dioxus/packages/core/tests/suspense.rs

use dioxus::core::ElementId;
use dioxus::core::{Mutation::*, SuspenseBoundary};
use dioxus::prelude::*;
use dioxus_core::SuspenseContext;
use std::future::IntoFuture;
use std::{rc::Rc, time::Duration};

#[tokio::test]
async fn it_works() {
    let mut dom = VirtualDom::new(app);

    let mutations = dom.rebuild().santize();

    // We should at least get the top-level template in before pausing for the children
    assert_eq!(
        mutations.template_mutations,
        [
            CreateElement { name: "div" },
            CreateStaticText { value: "Waiting for child..." },
            CreateStaticPlaceholder,
            AppendChildren { m: 2 },
            SaveTemplate { name: "template", m: 1 }
        ]
    );

    // And we should load it in and assign the placeholder properly
    assert_eq!(
        mutations.edits,
        [
            LoadTemplate { name: "template", index: 0, id: ElementId(1) },
            // hmmmmmmmmm.... with suspense how do we guarantee that IDs increase linearly?
            // can we even?
            AssignId { path: &[1], id: ElementId(3) },
            AppendChildren { m: 1 },
        ]
    );

    // wait just a moment, not enough time for the boundary to resolve

    dom.wait_for_work().await;
}

fn app(cx: Scope) -> Element {
    cx.render(rsx!(
        div {
            "Waiting for child..."
            suspense_boundary {}
        }
    ))
}

fn suspense_boundary(cx: Scope) -> Element {
    cx.use_hook(|| cx.provide_context(Rc::new(SuspenseBoundary::new(cx.scope_id()))));

    // Ensure the right types are found
    cx.has_context::<SuspenseContext>().unwrap();

    cx.render(rsx!(async_child {}))
}

async fn async_child(cx: Scope<'_>) -> Element {
    use_future!(cx, || tokio::time::sleep(Duration::from_millis(10))).await;
    cx.render(rsx!(async_text {}))
}

async fn async_text(cx: Scope<'_>) -> Element {
    let username = use_future!(cx, || async {
        tokio::time::sleep(std::time::Duration::from_secs(1)).await;
        "async child 1"
    });

    let age = use_future!(cx, || async {
        tokio::time::sleep(std::time::Duration::from_secs(2)).await;
        println!("long future completed");
        1234
    });

    let (_user, _age) = use_future!(cx, || async {
        tokio::join!(
            tokio::time::sleep(std::time::Duration::from_secs(1)),
            tokio::time::sleep(std::time::Duration::from_secs(2))
        );
        ("async child 1", 1234)
    })
    .await;

    let (username, age) = tokio::join!(username.into_future(), age.into_future());

    cx.render(rsx!( div { "Hello! {username}, you are {age}, {_user} {_age}" } ))
}