EntityBuilder has to know if a property should be single or multiple

[hkan]

Assuming the following entity definitions:

class Dog extends Entity {
  // ...
}

class Person extends Entity {
  @Type(Dog)
  bestFriend!: Dog;
}

If I create an instance of Person with the following data:

const p = EntityBuilder.buildOne(Person, {
  bestFriend: [
    { name: 'Good' },
    { name: 'Boy' }
  ]
})

(Assume the data comes from an API so it's not type-checkable on build-time.)

It will accept that data, and p.bestFriend will be Dog[] even though the prop definition was a non-array Dog. We should have a way to be explicit about if we want the prop to be an array or not, so that EntityBuilder can reject array data for a singular property.

Proposal: Typed collection decorator

One proposal is only being explicit about arrays so that EntityBuilder will reject arrays if the field is not annotated with the decorator.

class Person extends Entity {
  @Type(Dog)
  bestFriend!: Dog; // this will not be filled with array input

  @CollectionType(Dog)
  pets!: Dog[]; // this will be filled with ONLY array input
}

Proposal: Separate and single-purpose collection decorator

One proposal is only being explicit about arrays so that EntityBuilder will reject arrays if the field is not annotated with the decorator.

class Person extends Entity {
  @Type(Dog)
  bestFriend!: Dog; // this will not be filled with array input

  @Type(Dog)
  @Collection // can be before `@Type` as well.
  pets!: Dog[]; // this will be filled with ONLY array input
}

Upside of a single-purpose collection decorator is that they can be utilized for primitive type properties, as well.