feat: add "unhandledrejection" event support (denoland#12994)

This commit adds support for "unhandledrejection" event.

This event will trigger event listeners registered using:

"globalThis.addEventListener("unhandledrejection")
"globalThis.onunhandledrejection"
This is done by registering a default handler using
"Deno.core.setPromiseRejectCallback" that allows to
handle rejected promises in JavaScript instead of Rust.

This commit will make it possible to polyfill
"process.on("unhandledRejection")" in the Node compat
layer.

Co-authored-by: Colin Ihrig <[email protected]>

cli/dts/lib.deno.shared_globals.d.ts

@@ -400,6 +400,17 @@ declare class ErrorEvent extends Event {
   constructor(type: string, eventInitDict?: ErrorEventInit);
 }
 
+interface PromiseRejectionEventInit extends EventInit {
+  promise: Promise<any>;
+  reason?: any;
+}
+
+declare class PromiseRejectionEvent extends Event {
+  readonly promise: Promise<any>;
+  readonly reason: any;
+  constructor(type: string, eventInitDict?: PromiseRejectionEventInit);
+}
+
 interface AbstractWorkerEventMap {
   "error": ErrorEvent;
 }

cli/tests/integration/run_tests.rs

@@ -2744,3 +2744,8 @@ itest!(followup_dyn_import_resolved {
   args: "run --unstable --allow-read followup_dyn_import_resolves/main.ts",
   output: "followup_dyn_import_resolves/main.ts.out",
 });
+
+itest!(unhandled_rejection {
+  args: "run --allow-read unhandled_rejection.js",
+  output: "unhandled_rejection.js.out",
+});

cli/tests/testdata/unhandled_rejection.js

@@ -0,0 +1,11 @@
+globalThis.addEventListener("unhandledrejection", (e) => {
+  console.log("unhandled rejection at:", e.promise, "reason:", e.reason);
+  e.preventDefault();
+});
+
+function Foo() {
+  this.bar = Promise.reject(new Error("bar not available"));
+}
+
+new Foo();
+Promise.reject();

cli/tests/testdata/unhandled_rejection.js.out

@@ -0,0 +1,8 @@
+unhandled rejection at: Promise {
+  <rejected> Error: bar not available
+    at new Foo (file:///[WILDCARD]/testdata/unhandled_rejection.js:7:29)
+    at file:///[WILDCARD]/testdata/unhandled_rejection.js:10:1
+} reason: Error: bar not available
+    at new Foo (file:///[WILDCARD]/testdata/unhandled_rejection.js:7:29)
+    at file:///[WILDCARD]/testdata/unhandled_rejection.js:10:1
+unhandled rejection at: Promise { <rejected> undefined } reason: undefined

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 });

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();

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() {}

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)
+}

ext/web/02_event.js

@@ -1278,6 +1278,58 @@
     [SymbolToStringTag] = "ProgressEvent";
   }
 
+  class PromiseRejectionEvent extends Event {
+    #promise = null;
+    #reason = null;
+
+    get promise() {
+      return this.#promise;
+    }
+    get reason() {
+      return this.#reason;
+    }
+
+    constructor(
+      type,
+      {
+        bubbles,
+        cancelable,
+        composed,
+        promise,
+        reason,
+      } = {},
+    ) {
+      super(type, {
+        bubbles: bubbles,
+        cancelable: cancelable,
+        composed: composed,
+      });
+
+      this.#promise = promise;
+      this.#reason = reason;
+    }
+
+    [SymbolFor("Deno.privateCustomInspect")](inspect) {
+      return inspect(consoleInternal.createFilteredInspectProxy({
+        object: this,
+        evaluate: this instanceof PromiseRejectionEvent,
+        keys: [
+          ...EVENT_PROPS,
+          "promise",
+          "reason",
+        ],
+      }));
+    }
+
+    // TODO(lucacasonato): remove when this interface is spec aligned
+    [SymbolToStringTag] = "PromiseRejectionEvent";
+  }
+
+  defineEnumerableProps(PromiseRejectionEvent, [
+    "promise",
+    "reason",
+  ]);
+
   const _eventHandlers = Symbol("eventHandlers");
 
