DataSnapshot.val() throws error for nested child when parent doesn't exist

[bezysoftware]

Related issues

#1426

This is very similar to the linked issue, the difference is when accessing a nested property on an object which is already null. E.g. item is inserted (before is null) and accessing a nested property on it via child(...).val() will throw.

Here's a PR which fixed the previous issue: https://github.com/firebase/firebase-functions/pull/1432/files#diff-624712cd6925b4446aeb1f79d621685365ed0cc876000e58e1bf729ff806f34fR123

It seems clear from the code there needs to be a check if source is null when accessing it for the first time

[REQUIRED] Version info

node: 18
firebase-functions: 6.2.3
firebase-tools: 13.32.0
firebase-admin: 13.1.0

[REQUIRED] Test case

import * as functions from 'firebase-functions/v1';

export let test = functions
    .database
    .ref('/test/{id}')
    .onWrite((event, context) => console.log(event.before.child('anything').val()));

[REQUIRED] Steps to reproduce

Insert any new value to realtime database at /test/1/anything.

[REQUIRED] Expected behavior

Call to before.child(...).val() should return null

[REQUIRED] Actual behavior

TypeError: Cannot read properties of null (reading 'anything')

Were you able to successfully deploy your functions?

Yes, but errors are thrown during runtime.

[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.

[CorieW]

Hi @bezysoftware,

Thanks for reporting this issue! We’ve received it and are reviewing it. We’ll provide updates as soon as possible.