perf(core): generate inlined wrappers for async ops (#16428)

V8's JIT can do a better job knowing the argument count and also enable
fast call path (in future).

This also lets us call async ops without `opAsync`:

```js
const { ops } = Deno.core;
await ops.op_void_async();
```

this patch: 4405286 ops/sec
main: 3508771 ops/sec

bench_util/js_runtime.rs

@@ -63,7 +63,6 @@ pub fn bench_js_sync_with(
 
   let code = v8::String::new(scope, looped_src.as_ref()).unwrap();
   let script = v8::Script::compile(scope, code, None).unwrap();
-
   // Run once if profiling, otherwise regular bench loop
   if is_profiling() {
     script.run(scope).unwrap();
@@ -102,7 +101,9 @@ pub fn bench_js_async_with(
   };
   let looped = loop_code(inner_iters, src);
   let src = looped.as_ref();
-
+  runtime
+    .execute_script("init", "Deno.core.initializeAsyncOps();")
+    .unwrap();
   if is_profiling() {
     for _ in 0..opts.profiling_outer {
       tokio_runtime.block_on(inner_async(src, &mut runtime));

cli/bench/async_ops.js

@@ -5,7 +5,7 @@ let [total, count] = typeof Deno !== "undefined"
   : [process.argv[2], process.argv[3]];
 
 total = total ? parseInt(total, 0) : 50;
-count = count ? parseInt(count, 10) : 100000;
+count = count ? parseInt(count, 10) : 1000000;
 
 async function bench(fun) {
   const start = Date.now();
@@ -16,4 +16,5 @@ async function bench(fun) {
   if (--total) queueMicrotask(() => bench(fun));
 }
 
-bench(() => Deno.core.opAsync("op_void_async"));
+const { ops } = Deno.core;
+bench(() => ops.op_void_async());

cli/tests/unit/metrics_test.ts

@@ -84,6 +84,6 @@ Deno.test(function opNamesMatch() {
     // @ts-ignore: Deno.core allowed
     Deno.core.opNames().sort(),
     // @ts-ignore: Deno.core allowed
-    Object.keys(Deno.core.ops).sort(),
+    Object.keys(Deno.core.ops).sort().filter((name) => name !== "asyncOpsInfo"),
   );
 });

core/01_core.js

@@ -28,7 +28,7 @@
     SymbolFor,
     setQueueMicrotask,
   } = window.__bootstrap.primordials;
-  const ops = window.Deno.core.ops;
+  const { ops } = window.Deno.core;
 
   const errorMap = {};
   // Builtin v8 / JS errors
@@ -159,21 +159,63 @@
     return res;
   }
 
