feat(splicer): add destructor metadata (#345)

Author: vados-cosmonic

crates/spidermonkey-embedding-splicer/src/bindgen.rs

@@ -31,6 +31,7 @@ pub enum Resource {
     Constructor(String),
     Static(String),
     Method(String),
+    Destructor(String),
 }
 
 impl Resource {
@@ -40,6 +41,7 @@ impl Resource {
             Resource::Constructor(name) => format!("[constructor]{name}"),
             Resource::Static(name) => format!("[static]{name}.{fn_name}"),
             Resource::Method(name) => format!("[method]{name}.{fn_name}"),
+            Resource::Destructor(name) => format!("[dtor]{name}"),
         }
     }
 
@@ -67,6 +69,9 @@ impl Resource {
                     fn_name.to_lower_camel_case()
                 )
             }
+            Resource::Destructor(name) => {
+                format!("{}$dtor", name.to_lower_camel_case())
+            }
         }
     }
 }
@@ -193,7 +198,8 @@ pub fn componentize_bindgen(
                     Resource::None => None,
                     Resource::Method(name)
                     | Resource::Static(name)
-                    | Resource::Constructor(name) => Some(name),
+                    | Resource::Constructor(name)
+                    | Resource::Destructor(name) => Some(name),
                 })
                 .or_default()
                 .push(item);
@@ -439,10 +445,12 @@ impl JsBindgen<'_> {
                     id, stability: _, ..
                 } => {
                     let iface = &self.resolve.interfaces[*id];
-                    for id in iface.types.values() {
-                        if let TypeDefKind::Resource = &self.resolve.types[*id].kind {
+                    let iface_name = interface_name(self.resolve, *id);
+                    for ty_id in iface.types.values() {
+                        if let TypeDefKind::Resource = &self.resolve.types[*ty_id].kind {
                             self.resource_directions
-                                .insert(*id, AbiVariant::GuestExport);
+                                .insert(*ty_id, AbiVariant::GuestExport);
+                            self.resource_dtor_bindgen(name.clone(), iface_name.clone(), *ty_id);
                         }
                     }
                     for (func_name, func) in &iface.functions {
@@ -1030,6 +1038,59 @@ impl JsBindgen<'_> {
         ));
     }
 
+    fn resource_dtor_bindgen(
+        &mut self,
+        export_name: String,
+        iface_name: Option<String>,
+        resource: TypeId,
+    ) {
+        let resource_name = self.resolve.types[resource].name.as_ref().unwrap();
+        let resource_name_camel = resource_name.to_lower_camel_case();
+        let prefix = iface_name
+            .as_deref()
+            .map(|name| format!("{name}$"))
+            .unwrap_or_default();
+        let symbol_dispose = self.intrinsic(Intrinsic::SymbolDispose);
+        let symbol_resource_handle = self.intrinsic(Intrinsic::SymbolResourceHandle);
+        let binding_name = format!(
+            "export_{}",
+            binding_name(&format!("{resource_name_camel}$dtor"), &iface_name)
+        );
+
+        uwriteln!(
+            self.src,
+            "
+            async function {binding_name}(rep) {{
+                const entry = repTable.get(rep);
+                if (!entry) return;
+                repTable.delete(rep);
+                const resource = entry.rep;
+                delete resource[{symbol_resource_handle}];
+                finalizationRegistry_export${prefix}{resource_name_camel}.unregister(resource);
+                if (resource[{symbol_dispose}]) resource[{symbol_dispose}]();
+            }}
+            "
+        );
+
+        self.exports.push((
+            export_name,
+            BindingItem {
+                iface: true,
+                iface_name,
+                binding_name,
+                resource: Resource::Destructor(resource_name.clone()),
+                name: resource_name.clone(),
+                func: CoreFn {
+                    params: vec![CoreTy::I32],
+                    ret: None,
+                    retptr: false,
+                    retsize: 0,
+                    paramptr: false,
+                },
+            },
+        ));
+    }
+
     fn core_fn(&self, func: &Function, sig: &WasmSignature) -> CoreFn {
         CoreFn {
             retsize: if sig.retptr {

