Help us improve 🍉's TypeScript support

[radex]

0.25 came with a huge improvement in the quality and maintainability of 🍉's TypeScript types. There were some teething problems, requiring a few patch releases, and no doubt the increased type coverage revealed new TS errors that weren't there before.

Anyway, thanks a lot to @sidferreira @paulrostorp @enahum @mlecoq for their contributions

You can help. Here's a few TS maintenance items that need to be done:

• hook up prettier to run over .d.ts
• in package.json there are outdated TS-related dependencies… I'm not even sure that all of them should be there, given that much of the TS checking lives in examples/typescript
• remove // @flow comments from d.ts's
• there's tslint, but I don't think it's hooked up to run anywhere? shouldn't it be a part of yarn ci:check ?
• add usage of more 🍉 APIs to examples/typescript to test type-checking
• add typescript types to documentation

[lucaswitch]

Hello @radex, i just added some Typescript support on the Setup docs website section.
Can i continue or we need to change something?

[radex]

@lucaswitch PR?

[lucaswitch]

Just added the PR #1636

[dexter-stpierre]

Hoping to find time to contribute some types for this soon. FWIW I thought I'd let you know that tslint was deprecated in 2020. From what I can tell the eslint settings should handle linting the .ts files, but I can confirm when I find time to contribute to the types https://www.npmjs.com/package/tslint

[BrunnerLivio]

I created a little wrapper around the tableSchema function to make the column names & table name types secure and synched with the model.

import {Model, tableSchema} from '@nozbe/watermelondb'

type TableSchema = Parameters<typeof tableSchema>[0]
type Column = TableSchema['columns'][number]

type WatermelonModelFields = keyof Model
type Class<TModel extends typeof Model> = TModel extends {
  new (...args: any[]): infer U
}
  ? U
  : never

/**
 * Removes all fields that are inherited from the Watermelon Model class
 */
type ModelFieldNames<TModel extends Model> = Exclude<
  keyof TModel,
  WatermelonModelFields
>

export type ModelSchema<TModel extends typeof Model> = TableSchema & {
  name: TModel['table']
  columns: (Column & {
    name: ModelFieldNames<Class<TModel>> extends never
      ? string
      : ModelFieldNames<Class<TModel>>
  })[]
}

export const tableSchemaTypesecure = <
  TModel extends typeof Model = typeof Model,
>(
  arg0: ModelSchema<TModel>
) => tableSchema(arg0)

Usage:

class UserModel extends Model {
  // Needs to be `readonly` so that the type can be inferred
  static readonly table = 'users'

  @field('name') name!: string
}

const userSchema = tableSchemaTypesecure<typeof UserModel>({
  name: 'users',
  columns: [{name: 'name', type: 'string'}],
})

If you're interested I'll gladly try to make this work upstream & create a PR :)

Though there are better ways to solve this problem -- this would just be a simple way to provide typescurity without introducing a breaking change.