Ember-cli-typescript: Provide convenience types for hasMany and belongsTo relationships

[jamescdavis]

Which package(s) does this enhancement pertain to?

• [ ] @types/ember
• [ ] @types/ember__string
• [ ] @types/ember__polyfills
• [ ] @types/ember__object
• [ ] @types/ember__utils
• [ ] @types/ember__array
• [ ] @types/ember__engine
• [ ] @types/ember__debug
• [ ] @types/ember__runloop
• [ ] @types/ember__error
• [ ] @types/ember__controller
• [ ] @types/ember__component
• [ ] @types/ember__routing
• [ ] @types/ember__application
• [ ] @types/ember__test
• [ ] @types/ember__test-helpers
• [ ] @types/ember__service
• [x] @types/ember-data
• [ ] @types/rsvp
• [ ] Other
• [ ] I don't know

Please write a user story for this feature

As a developer, I want types importable from @ember-data/model that can be used to type model properties that represent async hasMany and belongsTo relationships.

These currently require importing from ember-data and using the somewhat esoteric PromiseManyArray (for hasMany) and PromiseObject (for belongsTo), e.g.

import Model, { hasMany, belongsTo } from `@ember-data/model`;
import DS from 'ember-data';

export default class MyModel extends Model {
  @hasMany('foo') foos!: DS.PromiseManyArray<Foo>;
  @belongsTo('bar') bar!: DS.PromiseObject<Bar> & Bar;
}

It would be nicer to have:

import Model, { hasMany, HasMany, belongsTo, BelongsTo } from `@ember-data/model`;

export default class MyModel extends Model {
  @hasMany('foo') foos!: HasMany<Foo>;
  @belongsTo('bar') bar!: BelongsTo<Bar>;
}

[lolmaus]

Many developers type relationships like this:

  @belongsTo('bar') bar!: Bar;
  @hasMany('foo') foos!: Foo[];

But this is problematic because it does not expose .meta, .reload(), etc.

The worst part of that wishful typing is that it assumes that this.foos[0] is possible, which is not the case.

Thus, I believe that when this is implemented, it should be documented somehow. Ember guides are not typed, so I don't know how/where. Maybe in the model blueprint?

Uhm, are blueprints even maintained? This is weird:
https://github.com/typed-ember/ember-cli-typescript-blueprints/blob/v3.0.0/blueprints/model/index.js#L70

[jamescdavis]

Uhm, are blueprints even maintained?

Unfortunately, they are quite out of date at this point. We are exploring a better way to do the blueprints than having to re-implement each one for TypeScript (and then continually update as the default blueprints change). This will likely involve some form of automatically codemodding the default blueprints.

[jamescdavis]

For the default async hasMany the type is:

DS.PromiseManyArray<T>

but for async: false it's:

DS.ManyArray<T>

I was thinking of creating AsyncHasMany and SyncHasMany but since async: true is default, maybe the async type should just be HasMany? Any thoughts on names?

[jamescdavis]

https://github.com/DefinitelyTyped/DefinitelyTyped/pull/50044

[jamescdavis]

👆🏼 that PR has been released as @types/[email protected] and @types/[email protected].