numeric literal possible?

[boredland]

Hi there! I would like to ensure that a parameter is part of a list of numeric values.

I tried something along the lines of:

const NumberEnum = <T extends number[]>(values: [...T]) =>
  t.Unsafe<T[number]>(t.Union(values.map((value) => t.Literal(value))));

Which of course only allows numbers in, but produces the correct type at least.

Has anybody done that?

[crishoj]

Have you tried...

const NumberEnum = <T extends number[]>(values: [...T]) => t.Unsafe<T[number]>({
    type: 'number', enum: values
})

[crishoj]

For runtime checks, a Typebox union of literals does the trick:

    const allowed = ['A', 'B', 'C']
    const S = t.Union(allowed.map((v) => t.Literal(v)))

[boredland]

so t.Unsafe isn't working?

[crishoj]

My understanding of t.Unsafe is lacking.

As far as I can tell, Value.Check requires the schema to have a [Kind] property matching an entry in Typebox' type registry:

https://github.com/sinclairzx81/typebox/blob/4e2158deb238b1fe958b0f78ad9e05f21e45041c/src/value/check/check.ts#L484

[boredland]

So as I get it, a union of "numerics", parsed as a number, isn't possible currently.

[crishoj]

I think you're right.

Assuming I understand your requirement correctly, this was what I came up with:

import Elysia, {t} from 'elysia'

const allowed = [1, 2, 3]
const schema = t.Object({
    num: t.Union(allowed.map(n => t.Literal(`${n}`)))
})

const app = new Elysia()
    .resolve(({params}) => params.num = Number.parseInt(params.num))
    .get('/test/:num', ({params: {num}}) => `num = ${num} (${typeof num})`, {
        params: schema
    })

const urls = [
    '/test/1',
    '/test/2',
    '/test/3',
    '/test/9',
]

for (const url of urls) {
    const res = await app.handle(new Request(`https://localhost${url}`))
    if (res.ok) {
        console.log(`GET ${url} → HTTP ${res.status} ${await res.text()}`)
    } else {
        console.log(`GET ${url} → HTTP ${res.status} ${(await res.json()).summary}`)
    }
}

GET /test/1 → HTTP 200 num = 1 (number)
GET /test/2 → HTTP 200 num = 2 (number)
GET /test/3 → HTTP 200 num = 3 (number)
GET /test/9 → HTTP 422 Property 'num' should be one of: 'string', 'string', 'string'

Curious to see a more idiomatic approach.