crates/spidermonkey-embedding-splicer/src/splice.rs

@@ -193,7 +193,11 @@ pub fn splice_bindings(
         } else {
             export_name.clone()
         };
-        exports.push((expt, map_core_fn(func)));
+        exports.push((
+            expt,
+            map_core_fn(func),
+            matches!(resource, bindgen::Resource::Destructor(_)),
+        ));
     }
 
     let mut imports = Vec::new();
@@ -334,7 +338,7 @@ pub fn splice_bindings(
 pub fn splice(
     engine: Vec<u8>,
     imports: Vec<(String, String, CoreFn, Option<i32>)>,
-    exports: Vec<(String, CoreFn)>,
+    exports: Vec<(String, CoreFn, bool)>,
     features: Vec<Feature>,
     debug: bool,
 ) -> Result<Vec<u8>> {
@@ -381,13 +385,13 @@ pub fn splice(
 
 fn remove_if_exported_by_js(
     module: &mut Module,
-    content_exports: &[(String, CoreFn)],
+    content_exports: &[(String, CoreFn, bool)],
     name_start: &str,
     name_end: &str,
 ) {
     let content_exports_run = content_exports
         .iter()
-        .any(|(name, _)| name.starts_with(name_start) && name.ends_with(name_end));
+        .any(|(name, _, _)| name.starts_with(name_start) && name.ends_with(name_end));
     if content_exports_run {
         let exported_run_fn = module
             .exports
@@ -859,7 +863,10 @@ fn synthesize_import_functions(
     Ok(())
 }
 
-fn synthesize_export_functions(module: &mut Module, exports: &[(String, CoreFn)]) -> Result<()> {
+fn synthesize_export_functions(
+    module: &mut Module,
+    exports: &[(String, CoreFn, bool)],
+) -> Result<()> {
     let cabi_realloc = get_export_fid(
         module,
         &module
@@ -880,7 +887,7 @@ fn synthesize_export_functions(module: &mut Module, exports: &[(String, CoreFn)]
 
     let memory = 0;
     // (2) Export call function synthesis
-    for (export_num, (expt_name, expt_sig)) in exports.iter().enumerate() {
+    for (export_num, (expt_name, expt_sig, inline_post_call)) in exports.iter().enumerate() {
         // Export function synthesis
         {
             // add the function type
@@ -1044,10 +1051,19 @@ fn synthesize_export_functions(module: &mut Module, exports: &[(String, CoreFn)]
                 }
             }
 
+            if *inline_post_call {
+                func.i32_const(export_num as i32);
+                func.call(post_call);
+            }
+
             let fid = func.finish_module(module);
             module.exports.add_export_func((*expt_name).clone(), *fid);
         }
 
+        if *inline_post_call {
+            continue;
+        }
+
         // Post export function synthesis
         // We always define a post-export since we use a bulk deallocation strategy
         // add the function type

test/cases/resource-disposal/source.js

@@ -0,0 +1,23 @@
+let disposeCount = 0;
+const disposeSymbol = Symbol.dispose || Symbol.for('dispose');
+
+class Example {
+  constructor(id) {
+    this.id = id;
+  }
+
+  getId() {
+    return this.id;
+  }
+
+  [disposeSymbol]() {
+    disposeCount += 1;
+  }
+}
+
+export const resources = {
+  Example,
+  disposeCount() {
+    return disposeCount;
+  },
+};

test/cases/resource-disposal/test.js

@@ -0,0 +1,14 @@
+import { strictEqual } from 'node:assert';
+
+const disposeSymbol = Symbol.dispose || Symbol.for('dispose');
+
+export function test(instance) {
+  const resource = new instance.resources.Example(42);
+
+  strictEqual(resource.getId(), 42);
+  resource[disposeSymbol]();
+  strictEqual(instance.resources.disposeCount(), 1);
+
+  resource[disposeSymbol]();
+  strictEqual(instance.resources.disposeCount(), 1);
+}

test/cases/resource-disposal/world.wit

@@ -0,0 +1,14 @@
+package test:test;
+
+interface resources {
+  resource example {
+    constructor(id: u32);
+    get-id: func() -> u32;
+  }
+
+  dispose-count: func() -> u32;
+}
+
+world test {
+  export resources;
+}