-  function opAsync(opName, ...args) {
-    const promiseId = nextPromiseId++;
-    let p = setPromise(promiseId);
-    try {
-      ops[opName](promiseId, ...args);
-    } catch (err) {
-      // Cleanup the just-created promise
-      getPromise(promiseId);
-      // Rethrow the error
-      throw err;
+  function rollPromiseId() {
+    return nextPromiseId++;
+  }
+
+  // Generate async op wrappers. See core/bindings.rs
+  function initializeAsyncOps() {
+    function genAsyncOp(op, name, args) {
+      return new Function(
+        "setPromise",
+        "getPromise",
+        "promiseIdSymbol",
+        "rollPromiseId",
+        "handleOpCallTracing",
+        "op",
+        "unwrapOpResult",
+        "PromisePrototypeThen",
+        `
+        return function ${name}(${args}) {
+          const id = rollPromiseId();
+          let promise = PromisePrototypeThen(setPromise(id), unwrapOpResult);
+          try {
+            op(id, ${args});
+          } catch (err) {
+            // Cleanup the just-created promise
+            getPromise(id);
+            // Rethrow the error
+            throw err;
+          }
+          handleOpCallTracing("${name}", id, promise);
+          promise[promiseIdSymbol] = id;          
+          return promise;
+        }
+      `,
+      )(
+        setPromise,
+        getPromise,
+        promiseIdSymbol,
+        rollPromiseId,
+        handleOpCallTracing,
+        op,
+        unwrapOpResult,
+        PromisePrototypeThen,
+      );
     }
-    p = PromisePrototypeThen(p, unwrapOpResult);
+
+    // { <name>: <argc>, ... }
+    for (const ele of Object.entries(ops.asyncOpsInfo())) {
+      if (!ele) continue;
+      const [name, argc] = ele;
+      const op = ops[name];
+      const args = Array.from({ length: argc }, (_, i) => `arg${i}`).join(", ");
+      ops[name] = genAsyncOp(op, name, args);
+    }
+  }
+
+  function handleOpCallTracing(opName, promiseId, p) {
     if (opCallTracingEnabled) {
-      // Capture a stack trace by creating a new `Error` object. We remove the
-      // first 6 characters (the `Error\n` prefix) to get just the stack trace.
       const stack = StringPrototypeSlice(new Error().stack, 6);
       MapPrototypeSet(opCallTraces, promiseId, { opName, stack });
       p = PromisePrototypeFinally(
@@ -181,9 +223,10 @@
         () => MapPrototypeDelete(opCallTraces, promiseId),
       );
     }
-    // Save the id on the promise so it can later be ref'ed or unref'ed
-    p[promiseIdSymbol] = promiseId;
-    return p;
+  }
+
+  function opAsync(opName, ...args) {
+    return ops[opName](...args);
   }
 
   function refOp(promiseId) {
@@ -303,6 +346,7 @@
   // Extra Deno.core.* exports
   const core = ObjectAssign(globalThis.Deno.core, {
     opAsync,
+    initializeAsyncOps,
     resources,
     metrics,
     registerErrorBuilder,
@@ -322,11 +366,11 @@
     setPromiseHooks,
     close: (rid) => ops.op_close(rid),
     tryClose: (rid) => ops.op_try_close(rid),
-    read: opAsync.bind(null, "op_read"),
-    readAll: opAsync.bind(null, "op_read_all"),
-    write: opAsync.bind(null, "op_write"),
-    writeAll: opAsync.bind(null, "op_write_all"),
-    shutdown: opAsync.bind(null, "op_shutdown"),
+    read: (rid, buffer) => ops.op_read(rid, buffer),
+    readAll: (rid) => ops.op_read_all(rid),
+    write: (rid, buffer) => ops.op_write(rid, buffer),
+    writeAll: (rid, buffer) => ops.op_write_all(rid, buffer),
+    shutdown: (rid) => ops.op_shutdown(rid),
     print: (msg, isErr) => ops.op_print(msg, isErr),
     setMacrotaskCallback: (fn) => ops.op_set_macrotask_callback(fn),
     setNextTickCallback: (fn) => ops.op_set_next_tick_callback(fn),

core/bindings.rs

@@ -97,6 +97,7 @@ pub fn initialize_context<'s>(
   scope: &mut v8::HandleScope<'s, ()>,
   op_ctxs: &[OpCtx],
   snapshot_loaded: bool,
+  will_snapshot: bool,
 ) -> v8::Local<'s, v8::Context> {
   let scope = &mut v8::EscapableHandleScope::new(scope);
 
@@ -116,7 +117,9 @@ pub fn initialize_context<'s>(
     let ops_obj = JsRuntime::grab_global::<v8::Object>(scope, "Deno.core.ops")
       .expect("Deno.core.ops to exist");
     initialize_ops(scope, ops_obj, op_ctxs, snapshot_loaded);
-
+    if !will_snapshot {
+      initialize_async_ops_info(scope, ops_obj, op_ctxs);
+    }
     return scope.escape(context);
   }
 
