[bug] command option's choises is of type unknown

[its-dibo]

let args  = yargs()
 .command('example', '...', {
   test:{
     choices: ["a", "b"] as const;
   }
})
.parseSync()

//<------- error: Argument of type 'unknown' is not assignable to parameter of type '"a" | "b"'.ts(2345)
test(args._[0].test)

function test(value: 'a' | 'b'){}

[shadowspawn]

I was not able to reproduce this problem. I created a new package and initialised the TypeScript configuration with npx tsc --init.

import yargsFactory from 'yargs/yargs';

const argv  = yargsFactory(process.argv.slice(2))
 .command('example', '...', {
   test:{
     choices: ["a", "b"] as const
   }
})
.parseSync();

console.log(argv);

% node ts.js example --test  
ts.js example

...

Options:
  --help     Show help                                                 [boolean]
  --version  Show version number                                       [boolean]
  --test                                                     [choices: "a", "b"]

Invalid values:
  Argument: test, Given: true, Choices: "a", "b"

[its-dibo]

% node ts.js example --test 

this is not the issue, yargs itself can detect the user's input.
but the issue is that there is no way to tell typescript the correct type, you need to always cast each arg before using it

To reproduce the issue:
1- starting from your snippet, add a single line argv.test
2- hover over argv.test to see its type. it should be something like a | b, but instead it is just unknown

[shadowspawn]

(I misunderstood the issue. Thanks for explaining. I will have another look.)

[shadowspawn]

Here is a way of defining the command that gets the choices into the types.

import yargsFactory from 'yargs/yargs';

const yargs = yargsFactory(process.argv.slice(2))
  .command('example [test]', '...',
    (yargs) => {
      return yargs.positional('test', {
        type: 'string',
        choices: ["a", "b"] as const
      });
    },
    (argv) => {
      console.log(argv);
      const inspect = argv.test; // <-- "a" | "b" | undefined
    });

yargs.parseSync();