Store an instance of the Rust type in the Element Class

src/lib.rs

@@ -1,19 +1,30 @@
 use js_sys::Function;
-use wasm_bindgen::JsValue;
+use wasm_bindgen::{convert::IntoWasmAbi, prelude::*, JsCast, JsValue};
 use web_sys::window;
 
 type Result<T> = std::result::Result<T, JsValue>;
 
-pub trait CustomElementImpl {
+pub trait CustomElementImpl: IntoWasmAbi {
     fn class_name() -> &'static str;
     fn element_name() -> &'static str;
+
+    fn construct() -> Self;
 }
 
-pub fn define_web_component<T: CustomElementImpl>() -> Result<JsValue> {
+pub struct WebComponentHandle<T: CustomElementImpl + 'static> {
+    pub impl_handle: Closure<dyn FnMut() -> T>,
+    pub element_constructor: Function,
+}
+
+pub fn define_web_component<T>() -> Result<WebComponentHandle<T>>
+where
+    T: CustomElementImpl + 'static,
+{
     let body = format!(
         "class {name} extends HTMLElement {{
     constructor() {{
         super();
+        //this.impl = impl();
     }}
 }}
 customElements.define(\"{element_name}\", {name});
@@ -22,17 +33,30 @@ return element;",
         name = T::class_name(),
         element_name = T::element_name(),
     );
-    let fun = Function::new_no_args(&body);
-    Ok(fun.call0(&window().unwrap())?)
+    let fun = Function::new_with_args("impl", &body);
+    let f: Box<dyn FnMut() -> T> = Box::new(|| T::construct());
+    // TODO(jwall): Check the lifetimes on this guy.
+    let constructor_handle = Closure::wrap(f);
+    let element = fun
+        .call1(
+            &window().unwrap(),
+            constructor_handle.as_ref().unchecked_ref::<Function>(),
+        )?
+        .dyn_into()?;
+    Ok(WebComponentHandle {
+        element_constructor: element,
+        impl_handle: constructor_handle,
+    })
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
-    use wasm_bindgen::{prelude::*, JsCast};
+    use wasm_bindgen::JsCast;
     use wasm_bindgen_test::wasm_bindgen_test;
     wasm_bindgen_test::wasm_bindgen_test_configure!(run_in_browser);
 
+    #[wasm_bindgen]
     pub struct MyElementImpl();
 
     impl CustomElementImpl for MyElementImpl {
@@ -43,6 +67,10 @@ mod tests {
         fn element_name() -> &'static str {
             "my-element"
         }
+
+        fn construct() -> Self {
+            Self()
+        }
     }
 
     #[wasm_bindgen]
@@ -56,7 +84,7 @@ mod tests {
     #[wasm_bindgen_test]
     fn test_component_definition() {
         let obj = define_web_component::<MyElementImpl>().expect("Failed to define web component");
-        let fun = obj.dyn_ref::<Function>().unwrap();
+        let fun = obj.element_constructor.dyn_ref::<Function>().unwrap();
         assert_eq!(fun.name(), MyElementImpl::class_name());
 
         let element = window()