Reply sum types need a discriminator

[archaeron]

I wanted to implement the loadFile command for atom.
I'm using

import { IdrisClient } from "idris-ide-client"
const client = new IdrisClient()
client.loadFile(filePath).then((loadFile: FinalReply.LoadFile) => {
   // here
})

but I can't really use loadFile where // here is because typescript needs a discriminator
to be able to properly use sum types.

So

 export type LoadFile =
    | {
        ok: null
        id: number
        type: ":return"
      }
    | { err: string; id: number; type: ":return" }

this would need to be something like this:

 export type LoadFile =
    | {
        ok: true
        id: number
        type: ":return"
      }
    | { ok: false, err: string; id: number; type: ":return" }

or:

 export type LoadFile =
    | {
        result: 'ok'
        id: number
        type: ":return"
      }
    | { result: 'error', err: string; id: number; type: ":return" }

[meraymond2]

Yeah, I'm not really satisfied with those types either. In the meantime, you can discriminate based on the presence of the key rather than the value:

if ("ok" in reply) {
  // do stuff
}

I do find that clunky though.

I like the idea of having an ok: boolean attribute. It would make it more pleasant to test the reply for success: if (reply.ok) is clearer. It's similar to how the fetch api works. And, I didn't like putting the reply payload in ok.

[archaeron]

I didn't know about this :)

if ("ok" in reply) {
  // do stuff
}

thanks.

I like the idea of having an ok: boolean attribute. It would make it more pleasant to test the reply for success: if (reply.ok) is clearer. It's similar to how the fetch api works. And, I didn't like putting the reply payload in ok.

and I agree with this