Error: Could not load the default credentials (Firebase function to firestore)

Question

I am attempting to write an onCall function for Firebase Cloud Functions that performs advanced querying tasks on a firestore database (i.e. checking a text query up against AutoML natural lang to get a category, etc) but I keep running into a problem trying to query the database from the function:

Error getting documents ::  Error: Could not load the default credentials. Browse to https://cloud.google.com/docs/authentication/getting-started for more information.
    at GoogleAuth.getApplicationDefaultAsync (/srv/node_modules/google-auth-library/build/src/auth/googleauth.js:161:19)
    at <anonymous>
    at process._tickDomainCallback (internal/process/next_tick.js:229:7)

Function:

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();
const db = admin.firestore();

exports.query = functions.https.onCall((data, context) => {
    const text = data.text;
    var results = [];
    const promise = db.collection('providers').get()
    promise.then((snapshot) => {
        console.log('marker');
        snapshot.forEach((doc) => {
            results.push({id: doc.id, data: doc.data()});
        });
        console.log('yessir');
        return {results: results};
    }).catch((err) => {
        console.log('Error getting documents :: ', err)
        console.log('nosir');
        return {results: "no results"};
    });
});

Longer output:

Function execution started
Function execution took 8ms, finished with status code: 200
Error getting documents :: (etc, same error)
nosir

Example 2 (no change in running):

Function execution started
Function execution took 1200 ms, finished with status code: 200
marker
yessir

I can't figure out where this problem is coming from or how to resolve it. Any help?

Regards.

Answer 1

I had the same error "Could not load the default credentials".

The error occured after updating my project dependencies with npm update. More precisely firebase-admin and firebase-functions.

Before update:

"dependencies": {
    "@google-cloud/firestore": "^1.3.0",
    "firebase-admin": "~7.0.0",
    "firebase-functions": "^2.2.0"
}

After update:

"dependencies": {
    "@google-cloud/firestore": "^1.3.0",
    "firebase-admin": "^8.6.0",
    "firebase-functions": "^3.3.0"
}

I added the serviceAccountKey.json to my project and changed the imports with the code provided at the service account setting of my firebase project.

From :

var admin = require('firebase-admin')

admin.initializeApp()

To:

var admin = require('firebase-admin');    
var serviceAccount = require('path/to/serviceAccountKey.json');

admin.initializeApp({
  credential: admin.credential.cert(serviceAccount),
  databaseURL: 'https://my-project.firebaseio.com'
});

See @Fernando Rocha's answer below to access the account setting of your firebase project.