How to trigger Select.Changed when reset the value of select field?

[Tim-Cao]

with VerticalScroll(id="nav-5"):
    DESCRIPTION_TYPE = [
        ("Steps to reproduce", "STR"),
        ("Test Cases", "TC"),
    ]

    yield Label("Enter the Jira ticket number: ")
    yield Input(id="jira-ticket-number-5")
    yield Label("Select the description type: ")
    yield Select(DESCRIPTION_TYPE, id="description-type")
    yield Label(
        "Enter the steps to reproduce: ",
        classes="unselected",
        id="steps-to-reproduce-label",
    )
    yield TextArea(STR, classes="unselected", id="steps-to-reproduce")
    yield Static()
    yield Button("Submit", variant="primary", id="button-5")


def write_description(self) -> None:
    ticket_number = self.query_one("#jira-ticket-number-5").value
    type = self.query_one("#description-type").value
    steps_to_reproduce = self.query_one("#steps-to-reproduce").text

    self.query_one("#button-5").disabled = True
    self.query_one(RichLog).clear()
    self.query_one(RichLog).begin_capture_print()

    write_description.main(ticket_number, type, steps_to_reproduce)

    self.query_one("#button-5").disabled = False
    self.query_one("#jira-ticket-number-5").value = ""
    self.query_one("#description-type").value = ""


def on_select_changed(self, event: Select.Changed) -> None:
    self.query_one("#steps-to-reproduce").set_class(event.value == "STR", "visible")
    self.query_one("#steps-to-reproduce-label").set_class(
        event.value == "STR", "visible"
    )

I would like to reset the classes of #steps-to-reproduce and #steps-to-reproduce-label when select #description-type is reset.

[davep]

It's not every clear from your question what you're actually asking for help with; the subject of the question doesn't seem to quite match the thing that's asked in the body and the code that's posted isn't really that helpful. Could I encourage you to reword your question, making it as clear as possible what you're looking for help with, and if code will help try and make it a MRE.

[davep]

So, is the question here: "should assignment to Select.value cause a Select.Changed event to be posted"? If so, then no, it's my understanding that Select, and a number of other widgets that have some sort of message that indicates a state-change, only post those messages when the user makes the change. Changes made by code don't and it's expected that the developer will know they're making the change and act accordingly.

So, for example, I think I'd have a method for clearing the values, and then when I want to clear those values in code I'd call that method; and in the handler for Select.Changed I'd see if the value is None and also call that clearing method.

[TomJGooding]

@davep Hm, that wasn't my understanding of messages! For example see this test where assigning the value will increment the changed hits.

[davep]

@TomJGooding You'd expect this to add things to the log with no input from you, in that case, right?

from itertools import cycle

from textual import on
from textual.app import App, ComposeResult
from textual.widgets import Log, Select

class SelectMessagesApp(App[None]):

    def compose(self) -> ComposeResult:
        yield Select[int](
            (("One", 0), ("Two", 1))
        )
        yield Log()

    def on_mount(self) -> None:
        self.selections = cycle((0, 1, None))
        self.set_interval(0.25, self.change_value)

    @on(Select.Changed)
    def log_select(self, event: Select.Changed) -> None:
        self.query_one(Log).write_line(f"{event!r} -> {event.value!r}")

    def change_value(self) -> None:
        self.query_one(Select).value = next(self.selections)

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

[Tim-Cao]

The correct way is to remove_class? @davep

        self.query_one("#steps-to-reproduce").remove_class("visible")

[davep]

You can confirm this in the Textual docs.

[TomJGooding]

@davep I would expect Select.Changed to behave like this message in other widgets, so actually @Tim-Cao I owe you an apology.

Here's just a few examples below. I understand if the Select message is different by design, but if that's the case perhaps this deserves a note in the docs.

Input.Changed

from itertools import cycle

from textual import on
from textual.app import App, ComposeResult
from textual.widgets import Input, Log


class MessagesApp(App[None]):
    def compose(self) -> ComposeResult:
        yield Input()
        yield Log()

    def on_mount(self) -> None:
        self.text = cycle(("foo", "bar", "baz"))
        self.set_interval(0.25, self.change_value)

    @on(Input.Changed)
    def log_select(self, event: Input.Changed) -> None:
        self.query_one(Log).write_line(f"{event!r} -> {event.value!r}")

    def change_value(self) -> None:
        self.query_one(Input).value = next(self.text)


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

Switch.Changed

from textual import on
from textual.app import App, ComposeResult
from textual.widgets import Log, Switch


class MessagesApp(App[None]):
    def compose(self) -> ComposeResult:
        yield Switch()
        yield Log()

    def on_mount(self) -> None:
        self.set_interval(0.25, self.change_value)

    @on(Switch.Changed)
    def log_select(self, event: Switch.Changed) -> None:
        self.query_one(Log).write_line(f"{event!r} -> {event.value!r}")

    def change_value(self) -> None:
        switch = self.query_one(Switch)
        switch.value = not switch.value


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

Checkbox.Changed

from textual import on
from textual.app import App, ComposeResult
from textual.widgets import Checkbox, Log


class MessagesApp(App[None]):
    def compose(self) -> ComposeResult:
        yield Checkbox("Foo")
        yield Log()

    def on_mount(self) -> None:
        self.set_interval(0.25, self.change_value)

    @on(Checkbox.Changed)
    def log_select(self, event: Checkbox.Changed) -> None:
        self.query_one(Log).write_line(f"{event!r} -> {event.value!r}")

    def change_value(self) -> None:
        checkbox = self.query_one(Checkbox)
        checkbox.value = not checkbox.value


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

[davep]

@TomJGooding Based on previous conversations I've been involved in, I think the design choice for Textual is that it's those widgets that are behaving "incorrectly" (for what it's worth my own personal taste is they're doing it correctly; but I don't get final say on that 😉).

I think you raise a good point and it's issue-worthy that one approach or another is settled on and applied across all widgets with such behaviour.

[TomJGooding]

(for what it's worth my own personal taste is they're doing it correctly; but I don't get final say on that 😉).

Also for what it's worth, I agree!

I think you raise a good point and it's issue-worthy that one approach or another is settled on and applied across all widgets with such behaviour.

Should I create a new issue? I'm just checking we aren't doubling up and perhaps it would better coming from you?