Change emit to post to self.

[rodrigogiraoserrao]

The point of this PR is that it makes it simpler to subclass widgets because you can capture messages that would be sent by the parent and repurpose them.

E.g., in the app below, the subclass of Input no longer emits Input.Submitted events, but rather MyInput.MyMessage events.

Code

from textual.app import App, ComposeResult
from textual.message import Message
from textual.widgets import Input, TextLog


class MyInput(Input):
    class MyMessage(Message):
        pass

    def on_input_submitted(self, event: Input.Submitted):
        event.stop()
        self.emit_no_wait(self.MyMessage(self))


class MyApp(App[None]):
    def compose(self) -> ComposeResult:
        yield MyInput()
        yield TextLog()

    def on_input_submitted(self) -> None:
        self.query_one(TextLog).write("input")

    def on_my_input_my_message(self) -> None:
        self.query_one(TextLog).write("mymessage")


app = MyApp()


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

[willmcgugan]

It occurs to me that emit and emit_no_wait are essentially the same as post_message and post_message_no_wait. Which is a strange state of affairs.

I'm wondering if there is a legitimate need for something which posts to a parent, or we just drop the concept altogether in favor of post_message.

[rodrigogiraoserrao]

I'm wondering if there is a legitimate need for something which posts to a parent, or we just drop the concept altogether in favor of post_message.

In my mind, I thought that emit would make a message go up the DOM and that post would send it to a specific widget without bubbling, but now it seems that it is the message itself that either bubbles or not, and that has nothing to do with the method that is used?

[rodrigogiraoserrao]

I also think it makes sense to have a shortcut for a widget to post a message to itself, but perhaps it'd be better named post_to_self instead of emit...

[willmcgugan]

But self.post_message already does post to self.

[rodrigogiraoserrao]

But self.post_message already does post to self.

Yeah, you are right 🤦
In that case, to me, it makes sense to get rid of emit altogether (or of post_message if we prefer the name emit).
Let me know and I'll pull the trigger.

[willmcgugan]

Give it a go.

I feel sad to get rid of emit for some reason. But one method is simpler than 2.

[rodrigogiraoserrao]

Give it a go.

I feel sad to get rid of emit for some reason. But one method is simpler than 2.

Done in bd719e0.

[willmcgugan]

Just one tiny error. Have you searched the entire code to make sure there aren't any emits hiding in docs or examples?

[rodrigogiraoserrao]

Have you searched the entire code to make sure there aren't any emits hiding in docs or examples?

Yes, I've searched the codebase and the documentation (and the examples therein).