Button name not updated when using reactive expression

[MarcSkovMadsen]

panel==1.3.8

I'm working on the Basic tutorials. I'm trying to explain a watch like pattern. I don't yet know if this is possible.

To get some rough, proxy example working I tried the below.

import panel as pn

pn.extension()

submit = pn.widgets.Button(name="Start the wind turbine")

def start_stop_wind_turbine(clicked):
    print(clicked, submit.clicks)
    if bool(submit.clicks%2):
        submit.name="Start the wind turbine"
    else:
        submit.name="Stop the wind turbine"
    return None

rx_start_stop_windturbine = pn.rx(start_stop_wind_turbine)(submit)

# Figure out how to watch

pn.Column(submit, pn.panel(rx_start_stop_windturbine)).servable()

But it did not behave as expected. As you can see it updates one of the submit buttons only when clicked.

not-updating.mp4

I would expect both Buttons to have their name updated when one of the buttons is clicked.

[MarcSkovMadsen]

A additional problem is seen in this example

import asyncio
import concurrent.futures
from time import sleep

import panel as pn

pn.extension()

is_stopped=pn.rx(True)
is_active = pn.rx(False)

def name(stopped):
    if stopped:
        return "Start the wind turbine"
    else:
        return "Stop the wind turbine"

rx_name = pn.rx(name)(is_stopped)

submit = pn.widgets.Button(name=rx_name, disabled=is_active, loading=is_active)

async def start_stop_wind_turbine(clicked):
    if not clicked:
        return
    is_active.rx.value=True
    with submit.param.update(loading=True, disabled=True):
        with concurrent.futures.ThreadPoolExecutor() as executor:
            future = executor.submit(sleep, 5)
            result = await asyncio.wrap_future(future)

        is_stopped.rx.value = not is_stopped.rx.value
    is_active.rx.value=False
    print("done")


b_stop_wind_turbine = pn.rx(start_stop_wind_turbine)(submit)

# Todo: Fix same problems as in Watch section

pn.Column(submit, b_stop_wind_turbine).servable()

Besides the original button not reacting we now have the problem that the rx button never gets enabled again.

not-stopping.mp4

[philippjfr]

I would very much like to discourage what you're doing in the first example.

The most concise way to write that example is this:

import panel as pn

pn.extension()

submit = pn.widgets.Button(name="Start the wind turbine")

submit.name = (submit.param.clicks.rx() % 2).rx.where("Start the wind turbine", "Stop the wind turbine")

submit.servable()

but I can appreciate that's not obvious. And I do appreciate that you might want to watch a expression and that can also be done already:

submit = pn.widgets.Button(name="Start the wind turbine")

def update_button(active):
    submit.name = "Start the wind turbine" if active else "Stop the wind turbine"

(submit.param.clicks.rx() % 2).rx.watch(update_button)

pn.Row(submit)

In your second example, everything works fine if you remove with submit.param.update(loading=True, disabled=True), which is superfluous. That does represent a Param issue though since the context manager should restore the parameter reference.

[philippjfr]

Between your issue holoviz/param#913 and my issue holoviz/param#914 and the fact that .param.watch exists for the callback based use case I think all issues here are covered.