@@ -128,8 +131,10 @@ pub fn initialize_context<'s>(
 
   // Bind functions to Deno.core.ops.*
   let ops_obj = JsRuntime::ensure_objs(scope, global, "Deno.core.ops").unwrap();
-
-  initialize_ops(scope, ops_obj, op_ctxs, snapshot_loaded);
+  if !will_snapshot {
+    initialize_async_ops_info(scope, ops_obj, op_ctxs);
+  }
+  initialize_ops(scope, ops_obj, op_ctxs, !will_snapshot);
   scope.escape(context)
 }
 
@@ -590,3 +595,84 @@ pub fn throw_type_error(scope: &mut v8::HandleScope, message: impl AsRef<str>) {
   let exception = v8::Exception::type_error(scope, message);
   scope.throw_exception(exception);
 }
+
+struct AsyncOpsInfo {
+  ptr: *const OpCtx,
+  len: usize,
+}
+
+impl<'s> IntoIterator for &'s AsyncOpsInfo {
+  type Item = &'s OpCtx;
+  type IntoIter = AsyncOpsInfoIterator<'s>;
+
+  fn into_iter(self) -> Self::IntoIter {
+    AsyncOpsInfoIterator {
+      // SAFETY: OpCtx slice is valid for the lifetime of the Isolate
+      info: unsafe { std::slice::from_raw_parts(self.ptr, self.len) },
+      index: 0,
+    }
+  }
+}
+
+struct AsyncOpsInfoIterator<'s> {
+  info: &'s [OpCtx],
+  index: usize,
+}
+
+impl<'s> Iterator for AsyncOpsInfoIterator<'s> {
+  type Item = &'s OpCtx;
+
+  fn next(&mut self) -> Option<Self::Item> {
+    loop {
+      match self.info.get(self.index) {
+        Some(ctx) if ctx.decl.is_async => {
+          self.index += 1;
+          return Some(ctx);
+        }
+        Some(_) => {
+          self.index += 1;
+        }
+        None => return None,
+      }
+    }
+  }
+}
+
+fn async_ops_info(
+  scope: &mut v8::HandleScope,
+  args: v8::FunctionCallbackArguments,
+  mut rv: v8::ReturnValue,
+) {
+  let async_op_names = v8::Object::new(scope);
+  let external: v8::Local<v8::External> = args.data().try_into().unwrap();
+  let info: &AsyncOpsInfo =
+    // SAFETY: external is guaranteed to be a valid pointer to AsyncOpsInfo
+    unsafe { &*(external.value() as *const AsyncOpsInfo) };
+  for ctx in info {
+    let name = v8::String::new(scope, ctx.decl.name).unwrap();
+    let argc = v8::Integer::new(scope, ctx.decl.argc as i32);
+    async_op_names.set(scope, name.into(), argc.into());
+  }
+  rv.set(async_op_names.into());
+}
+
+fn initialize_async_ops_info(
+  scope: &mut v8::HandleScope,
+  ops_obj: v8::Local<v8::Object>,
+  op_ctxs: &[OpCtx],
+) {
+  let key = v8::String::new(scope, "asyncOpsInfo").unwrap();
+  let external = v8::External::new(
+    scope,
+    Box::into_raw(Box::new(AsyncOpsInfo {
+      ptr: op_ctxs as *const [OpCtx] as _,
+      len: op_ctxs.len(),
+    })) as *mut c_void,
+  );
+  let val = v8::Function::builder(async_ops_info)
+    .data(external.into())
+    .build(scope)
+    .unwrap();
+  val.set_name(key);
+  ops_obj.set(scope, key.into(), val.into());
+}

core/examples/http_bench_json_ops.js

@@ -2,6 +2,8 @@
 // This is not a real HTTP server. We read blindly one time into 'requestBuf',
 // then write this fixed 'responseBuf'. The point of this benchmark is to
 // exercise the event loop in a simple yet semi-realistic way.
+Deno.core.initializeAsyncOps();
+
 const requestBuf = new Uint8Array(64 * 1024);
 const responseBuf = new Uint8Array(
   "HTTP/1.1 200 OK\r\nContent-Length: 12\r\n\r\nHello World\n"
@@ -16,7 +18,7 @@ function listen() {
 
