Use of command palette cancels previously-running non-thread workers

[davep]

Discussed in #3613

^{Originally posted by otherjason October 30, 2023}
I have an app that uses several long-lived workers to asynchronously poll external services for data and update the UI. I found that closing the command palette, either via ESC or by selecting a command, seems to cancel any pending workers. Here's a small example:

import asyncio
from textual import work
from textual.app import App, ComposeResult
from textual.widgets import RichLog

class Test(App):
    CSS = '''
    RichLog {
        height: 100%;
    }
    '''
    def compose(self) -> ComposeResult:
        yield RichLog(id = 'log')

        self.my_worker()

    @work(exclusive = False)
    async def my_worker(self):
        counter = 1

        log = self.query_one('#log')
        while True:
            log.write(f'test {counter}')
            counter += 1
            await asyncio.sleep(1)

if __name__ == "__main__":
    Test().run()

When running the above, it will print a new line to the RichLog every second. If you open the command palette, then the worker stays running. But it seems that after the palette comes up, as soon as I press a key, the worker stops running.

Is this behavior intended, or is this a bug?

[davep]

Hat tip to @otherjason for reporting this.

Bumping straight to the todo list as it's a bit of a show-stopper.

[davep]

As mentioned in the discussion, I would suspect that:

self.workers.cancel_all()

is doing more than I expected it to (I expected self.workers to be all the workers running against the current screen/widget). Don't know for sure, but that's the first thing I'd double-check.

Also, in retrospect, it might make sense to ensure that any worker in the command palette is in an "internal" group of some sort?

[rodrigogiraoserrao]

self.workers is a property that points to self.app.workers, so the fact that self.workers.cancel_all() is stopping all workers definitely looks like it is intended behaviour.

Having self.workers be an alias to self.app.workers looks like a terrible idea to me...

And I guess you're right in that it makes sense to have the command palette workers have an internal group of some sort.

[rodrigogiraoserrao]

You'd probably want to use either self.workers.cancel_node(self), or self.workers.cancel_group with the aforementioned worker group that needs to be created.

[davep]

Having self.workers be an alias to self.app.workers looks like a terrible idea to me...

Yeah, that's a very curious choice. I wonder if we should review that?

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