Support async functions for pn.bind

[MarcSkovMadsen]

I would like it to be as simple as possible to create performant data apps as possible. This includes sprinkling in async once in a while.

It would make it super easy to use async if pn.bind and pn.depends supported it. But it does not.

When I run the below code I get

c:\repos\private\awesome-panel\.venv\lib\site-packages\param\parameterized.py:2000: RuntimeWarning: coroutine 'train' was never awaited
  watcher.fn(*args, **kwargs)

import panel as pn
import sys
import asyncio


pn.extension(sizing_mode="stretch_width")

terminal = pn.widgets.Terminal(height=400).servable()

sys.stdout=terminal

async def train(e, n=5):
    print("train")
    for n in range(n):
        await asyncio.sleep(1)
        print(n)

button = pn.widgets.Button(name="Train", button_type="primary").servable()

pn.bind(train, e=button, watch=True)

import panel as pn
import sys
import asyncio


pn.extension(sizing_mode="stretch_width")

terminal = pn.widgets.Terminal(height=400).servable()

sys.stdout=terminal

button = pn.widgets.Button(name="Train", button_type="primary").servable()

@pn.depends(button, watch=True)
async def train(e, n=5):
    print("train")
    for n in range(n):
        await asyncio.sleep(1)
        print(n)

My Feature Request is to support async for pn.bind and pn.depends.

[hoxbro]

I think I got this to work. Two changes are needed one in param and another in panel. Both are by checking if the function to watch is an async function and then making the wrapped/cb function an async function too. I will submit PR to get this implemented.

In param:
https://github.com/holoviz/param/blob/fb6f4d92d7ce9006deb269669ebe34cdaa006d4a/param/parameterized.py#L432-L435

In panel:

panel/panel/depends.py

Lines 151 to 172 in 98a63e8

	@depends(**dependencies, watch=watch)
	def wrapped(*wargs, **wkwargs):
	combined_args = []
	for arg in args:
	if hasattr(arg, '_dinfo'):
	arg = arg()
	elif isinstance(arg, param.Parameter):
	arg = getattr(arg.owner, arg.name)
	combined_args.append(arg)
	combined_args += list(wargs)
	combined_kwargs = {}
	for kw, arg in kwargs.items():
	if hasattr(arg, '_dinfo'):
	arg = arg()
	elif isinstance(arg, param.Parameter):
	arg = getattr(arg.owner, arg.name)
	combined_kwargs[kw] = arg
	for kw, arg in wkwargs.items():
	if kw.startswith('__arg') or kw.startswith('__kwarg'):
	continue
	combined_kwargs[kw] = arg
	return function(*combined_args, **combined_kwargs)

[philippjfr]

Yeah, looks like I handled it for non-watched functions but not for watch=True.