 /** Accepts a connection, returns rid. */
 function accept(serverRid) {
-  return Deno.core.opAsync("op_accept", serverRid);
+  return Deno.core.ops.op_accept(serverRid);
 }
 
 async function serve(rid) {

core/extensions.rs

@@ -16,6 +16,9 @@ pub struct OpDecl {
   pub enabled: bool,
   pub is_async: bool,
   pub is_unstable: bool,
+  /// V8 argument count. Used as an optimization
+  /// hint by `core.initalizeAsyncOps`.
+  pub argc: usize,
   pub is_v8: bool,
   pub fast_fn: Option<Box<dyn FastFunction>>,
 }

core/runtime.rs

@@ -384,7 +384,8 @@ impl JsRuntime {
           isolate_ptr.read()
         };
         let scope = &mut v8::HandleScope::new(&mut isolate);
-        let context = bindings::initialize_context(scope, &op_ctxs, false);
+        let context =
+          bindings::initialize_context(scope, &op_ctxs, false, true);
         global_context = v8::Global::new(scope, context);
         scope.set_default_context(context);
       }
@@ -422,7 +423,7 @@ impl JsRuntime {
         };
         let scope = &mut v8::HandleScope::new(&mut isolate);
         let context =
-          bindings::initialize_context(scope, &op_ctxs, snapshot_loaded);
+          bindings::initialize_context(scope, &op_ctxs, snapshot_loaded, false);
 
         global_context = v8::Global::new(scope, context);
       }
@@ -550,6 +551,7 @@ impl JsRuntime {
         scope,
         &self.state.borrow().op_ctxs,
         self.built_from_snapshot,
+        false,
       );
       JsRealm::new(v8::Global::new(scope, context))
     };
@@ -2243,6 +2245,7 @@ pub mod tests {
   #[derive(Copy, Clone)]
   enum Mode {
     Async,
+    AsyncDeferred,
     AsyncZeroCopy(bool),
   }
 
@@ -2251,20 +2254,28 @@ pub mod tests {
     dispatch_count: Arc<AtomicUsize>,
   }
 
-  #[op(deferred)]
+  #[op]
   async fn op_test(
     rc_op_state: Rc<RefCell<OpState>>,
     control: u8,
     buf: Option<ZeroCopyBuf>,
   ) -> Result<u8, AnyError> {
+    #![allow(clippy::await_holding_refcell_ref)] // False positive.
     let op_state_ = rc_op_state.borrow();
     let test_state = op_state_.borrow::<TestState>();
     test_state.dispatch_count.fetch_add(1, Ordering::Relaxed);
-    match test_state.mode {
+    let mode = test_state.mode;
+    drop(op_state_);
+    match mode {
       Mode::Async => {
         assert_eq!(control, 42);
         Ok(43)
       }
+      Mode::AsyncDeferred => {
+        tokio::task::yield_now().await;
+        assert_eq!(control, 42);
+        Ok(43)
+      }
       Mode::AsyncZeroCopy(has_buffer) => {
         assert_eq!(buf.is_some(), has_buffer);
         if let Some(buf) = buf {
@@ -2314,14 +2325,15 @@ pub mod tests {
 
