document 与 eval

pub fn document() -> Rc<dyn Document> {
    match dioxus_core::try_consume_context::<Rc<dyn Document>>() {
        Some(document) => document,
        None => {
            tracing::error!(
                "Unable to find a document in the renderer. Using the default no-op document."
            );
            Rc::new(NoOpDocument)
        }
    }
}

fn app() -> Element {
  use_hook(|| {
    spawn(async {
      let r = document::eval("return 1 + 1;").await;
      println!("eval in a plain VirtualDom: {r:?}");
      use dioxus::document::Document as _;
      let r = dioxus::document::NoOpDocument.eval("return 1;".into()).await;
      println!("NoOpDocument.eval: {r:?}");
    })
  });
  rsx! {
    document::Title { "hello" }
    document::Meta { name: "description", content: "x" }
    p { "body" }
  }
}

ERROR Unable to find a document in the renderer. Using the default no-op document.
ERROR Unable to find a document in the renderer. Using the default no-op document.
ERROR Unable to find a document in the renderer. Using the default no-op document.
eval in a plain VirtualDom: Err(Finished)
NoOpDocument.eval: Err(Finished)
ssr: <p>body</p>

pub fn Meta(props: MetaProps) -> Element {
    use_update_warning(&props, "Meta {}");

    use_hook(|| {
        let document = document();
        let insert_link = document.create_head_component();

        if !insert_link {
            return;
        }

        document.create_meta(props);
    });

    VNode::empty()
}

    // Update the title as it changes. NOTE: We don't use use_effect here because we need this to run on the server
    let document = use_hook(document);
    let last_text = use_hook(|| {
        // Set the title initially
        document.set_title(text.clone());
        Rc::new(RefCell::new(text.clone()))
    });

    // If the text changes, update the title
    let mut last_text = last_text.borrow_mut();
    if text != *last_text {
        document.set_title(text.clone());
        *last_text = text;
    }

    /// Set the title of the document
    fn set_title(&self, title: String) {
        let myself = self.clone();
        queue_effect(move || {
            myself.eval(format!("document.title = {title:?};"));
        });
    }

    /// Create a new meta tag in the head
    fn create_meta(&self, props: MetaProps) {
        queue_effect(move || {
            _ = append_element_to_head("meta", &props.attributes(), None);
        });
    }

#[derive(Default)]
struct ServerDocumentInner {
    streaming: bool,
    title: Option<String>,
    meta: Vec<Element>,
    link: Vec<Element>,
    script: Vec<Element>,
}

fn app() -> Element {
  let mut n = use_signal(|| 0);
  let mut eval_out = use_signal(String::new);
  // runs on the server during SSR; the client reuses the serialized value
  let server_eval = use_server_future(move || async move {
    format!("{:?}", document::eval("return 1 + 1;").await)
  })?;
  rsx! {
    document::Title { "count {n}" }
    document::Meta { name: "description", content: "web-fs experiment" }
    document::Link { rel: "icon", href: "/favicon.ico" }
    document::Link { rel: "icon", href: "/favicon.ico" }
    document::Style { "#srv {{ color: teal; }}" }
    document::Script { "window.__script_runs = (window.__script_runs || 0) + 1;" }
    div { id: "srv", "server eval: {server_eval():?}" }
    button { id: "inc", onclick: move |_| n += 1, "+" }
    if n() > 0 {
      Late {}
    }
    // ... 几个调 eval 的按钮，见最后一节
  }
}

#[component]
fn Late() -> Element {
  rsx! {
    document::Meta { name: "late", content: "mounted after hydration" }
    document::Link { rel: "icon", href: "/favicon.ico" }
    span { id: "late", "late" }
  }
}

<head>
        <title>count 0</title>
        <meta content="text/html;charset=utf-8" http-equiv="Content-Type">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <meta charset="UTF-8">
        <style>/* dx toast css … */</style>
        <script>/* dx toast js … */</script>
    <meta name="description" content="web-fs experiment"/><link rel="icon" href="/favicon.ico"/><style>#srv { color: teal; }</style><script>window.__script_runs = (window.__script_runs || 0) + 1;</script></head>

