Firebase function using Typescript nested promise

Question

I am trying to create an API for my Firebase project using functions. The difficult part is that I am using TypeScript and I keep running into typing problems.

This is my sign up route:

app.post('/signup', (req: Request, res: Response) =>{
  const newUser = {
    email: req.body.email,
    password: req.body.password,
    confirmPassword: req.body.confirmPassword,
    handle: req.body.handle
  }
  // TODO: validate data
  db.doc(`/users/${newUser.handle}`).get()
    .then( doc => {
      // Duplicated handle
      if(doc.exists){
        return res.status(400).json({ handle: 'this handle is already taken'});
      }
      // Valid handle
      else {
        return firebase.auth().createUserWithEmailAndPassword(newUser.email, newUser.password); 
      }
    })
    .then( data => {
      return data.user.getIdToken();
    })
    .then( token => {
      return res.status(201).json({ token });
    })
    .catch( err => {
      console.error(err);
      return res.status(500).json({ error: err.code })
    });
})

Errors:

The doc in the first has the following error

Argument of type '(doc: DocumentSnapshot) => Response | Promise' is not assignable to parameter of type '(value: DocumentSnapshot) => UserCredential | PromiseLike'.

This is because I am returning a response status if the handle already exists, to avoid duplicates. From my understanding, this would go to the catch; and the valid handle would return a Promise that the next then would take. However, this is not working

data.user.getIdToken() says that

Property 'user' does not exist on type 'DocumentSnapshot'. Tried delcaring a const for user before using it, but get the same message.

I have other functions for post and get from firestore working, but can't get the authentication ones to work.

Thanks for the help!

Renaud Tarnec · Accepted Answer · 2020-06-16 14:27:10Z

1

I've not tested your code but both your problems most probably come from the fact that you are calling firebase.auth().createUserWithEmailAndPassword() and getIdToken(), which are methods of the JavaScript SDK.

In a Cloud function, you need to use the Admin SDK, and therefore call the createuser() method.

  db.doc(`/users/${newUser.handle}`).get()
    .then( doc => {
      // Duplicated handle
      if(doc.exists){
        return res.status(400).json({ handle: 'this handle is already taken'});
      }
      // Valid handle
      else {
        return admin.auth().createUser(newUser.email, newUser.password); 
      }
    })
    .then(userRecord => {
      //... see below 
    })

Note that we replace firebase by admin, in order to use the Admin SDK. Don't forget to initialize it with const admin = require('firebase-admin'); admin.initializeApp();. See https://firebase.google.com/docs/functions/get-started?authuser=0#import-the-required-modules-and-initialize-an-app.

Then, you are using getIdToken() which is, again, a method from the JavaScript SDK.

You need to adapt your code depending on what was your exact goal by sending back a token to the front-end.

If you want to login the user in the front-end, just send back the info that the user was successfully created, and, in the front-end, call the signInWithEmailAndPassword() method.

Finally note two other important points:

You should use a Transaction to check that the user doc is not existing
The db variable shall be declared as admin.firestore().

edited Jun 16, 2020 at 14:27

answered Jun 16, 2020 at 7:35

Renaud Tarnec

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2 Comments

EPaz Over a year ago

createUser(newUser.email, newUser.password) does not exist on type auth, so that didn't help. I'll try to look more into Admin SDK documentation. Thanks anyways!

Renaud Tarnec Over a year ago

Sorry it was a mistake from my side: I didn't replace all what needed to be replaced... you need to do admin.auth().createUser(newUser.email, newUser.password); instead of firebase.auth().createUserWithEmailAndPassword(newUser.email, newUser.password);. Note that we replace firebase by admin, to use the Admin SDK. Don't forget to initialize with const admin = require('firebase-admin'); admin.initializeApp();

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