JSON Schema const type about typebox

[sinclairzx81]

@wyozi Hi, You can achieve this using Type.Literal(...). Example here and below

import { Type, Static } from '@sinclair/typebox'

const ItemAddedEvent = Type.Object({
  name: Type.Literal('item.added'),
  added: Type.String()
})

const ItemModifiedEvent = Type.Object({
  name: Type.Literal('item.modified'),
  modified: Type.String()
})

const Event = Type.Union([
  ItemAddedEvent,
  ItemModifiedEvent
])

function on(event: Static<typeof Event>) {
    switch(event.name) {
        case 'item.added': console.log(event.added); break;
        case 'item.modified': console.log(event.modified); break;
    }
}

Hope this helps

[sinclairzx81]

@seangenabe Hi, no reason in particular other than enum is expected to cast the widest net in terms of validators. However, I'd like to standardize on draft 6 (as a minimum requirement for validators). I am happy to accept PR's if you prefer to see const used over enum in the places where it's applicable.

Ill leave this issue open for the time being.
Cheers
S

[sinclairzx81]

Will close off this issue. For the time being keeping on with enum should be fine as it's largely identical to the singular const, but may review again in future. Thanks for letting me know.

[wyozi]

Hello again :)

I have a usecase where I believe this would be required. I'm trying to build a type that can accept any of given disjoint unions:

const ItemAddedEvent = Type.Object({
  name: Type.Const('item.added'),
  // ...
})

const ItemModifiedEvent = Type.Object({
  name: Type.Const('item.modified'),
  // ...
})

const Event = Type.Union([
  ItemAddedEvent,
  ItemModifiedEvent
])

type X = Static<typeof Event>
// should be { name: 'item.added' } | { name: 'item.modified' }

Is there a way to achieve this currently or does this need const?