Implement OptionIntoWasmAbi for Closure references (#2768)

* Implement OptionIntoWasmAbi for Closure references

* Add tests for optional closure arguments

* Uncomment None test for optional closure argument

* Tighten None test for optional closure argument

* Add tests for dropping optional closures

Co-authored-by: Billy Bradley <billy@squeno.com>

src/closure.rs

@@ -491,6 +491,15 @@ where
     }
 }
 
+impl<'a, T> OptionIntoWasmAbi for &'a Closure<T>
+where
+    T: WasmClosure + ?Sized,
+{
+    fn none() -> Self::Abi {
+        0
+    }
+}
+
 fn _check() {
     fn _assert<T: IntoWasmAbi>() {}
     _assert::<&Closure<dyn Fn()>>();

tests/wasm/closures.js

@@ -51,6 +51,18 @@ exports.many_arity_call9 = a => {
     a(1, 2, 3, 4, 5, 6, 7, 8);
 };
 
+exports.option_call1 = a => {
+    if (a) {
+        a();
+    }
+};
+exports.option_call2 = a => {
+    if (a) {
+        return a(2);
+    }
+};
+exports.option_call3 = a => a == undefined;
+
 let LONG_LIVED_DROPPING_CACHE = null;
 
 exports.long_lived_dropping_cache = a => {
@@ -60,6 +72,20 @@ exports.long_lived_dropping_call = () => {
     LONG_LIVED_DROPPING_CACHE();
 };
 
+let LONG_LIVED_OPTION_DROPPING_CACHE = null;
+
+exports.long_lived_option_dropping_cache = a => {
+    if (a) {
+        LONG_LIVED_OPTION_DROPPING_CACHE = a;
+        return true;
+    } else {
+        return false;
+    }
+}
+exports.long_lived_option_dropping_call = () => {
+    LONG_LIVED_OPTION_DROPPING_CACHE();
+}
+
 let LONG_FNMUT_RECURSIVE_CACHE = null;
 
 exports.long_fnmut_recursive_cache = a => {

tests/wasm/closures.rs

@@ -46,6 +46,10 @@ extern "C" {
     #[wasm_bindgen(js_name = many_arity_call9)]
     fn many_arity_call_mut9(a: &Closure<dyn FnMut(u32, u32, u32, u32, u32, u32, u32, u32)>);
 
+    fn option_call1(a: Option<&Closure<dyn Fn()>>);
+    fn option_call2(a: Option<&Closure<dyn FnMut(u32) -> u32>>) -> u32;
+    fn option_call3(a: Option<&Closure<dyn Fn()>>) -> bool;
+
     #[wasm_bindgen(js_name = many_arity_call1)]
     fn many_arity_stack1(a: &dyn Fn());
     #[wasm_bindgen(js_name = many_arity_call2)]
@@ -69,6 +73,10 @@ extern "C" {
     #[wasm_bindgen(catch)]
     fn long_lived_dropping_call() -> Result<(), JsValue>;
 
+    fn long_lived_option_dropping_cache(a: Option<&Closure<dyn Fn()>>) -> bool;
+    #[wasm_bindgen(catch)]
+    fn long_lived_option_dropping_call() -> Result<(), JsValue>;
+
     fn long_fnmut_recursive_cache(a: &Closure<dyn FnMut()>);
     #[wasm_bindgen(catch)]
     fn long_fnmut_recursive_call() -> Result<(), JsValue>;
@@ -235,6 +243,29 @@ fn many_arity() {
     );
 }
 
+#[wasm_bindgen_test]
+fn option() {
+    let hit = Rc::new(Cell::new(false));
+    let hit2 = hit.clone();
+    let a = Closure::new(move || hit2.set(true));
+    assert!(!hit.get());
+    option_call1(Some(&a));
+    assert!(hit.get());
+
+    let hit = Rc::new(Cell::new(false));
+    {
+        let hit = hit.clone();
+        let a = Closure::new(move |x| {
+            hit.set(true);
+            x + 3
+        });
+        assert_eq!(option_call2(Some(&a)), 5);
+    }
+    assert!(hit.get());
+
+    assert!(option_call3(None));
+}
+
 struct Dropper(Rc<Cell<bool>>);
 impl Drop for Dropper {
     fn drop(&mut self) {
@@ -300,6 +331,24 @@ fn long_lived_dropping() {
     assert!(long_lived_dropping_call().is_err());
 }
 
+#[wasm_bindgen_test]
+fn long_lived_option_dropping() {
+    let hit = Rc::new(Cell::new(false));
+    let hit2 = hit.clone();
+
+    let a = Closure::new(move || hit2.set(true));
+
+    assert!(!long_lived_option_dropping_cache(None));
+    assert!(long_lived_option_dropping_cache(Some(&a)));
+
+    assert!(!hit.get());
+    assert!(long_lived_option_dropping_call().is_ok());
+    assert!(hit.get());
+
+    drop(a);
+    assert!(long_lived_option_dropping_call().is_err());
+}
+
 #[wasm_bindgen_test]
 fn long_fnmut_recursive() {
     let a = Closure::new(|| {