CancelledError when using yield and TabbedContent.add_pane(TabPane(..., some_child_widget, ...) in a threaded worker

[iscas-zac]

The issue

When I'm working with yielders, the app prints a lot of traceback after I close it.

The sample code is like this, which I run with textual run --dev main.py with main.py containing just a app.run():

class TestApp(App):
    def compose(self) -> ComposeResult:
        yield TabbedContent()
        yield Input()

    async def on_mount(self):
        self.async_caller()

    @work(thread=True, exit_on_error=False)
    async def async_caller(self):
        a = self.call_from_thread(self.yielder)
        next(a)

    def yielder(self):
        tc = self.query_one(TabbedContent)
        # tp = TabPane("1234", id="_1234")
        # tc.add_pane(tp)
        tc.add_pane(TabPane("1234", Static(), id="_1234"))
        yield "the work is done now. close it"

After I Ctrl-C it, it exits and prints

Traceback (most recent call last):
  File "C:\Python310\lib\site-packages\textual\message_pump.py", line 483, in _process_messages   
    if not await self._pre_process():
  File "C:\Python310\lib\site-packages\textual\message_pump.py", line 507, in _pre_process        
    await self._dispatch_message(events.Compose())
  File "C:\Python310\lib\site-packages\textual\message_pump.py", line 614, in _dispatch_message   
    await self.on_event(message)
  File "C:\Python310\lib\site-packages\textual\message_pump.py", line 683, in on_event
    await self._on_message(event)
  File "C:\Python310\lib\site-packages\textual\message_pump.py", line 704, in _on_message
    await invoke(method, message)
  File "C:\Python310\lib\site-packages\textual\_callback.py", line 81, in invoke
    return await _invoke(callback, *params)
  File "C:\Python310\lib\site-packages\textual\_callback.py", line 47, in _invoke
    result = await result
  File "C:\Python310\lib\site-packages\textual\widget.py", line 3384, in _on_compose
    await self.mount(*widgets)
  File "C:\Python310\lib\site-packages\textual\widget.py", line 117, in await_mount
    await wait(aws)
  File "C:\Python310\lib\asyncio\tasks.py", line 384, in wait
    return await _wait(fs, timeout, return_when, loop)
  File "C:\Python310\lib\asyncio\tasks.py", line 491, in _wait
    await waiter
asyncio.exceptions.CancelledError

During handling of the above exception, another exception occurred:

asyncio.exceptions.CancelledError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Python310\lib\site-packages\textual\app.py", line 1441, in run_app
    await self.run_async(
  File "C:\Python310\lib\site-packages\textual\app.py", line 1413, in run_async
    await app._shutdown()
  File "C:\Python310\lib\site-packages\textual\app.py", line 2502, in _shutdown
    await self._close_all()
  File "C:\Python310\lib\site-packages\textual\app.py", line 2482, in _close_all
    await self._prune_node(stack_screen)
  File "C:\Python310\lib\site-packages\textual\app.py", line 3030, in _prune_node
    await asyncio.gather(*close_messages)
asyncio.exceptions.CancelledError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "**********\main.py", line 7, in <module>
    app.run()
  File "C:\Python310\lib\site-packages\textual\app.py", line 1452, in run
    asyncio.run(run_app())
  File "C:\Python310\lib\asyncio\runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "C:\Python310\lib\asyncio\base_events.py", line 646, in run_until_complete
    return future.result()
asyncio.exceptions.CancelledError

Triggering conditions

The issue involves some patterns.

• The add_pane() should sit in a yielder.
• If I remove the worker statement and put the yielder in the async on_mount() function, it won't trigger.
• Also the TabPane must contain a child widget (the child can also be added afterwards instead of as a parameter, both will trigger).

My textual diagnose output

Textual Diagnostics

Versions

Name	Value
Textual	0.45.1
Rich	13.3.5

Python

Name	Value
Version	3.10.7
Implementation	CPython
Compiler	MSC v.1933 64 bit (AMD64)
Executable	C:\Python310\python.exe

Operating System

Name	Value
System	Windows
Release	10
Version	10.0.22635

Terminal

Name	Value
Terminal Application	vscode (1.86.0-insider)
TERM	Not set
COLORTERM	truecolor
FORCE_COLOR	Not set
NO_COLOR	Not set

Rich Console options

Name	Value
size	width=98, height=13
legacy_windows	False
min_width	1
max_width	98
is_terminal	True
encoding	utf-8
max_height	13
justify	None
overflow	None
no_wrap	False
highlight	None
markup	None
height	None

Afterwords

I'm not sure if I use it right. I want the computation-heavy yielder task both to give some feedback when running and to run in a different thread, so I write codes with workers and yield statements. The problem doesn't affect my experience when it runs, so I guess I'll be OK if this isn't fixed.