panel: Slow Jupyter lab response following Panel 0.13 installation

ALL software version info

Windows 10 Business, 10.0.19044 Build 19044 Python 3.9.12 Conda 4.12.0 jupyterlab 3.4.2 panel 0.13.0 (and various others; see requirements.txt below)

Description of expected behavior and the observed behavior

Following installation of Panel 0.13.0, Jupyter lab becomes very slow to respond. This can be seen in various operations, e.g. cell evaluation, autocompletion, or interactive widget response. Operation which are normally instantaneous (e.g. evaluating a=5) can take several seconds (2 up to 5) to complete. Note that this is without importing anything, specifically not even Panel.

Trying to narrow down the origin of the problem, it seems that previous versions of Panel do not exhibit this behavior. Specifically, I’ve downgraded to Panel=0.12.6 or 0.12.7, and everything goes back to normal.

Complete, minimal, self-contained example code that reproduces the issue

Creating a new minimal env:

conda create --name Panel_test_0 python=3.9 jupyterlab panel

yields the following slow environment - requirements[Panel_0.13.0].txt

This is fixed by downgrading to Panel=0.12:

conda install panel=0.12

which yields a normal-response environment - requirements[Panel_0.12.6].txt

(checked with 0.12.7, which produces the same results as 0.12.6)

Stack traceback and/or browser JavaScript console output

N/A

Screenshots or screencasts of the bug in action

(I can added if needed)