Reading Google Sheets from Firebase cloud functions using javascript promises

Question

For hours I've been struggling with a problem involving Firebase Cloud Functions & Google Sheets API. I'm simply trying to read some cells in my spreadsheet upon a POST request to my Cloud Function.

The following code, where I read from the spreadsheet using a function readCells works just fine:

const {google} = require('googleapis');
const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
var db = admin.firestore();

// magic function (?)
function readCells(auth, ssheetId) {
    const sheets = google.sheets({version: 'v4', auth});
    return new Promise((resolve, reject) => {
        sheets.spreadsheets.values.get({spreadsheetId:ssheetId,
                                        range:'MySheet!A1:A2'},
                                        (err, result) => {
            if (err) {
                reject(err);
            }
            resolve(result);
        });
    });
}

exports.test = functions.https.onRequest((request, response) => {
    // read auth token & spreadsheet ID from Cloud Firestore        
    let tokenPromise = db.doc('config/token').get();
    let spreadsheetPromise = db.doc('config/spreadsheet').get();

    // read from spreadsheet
    return Promise.all([tokenPromise, spreadsheetPromise]).then(results => {
        const token = results[0].data();
        const ssheetId = results[1].data().id;
        const oAuth2Client = new google.auth.OAuth2(token.client_id, token.client_secret, "");
        oAuth2Client.setCredentials(token);
        return readCells(oAuth2Client, ssheetId);
    })
    .then(result => {
        console.log(result.data.values);
        return response.status(200).end();
    })
    .catch(err => {
        console.error(err);
        return response.status(500).end();
    });
});

Then I get rid of readCells and do everything in the HTTPS cloud function test:

exports.test = functions.https.onRequest((request, response) => {
    // read auth token & spreadsheet ID from Cloud Firestore
    let tokenPromise = db.doc('config/token').get();
    let spreadsheetPromise = db.doc('config/spreadsheet').get();

    // read from spreadsheet
    return Promise.all([tokenPromise, spreadsheetPromise]).then(results => {
        const token = results[0].data();
        const ssheetId = results[1].data().id;
        const oAuth2Client = new google.auth.OAuth2(token.client_id, token.client_secret, "");
        oAuth2Client.setCredentials(token);
        const sheets = google.sheets({version: 'v4', oAuth2Client});
        return new Promise((resolve, reject) => {
            sheets.spreadsheets.values.get({spreadsheetId:ssheetId,
                                            range:'MySheet!A1:A2'},
                                            (err, result) => {
                if (err) {
                    reject(err);
                }
                resolve(result);
            });
        });
    })
    .then(result => {
        console.log(result.data.values);
        return response.status(200).end();
    })
    .catch(err => {
        console.error(err);
        return response.status(500).end();
    });
});

But I get the following error:

error: { Error: The request is missing a valid API key.
    at createError (/<path_to_functions>/node_modules/axios/lib/core/createError.js:16:15)
    at settle (/<path_to_functions>/node_modules/axios/lib/core/settle.js:18:12)
    at IncomingMessage.handleStreamEnd (/<path_to_functions>/node_modules/axios/lib/adapters/http.js:201:11)
    at emitNone (events.js:111:20)
    at IncomingMessage.emit (events.js:208:7)
    at endReadableNT (_stream_readable.js:1064:12)
    at _combinedTickCallback (internal/process/next_tick.js:138:11)
    at process._tickCallback (internal/process/next_tick.js:180:9)
    ...
    more stuff
    ...

And also:

error: (node:3308) UnhandledPromiseRejectionWarning: 
Unhandled promise rejection. This error originated either by throwing
inside of an async function without a catch block,
or by rejecting a promise which was not handled with .catch(). (rejection id: 2)
(node:3308) [DEP0018] DeprecationWarning: Unhandled promise rejections
are deprecated. In the future, promise rejections that are not handled
will terminate the Node.js process with a non-zero exit code.

I don't understand this behaviour at all. I do the same thing only without using a function. I'm not very experienced in Javascript or Node.js; any help would be appreciated.

Answer 1

I managed to solve the problem by replacing the line

const sheets = google.sheets({version: 'v4', oAuth2Client});

with

const sheets = google.sheets('v4');

and passing the auth client directly to sheets.spreadsheets.values.get function.

So it became like this:

exports.test = functions.https.onRequest((request, response) => {
    let tokenPromise = db.doc('config/token').get();
    let spreadsheetPromise = db.doc('config/spreadsheet').get();
    return Promise.all([tokenPromise, spreadsheetPromise]).then(results => {
        const token = results[0].data();
        const ssheetId = results[1].data().id;
        const oAuth2Client = new google.auth.OAuth2(token.client_id, token.client_secret);
        oAuth2Client.setCredentials(token);
        const sheets = google.sheets('v4');
        return new Promise((resolve, reject) => {
            sheets.spreadsheets.values.get({spreadsheetId: ssheetId,
                                            auth: oAuth2Client,
                                            range: "MySheet!A1:A2"}, (err, result) => {
                if (err) {
                    reject(err);
                }
                resolve(result);
            });
        })
    })
    .then(result => {
        console.log(result.data.values[0][0]);
        return response.status(200).end();
    })
    .catch(err => {
        console.error(err);
        return response.status(500).end();
    });
});