JavaScript Promise EsLint 部署 Firebase-Cloud-Function 时出现问题

Question

I get the following errors, when I try to deploy the following Firebase Javascript Function via the command "firebase deploy --only functions" from Firebase-Tools CLI in Version 8.6.0.

exports.notifyNewMessage = functions.firestore.document("posts/{postId}").onCreate((docSnapshot, context) => {
    firestore.collection('accounts').get().then(function (querySnapshot) {
        querySnapshot.forEach(function (doc) {
            // doc.data() is never undefined for query doc snapshots
            console.log(doc.id, " => ", doc.data());
            return  doc.data().name;
        });
    });
});

I found this example code on the official firebase documentation: https://firebase.google.com/docs/firestore/query-data/get-data#get_all_documents_in_a_collection

When I try to deploy the code there is running an esLint Check and I get the following errors:

 2:5   error    Expected catch() or return                  promise/catch-or-return
 2:49  warning  Unexpected function expression              prefer-arrow-callback
 2:49  error    Each then() should return a value or throw  promise/always-return
 3:31  warning  Unexpected function expression              prefer-arrow-callback

How I have to fix these errors? Can someone give me an example, how the Promise with Catch have to look like?

My goal is to get the users accounts data logged in the console to do further operations later. But I don't know how to get these user data logged in the console yet.

Answer 1

If your goal is to log to the Cloud Function console the documents of the accounts collection, the following should do the trick:

exports.notifyNewMessage = functions.firestore.document("posts/{postId}").onCreate((docSnapshot, context) => {
    return firestore.collection('accounts').get()   // We return the promise chain, see the video series mentioned below
    .then(querySnapshot => {    //  Unexpected function expression 
        querySnapshot.forEach(doc => {   // Unexpected function expression 
            // doc.data() is never undefined for query doc snapshots
            console.log(doc.id, " => ", doc.data());
        });
        return null;    // Each then() should return a value or throw 
    })
    .catch(error => {
        console.log(error.message);
        return null;
});

Note that you MUST return a Promise or a value in a background triggered Cloud Function. I would suggest you watch the 3 videos about "JavaScript Promises" from the Firebase video series: https://firebase.google.com/docs/functions/video-series/ which explain this key point.

---

Note also that you need to use the Admin SDK in a Cloud Function so firestore should be declared as follows:

// The Cloud Functions for Firebase SDK to create Cloud Functions and setup triggers.
const functions = require('firebase-functions');

// The Firebase Admin SDK to access Cloud Firestore.
const admin = require('firebase-admin');
admin.initializeApp();

const firestore = admin.firestore();


exports.notifyNewMessage = functions.firestore
    .document("posts/{postId}")
    .onCreate((docSnapshot, context) => {...});

Reference: https://firebase.google.com/docs/functions/get-started

Answer 2

Try this

exports.notifyNewMessage = functions.firestore
    .document("posts/{postId}")
    .onCreate((docSnapshot, context) => {
        firestore.collection('accounts')
            .get()
            .then((querySnapshot) => {
                return querySnapshot.forEach((doc) => {
                    console.log(doc.id, " => ", doc.data());
                    return  doc.data().name;
                });
            })
            .catch((err) => err)
    });

Or create an eslintrc file and modify the rules

Find out about configuring Eslint here