Reactive tracking warning not shown correctly

[veigaribo]

Describe the bug

Consider this small repository: https://github.com/veigaribo/leptos-reactive-tracking-warning-issue

If it's run as it is (commit ID 5038489), the client JS+WASM will display the following warning:

At /.../leptos/reactive_graph/src/wrappers.rs:477:35, you access a reactive_graph::signal::arc_read::ArcReadSignal<core::option::Option<alloc::string::String>> (defined at /.../leptos/reactive_graph/src/signal/rw.rs:180:40) outside a reactive tracking context. This might mean your app is not responding to changes in signal values in the way you expect.

Which is of course not very useful, as none of the mentioned code pertains to the repository in question.
However, in src/app.rs, if line 25 is commented and line 24 uncommented:

#[component]
pub fn App() -> impl IntoView {
-    // let (x, set_x) = signal("Test");
-    let (x, set_x) = use_cookie::<String, FromToStringCodec>("test");
+    let (x, set_x) = signal("Test");
+    // let (x, set_x) = use_cookie::<String, FromToStringCodec>("test");

    view! { <button>{x.get()}</button> }
}

Then the new code will not produce any warning at all — which I believe is wrong, because the signal access in line 27 is still not tracked. In fact, the signal access is exactly the same; only the signal definition is different.

Leptos Dependencies

leptos = { version = "0.7.0", features = ["nightly"] }
leptos_meta = { version = "0.7.0" }
leptos_actix = { version = "0.7.0", optional = true }
leptos_router = { version = "0.7.0" }

Though I did some testing with

[patch.crates-io]
leptos = { path = "../../../leptos/leptos" }
leptos_meta = { path = "../../../leptos/meta" }
leptos_actix = { path = "../../../leptos/integrations/actix" }
leptos_router = { path = "../../../leptos/router" }

On a repository checked out on tag v0.7.0

To Reproduce

Steps to reproduce the behavior:

1. Clone the repository at https://github.com/veigaribo/leptos-reactive-tracking-warning-issue/
2. Run with e.g. cargo leptos watch --hot-reload --bin-features=ssr_actix (see README)
3. Access the application in your browser
4. Open the developer tools console and see the warning
5. Optionally do the mentioned modifications and see the absence of any warning

Expected behavior

I expected that the warning would be shown in both cases of the example code, and that the call and definition sites presented on the warning would not point to code internal to the project.

Additional context

use_cookie is defined here: https://github.com/Synphonyte/leptos-use/blob/18cdd812f292ba83443bf868957291aedf1d9585/src/use_cookie.rs#L145. I kept it from my actual application code, where I found this issue, because I don't yet know what causes it to behave differently.

When I was trying to understand this behavior, I noticed that, if I changed ArcRwSignal::read_only to propagate self.defined_at, instead of creating a new Location with Location::caller(), the resulting warning does include the correct signal definition, which is in leptos-use.

    /// Returns a read-only handle to the signal.
    #[track_caller]
    pub fn read_only(&self) -> ArcReadSignal<T> {
        ArcReadSignal {
            #[cfg(debug_assertions)]
-           defined_at: Location::caller(),
+           defined_at: self.defined_at,
            value: Arc::clone(&self.value),
            inner: Arc::clone(&self.inner),
        }
    }

At /.../leptos/reactive_graph/src/wrappers.rs:477:35, you access a reactive_graph::signal::arc_read::ArcReadSignal<core::option::Option<alloc::string::String>> (defined at /.../leptos-use-0.14.0-rc5/src/use_cookie.rs:189:32) outside a reactive tracking context. This might mean your app is not responding to changes in signal values in the way you expect.

And also saw that the immediate reason why the patched example repository code does not produce a warning is because it is in the SpecialNonReactiveZone. That is all the understanding I gathered.