[d8] Exit with error code upon unhandled promise rejection

With this CL d8 exits with an error code if there is an unhandled
promise rejection, e.g. due tue a failed assertion in a promise. Up
until now these assertions were just ignored.

Bug: v8:10556
Change-Id: I25f20e4be45a2de130562deb15f6a144f0ac976f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2238569Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68503}

src/d8/d8.cc

@@ -12,6 +12,7 @@
 #include <iomanip>
 #include <iterator>
 #include <string>
+#include <tuple>
 #include <unordered_map>
 #include <utility>
 #include <vector>
@@ -464,6 +465,7 @@ std::map<v8::Isolate*, int> Shell::isolate_running_streaming_tasks_;
 base::LazyMutex Shell::cached_code_mutex_;
 std::map<std::string, std::unique_ptr<ScriptCompiler::CachedData>>
     Shell::cached_code_map_;
+std::atomic<int> Shell::unhandled_promise_rejections_{0};
 
 Global<Context> Shell::evaluation_context_;
 ArrayBuffer::Allocator* Shell::array_buffer_allocator;
@@ -665,7 +667,10 @@ bool Shell::ExecuteString(Isolate* isolate, Local<String> source,
       StoreInCodeCache(isolate, source, cached_data);
       delete cached_data;
     }
-    if (process_message_queue && !EmptyMessageQueues(isolate)) success = false;
+    if (process_message_queue) {
+      if (!EmptyMessageQueues(isolate)) success = false;
+      if (!HandleUnhandledPromiseRejections(isolate)) success = false;
+    }
     data->realm_current_ = data->realm_switch_;
   }
   Local<Value> result;
@@ -1161,6 +1166,45 @@ MaybeLocal<Context> PerIsolateData::GetTimeoutContext() {
   return result;
 }
 
+void PerIsolateData::RemoveUnhandledPromise(Local<Promise> promise) {
+  // Remove handled promises from the list
+  DCHECK_EQ(promise->GetIsolate(), isolate_);
+  for (auto it = unhandled_promises_.begin(); it != unhandled_promises_.end();
+       ++it) {
+    v8::Local<v8::Promise> unhandled_promise = std::get<0>(*it).Get(isolate_);
+    if (unhandled_promise == promise) {
+      unhandled_promises_.erase(it--);
+    }
+  }
+}
+
+void PerIsolateData::AddUnhandledPromise(Local<Promise> promise,
+                                         Local<Message> message,
+                                         Local<Value> exception) {
+  DCHECK_EQ(promise->GetIsolate(), isolate_);
+  unhandled_promises_.push_back(
+      std::make_tuple(v8::Global<v8::Promise>(isolate_, promise),
+                      v8::Global<v8::Message>(isolate_, message),
+                      v8::Global<v8::Value>(isolate_, exception)));
+}
+
+size_t PerIsolateData::GetUnhandledPromiseCount() {
+  return unhandled_promises_.size();
+}
+
+int PerIsolateData::HandleUnhandledPromiseRejections() {
+  int unhandled_promises_count = 0;
+  v8::HandleScope scope(isolate_);
+  for (auto& tuple : unhandled_promises_) {
+    Local<v8::Message> message = std::get<1>(tuple).Get(isolate_);
+    Local<v8::Value> value = std::get<2>(tuple).Get(isolate_);
+    Shell::ReportException(isolate_, message, value);
+    unhandled_promises_count++;
+  }
+  unhandled_promises_.clear();
+  return unhandled_promises_count;
+}
+
 PerIsolateData::RealmScope::RealmScope(PerIsolateData* data) : data_(data) {
   data_->realm_count_ = 1;
   data_->realm_current_ = 0;
@@ -2159,8 +2203,50 @@ static void PrintMessageCallback(Local<Message> message, Local<Value> error) {
   printf("%s:%i: %s\n", filename_string, linenum, msg_string);
 }
 