   #[test]
   fn test_ref_unref_ops() {
-    let (mut runtime, _dispatch_count) = setup(Mode::Async);
+    let (mut runtime, _dispatch_count) = setup(Mode::AsyncDeferred);
     runtime
       .execute_script(
         "filename.js",
         r#"
+        Deno.core.initializeAsyncOps();
         var promiseIdSymbol = Symbol.for("Deno.core.internalPromiseId");
-        var p1 = Deno.core.opAsync("op_test", 42);
-        var p2 = Deno.core.opAsync("op_test", 42);
+        var p1 = Deno.core.ops.op_test(42);
+        var p2 = Deno.core.ops.op_test(42);
         "#,
       )
       .unwrap();
@@ -2374,6 +2386,7 @@ pub mod tests {
         "filename.js",
         r#"
         let control = 42;
+        Deno.core.initializeAsyncOps();
         Deno.core.opAsync("op_test", control);
         async function main() {
           Deno.core.opAsync("op_test", control);
@@ -2392,6 +2405,7 @@ pub mod tests {
       .execute_script(
         "filename.js",
         r#"
+        Deno.core.initializeAsyncOps();
         const p = Deno.core.opAsync("op_test", 42);
         if (p[Symbol.for("Deno.core.internalPromiseId")] == undefined) {
           throw new Error("missing id on returned promise");
@@ -2408,6 +2422,7 @@ pub mod tests {
       .execute_script(
         "filename.js",
         r#"
+        Deno.core.initializeAsyncOps();
         Deno.core.opAsync("op_test");
         "#,
       )
@@ -2422,6 +2437,7 @@ pub mod tests {
       .execute_script(
         "filename.js",
         r#"
+        Deno.core.initializeAsyncOps();
         let zero_copy_a = new Uint8Array([0]);
         Deno.core.opAsync("op_test", null, zero_copy_a);
         "#,
@@ -3021,7 +3037,6 @@ pub mod tests {
 function main() {
   console.log("asdf);
 }
-
 main();
 "#,
     );
@@ -3041,18 +3056,16 @@ function assert(cond) {
     throw Error("assert");
   }
 }
-
 function main() {
   assert(false);
 }
-
 main();
         "#,
     );
     let expected_error = r#"Error: assert
     at assert (error_stack.js:4:11)
-    at main (error_stack.js:9:3)
-    at error_stack.js:12:1"#;
+    at main (error_stack.js:8:3)
+    at error_stack.js:10:1"#;
     assert_eq!(result.unwrap_err().to_string(), expected_error);
   }
 
@@ -3070,7 +3083,6 @@ main();
       throw new Error("async");
     });
   })();
-
   try {
     await p;
   } catch (error) {
@@ -3083,7 +3095,7 @@ main();
       let expected_error = r#"Error: async
     at error_async_stack.js:5:13
     at async error_async_stack.js:4:5
-    at async error_async_stack.js:10:5"#;
+    at async error_async_stack.js:9:5"#;
 
       match runtime.poll_event_loop(cx, false) {
         Poll::Ready(Err(e)) => {
@@ -3176,7 +3188,6 @@ function assertEquals(a, b) {
 const sab = new SharedArrayBuffer(16);
 const i32a = new Int32Array(sab);
 globalThis.resolved = false;
-
 (function() {
   const result = Atomics.waitAsync(i32a, 0, 0);
   result.value.then(
@@ -3184,7 +3195,6 @@ globalThis.resolved = false;
     () => { assertUnreachable();
   });
 })();
-
 const notify_return_value = Atomics.notify(i32a, 0, 1);
 assertEquals(1, notify_return_value);
 "#,
@@ -3294,7 +3304,7 @@ assertEquals(1, notify_return_value);
     runtime
       .execute_script(
         "op_async_borrow.js",
-        "Deno.core.opAsync('op_async_borrow')",
+        "Deno.core.initializeAsyncOps(); Deno.core.ops.op_async_borrow()",
       )
       .unwrap();
     runtime.run_event_loop(false).await.unwrap();
@@ -3368,7 +3378,8 @@ Deno.core.ops.op_sync_serialize_object_with_numbers_as_keys({
       .execute_script(
         "op_async_serialize_object_with_numbers_as_keys.js",
         r#"
-Deno.core.opAsync('op_async_serialize_object_with_numbers_as_keys', {
+Deno.core.initializeAsyncOps();
+Deno.core.ops.op_async_serialize_object_with_numbers_as_keys({
   lines: {
     100: {
       unit: "m"
@@ -3406,6 +3417,7 @@ Deno.core.opAsync('op_async_serialize_object_with_numbers_as_keys', {
       .execute_script(
         "macrotasks_and_nextticks.js",
         r#"
+        Deno.core.initializeAsyncOps();
         (async function () {
           const results = [];
           Deno.core.ops.op_set_macrotask_callback(() => {
@@ -3416,7 +3428,6 @@ Deno.core.opAsync('op_async_serialize_object_with_numbers_as_keys', {
             results.push("nextTick");
             Deno.core.ops.op_set_has_tick_scheduled(false);
           });
-
           Deno.core.ops.op_set_has_tick_scheduled(true);
           await Deno.core.opAsync('op_async_sleep');
           if (results[0] != "nextTick") {
@@ -3627,7 +3638,6 @@ Deno.core.opAsync('op_async_serialize_object_with_numbers_as_keys', {
           Deno.core.ops.op_store_pending_promise_exception(promise);
           Deno.core.ops.op_promise_reject();
         });
-
         new Promise((_, reject) => reject(Error("reject")));
         "#,
       )
@@ -3645,7 +3655,6 @@ Deno.core.opAsync('op_async_serialize_object_with_numbers_as_keys', {
             prev(...args);
           });
         }
-
         new Promise((_, reject) => reject(Error("reject")));
         "#,
       )
@@ -3695,7 +3704,6 @@ Deno.core.opAsync('op_async_serialize_object_with_numbers_as_keys', {
         Deno.core.ops.op_set_promise_reject_callback((type, promise, reason) => {
           Deno.core.ops.op_promise_reject();
         });
-
         throw new Error('top level throw');
         "#;
 