    /// Write the head element into the serialized context for hydration
    /// We write true if the head element was written to the DOM during server side rendering
    #[track_caller]
    pub(crate) fn serialize_for_hydration(&self) {
        // We only serialize the head elements if the web document feature is enabled
        #[cfg(feature = "document")]
        {
            dioxus_fullstack_core::head_element_hydration_entry()
                .insert(&!self.0.borrow().streaming, std::panic::Location::caller());
        }
    }

    fn create_head_component(&self) -> bool {
        !head_element_written_on_server()
    }

window.initial_dioxus_hydration_debug_types=["core::option::Option<dioxus_core::render_error::CapturedError>","unknown","unknown","unknown","unknown","unknown","alloc::string::String","unknown","bool","unknown","bool","unknown","bool","unknown","bool","unknown","bool"];
window.initial_dioxus_hydration_debug_locations=["…/dioxus-server-0.7.10/src/ssr.rs:556:29","unknown","unknown","unknown","unknown","unknown","src/main.rs:7:21","unknown","…/dioxus-server-0.7.10/src/document.rs:163:14","unknown","…/dioxus-server-0.7.10/src/document.rs:163:14","unknown","…/dioxus-server-0.7.10/src/document.rs:163:14","unknown","…/dioxus-server-0.7.10/src/document.rs:163:14","unknown","…/dioxus-server-0.7.10/src/document.rs:163:14"];

--- head after hydration (dx toast style/script omitted) ---
<title>count 0</title>
<meta content="text/html;charset=utf-8" http-equiv="Content-Type">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta charset="UTF-8">
<meta name="description" content="web-fs experiment">
<link rel="icon" href="/favicon.ico">
<style>#srv { color: teal; }</style>
<script>window.__script_runs = (window.__script_runs || 0) + 1;</script>
document.title = "count 0"  __script_runs = 1
--- click #inc twice (Title changes, Late mounts) ---
document.title = "count 1"  <title> elements: 1
document.title = "count 2"
<title>count 2</title>
<meta content="text/html;charset=utf-8" http-equiv="Content-Type">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta charset="UTF-8">
<meta name="description" content="web-fs experiment">
<link rel="icon" href="/favicon.ico">
<style>#srv { color: teal; }</style>
<script>window.__script_runs = (window.__script_runs || 0) + 1;</script>
<meta name="late" content="mounted after hydration">

[console.log] WARN …/dioxus-document-0.7.10/src/elements/mod.rs:34 Changing the props of `Style {}` is not supported 
[console.log] WARN …/dioxus-document-0.7.10/src/elements/mod.rs:34 Changing the props of `Script {}` is not supported 

        let owner = UnsyncStorage::owner();

        // add the drop handler to DioxusChannel so that it gets dropped when the channel is dropped in js
        let channels = WebDioxusChannel::new(JSOwner::new(owner.clone()));

        // The Rust side of the channel is a weak reference to the DioxusChannel
        let weak_channels = channels.weak();

        // Wrap the evaluated JS in a promise so that wasm can continue running (send/receive data from js)
        let code = PROMISE_WRAPPER.replace("{JS_CODE}", &js);

        let result = match Function::new_with_args("dioxus", &code).call1(&JsValue::NULL, &channels)

const PROMISE_WRAPPER: &str = r#"
    return (async function(){
        {JS_CODE}

        dioxus.close();
    })();
"#;

        let mut ev = document::eval(
          r#"
            const x = await dioxus.recv();
            dioxus.send(x * 10);
            return "done " + x;
          "#,
        );
        ev.send(4).unwrap();
        let got: i32 = ev.recv().await.unwrap();
        let joined = ev.join::<String>().await;
        eval_out.set(format!("recv = {got}, join = {joined:?}"));

#evalout: recv = 40, join = Ok("done 4")

--- channels left in globalThis.__channels ---
before: 1 live of 4
after 10 evals without return: 1 live of 14
after 10 evals with return: 11 live of 24
after a forced GC: 11 live of 24

click #bad_js -> click() returned normally
[exception] SyntaxError: Unexpected identifier 'is'
#evalout: ""
...
[console.error] panicked at …/dioxus-core-0.7.10/src/arena.rs:59:50:
RefCell already borrowed
...
[exception] RuntimeError: unreachable
after clicking #inc: title = "count 0"
after #roundtrip: #evalout = ""

impl Document for NoOpDocument {
    fn eval(&self, _: String) -> Eval {
        let owner = generational_box::Owner::default();
        struct NoOpEvaluator;
        impl Evaluator for NoOpEvaluator {
            fn poll_join(
                &mut self,
                _: &mut std::task::Context<'_>,
            ) -> std::task::Poll<Result<serde_json::Value, EvalError>> {
                std::task::Poll::Ready(Err(EvalError::Unsupported))
            }
            // ...
        }
        Eval::new(owner.insert(Box::new(NoOpEvaluator)))
    }

<div id="srv" data-node-hydration="6"><!--node-id7-->server eval: Some(&#34;Err(Finished)&#34;)<!--#--></div>