: string;

  public getName(): string {
    return 'CatGetName';
  }
}

class MaineCoon extends Cat {
  @prop({ default: 'MaineCoonSubType' })
  public subtype?: string;

  public getName(): string {
    return 'MaineCoonGetName';
  }
}

const MaineCoonModel = getModelForClass(MaineCoon);
const CatModel = getModelForClass(Cat);
const AnimalModel = getModelForClass(Animal);
(async () => {
  await mongoose.connect(`mongodb://localhost:27017/`, {
    dbName: 'verifyMASTER',
    useCreateIndex: true,
    useNewUrlParser: true,
    useUnifiedTopology: true,
  });

  const animaldoc = await AnimalModel.create({});

  console.log(animaldoc.type, animaldoc.getName());
  assertion(animaldoc.type === 'AnimalType');
  assertion(animaldoc.getName() === 'AnimalGetName');

  const catdoc = await CatModel.create({});

  console.log(catdoc.type, catdoc.subtype, catdoc.getName());
  assertion(catdoc.type === 'CatType');
  assertion(catdoc.subtype === 'unknownSubType');
  assertion(catdoc.getName() === 'CatGetName');

  const mainecoondoc = await MaineCoonModel.create({});

  console.log(mainecoondoc.type, mainecoondoc.subtype, mainecoondoc.getName());
  assertion(mainecoondoc.type === 'AnimalType'); // notice this
  assertion(mainecoondoc.subtype === 'MaineCoonSubType');
  assertion(mainecoondoc.getName() === 'MaineCoonGetName');

  await mongoose.disconnect();
})();

with output:

AnimalType AnimalGetName
CatType unknownSubType CatGetName
AnimalType MaineCoonSubType MaineCoonGetName

and on 9.2.0:

// NodeJS: 16.11.0
// MongoDB: 4.2-bionic (Docker)
import { getModelForClass, prop } from '@typegoose/typegoose'; // @typegoose/typegoose@9.2.0
import { assertion } from '@typegoose/typegoose/lib/internal/utils';
import * as mongoose from 'mongoose'; // mongoose@6.0.12

class Animal {
  @prop({ default: 'AnimalType' })
  public type?: string;

  public getName(): string {
    return 'AnimalGetName';
  }
}

class Cat extends Animal {
  @prop({ default: 'CatType' })
  public type?: string;

  @prop({ default: 'unknownSubType' })
  public subtype?: string;

  public getName(): string {
    return 'CatGetName';
  }
}

class MaineCoon extends Cat {
  @prop({ default: 'MaineCoonSubType' })
  public subtype?: string;

  public getName(): string {
    return 'MaineCoonGetName';
  }
}

const MaineCoonModel = getModelForClass(MaineCoon);
const CatModel = getModelForClass(Cat);
const AnimalModel = getModelForClass(Animal);
(async () => {
  await mongoose.connect(`mongodb://localhost:27017/`, {
    dbName: 'verifyMASTER',
  });

  const animaldoc = await AnimalModel.create({});

  console.log(animaldoc.type, animaldoc.getName());
  assertion(animaldoc.type === 'AnimalType');
  assertion(animaldoc.getName() === 'AnimalGetName');

  const catdoc = await CatModel.create({});

  console.log(catdoc.type, catdoc.subtype, catdoc.getName());
  assertion(catdoc.type === 'CatType');
  assertion(catdoc.subtype === 'unknownSubType');
  assertion(catdoc.getName() === 'CatGetName');

  const mainecoondoc = await MaineCoonModel.create({});

  console.log(mainecoondoc.type, mainecoondoc.subtype, mainecoondoc.getName());
  assertion(mainecoondoc.type === 'CatType'); // this changed
  assertion(mainecoondoc.subtype === 'MaineCoonSubType');
  assertion(mainecoondoc.getName() === 'MaineCoonGetName');

  await mongoose.disconnect();
})();

with output:

AnimalType AnimalGetName
CatType unknownSubType CatGetName
CatType MaineCoonSubType MaineCoonGetName

---

the order until 8.x for class MaineCoon was:

• Build and Apply class Cat // first, creates schema
• Build and Apply class Animal // second, applied on top of first schema
• Build and Apply class MaineCoon // third, applied on top of second schema, this is not before "Cat" to mitigate top-level overwrite in earlier versions (like function getName)

the order in 9.x and forward for class MaineCoon is:

• Build and Apply class Animal // first, creates schema
• Build and Apply class Cat // second, applied on top of first schema
• Build and Apply class MaineCoon // third, applied on top of second schema

TL;DR: if classes extend some classes, and have functions defined and overwritten in the extended from classes and not overwritten in top-level class, then the overwrite is basically not applied

because this is a change in behavior, it is a breaking change that could affect some environments that worked-around this issue or somehow made use of it