doc: incorrect readline.question promisify example

[accetone]

📗 API Reference Docs Problem

• Version: 15.13.0

• Platform: Windows 10 x64

• Subsystem: readline

Location

Section of the site where the content exists

Affected URL(s):

• https://nodejs.org/api/readline.html#readline_rl_question_query_options_callback

Description

Concise explanation of the problem

Here is a suggested code sample from docs that should allow to use question method with Promise-based API:

const readline = require('readline');
const util = require('util');

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
});

const question = util.promisify(rl.question).bind(rl);

async function questionExample() {
  try {
    const answer = await question('What is you favorite food? ');
    console.log(`Oh, so your favorite food is ${answer}`);
  } catch (err) {
    console.error('Question rejected', err);
  }
}

questionExample();

The problem with code above is that it will go into catch section on user input. Cause of this is that question method callback accept user answer as first parameter which conflict with node-style callback convention used by util.promisify.

So readline.question can't be used alongside with util.promisify. I see two possible solutions: a) remove this section from docs or b) provide code snippet that shows how to correctly wrap this method with Promise. If you interested in correct code snippet I can work on draft.

---

• I would like to work on this issue and
  submit a pull request.

[Ayase-252]

From the utils docs

If there is an original[util.promisify.custom] property present, promisify will return its value, see Custom promisified functions.

In the case, readline.question did implement promisify.custom property here,

node/lib/readline.js

Line 418 in 1bead01

Interface.prototype.question[promisify.custom] = function(query, options) {

therefore, the custom will be used here. IMO, the example in question is valid.