@@ -3826,8 +3834,6 @@ Deno.core.opAsync('op_async_serialize_object_with_numbers_as_keys', {
         const a1b = a1.subarray(0, 3);
         const a2 = new Uint8Array([5,10,15]);
         const a2b = a2.subarray(0, 3);
-
-
         if (!(a1.length > 0 && a1b.length > 0)) {
           throw new Error("a1 & a1b should have a length");
         }
@@ -3838,7 +3844,6 @@ Deno.core.opAsync('op_async_serialize_object_with_numbers_as_keys', {
         if (a1.length > 0 || a1b.length > 0) {
           throw new Error("expecting a1 & a1b to be detached");
         }
-
         const a3 = Deno.core.ops.op_boomerang(a2b);
         if (a3.byteLength != 3) {
           throw new Error(`Expected a3.byteLength === 3, got ${a3.byteLength}`);
@@ -3849,7 +3854,6 @@ Deno.core.opAsync('op_async_serialize_object_with_numbers_as_keys', {
         if (a2.byteLength > 0 || a2b.byteLength > 0) {
           throw new Error("expecting a2 & a2b to be detached, a3 re-attached");
         }
-
         const wmem = new WebAssembly.Memory({ initial: 1, maximum: 2 });
         const w32 = new Uint32Array(wmem.buffer);
         w32[0] = 1; w32[1] = 2; w32[2] = 3;

ops/lib.rs

@@ -118,7 +118,7 @@ pub fn op(attr: TokenStream, item: TokenStream) -> TokenStream {
   let (has_fallible_fast_call, fast_impl, fast_field) =
     codegen_fast_impl(&core, &func, name, is_async, must_be_fast);
 
-  let v8_body = if is_async {
+  let (v8_body, argc) = if is_async {
     codegen_v8_async(&core, &func, margs, asyncness, deferred)
   } else {
     codegen_v8_sync(&core, &func, margs, has_fallible_fast_call)
@@ -154,6 +154,7 @@ pub fn op(attr: TokenStream, item: TokenStream) -> TokenStream {
           is_async: #is_async,
           is_unstable: #is_unstable,
           is_v8: #is_v8,
+          argc: #argc,
         }
       }
 