+void Shell::PromiseRejectCallback(v8::PromiseRejectMessage data) {
+  if (options.ignore_unhandled_promises) return;
+  if (data.GetEvent() == v8::kPromiseRejectAfterResolved ||
+      data.GetEvent() == v8::kPromiseResolveAfterResolved) {
+    // Ignore reject/resolve after resolved.
+    return;
+  }
+  v8::Local<v8::Promise> promise = data.GetPromise();
+  v8::Isolate* isolate = promise->GetIsolate();
+  PerIsolateData* isolate_data = PerIsolateData::Get(isolate);
+
+  if (data.GetEvent() == v8::kPromiseHandlerAddedAfterReject) {
+    isolate_data->RemoveUnhandledPromise(promise);
+    return;
+  }
+
+  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  bool capture_exceptions =
+      i_isolate->get_capture_stack_trace_for_uncaught_exceptions();
+  isolate->SetCaptureStackTraceForUncaughtExceptions(true);
+  v8::Local<Value> exception = data.GetValue();
+  v8::Local<Message> message;
+  // Assume that all objects are stack-traces.
+  if (exception->IsObject()) {
+    message = v8::Exception::CreateMessage(isolate, exception);
+  }
+  if (!exception->IsNativeError() &&
+      (message.IsEmpty() || message->GetStackTrace().IsEmpty())) {
+    // If there is no real Error object, manually throw and catch a stack trace.
+    v8::TryCatch try_catch(isolate);
+    try_catch.SetVerbose(true);
+    isolate->ThrowException(v8::Exception::Error(
+        v8::String::NewFromUtf8Literal(isolate, "Unhandled Promise.")));
+    message = try_catch.Message();
+    exception = try_catch.Exception();
+  }
+  isolate->SetCaptureStackTraceForUncaughtExceptions(capture_exceptions);
+
+  isolate_data->AddUnhandledPromise(promise, message, exception);
+}
+
 void Shell::Initialize(Isolate* isolate, D8Console* console,
                        bool isOnMainThread) {
+  isolate->SetPromiseRejectCallback(PromiseRejectCallback);
   if (isOnMainThread) {
     // Set up counters
     if (i::FLAG_map_counters[0] != '\0') {
@@ -2968,9 +3054,7 @@ void Worker::ExecuteInThread() {
               in_semaphore_.Wait();
               std::unique_ptr<SerializationData> data;
               if (!in_queue_.Dequeue(&data)) continue;
-              if (!data) {
-                break;
-              }
+              if (!data) break;
               v8::TryCatch try_catch(isolate);
               try_catch.SetVerbose(true);
               HandleScope scope(isolate);
@@ -2983,6 +3067,7 @@ void Worker::ExecuteInThread() {
                 USE(result);
               }
             }
+            // TODO(cbruni): Check for unhandled promises here.
           }
         }
       }
@@ -3083,6 +3168,9 @@ bool Shell::SetOptions(int argc, char* argv[]) {
       // Ignore any -f flags for compatibility with other stand-alone
       // JavaScript engines.
       continue;
+    } else if (strcmp(argv[i], "--ignore-unhandled-promises") == 0) {
+      options.ignore_unhandled_promises = true;
+      argv[i] = nullptr;
     } else if (strcmp(argv[i], "--isolate") == 0) {
       options.num_isolates++;
     } else if (strcmp(argv[i], "--throws") == 0) {
@@ -3240,6 +3328,7 @@ int Shell::RunMain(Isolate* isolate, bool last_run) {
       PerIsolateData::RealmScope realm_scope(PerIsolateData::Get(isolate));
       if (!options.isolate_sources[0].Execute(isolate)) success = false;
       if (!CompleteMessageLoop(isolate)) success = false;
+      if (!HandleUnhandledPromiseRejections(isolate)) success = false;
     }
     if (!use_existing_context) {
       DisposeModuleEmbedderData(context);
@@ -3267,6 +3356,11 @@ int Shell::RunMain(Isolate* isolate, bool last_run) {
     }
   }
   WaitForRunningWorkers();
+  if (Shell::unhandled_promise_rejections_.load() > 0) {
+    printf("%i pending unhandled Promise rejection(s) detected.\n",
+           Shell::unhandled_promise_rejections_.load());
+    success = false;
+  }
   // In order to finish successfully, success must be != expected_to_throw.
   return success == Shell::options.expected_to_throw ? 1 : 0;
 }
@@ -3389,6 +3483,15 @@ void Shell::PostBlockingBackgroundTask(std::unique_ptr<Task> task) {
   g_default_platform->CallBlockingTaskOnWorkerThread(std::move(task));
 }
 
