TypeScript resolve exact types from json file

Question

I have a json configuration file

[{ name: "apple", weight: 1.0 }, { name: "banana", weight: 2.0 }]

I create type that describes this configuration

type Config = { name: "apple" | "banana", weight: number }[];

Now I create a function that returns that configuration

import Configuration from './configuration.json';

function getConfig(): Config {
   return Configuration;
}

I get error saying that

Type 'string' is not assignable to type '"apple" | "banana"'

I understand that the problem is with the field name which type is resolved to string and not "apple" | "banana" "apple" | "banana" .

It it possible to resolve .json files with exact types? So that I can be sure that the .json file has the correct structure using only TypeScript type system?

Answer 1

It is a cast problem. Try casting it like this.

function getConfig(): Config {
   return Configuration as Config;
}