Listeners functions do not catch their trigger if the widget is not fully loaded

[ManonMarchand]

What happens

Sometimes, the widget has not finished loading when the user attempts to call one of the listeners functions (add_table, target...)
This can be trigered in two ways:

• users call the listeners in the same cells than the widget
• use of automatic executions of cells (like in testing or regeneration tools)

Possible ideas for fixes

• Implement an await on python side or async on javascript side?
• Rework the way we handle listenners

[ManonMarchand]

Refer to this doc for the choice of the solution : https://ipywidgets.readthedocs.io/en/stable/examples/Widget%20Low%20Level.html

[ManonMarchand]

Update: await on python side is a dead end.

[ManonMarchand]

Update2: doing the flag change in a thread as suggested here https://ipywidgets.readthedocs.io/en/7.6.5/examples/Widget%20Asynchronous.html did not work neither

import threading
thread = threading.Thread(target=exec, args=("self.update_wcs_flag = not self.update_wcs_flag", {'self': self}))
thread.daemon = True
thread.start()