Removing a widget initialized w/ argument results in "compose() returned an invalid response; compose() missing 1 required positional argument"

[randerzander]

I am probably misunderstanding something basic from the stopwatch tutorial, but in trying to create my own "dynamic widgets" example app, I ran into what seems like buggy behavior for calling remove() on widgets that have been initialized w/ an argument.

Maybe I should be passing arguments to a class's compose method in some other way?

from textual.app import App, ComposeResult
from textual.containers import Container
from textual.widgets import Static


class Thing(Static):
  def compose(self, text) -> ComposeResult:
    yield Static(text)

class ThingApp(App):
  BINDINGS = [
    ("d", "remove_thing", "Remove Thing")
  ]

  def compose(self) -> ComposeResult:
    yield Container(Thing("thing_1"), id="things")

  def action_remove_thing(self) -> None:
    things = self.query("Thing")
    if len(things) > 0:
      things.last().remove()

if __name__ == "__main__":
  app = ThingApp()
  app.run()

Result:

Traceback (most recent call last):
  File "/home/dev/projects/football/test.py", line 40, in <module>
    app.run()
  File "/home/dev/miniconda3/lib/python3.9/site-packages/textual/app.py", line 866, in run
    event_loop.run_until_complete(run_app())
  File "/home/dev/miniconda3/lib/python3.9/asyncio/base_events.py", line 647, in run_until_complete
    return future.result()
  File "/home/dev/miniconda3/lib/python3.9/site-packages/textual/app.py", line 854, in run_app
    await self.run_async(
  File "/home/dev/miniconda3/lib/python3.9/site-packages/textual/app.py", line 829, in run_async
    await app._shutdown()
  File "/home/dev/miniconda3/lib/python3.9/site-packages/textual/app.py", line 1570, in _shutdown
    await self._close_all()
  File "/home/dev/miniconda3/lib/python3.9/site-packages/textual/app.py", line 1550, in _close_all
    await self._prune_node(screen)
  File "/home/dev/miniconda3/lib/python3.9/site-packages/textual/app.py", line 1880, in _prune_node
    await asyncio.gather(*close_messages)
  File "/home/dev/miniconda3/lib/python3.9/site-packages/textual/message_pump.py", line 291, in _close_messages
    await self._task
  File "/home/dev/miniconda3/lib/python3.9/site-packages/textual/message_pump.py", line 301, in _process_messages
    await self._pre_process()
  File "/home/dev/miniconda3/lib/python3.9/site-packages/textual/message_pump.py", line 317, in _pre_process
    await self._dispatch_message(events.Compose(sender=self))
  File "/home/dev/miniconda3/lib/python3.9/site-packages/textual/message_pump.py", line 393, in _dispatch_message
    await self.on_event(message)
  File "/home/dev/miniconda3/lib/python3.9/site-packages/textual/message_pump.py", line 421, in on_event
    await self._on_message(event)
  File "/home/dev/miniconda3/lib/python3.9/site-packages/textual/message_pump.py", line 442, in _on_message
    await invoke(method, message)
  File "/home/dev/miniconda3/lib/python3.9/site-packages/textual/_callback.py", line 28, in invoke
    result = await result
  File "/home/dev/miniconda3/lib/python3.9/site-packages/textual/widget.py", line 2043, in _on_compose
    raise TypeError(
TypeError: Thing() compose() returned an invalid response; compose() missing 1 required positional argument: 'text'

[davep]

Maybe I should be passing arguments to a class's compose method in some other way?

Glancing at your code, I think the main issue you have here is that you're passing extra arguments to compose at all. From what I can tell you're wanting to create your own widget type that you can pass parameters to. As with any Python class you handle construction-based parameters via __init__. So, to take your example code, it would be more like this:

from textual.app import App, ComposeResult
from textual.containers import Container
from textual.widgets import Static


class Thing(Static):

    def __init__( self, text ) -> None:
        self._text = text
        super().__init__()

    def compose(self) -> ComposeResult:
        yield Static(self._text)

class ThingApp(App):

    BINDINGS = [
        ("d", "remove_thing", "Remove Thing")
    ]

    def compose(self) -> ComposeResult:
        yield Container(Thing("thing_1"), id="things")

    def action_remove_thing(self) -> None:
        things = self.query("Thing")
        if len(things) > 0:
            things.last().remove()

if __name__ == "__main__":
    app = ThingApp()
    app.run()

Now, perhaps your code is going to add more complexity to your Thing widget, but it's also worth me pointing out that in this specific example you could reduce your code to this:

from textual.app import App, ComposeResult
from textual.containers import Container
from textual.widgets import Static


class Thing(Static):
    pass

class ThingApp(App):

    BINDINGS = [
        ("d", "remove_thing", "Remove Thing")
    ]

    def compose(self) -> ComposeResult:
        yield Container(Thing("thing_1"), id="things")

    def action_remove_thing(self) -> None:
        things = self.query("Thing")
        if len(things) > 0:
            things.last().remove()

if __name__ == "__main__":
    app = ThingApp()
    app.run()

The change being that your Thing class inherited from a Static and also composed emitting a Static while only really doing what a Static does, so it can be reduced to just this:

class Thing(Static):
    pass

[randerzander]

Now, perhaps your code is going to add more complexity to your Thing widget

Exactly my intent.

Thanks for the quick, helpful response!

[davep]

Most welcome. Glad it helped. 🙂