potential bug in Select - when drop down is open and the current view is closed, a RefCell already borrowed panic occurs

[ronnybremer]

I have an element, which display a Select component. Outside the component is a "close" button, which basically calls a callback from the parent element, removing this element from view.
When I display this element again, a new Select is rendered. As expected, I can do this process many times without any issues.

However, if I click on the close button while the drop down is open and I display the element again, I get:

18:53:43 [web] panicked at /home/dev/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/dioxus-core-0.7.9/src/arena.rs:59:50:
RefCell already borrowed

panic.

What is the best way to troubleshoot this issue? Thank you.

[ealmloff]

That is a bug in dioxus itself. Something causing re-entrant rendering from an event handler? Could you try to create a standalone reproduction?

[nicoburns]

I'm getting a similar issue in Dioxus Native just from opening a dropdown (or anything that uses the focus-based open state). I think it could be due to async handling of focus setting?

[ealmloff]

You can trigger the same bug in blitz without any async with this code:

use std::rc::Rc;

use dioxus::prelude::*;

fn main() {
    dioxus::launch(App);
}

#[component]
fn App() -> Element {
    let mut clicks = use_signal(|| 0usize);
    let mut element = use_signal(|| None::<Rc<MountedData>>);

    if clicks() > 0 {
        if let Some(data) = element() {
            _ = data.set_focus(true);
        }
    }

    rsx! {
        div {
            style: "padding: 80px 220px; font-family: system-ui, sans-serif;",
            FocusButton {
                on_mounted: move |data| element.set(Some(data)),
                on_click: move || clicks += 1,
            }
            p { "clicks: {clicks}" }
        }
    }
}

#[component]
fn FocusButton(on_mounted: EventHandler<Rc<MountedData>>, on_click: EventHandler<()>) -> Element {
    rsx! {
        button {
            id: "focus-trigger",
            r#type: "button",
            style: "min-width: 280px; min-height: 80px; font-size: 32px;",
            onmounted: move |event| {
                on_mounted.call(event.data());
            },
            onclick: move |_| {
                on_click.call(());
            },
            "Focus me"
        }
    }
}

I think this is caused by blitz both borrowing the refcell while running user code and requiring no borrows to exist for set_focus.

[nicoburns]

I think this is caused by blitz both borrowing the refcell while running user code and requiring no borrows to exist for set_focus.

Something like that, but I don't quite fully understand what's going on here. Notably the Browser UI is able to call set_focus without triggering a panic, so it works sometimes.