docs: Fix example of coerce

[regseb]

The first example of .coerce(key, fn) is invalid: an await is used in a non-async function.

var argv = require('yargs/yargs')(process.argv.slice(2))
  .coerce('file', function (arg) {
    return await require('fs').promises.readFile(arg, 'utf8')
  })
  .argv

[shadowspawn]

Making the examples correct is a good thing. The example was updated as part of adding async support to .coerce() in #1872 but was not complete, and I would rather make the example work with async than remove the async.

Would you like to do that?

[regseb]

I modified the example to add an async / await.

[shadowspawn]

I like the direction of getting away from require embedded in the code.

It is much easier to run the example in a module where top-level await is available. How about about making this example esm? e.g.

import { readFile } from 'node:fs/promises';
import yargs from 'yargs';
const argv = await yargs(process.argv.slice(2))
   .coerce('file', async (arg) => readFile(arg, 'utf8'))
   .parseAsync();

[regseb]

In your example, the async is useless because the function has no await (require-await). It would be useless to add an await before the return: .coerce('file', async (arg) => await readFile(arg, 'utf8')) (no-return-await).

I propose to add an intermediate variable (which is useless, but there is no ESLint rule to detect it) to have an excuse to use an await.

import { readFile } from 'node:fs/promises';
import yargs from 'yargs';
const argv = await yargs(process.argv.slice(2))
  .coerce('file', async (arg) => {
    const content = await readFile(arg, 'utf8');
    return content;
  })
  .parseAsync();

[shadowspawn]

Good points. I suggest adding JSON.parse on the contents. Then the await is needed and the async function makes sense.

[regseb]

I added JSON.parse() in the example.

[shadowspawn]

LGTM

[shadowspawn]

Thanks for the PR and conversation @regseb.