Terminal broken. Raises lots of exceptions in browser console.

[MarcSkovMadsen]

I'm on the current main branch of Panel trying to help Ignozalezsa in https://discourse.holoviz.org/t/terminal-how-to-finish-one-terminal-subprocess-run-before-starting-another/3004/2?u=marc.

I'm trying to show how he can subprocess.run multiple tasks one after the other.

I would expect the below code to work. But as you can see in the video

• it raises lots of errors in the browser console
• it writes the same text multiple times to the Terminal
• the text from the .write command sometimes arrives before the text from subprocess.run

https://github.com/holoviz/panel/assets/42288570/5be9ed2b-cdfe-4c87-9548-4e76bceaba56

import panel as pn
import param
from time import sleep

class Runner(pn.viewable.Viewer):
    value = param.List(constant=True)

    _terminal = param.ClassSelector(class_=pn.widgets.Terminal, constant=True)

    def __init__(self, **params):
        if not "value" in params:
            params["value"]=[]
        params["_terminal"]=pn.widgets.Terminal(sizing_mode="stretch_width", height=500)

        super().__init__(**params)

        self._terminal.write("Hi. I'm the Panel terminal ❤️ 🐍 😊\n\n")

    @pn.depends("value", "_terminal.subprocess.running", watch=True)
    def _run_next_task(self):
        if not self.value:
            print("no task to run")
            return
        if self._terminal.subprocess.running:
            print("already running")
            return

        task = self.value.pop(0)
        self._terminal.write(f"\nRUNNING: {' '.join(task)}\n")
        self._terminal.subprocess.run(*task)
        self.param.trigger("value")
        print("left", self.value)

    def run(self, *tasks):
        with param.edit_constant(self):
            self.value = [*self.value] + [*tasks]

    def __panel__(self):
        return self._terminal

runner = Runner()

def _add_tasks(_):
    runner.run(
        ["ls"], ["echo", "sleeping"], ["sleep", "2"], ["echo", "finished sleeping!"]
    )

add_tasks = pn.widgets.Button(name="Add Tasks", on_click=_add_tasks)

pn.Column(add_tasks, runner, runner.param.value).servable()

[hoxbro]

Somewhat related is the problem raised here, where the sidebar is not loaded when the terminal is in an accordion.

import panel as pn

pn.extension("terminal")
terminal_accordion = pn.Accordion(("Terminal", pn.widgets.Terminal()))
pn.template.FastListTemplate(main=[terminal_accordion], sidebar=["test"]).servable()

[philippjfr]

Looked at this, the problem here is that the Terminal.subprocess.run method forks the process including the entire server, which means both processes will then send events via the websocket, messing up the protocol. There's no straightforward fix as far as I can see.