TypeScript: Infer `prompt()` return type object shape from question objects

[karlhorky]

Hi, first of all, thanks for enquirer 👍 Nice library!

Currently, enquirer has a return type of Promise<object>:

import { prompt } from 'enquirer';

const questions = [
  {
    type: 'input',
    name: 'name',
    message: 'What is your name?',
  },
  {
    type: 'input',
    name: 'username',
    message: 'What is your username?',
  },
];
const result = await prompt(questions);
   // ^? const result: object

Playground

It would be great if prompt() would infer the types from the questions object:

import { prompt } from 'enquirer';

const questions = [
  {
    type: 'input',
    name: 'name',
    message: 'What is your name?',
  },
  {
    type: 'input',
    name: 'username',
    message: 'What is your username?',
  },
];
const result = await prompt(questions);
   // ^? const result: { name: string; username: string; }

Alternatives considered

Pass in generics, this works today, but requires careful synchronization of the type and the questions - easy to make mistakes:

import { prompt } from 'enquirer';

type Result = {
  name: string;
  username: string;
};

const questions = [
  {
    type: 'input',
    name: 'name',
    message: 'What is your name?',
  },
  {
    type: 'input',
    name: 'username',
    message: 'What is your username?',
  },
];
const result = await prompt<Result>(questions);
   // ^? const result: { name: string; username: string; }

[cubxx]

type Question = Exclude<Parameters<typeof prompt>[0], Function | unknown[]>;
type Answers<Qs extends Question[], As = {}> = Qs extends [
  infer L extends Question & { name: string },
  ...infer R extends Question[],
]
  ? Answers<R, As & { [K in L['name']]: L['initial'] }>
  : As;
const typedPrompt = <const T extends Question[]>(questions: T) =>
  prompt<Answers<T>>(questions);

const answers = await typedPrompt([
  {
    name: 'projectName',
    type: 'input',
    message: 'Project name:',
    initial: 'my-project',
    result: (v) => v.trim(),
  },
  {
    name: 'useTypeScript',
    type: 'confirm',
    message: 'Use TypeScript?',
    initial: false,
  },
]);