+bool Shell::HandleUnhandledPromiseRejections(Isolate* isolate) {
+  if (options.ignore_unhandled_promises) return true;
+  PerIsolateData* data = PerIsolateData::Get(isolate);
+  int count = data->HandleUnhandledPromiseRejections();
+  Shell::unhandled_promise_rejections_.store(
+      Shell::unhandled_promise_rejections_.load() + count);
+  return count == 0;
+}
+
 class Serializer : public ValueSerializer::Delegate {
  public:
   explicit Serializer(Isolate* isolate)

src/d8/d8.h

@@ -234,6 +234,12 @@ class PerIsolateData {
 
   AsyncHooks* GetAsyncHooks() { return async_hooks_wrapper_; }
 
+  void RemoveUnhandledPromise(Local<Promise> promise);
+  void AddUnhandledPromise(Local<Promise> promise, Local<Message> message,
+                           Local<Value> exception);
+  int HandleUnhandledPromiseRejections();
+  size_t GetUnhandledPromiseCount();
+
  private:
   friend class Shell;
   friend class RealmScope;
@@ -245,6 +251,8 @@ class PerIsolateData {
   Global<Value> realm_shared_;
   std::queue<Global<Function>> set_timeout_callbacks_;
   std::queue<Global<Context>> set_timeout_contexts_;
+  std::vector<std::tuple<Global<Promise>, Global<Message>, Global<Value>>>
+      unhandled_promises_;
   AsyncHooks* async_hooks_wrapper_;
 
   int RealmIndexOrThrow(const v8::FunctionCallbackInfo<v8::Value>& args,
@@ -272,6 +280,7 @@ class ShellOptions {
   bool interactive_shell = false;
   bool test_shell = false;
   bool expected_to_throw = false;
+  bool ignore_unhandled_promises = false;
   bool mock_arraybuffer_allocator = false;
   size_t mock_arraybuffer_allocator_limit = 0;
   bool multi_mapped_mock_allocator = false;
@@ -332,6 +341,8 @@ class Shell : public i::AllStatic {
   static bool EmptyMessageQueues(Isolate* isolate);
   static bool CompleteMessageLoop(Isolate* isolate);
 
+  static bool HandleUnhandledPromiseRejections(Isolate* isolate);
+
   static void PostForegroundTask(Isolate* isolate, std::unique_ptr<Task> task);
   static void PostBlockingBackgroundTask(std::unique_ptr<Task> task);
 
@@ -472,6 +483,8 @@ class Shell : public i::AllStatic {
   static void Initialize(Isolate* isolate, D8Console* console,
                          bool isOnMainThread = true);
 
+  static void PromiseRejectCallback(v8::PromiseRejectMessage reject_message);
+
  private:
   static Global<Context> evaluation_context_;
   static base::OnceType quit_once_;
@@ -521,6 +534,7 @@ class Shell : public i::AllStatic {
   static base::LazyMutex cached_code_mutex_;
   static std::map<std::string, std::unique_ptr<ScriptCompiler::CachedData>>
       cached_code_map_;
+  static std::atomic<int> unhandled_promise_rejections_;
 };
 
 }  // namespace v8

src/execution/isolate.cc

@@ -2516,6 +2516,10 @@ void Isolate::SetCaptureStackTraceForUncaughtExceptions(
   stack_trace_for_uncaught_exceptions_options_ = options;
 }
 
+bool Isolate::get_capture_stack_trace_for_uncaught_exceptions() const {
+  return capture_stack_trace_for_uncaught_exceptions_;
+}
+
 void Isolate::SetAbortOnUncaughtExceptionCallback(
     v8::Isolate::AbortOnUncaughtExceptionCallback callback) {
   abort_on_uncaught_exception_callback_ = callback;

src/execution/isolate.h

@@ -733,6 +733,7 @@ class V8_EXPORT_PRIVATE Isolate final : private HiddenFactory {
 
   void SetCaptureStackTraceForUncaughtExceptions(
       bool capture, int frame_limit, StackTrace::StackTraceOptions options);
+  bool get_capture_stack_trace_for_uncaught_exceptions() const;
 
   void SetAbortOnUncaughtExceptionCallback(
       v8::Isolate::AbortOnUncaughtExceptionCallback callback);

src/flags/flag-definitions.h

@@ -1448,7 +1448,6 @@ DEFINE_BOOL(dump_counters, false, "Dump counters on exit")
 DEFINE_BOOL(dump_counters_nvp, false,
             "Dump counters as name-value pairs on exit")
 DEFINE_BOOL(use_external_strings, false, "Use external strings for source code")
-
 DEFINE_STRING(map_counters, "", "Map counters to a file")
 DEFINE_BOOL(mock_arraybuffer_allocator, false,
             "Use a mock ArrayBuffer allocator for testing.")