   function makeWrappedHandler(handler, isSpecialErrorEventHandler) {
@@ -1426,6 +1478,7 @@
   window.MessageEvent = MessageEvent;
   window.CustomEvent = CustomEvent;
   window.ProgressEvent = ProgressEvent;
+  window.PromiseRejectionEvent = PromiseRejectionEvent;
   window.dispatchEvent = EventTarget.prototype.dispatchEvent;
   window.addEventListener = EventTarget.prototype.addEventListener;
   window.removeEventListener = EventTarget.prototype.removeEventListener;

runtime/js/99_main.js

@@ -411,6 +411,7 @@ delete Intl.v8BreakIterator;
     PerformanceEntry: util.nonEnumerable(performance.PerformanceEntry),
     PerformanceMark: util.nonEnumerable(performance.PerformanceMark),
     PerformanceMeasure: util.nonEnumerable(performance.PerformanceMeasure),
+    PromiseRejectionEvent: util.nonEnumerable(PromiseRejectionEvent),
     ProgressEvent: util.nonEnumerable(ProgressEvent),
     ReadableStream: util.nonEnumerable(streams.ReadableStream),
     ReadableStreamDefaultReader: util.nonEnumerable(
@@ -553,6 +554,43 @@ delete Intl.v8BreakIterator;
     postMessage: util.writable(postMessage),
   };
 
+  function promiseRejectCallback(type, promise, reason) {
+    switch (type) {
+      case 0: {
+        core.opSync("op_store_pending_promise_exception", promise, reason);
+        break;
+      }
+      case 1: {
+        core.opSync("op_remove_pending_promise_exception", promise);
+        break;
+      }
+      default:
+        return;
+    }
+    core.opAsync("op_next_task").then(() => {
+      const hasPendingException = core.opSync(
+        "op_has_pending_promise_exception",
+        promise,
+      );
+
+      if (!hasPendingException) {
+        return;
+      }
+
+      const event = new PromiseRejectionEvent("unhandledrejection", {
+        cancelable: true,
+        promise,
+        reason,
+      });
+      globalThis.dispatchEvent(event);
+
+      // If event was not prevented we will let Rust side handle it.
+      if (event.defaultPrevented) {
+        core.opSync("op_remove_pending_promise_exception", promise);
+      }
+    });
+  }
+
   let hasBootstrapped = false;
 
   function bootstrapMainRuntime(runtimeOptions) {
@@ -585,6 +623,10 @@ delete Intl.v8BreakIterator;
     defineEventHandler(window, "load");
     defineEventHandler(window, "beforeunload");
     defineEventHandler(window, "unload");
+    defineEventHandler(window, "unhandledrejection");
+
+    core.setPromiseRejectCallback(promiseRejectCallback);
+
     const isUnloadDispatched = SymbolFor("isUnloadDispatched");
     // Stores the flag for checking whether unload is dispatched or not.
     // This prevents the recursive dispatches of unload events.
@@ -685,6 +727,10 @@ delete Intl.v8BreakIterator;
 
     defineEventHandler(self, "message");
     defineEventHandler(self, "error", undefined, true);
+    defineEventHandler(self, "unhandledrejection");
+
+    core.setPromiseRejectCallback(promiseRejectCallback);
+
     // `Deno.exit()` is an alias to `self.close()`. Setting and exit
     // code using an op in worker context is a no-op.
     os.setExitHandler((_exitCode) => {

tools/wpt/expectation.json

@@ -4360,7 +4360,6 @@
           "The CanvasPath interface object should be exposed.",
           "The TextMetrics interface object should be exposed.",
           "The Path2D interface object should be exposed.",
-          "The PromiseRejectionEvent interface object should be exposed.",
           "The EventSource interface object should be exposed.",
           "The XMLHttpRequestEventTarget interface object should be exposed.",
           "The XMLHttpRequestUpload interface object should be exposed.",