Resource + Signal in Memo?

[duelafn]

Hello, I'm having a problem with reading a resource in hydrate mode outside a <Suspense/> or <Transition/> warnings when using a Resource and Signal in a Memo. I do not get any warnings if I replace the Memo with a closure. The component in question is included below, I have a (somewhat) minimal example available at: https://gist.github.com/duelafn/dcd62842fa6efa3627a4bbb01ef06ba5

The Memo version has resource outside Suspense warning when I attempt to access visitor in compute_mode().

#[component]
pub fn ContractViewA() -> impl IntoView {
    let visitor: Resource<Visitor> = expect_context();
    let (req_mode, set_mode) = signal::<Option<&'static str>>(None);
    let real_mode = Memo::new(move |_| compute_mode(req_mode.get(), visitor));

    view! {
        <Suspense>
            <p>
                <button on:click={move |_| set_mode.set(None)}>"Nav"</button>
                <button on:click={move |_| set_mode.set(Some("edit"))}>"Edit"</button>
                <button on:click={move |_| set_mode.set(Some("view"))}>"View"</button>
            </p>

            <p>{ move || real_mode.get() }</p>
        </Suspense>
    }
}

The closure version emits no warnings.

#[component]
pub fn ContractViewB() -> impl IntoView {
    let visitor: Resource<Visitor> = expect_context();
    let (req_mode, set_mode) = signal::<Option<&'static str>>(None);
    let real_mode = move || compute_mode(req_mode.get(), visitor);

    view! {
        <Suspense>
            <p>
                <button on:click={move |_| set_mode.set(None)}>"Nav"</button>
                <button on:click={move |_| set_mode.set(Some("edit"))}>"Edit"</button>
                <button on:click={move |_| set_mode.set(Some("view"))}>"View"</button>
            </p>

            <p>{ move || real_mode() }</p>
        </Suspense>
    }
}

Both versions appear to work in that the paragraph text updates so I guess this could be a false warning? -- but more likely I'm doing something wrong or misunderstanding something.

I also apologize if this was asked before (it seems like it should have been), I've searched several times but found nothing that seems related.

Suggestions?

Thanks!

[duelafn]

Ah-ha! of course I find it after posting, but I've found an explanation here: #3638 (comment)

When the Resource is read inside the Memo, the Memo looks up the tree searching for a
Suspense. However, it looks up the tree starting from where the Memo is created, not
from where the Memo is read. Because the Memo is created above/outside the Suspense,
it doesn't find it.

You can fix this by delaying the creation of the Memo until you're actually inside the Suspense.

And indeed, the following works without emitting any warnings.

#[component]
pub fn ContractViewC() -> impl IntoView {
    let visitor: Resource<Visitor> = expect_context();
    let (req_mode, set_mode) = signal::<Option<&'static str>>(None);

    view! {
        <Suspense>
            <p>
                <button on:click={move |_| set_mode.set(None)}>"Nav"</button>
                <button on:click={move |_| set_mode.set(Some("edit"))}>"Edit"</button>
                <button on:click={move |_| set_mode.set(Some("view"))}>"View"</button>
            </p>

            <p>{ let real_mode = Memo::new(move |_| compute_mode(req_mode.get(), visitor)); move || real_mode.get() }</p>
        </Suspense>
    }
}

So, I guess it is a false positive warning.