test/debugger/debug/es6/debug-promises/promise-all-uncaught.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 // Test debug events when we only listen to uncaught exceptions and a
 // Promise p3 created by Promise.all has no catch handler, and is rejected

test/debugger/debug/es6/debug-promises/promise-any-uncaught.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
-// Flags: --harmony-promise-any
+// Flags: --harmony-promise-any --ignore-unhandled-promises
 
 // Test debug events when we only listen to uncaught exceptions and a
 // Promise p3 created by Promise.any has no catch handler, and is rejected

test/debugger/debug/es6/debug-promises/promise-race-uncaught.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 // Test debug events when we only listen to uncaught exceptions and a
 // Promise p3 created by Promise.race has no catch handler, and is rejected

test/debugger/debug/es6/debug-promises/proxy-as-promise.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+ // Flags: --ignore-unhandled-promises
 
 // Test debug events when we listen to all exceptions and
 // there is a catch handler for the exception thrown in a Promise.

test/debugger/debug/es6/debug-promises/reject-caught-by-default-reject-handler.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 // Test debug events when we only listen to uncaught exceptions and
 // there is only a default reject handler for the to-be-rejected Promise.

test/debugger/debug/es6/debug-promises/reject-in-constructor-opt.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 // Test exercises code paths for catching exceptions in the promise constructor
 // in conjunction with deoptimization.

test/debugger/debug/es6/debug-promises/reject-in-constructor.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 // Test debug events when we only listen to uncaught exceptions and
 // the Promise is rejected in the Promise constructor.

test/debugger/debug/es6/debug-promises/reject-uncaught-all.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 // Test debug events when we listen to all exceptions and
 // there is a catch handler for the to-be-rejected Promise.

test/debugger/debug/es6/debug-promises/reject-uncaught-late.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 // Test debug events when we only listen to uncaught exceptions and
 // there is a catch handler for the to-be-rejected Promise.

test/debugger/debug/es6/debug-promises/reject-uncaught-uncaught.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 // Test debug events when we only listen to uncaught exceptions and
 // there is no catch handler for the to-be-rejected Promise.

test/debugger/debug/es6/debug-promises/throw-caught-by-default-reject-handler.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 // Test debug events when we only listen to uncaught exceptions and
 // there is only a default reject handler for the to-be-rejected Promise.

test/debugger/debug/es6/debug-promises/throw-in-constructor.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 // Test debug events when we only listen to uncaught exceptions and
 // an exception is thrown in the Promise constructor.

test/debugger/debug/es6/debug-promises/throw-uncaught-all.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 // Test debug events when we listen to all exceptions and
 // there is no catch handler for the exception thrown in a Promise.

test/debugger/debug/es6/debug-promises/throw-uncaught-uncaught.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 // Test debug events when we only listen to uncaught exceptions and
 // there is a catch handler for the exception thrown in a Promise.

test/debugger/debug/es6/debug-promises/try-reject-in-constructor.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 // Test debug events when we only listen to uncaught exceptions and
 // the Promise is rejected within a try-catch in the Promise constructor.

test/debugger/debug/es6/debug-promises/try-throw-reject-in-constructor.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 // Test debug events when we only listen to uncaught exceptions and
 // an exception is thrown in the Promise constructor, but caught in an

test/debugger/debug/es8/async-debug-basic.js

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
+
 Debug = debug.Debug
 
 let listenerComplete = false;

test/debugger/debug/es8/async-debug-builtin-predictions.js

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
+
 Debug = debug.Debug
 
 var exception = null;

test/debugger/debug/es8/async-debug-caught-exception-cases.js

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
+
 Debug = debug.Debug
 
 let events = 0;

test/debugger/debug/es8/async-debug-caught-exception-cases0.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 // Files: test/debugger/debug/es8/async-debug-caught-exception-cases.js
 
 runPart(0);

test/debugger/debug/es8/async-debug-caught-exception-cases1.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 // Files: test/debugger/debug/es8/async-debug-caught-exception-cases.js
 
 runPart(1);

test/debugger/debug/es8/async-debug-caught-exception-cases2.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 // Files: test/debugger/debug/es8/async-debug-caught-exception-cases.js
 
 runPart(2);

test/debugger/debug/es8/async-debug-caught-exception-cases3.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 // Files: test/debugger/debug/es8/async-debug-caught-exception-cases.js
 
