Background Functions onCreate first argument (snap) contains empty object when Firestore document added to collection

[gagamil]

[READ] Step 1: Are you in the right place?

• For issues or feature requests related to the code in this repository
  file a Github issue.
  • If this is a feature request make sure the issue title starts with "FR:".
• For general technical questions, post a question on StackOverflow
  with the firebase tag.
• For general Firebase discussion, use the firebase-talk
  google group.
• For help troubleshooting your application that does not fall under one
  of the above categories, reach out to the personalized
  Firebase support channel.

[REQUIRED] Step 2: Describe your environment

• Operating System version: MacOS Mojave 10.14.4
• Firebase SDK version:
  Python:
  firebase-admin==3.1.0; google-api-core==1.14.3; google-api-python-client==1.7.11; google-cloud-core==1.0.3; google-cloud-firestore==1.5.0
  Node:
  "firebase-admin": "^8.0.0"; "firebase-functions": "^3.1.0"
• Library version: _____
• Firebase Product: Firestore; Functions

[REQUIRED] Step 3: Describe the problem

When using Python Firestore client to add (not set document with id) document to a collection the respective Firestore background functions snap has empty object instead of the data. However the snap.id is correct.

Steps to reproduce:

• Init Python Firestore Client.
• Add document with data to a collection
• Write and deploy a Firestore function (onCreate)
• Check functions logs and see that snap.data() === {}

Relevant Code:

shell: export GOOGLE_APPLICATION_CREDENTIALS='<PATH_TO_JSON_FILE>'

Python:
import firebase_admin
from firebase_admin import credentials
firebase_admin.initialize_app()
from google.cloud import firestore
db = firestore.Client()
db.collection('messages').add({'message':'Hello world'})

Functions index.js:
const functions = require("firebase-functions");

exports.onNewMessage = functions.firestore
.document("messages/{messageId}")
.onCreate((snap, context) => {
console.log("Data: ", snap.data());

Now check Functions logs:

Data: {}

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[hiranya911]

Does the saved document contain data when viewed from the Firebase Console?

[gagamil]

Does the saved document contain data when viewed from the Firebase Console?

Yes.

[gagamil]

Tried the Node API SDK client: works as expected: snap.data() is populated with the document contents.

Equivalent to previously posted Python program text in Node:

var admin = require("firebase-admin");
var serviceAccount = require(<PATH_TO_FILE_WITH_JSON>)
admin.initializeApp({credential: admin.credential.cert(serviceAccount), databaseURL:<DB_URL>})
const dbfs = admin.firestore();
dbfs.collection('messages').add({message:'Hello from Node'})

[samtstern]

This looks the same as #574 which I just closed and filed on the Google Cloud Python SDK. Thanks for the feedback!