@@ -181,7 +182,7 @@ fn codegen_v8_async(
   margs: MacroArgs,
   asyncness: bool,
   deferred: bool,
-) -> TokenStream2 {
+) -> (TokenStream2, usize) {
   let MacroArgs { is_v8, .. } = margs;
   let special_args = f
     .sig
@@ -194,7 +195,7 @@ fn codegen_v8_async(
   let rust_i0 = special_args.len();
   let args_head = special_args.into_iter().collect::<TokenStream2>();
 
-  let (arg_decls, args_tail) = codegen_args(core, f, rust_i0, 1);
+  let (arg_decls, args_tail, argc) = codegen_args(core, f, rust_i0, 1);
   let type_params = exclude_lifetime_params(&f.sig.generics.params);
 
   let (pre_result, mut result_fut) = match asyncness {
@@ -225,44 +226,47 @@ fn codegen_v8_async(
     false => quote! { let result = Ok(result); },
   };
 
-  quote! {
-    use #core::futures::FutureExt;
-    // SAFETY: #core guarantees args.data() is a v8 External pointing to an OpCtx for the isolates lifetime
-    let ctx = unsafe {
-      &*(#core::v8::Local::<#core::v8::External>::cast(args.data()).value()
-      as *const #core::_ops::OpCtx)
-    };
-    let op_id = ctx.id;
+  (
+    quote! {
+      use #core::futures::FutureExt;
+      // SAFETY: #core guarantees args.data() is a v8 External pointing to an OpCtx for the isolates lifetime
+      let ctx = unsafe {
+        &*(#core::v8::Local::<#core::v8::External>::cast(args.data()).value()
+        as *const #core::_ops::OpCtx)
+      };
+      let op_id = ctx.id;
 
-    let promise_id = args.get(0);
-    let promise_id = #core::v8::Local::<#core::v8::Integer>::try_from(promise_id)
-      .map(|l| l.value() as #core::PromiseId)
-      .map_err(#core::anyhow::Error::from);
-    // Fail if promise id invalid (not an int)
-    let promise_id: #core::PromiseId = match promise_id {
-      Ok(promise_id) => promise_id,
-      Err(err) => {
-        #core::_ops::throw_type_error(scope, format!("invalid promise id: {}", err));
-        return;
-      }
-    };
+      let promise_id = args.get(0);
+      let promise_id = #core::v8::Local::<#core::v8::Integer>::try_from(promise_id)
+        .map(|l| l.value() as #core::PromiseId)
+        .map_err(#core::anyhow::Error::from);
+      // Fail if promise id invalid (not an int)
+      let promise_id: #core::PromiseId = match promise_id {
+        Ok(promise_id) => promise_id,
+        Err(err) => {
+          #core::_ops::throw_type_error(scope, format!("invalid promise id: {}", err));
+          return;
+        }
+      };
 
-    #arg_decls
+      #arg_decls
 
-    // Track async call & get copy of get_error_class_fn
-    let get_class = {
-      let state = ::std::cell::RefCell::borrow(&ctx.state);
-      state.tracker.track_async(op_id);
-      state.get_error_class_fn
-    };
+      // Track async call & get copy of get_error_class_fn
+      let get_class = {
+        let state = ::std::cell::RefCell::borrow(&ctx.state);
+        state.tracker.track_async(op_id);
+        state.get_error_class_fn
+      };
 
-    #pre_result
-    #core::_ops::queue_async_op(ctx, scope, #deferred, async move {
-      let result = #result_fut
-      #result_wrapper
-      (promise_id, op_id, #core::_ops::to_op_result(get_class, result))
-    });
-  }
+      #pre_result
+      #core::_ops::queue_async_op(ctx, scope, #deferred, async move {
+        let result = #result_fut
+        #result_wrapper
+        (promise_id, op_id, #core::_ops::to_op_result(get_class, result))
+      });
+    },
+    argc,
+  )
 }
 
