[TS] Any way to predefine the flags then typecheck them in options?

Currently the type of flags are difficult to predefine, it’ll be easier to write the meow(..., ...) function then get the returned type.

But I’m trying to predefine the flags’ type then use it to typecheck the meow() function. e.g.:

// interfaces/config.ts

export interface IFlags {
  flag1: string;
  flag2: boolean;
  flag3: number;
}

export interface IConfig {
  argv: meow.IResult<IFlags>; // similar to meow.Result but pass in flag type not flag def
  some: string;
  other: boolean;
  configs: number[];
}

// config.ts

import {IFlags, IConfig} from './interfaces/config.ts';

const argv = anotherWayToMeow<IFlags>( // similar to current meow() but pass in flag type not def
  `Usage: xxxxxxx`,
  {
    flags: {
      // better to have typecheck here,
      // if not at least can predefine the result flags
      flag1: { alias: 'a', type: 'string' },
      flag2: { alias: 'b' }, // error because missing type: 'boolean'
      // error because missing flag3
    },
  },
)

const some = 'xxxx';
const other = process.env.MY_ENV === 'other';
const configs = [1,2,3];

const config: IConfig = { argv, some, other, configs };

export default config;

[NiGhTTraX]

@whitetrefoil you don’t need to pass a generic type to meow if you can define your expected result type:

type Flags = {
  foo: number;
}

const cli: { flags: Flags } = meow({
  flags: {
    foo: { type: 'number' }
  }
});

You would get a type error if you tried to use type: 'string' instead because the result wouldn’t be assignable to your type.

[voxpelli]

The solution suggested by @NiGhTTraX sounds like the proper one to me.

It’s even the one used in meow’s type tests:

https://github.com/sindresorhus/meow/blob/629af48c24a2f19636512b2f532cfcd9419f9be1/index.test-d.ts#L8-L16