Return promise when callback not provided

In the example of custom error handling on the project page, it is

var upload = multer().single('avatar')

app.post('/profile', function (req, res) {
  upload(req, res, function (err) {
    if (err) {
      // An error occurred when uploading 
      return
    }

    // Everything went fine 
  })
})

I’m using ES7 async/await through Babel, and if the upload function returns a Promise when the error callback isn’t provided, it would be possible to have something like

var upload = multer().single('avatar')

app.post('/profile', wrap(async function (req, res) {
  try {
    await upload(req, res);
    // Everything went fine
    console.log(req.file);
  } catch(err) {
    // An error occurred when uploading 
    return
  }
}));

Or at least make it possible to use along with packages like https://www.npmjs.com/package/thenify or https://www.npmjs.com/package/thenify-all. I tried but couldn’t get it to work.

  var uploadsingle = require('thenify')(upload.single.bind(upload));
  await uploadsingle('file');  // It hangs at this statement

[xpepermint]

Can we reopen this please? The latest express package already supports Promises.

[LinusU]

You’re almost there! This should work:

const pify = require('pify')
const multer = require('multer')

const upload = pify(multer().single('avatar'))

app.post('/profile', wrap(async function (req, res) {
  try {
    await upload(req, res)
    // Everything went fine
    console.log(req.file)
  } catch(err) {
    // An error occurred when uploading 
    return
  }
}))

Is this an acceptable solution?

I think that pify and thenify works the same, whichever should work