Cloud Functions Firestore get key value for increment - node.js

Question

I'm trying to get the updated number for a Member Number from a document using Cloud Functions when an admin creates a user.
What should happen is when an Admin creates a user in their dashboard, the user is added to firebase, then the member number updates, and is applied to newMemNum, then updated in the user document.
My Code:
const memNumInc = admin.firestore.FieldValue.increment(1);
const memCounter = admin.firestore().collection(`mem_num`).doc(`a1lDbrsoXjfKeosEkDtw`);
memCounter.update({number: memNumInc}).then(() =>
memCounter.get()
.then((snap) => {
const id = snap.id;
const data = snap.data()
newMemNum = data['number']
console.log('New Member Number: ' + newMemNum);
return {id, ...data};
})
);
The increment goes ok (i.e. number goes up by 1 which is expected), but the next part of the code doesn't run and doesn't throw an error.
Also, the next part of the code that updates the user document doesn't fire at all, and no errors.
Entire Code:
// Create User Document onCreate
const createProfile = (userRecord) => {
const uid = userRecord.uid;
const docId = userRecord.uid;
const fullName = userRecord.displayName || 'New User';
const memStatus = 'Unfinancial';
const isAdmin = false;
const isNew = true;
const email = userRecord.email;
const photoUrl = userRecord.photoUrl;
const phone = '0444 123 456';
const createdAt = admin.firestore.FieldValue.serverTimestamp();
const memNumInc = admin.firestore.FieldValue.increment(1);
const memCounter = admin.firestore().collection(`mem_num`).doc(`a1lDbrsoXjfKeosEkDtw`);
memCounter.update({number: memNumInc}).then(() =>
memCounter.get()
.then((snap) => {
const id = snap.id;
const data = snap.data()
newMemNum = data['number']
console.log('New Member Number: ' + newMemNum);
return {id, ...data};
})
);
return afs
.collection(`users`)
.doc(docId)
.set({
uid: uid,
docId: docId,
fullName: fullName,
joined: createdAt,
memNum: newMemNum,
memStatus: memStatus,
isAdmin: isAdmin,
isNew: isNew,
email: email,
photoUrl: photoUrl,
phone: phone,
addedOn: createdAt,
updatedOn: createdAt
})
.then(() => console.log('User Creaeted Successfuly: ' + uid))
.catch((e) => console.log('User Creation Error: ' + e.message));
}
exports.authOnCreate = functions.auth.user().onCreate(createProfile);
If I remove the memCounter code, the rest executes no problem.

Answer 1

You have another return statement that most likely runs before the promise returned by get() is resolved. Try refactoring the code using async-await syntax as shown below:
const createProfile = async (userRecord) => {
// const vars ....
const memNumInc = admin.firestore.FieldValue.increment(1);
const memCounter = admin.firestore().collection(`mem_num`).doc(`a1lDbrsoXjfKeosEkDtw`);
// Update documents
await memCounter.update({
number: memNumInc
})
// Get update document data
const snap = await memCounter.get()
const id = snap.id;
const data = snap.data()
newMemNum = data['number']
console.log('New Member Number: ' + newMemNum);
return afs
.collection(`users`)
.doc(docId)
.set({ ... })
}
However, if multiple users are created simultaneously, there's a chance that they'll get the same newMemNum so a transaction might be useful as well.
Firestore also introduced a new COUNT() function that can be used to get total number of documents in a collection instead of incrementing the count every time.