4 files changed, 59 insertions, 9 deletions
diff --git a/core/01_core.js b/core/01_core.js
index 156300327..21376b695 100644
--- a/core/01_core.js
+++ b/core/01_core.js
@@ -268,6 +268,10 @@
     terminate: opSync.bind(null, "op_terminate"),
     opNames: opSync.bind(null, "op_op_names"),
     eventLoopHasMoreWork: opSync.bind(null, "op_event_loop_has_more_work"),
+    setPromiseRejectCallback: opSync.bind(
+      null,
+      "op_set_promise_reject_callback",
+    ),
   });
 
   ObjectAssign(globalThis.__bootstrap, { core });
diff --git a/core/bindings.rs b/core/bindings.rs
index a88e54af7..47632d00d 100644
--- a/core/bindings.rs
+++ b/core/bindings.rs
@@ -282,14 +282,6 @@ pub extern "C" fn promise_reject_callback(message: v8::PromiseRejectMessage) {
   let state_rc = JsRuntime::state(scope);
   let mut state = state_rc.borrow_mut();
 
-  // Node compat: perform synchronous process.emit("unhandledRejection").
-  //
-  // Note the callback follows the (type, promise, reason) signature of Node's
-  // internal promiseRejectHandler from lib/internal/process/promises.js, not
-  // the (promise, reason) signature of the "unhandledRejection" event listener.
-  //
-  // Short-circuits Deno's regular unhandled rejection logic because that's
-  // a) asynchronous, and b) always terminates.
   if let Some(js_promise_reject_cb) = state.js_promise_reject_cb.clone() {
     let js_uncaught_exception_cb = state.js_uncaught_exception_cb.clone();
     drop(state); // Drop borrow, callbacks can call back into runtime.
@@ -323,6 +315,7 @@ pub extern "C" fn promise_reject_callback(message: v8::PromiseRejectMessage) {
     }
 
     if tc_scope.has_caught() {
+      // TODO(bartlomieju): ensure that TODO provided below is still valid.
       // If we get here, an exception was thrown by the unhandledRejection
       // handler and there is ether no uncaughtException handler or the
       // handler threw an exception of its own.
@@ -340,7 +333,6 @@ pub extern "C" fn promise_reject_callback(message: v8::PromiseRejectMessage) {
   } else {
     let promise = message.get_promise();
     let promise_global = v8::Global::new(scope, promise);
-
     match message.get_event() {
       PromiseRejectWithNoHandler => {
         let error = message.get_value().unwrap();
diff --git a/core/ops_builtin.rs b/core/ops_builtin.rs
index a42c0bae8..53f2bd706 100644
--- a/core/ops_builtin.rs
+++ b/core/ops_builtin.rs
@@ -38,6 +38,7 @@ pub(crate) fn init_builtins() -> Extension {
       op_metrics::decl(),
       op_format_file_name::decl(),
       op_is_proxy::decl(),
+      op_next_task::decl(),
     ])
     .ops(crate::ops_builtin_v8::init_builtins_v8())
     .build()
@@ -189,3 +190,8 @@ fn op_format_file_name(file_name: String) -> String {
 fn op_is_proxy(value: serde_v8::Value) -> bool {
   value.v8_value.is_proxy()
 }
+
+/// Empty op that when awaited forces a macrotask to run. Useful for
+/// "unhandledrejection" event.
+#[op]
+async fn op_next_task() {}
diff --git a/core/ops_builtin_v8.rs b/core/ops_builtin_v8.rs
index 4bc80faa5..8af50f860 100644
--- a/core/ops_builtin_v8.rs
+++ b/core/ops_builtin_v8.rs
@@ -48,6 +48,9 @@ pub(crate) fn init_builtins_v8() -> Vec<OpDecl> {
     op_apply_source_map::decl(),
     op_set_format_exception_callback::decl(),
     op_event_loop_has_more_work::decl(),
+    op_store_pending_promise_exception::decl(),
+    op_remove_pending_promise_exception::decl(),
+    op_has_pending_promise_exception::decl(),
   ]
 }
 
@@ -810,3 +813,48 @@ fn op_event_loop_has_more_work(scope: &mut v8::HandleScope) -> bool {
     || has_pending_background_tasks
     || has_tick_scheduled
 }
+
+#[op(v8)]
+fn op_store_pending_promise_exception<'a>(
+  scope: &mut v8::HandleScope<'a>,
+  promise: serde_v8::Value<'a>,
+  reason: serde_v8::Value<'a>,
+) {
+  let state_rc = JsRuntime::state(scope);
+  let mut state = state_rc.borrow_mut();
+  let promise_value =
+    v8::Local::<v8::Promise>::try_from(promise.v8_value).unwrap();
+  let promise_global = v8::Global::new(scope, promise_value);
+  let error_global = v8::Global::new(scope, reason.v8_value);
+  state
+    .pending_promise_exceptions
+    .insert(promise_global, error_global);
+}
+
+#[op(v8)]
+fn op_remove_pending_promise_exception<'a>(
+  scope: &mut v8::HandleScope<'a>,
+  promise: serde_v8::Value<'a>,
+) {
+  let state_rc = JsRuntime::state(scope);
+  let mut state = state_rc.borrow_mut();
+  let promise_value =
+    v8::Local::<v8::Promise>::try_from(promise.v8_value).unwrap();
+  let promise_global = v8::Global::new(scope, promise_value);
+  state.pending_promise_exceptions.remove(&promise_global);
+}
+
+#[op(v8)]
+fn op_has_pending_promise_exception<'a>(
+  scope: &mut v8::HandleScope<'a>,
+  promise: serde_v8::Value<'a>,
+) -> bool {
+  let state_rc = JsRuntime::state(scope);
+  let state = state_rc.borrow();
+  let promise_value =
+    v8::Local::<v8::Promise>::try_from(promise.v8_value).unwrap();
+  let promise_global = v8::Global::new(scope, promise_value);
+  state
+    .pending_promise_exceptions
+    .contains_key(&promise_global)
+}