[feature request] define constraints at the type-level

[ducaale]

Sometimes, I have a type A that might be used in other types. If I need to add constraints on that type, I would have to repeat those constraints every time I create a validator for a type that references type A.

type Url = string

type Video = {
  url: Url
  length: number
}

type Image = {
  url: Url
  width: number
  height: number
}

registerType('Video')
register('Image')

const imageValidator = createValidator<Image>(undefined, {
  constraints: {
    Url: x => x.startsWith('http://') // this can't be moved to an object or babel-macro will complain
  }
})

const videoValidator = createValidator<Video>(undefined, {
  constraints: {
    Url: x => x.startsWith('http://')
  }
})

It would be nice if one of the following was possible:

• Type constraints can be defined when registering the corresponding type

  type Url = string
  
  type Video = {
    url: Url
    length: number
  }
  
  type Image = {
    url: Url
    width: number
    height: number
  }
  
  registerType('Url', x => x.startsWith('http://'))
  registerType('Video')
  register('Image')
  
  const x = createValidator<Image>()
  const x = createValidator<Video>()

• Type constraints can be defined globally

  type Url = string
  
  type Video = {
    url: Url
    length: number
  }
  
  type Image = {
    url: Url
    width: number
    height: number
  }
  
  registerType('Video')
  register('Image')
  
  registerConstraints({
    Url: x => x.startsWith('http://')
  })
  const x = createValidator<Image>()
  const x = createValidator<Video>()

[vedantroy]

Hey! This makes a lot of sense. will look into this.