Error in firebase_functions/private/util.py processing event time attribute

[ekalosak]

After updating firebase-tools, using the functions emulator, any time an @firestore_fn-decorated function is executed, I get this error:

...
>    File "/.../venv/lib/python3.11/site-packages/firebase_functions/firestore_fn.py", line 115, in _firestore_endpoint_handler
>      is_nanoseconds = _util.is_precision_timestamp(time)
>                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>    File "/.../venv/lib/python3.11/site-packages/firebase_functions/private/util.py", line 333, in is_precision_timestamp
>      _, s_fraction = time.split(".")
>      ^^^^^^^^^^^^^
>  ValueError: not enough values to unpack (expected 2, got 1)

The relevant code includes this block from firebase_fn.py and this block from private/util.py.

After upgrading to the latest firebase tools npm install -g firebase-tools to v12.5.4, the CloudEvent event's time attribute has this iso format: 2023-09-16T13:32:06Z extracted by adding a print() call to the firebase_functions' site-package source.

So, that unprotected time.split('.') call isn't accounting for the ostensible change to the time attribute's format.

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I'm using Python 3.11.4 on macOS 12.6 with firebase-functions v0.1.1 (latest).