panel.io.hold not working in threaded app

[TheoMathurin]

Software Version Info

panel 1.5.5
bokeh 3.6.2

When automatic threading is enabled, using hold does not work and an error appears in the logs.

In foo.py:

import panel as pn
from panel.io import hold

@hold()
def increment(e):
    for obj in column_1:
        obj.object = str(e.new)

column_1 = pn.FlexBox(*['0']*100)
button = pn.widgets.Button(name='Increment', on_click=increment)

pn.Column(column_1, button).servable()

and

panel serve foo.py --num-threads 4

Stack traceback and/or browser JavaScript console output

ERROR: panel.io.document - Using the unlocked decorator when running inside a thread is not safe! Ensure you check that pn.state._current_thread matches the current thread id.

[jp-gr]

I came across a similar issue just this morning. It looks like you can use param.parameterized.batch_call_watchers(param) instead, here is an example:

import panel as pn
import param

pn.extension()

class AppParameters(param.Parameterized):
    value_1 = param.String()
    value_2 = param.String()

app_params = AppParameters()

text_box_1 = pn.widgets.StaticText.from_param(app_params.param.value_1)
text_box_2 = pn.widgets.StaticText.from_param(app_params.param.value_2)

@pn.depends(app_params.param.value_1, app_params.param.value_2)
def logging_function(value, *kwargs):
    print(f"{value}")
    return f"Logged value 1: {value}"

def increment(e):
    with param.parameterized.batch_call_watchers(app_params):
        new_value = str(e.new)
        app_params.value_1 = new_value
        app_params.value_2 = new_value

button = pn.widgets.Button(name='Increment', on_click=increment)

layout = pn.Column(
    pn.pane.Markdown("# Batched Updates Example"),
    text_box_1,
    text_box_2,
    button,
    logging_function,
)

layout.servable()

Then it seems logging_function only gets triggered once per update, if you remove

with param.parameterized.batch_call_watchers(app_params):

then you'll see each log line twice

[TheoMathurin]

Closed through #8113

[TheoMathurin]

My mistake, it's actually still there.