Realtime Database After Event Missing values

[JJ11teen]

Hello! 👋

There is a bug in the logic to generate the "after" state of a (realtime) database change. The bug appears to be in the below lines of code, only a shallow copy/merge is performed but a deep one is needed.

firebase-functions-python/src/firebase_functions/db_fn.py

Lines 92 to 94 in 14676e5

	# Merge delta into data to generate an 'after' view of the data.
	if isinstance(before, dict) and isinstance(after, dict):
	after = _util.prune_nones({**before, **after})

As an example of a failure case, I had just changed allocation/change from F to G in the following:

However I have a listener setup on the root object of the screenshot and the event.data object that is generated by that change was:

Change(
    before={'allocation': {'change': 'F', 'role': 'admin', 'third': 3}, 'details': <redacted>},
    after={'allocation': {'change': 'G'}, 'details': <redacted>})

It should be:

Change(
    before={'allocation': {'change': 'F', 'role': 'admin', 'third': 3}, 'details': <redacted>},
    after={'allocation': {'change': 'G', 'role': 'admin', 'third': 3}, 'details': <redacted>})

Let me know if you need any more info.

Thanks!

[exaby73]

Hello @JJ11teen. Unfortunately, I am having some trouble reproducing this issue. Are you able to reproduce this on the Firebase emulator? Could you provide some reproduction code that I may test against?

[JJ11teen]

Hey @exaby73, unfortunately I don't have time to create complete minimal reproducible code for you. Is there any other way I can help you understand the problem I am describing? If you look at the code I have pointed out in db_fn.py it should make sense why the issue is arising without needing to reproduce the problem on your side - The code {**before, **after} is a shallow merge of the before & after dictionaries ("after" at this point is actually the delta). A deep merge is required to accurately construct an "after" state.

For anyone else following along I've worked around this issue in the mean time by (re)querying the current state of the DB to determine the after state.

[JJ11teen]

Thanks for the fix @exaby73! Do you know roughly when the next release is expected?

[exaby73]

Hey @JJ11teen. I couldn't be sure but hopefully soon :)