节点正确返回错误（例如，验证错误）

Question

I'm refactoring our code into promises.

Two blocks with sample code:

user.service.js

export function updateUserProfileByUsername(req, res) {
userController.getUserByUsername(req.params.username)
    .then((userProfile) => {
        return userController.saveUserProfileByUser(userProfile,
            req.body.email,
            req.body.username,
            req.body.firstname,
            req.body.lastname)
    })
    .then((updated_user) => {
        res.status(200).json(updated_user.profile);
    })
    .catch((err) => {
        res.status(404).send('something went wrong');
    });
}

export function getUserProfileByUsername(req, res) {
userController.getUserProfileByUsername(req.params.username)
    .then((userProfile) => {
        res.status(200).json(userProfile);
    })
    .catch((err) => {
        res.status(404).send('something went wrong');
    })
}

user.controller.js

export function getUserProfileByUsername(username) {
return User.findOne({
        'username': username
    }).exec()
    .then((user) => {
        if (user)
            return user.profile;
        else
            throw new Error("user not found!");
    });
}

export function getUserByUsername(username) {
return User.findOne({
        'username': username
    }).exec()
    .then((user) => {
        if (user)
            return user;
        else
            throw new Error("user not found!");
    });
}

export function saveUserProfileByUser(user, email, username, firstname, lastname) {
  user.email = email;
  user.username = username;
  user.firstname = firstname;
  user.lastname = lastname;
  return user.save(); // returns a promise
}

Our routes enter in user/index.js, go into service.js and the controller handles our database work and errors.

What I am trying to achieve is to send fitting errors to the client. Like: 'the user does not exist' or 'username is too long' when updating a wrong user, etc.

if I try to send the error to the client, i'll just get a empty json as result ({}). If I log the error, i get the full stack trace, including validation errors.

.catch((err) => {
        console.log(err) // shows me full stacktrace of the error
        res.status(404).send(err); //sends {} to the client
    })

How can I implement this with promises? Should i add extra middleware sending correct error messages?

I would really appreciate some hints in the right direction for this one. Thanks in advance!

Answer 1

Because err is an object I assume express is converting to JSON for you. However, when you stringify an error you get '{}';

If you want to return the stacktrace try .send(err.stack).

Alternatively if you only want the message and not the entire stack you can use err.message.

.catch((err) => {
    console.log(err)
    res.status(404).send(err.stack);
})