dioxus/packages/core/tests/cycle.rs

use dioxus::core::{ElementId, Mutation::*};
use dioxus::prelude::*;

/// As we clean up old templates, the ID for the node should cycle
#[test]
fn cycling_elements() {
    let mut dom = VirtualDom::new(|cx| {
        cx.render(match cx.generation() % 2 {
            0 => rsx! { div { "wasd" } },
            1 => rsx! { div { "abcd" } },
            _ => unreachable!(),
        })
    });

    let edits = dom.rebuild().santize();
    assert_eq!(
        edits.edits,
        [
            LoadTemplate { name: "template", index: 0, id: ElementId(1,) },
            AppendChildren { m: 1 },
        ]
    );

    dom.mark_dirty_scope(ScopeId(0));
    assert_eq!(
        dom.render_immediate().santize().edits,
        [
            LoadTemplate { name: "template", index: 0, id: ElementId(2,) },
            ReplaceWith { id: ElementId(1,), m: 1 },
        ]
    );

    // notice that the IDs cycle back to ElementId(1), preserving a minimal memory footprint
    dom.mark_dirty_scope(ScopeId(0));
    assert_eq!(
        dom.render_immediate().santize().edits,
        [
            LoadTemplate { name: "template", index: 0, id: ElementId(1,) },
            ReplaceWith { id: ElementId(2,), m: 1 },
        ]
    );

    dom.mark_dirty_scope(ScopeId(0));
    assert_eq!(
        dom.render_immediate().santize().edits,
        [
            LoadTemplate { name: "template", index: 0, id: ElementId(2,) },
            ReplaceWith { id: ElementId(1,), m: 1 },
        ]
    );
}