 fn scope_arg(arg: &FnArg) -> Option<TokenStream2> {
@@ -516,7 +520,7 @@ fn codegen_v8_sync(
   f: &syn::ItemFn,
   margs: MacroArgs,
   has_fallible_fast_call: bool,
-) -> TokenStream2 {
+) -> (TokenStream2, usize) {
   let MacroArgs { is_v8, .. } = margs;
   let special_args = f
     .sig
@@ -528,7 +532,7 @@ fn codegen_v8_sync(
     .collect::<Vec<_>>();
   let rust_i0 = special_args.len();
   let args_head = special_args.into_iter().collect::<TokenStream2>();
-  let (arg_decls, args_tail) = codegen_args(core, f, rust_i0, 0);
+  let (arg_decls, args_tail, argc) = codegen_args(core, f, rust_i0, 0);
   let ret = codegen_sync_ret(core, &f.sig.output);
   let type_params = exclude_lifetime_params(&f.sig.generics.params);
 
@@ -547,24 +551,27 @@ fn codegen_v8_sync(
     quote! {}
   };
 
-  quote! {
-    // SAFETY: #core guarantees args.data() is a v8 External pointing to an OpCtx for the isolates lifetime
-    let ctx = unsafe {
-      &*(#core::v8::Local::<#core::v8::External>::cast(args.data()).value()
-      as *const #core::_ops::OpCtx)
-    };
+  (
+    quote! {
+      // SAFETY: #core guarantees args.data() is a v8 External pointing to an OpCtx for the isolates lifetime
+      let ctx = unsafe {
+        &*(#core::v8::Local::<#core::v8::External>::cast(args.data()).value()
+        as *const #core::_ops::OpCtx)
+      };
 
-    #fast_error_handler
-    #arg_decls
+      #fast_error_handler
+      #arg_decls
 
-    let result = Self::call::<#type_params>(#args_head #args_tail);
+      let result = Self::call::<#type_params>(#args_head #args_tail);
 
-    // use RefCell::borrow instead of state.borrow to avoid clash with std::borrow::Borrow
-    let op_state = ::std::cell::RefCell::borrow(&*ctx.state);
-    op_state.tracker.track_sync(ctx.id);
+      // use RefCell::borrow instead of state.borrow to avoid clash with std::borrow::Borrow
+      let op_state = ::std::cell::RefCell::borrow(&*ctx.state);
+      op_state.tracker.track_sync(ctx.id);
 
-    #ret
-  }
+      #ret
+    },
+    argc,
+  )
 }
 
 struct FastApiSyn {
@@ -803,12 +810,15 @@ fn is_fast_scalar(
   }
 }
 
+/// (full declarations, idents, v8 argument count)
+type ArgumentDecl = (TokenStream2, TokenStream2, usize);
+
 fn codegen_args(
   core: &TokenStream2,
   f: &syn::ItemFn,
   rust_i0: usize, // Index of first generic arg in rust
   v8_i0: usize,   // Index of first generic arg in v8/js
-) -> (TokenStream2, TokenStream2) {
+) -> ArgumentDecl {
   let inputs = &f.sig.inputs.iter().skip(rust_i0).enumerate();
   let ident_seq: TokenStream2 = inputs
     .clone()
@@ -823,7 +833,7 @@ fn codegen_args(
       codegen_arg(core, arg, format!("arg_{i}").as_ref(), v8_i0 + i)
     })
     .collect();
-  (decls, ident_seq)
+  (decls, ident_seq, inputs.len())
 }
 
 fn codegen_arg(

runtime/js/99_main.js

@@ -692,6 +692,7 @@ delete Intl.v8BreakIterator;
       throw new Error("Worker runtime already bootstrapped");
     }
 
+    core.initializeAsyncOps();
     performance.setTimeOrigin(DateNow());
     net.setup(runtimeOptions.unstableFlag);
 
@@ -791,6 +792,7 @@ delete Intl.v8BreakIterator;
       throw new Error("Worker runtime already bootstrapped");
     }
 
+    core.initializeAsyncOps();
     performance.setTimeOrigin(DateNow());
     net.setup(runtimeOptions.unstableFlag);