promisified version of req.logout

[anderskiaer]

Sorry if this has already been discussed (a quick search didn't give any hits).

Starting from 0.6.0, req.logout is an asynchronous function and requires a callback function. This is explained in the documentation https://www.passportjs.org/concepts/authentication/logout/:

app.post('/logout', function(req, res){
  req.logout(function(err) {
    if (err) { return next(err); }
    res.redirect('/');
  });
});

If possible, it would be nice to have a "promisified" version of req.logout available for writing more readable code. Another benefit: starting with express-5 (currently in beta), when functions returning a promise throw an error, express will automatically call next(err) (https://expressjs.com/en/guide/error-handling.html). Writing a passport based logout route could then probably be simplified to something like:

app.post('/logout', async function(req, res){
  await req.logout();
  res.redirect('/');
});

---

On a related note, in the current logout snippet example in the documentation, how is next made available to the callback function in cases of req.logout throwing an error? I would expected something like

-app.post('/logout', function(req, res){
+app.post('/logout', function(req, res, next){
-  req.logout(function(err) {
+  req.logout(err => {
     if (err) { return next(err); }
     res.redirect('/');
   });
 });

Thanks 🙇

[karlbecker]

Beyond that, it sure seems like

req#logout() is now an asynchronous function and requires a callback function as the last argument.

means passport should have a semantic versioning update to 1.0.0, since this change breaks existing calls to logout.

Agreed?

[anderskiaer]

[...] passport should have a semantic versioning update to 1.0.0, since this change breaks existing calls to logout.

Agreed?

As long as passport is on 0.y.z, according to semver alone, the API can change on any release. Bumping major version when introducing breaking changes is a requirement when already at major version > 0.

[msrumon]

+1. It's long due to promisify this. So that we can use it like the following:

try {
  await req.logout();
  return res.redirect('/login');
} catch (error) {
  return next(error);
}

---

By the way, await promisify(req.logout)() didn't work for me for some reasons. Maybe I did something wrong, I'll investigate.

[tilleps]

@msrumon Example on how to promisify was posted on #536 (comment)