Bug in sample: presence-firestore

[dtran320]

Which sample has a bug?

presence-firestore

How to reproduce the issue

1. Install and deploy both the Firebase function and public directory to Firebase Hosting: cd functions && npm install && cd ../ && firebase deploy
2. Visit the public endpoint for the deployed sample app to Firebase Hosting, e.g. example-123.web.app
3. History of user presence (since this page was opened) shows on index.html, but index.js errors out due to missing firebase-database include.

Debug output

[Warning] TypeError: firebase.database is not a function. (In 'firebase.database()', 'firebase.database' is undefined) (index.js, line 155)
rtdb_and_local_fs_presence — index.js:70
(anonymous function) — index.js:152
(anonymous function) — promise.js:826
Re — promise.js:1166
Ce — promise.js:1140
(anonymous function) — promise.js:1111
fe — run.js:124
promiseReactionJob

[Warning] Please enable Anonymous Authentication in your Firebase project! (index.js, line 156)

Expected behavior

The following code in index.js results in User <Anonymous user id> is online being appended to the #history div in index.html, a status collection gets created in firestorm with a document for <Anonymous user id> and status/<Anonymous user id> gets added to Realtime Database.

firebase.firestore().collection('status')
        .where('state', '==', 'online')
        .onSnapshot(function(snapshot) {
            snapshot.docChanges().forEach(function(change) {
                if (change.type === 'added') {
                    var msg = 'User ' + change.doc.id + ' is online.';
                    console.log(msg);
                    // [START_EXCLUDE]
                    history.innerHTML += msg + '<br />';
                    // [END_EXCLUDE]
                }
                if (change.type === 'removed') {
                    var msg = 'User ' + change.doc.id + ' is offline.';
                    console.log(msg);
                    // [START_EXCLUDE]
                    history.innerHTML += msg + '<br />'
                    // [END_EXCLUDE]
                }
            });
        });

Actual behavior

The page errors out with the above javascript error due to the missing firebase.database function. Nothing gets written to Firestore or Realtime Database from the client as a result of running this sample.