Map choices array to union types

[Nicholaiii]

This is a great QoL addition that I've been using a lot from ts-dotenv, but the implementation details of this library is so different that another approach is better.
In ts-dotenv you specify an array that are cast as const as so:

LOG_LEVEL: {
    type: [
      'fatal' as const,
      'error' as const,
      'warn' as const,
      'info' as const,
      'debug' as const,
      'trace' as const
    ],
    default: 'info'
  },

which gives you the type

'fatal' | 'error' | 'warn' | 'info' | 'debug' | 'trace'

It would be amazing if we could conditionally do this for choices. Here is an example of how it can be done:

function stringLiteralArray<T extends string>(a: T[]) {
    return a;
}

const fruits = stringLiteralArray(["Apple", "Orange", "Pear"]);
type Fruits = typeof fruits[number]

[KATT]

Agreed! Would be nice.

[KATT]

I've actually started using zod for env vars instead of my own package as I have it installed anyway. See here for an example:

• https://github.com/trpc/examples-next-prisma-starter/blob/main/src/server/env.js
• Validated as part of the build: https://github.com/trpc/examples-next-prisma-starter/blob/main/next.config.js#L3
• Specific env vars can be exposed to client: https://github.com/trpc/examples-next-prisma-starter/blob/main/next.config.js#L27 and inferred safely https://github.com/trpc/examples-next-prisma-starter/blob/main/src/utils/publicRuntimeConfig.ts