 runPart(3);

test/debugger/debug/es8/async-debug-caught-exception.js

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
+
 Debug = debug.Debug
 
 var exception = null;

test/debugger/debug/regress/regress-662935.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 Debug = debug.Debug
 function overflow() {

test/debugger/debug/regress/regress-crbug-568477-1.js

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
+
 
 var Debug = debug.Debug;
 var expected = ["debugger;", "var x = y;", "debugger;", "var x = y;"];

test/debugger/debug/regress/regress-crbug-568477-2.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 var Debug = debug.Debug;
 var expected = ["debugger;",

test/debugger/debug/regress/regress-crbug-568477-3.js

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
 
 var Debug = debug.Debug;
 var expected = ["debugger;", "var x = y;", "debugger;", "var x = y;"];

test/debugger/regress/regress-crbug-808973.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --allow-natives-syntax --enable-inspector
+// Flags: --allow-natives-syntax --enable-inspector --ignore-unhandled-promises
 
 const Debug = debug.Debug;
 Debug.setListener(() => {});

test/message/fail/modules-import-top-level-await-fail-1.mjs

@@ -4,6 +4,6 @@
 //
 // MODULE
 //
-// Flags: --harmony-top-level-await
+// Flags: --harmony-top-level-await --ignore-unhandled-promises
 
 import "modules-skip-1-top-level-await-fail.mjs"

test/message/fail/modules-import-top-level-await-fail-2.mjs

@@ -4,6 +4,6 @@
 //
 // MODULE
 //
-// Flags: --harmony-top-level-await
+// Flags: --harmony-top-level-await --ignore-unhandled-promises
 
 import "modules-skip-2-top-level-await-fail.mjs"

test/message/mjsunit/fail/assert-in-promise-fail.js

+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+load('test/mjsunit/mjsunit.js');
+
+Promise.resolve().then(() => {
+  assertEquals('foo', 'bar');
+});

test/message/mjsunit/fail/assert-in-promise-fail.out

+undefined:0: Failure: expected <"foo"> found <"bar">
+
+Stack: MjsUnitAssertionError
+    at assertEquals test/mjsunit/mjsunit.js {NUMBER}:{NUMBER}
+    at *%(basename)s 8:3
+
+
+MjsUnitAssertionError
+    at assertEquals test/mjsunit/mjsunit.js {NUMBER}:{NUMBER}
+    at *%(basename)s 8:3
+
+1 pending unhandled Promise rejection(s) detected.

test/mjsunit/compiler/promise-capability-default-closures.js

@@ -43,8 +43,8 @@
   var value;
   function foo(x) { return new Promise((resolve, reject) => reject(x)); }
   %PrepareFunctionForOptimization(foo);
-  foo(1);
-  foo(1);
+  foo(1).catch(() => { /* ignore */ });
+  foo(1).catch(() => { /* ignore */ });
   %OptimizeFunctionOnNextCall(foo);
   foo(1).catch(v => value = v);
   setTimeout(_ => assertEquals(1, value));

test/mjsunit/compiler/promise-constructor.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --allow-natives-syntax
+// Flags: --allow-natives-syntax --ignore-unhandled-promises
 
 // We have to patch mjsunit because normal assertion failures just throw
 // exceptions which are swallowed in a then clause.

test/mjsunit/compiler/regress-1092011.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --always-opt
+// Flags: --always-opt --ignore-unhandled-promises
 
 var __caught = 0;
 

test/mjsunit/compiler/regress-902608.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --allow-natives-syntax
+// Flags: --allow-natives-syntax --ignore-unhandled-promises
 
 async function f() {
   var a = [...new Int8Array([, ...new Uint8Array(65536)])];

test/mjsunit/es6/debug-promises/throw-with-undefined-reject.js

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 // A non-callable reject function throws eagerly
-
+var log = [];
 var p = new Promise(function(resolve, reject) {
   log.push("resolve");
   resolve();

test/mjsunit/es6/promises.js

@@ -25,7 +25,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Flags: --allow-natives-syntax
+// Flags: --allow-natives-syntax --ignore-unhandled-promises
 
 // Make sure we don't rely on functions patchable by monkeys.
 var call = Function.prototype.call.call.bind(Function.prototype.call)

test/mjsunit/es8/async-await-interleaved.js

@@ -25,6 +25,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+// Flags: --ignore-unhandled-promises
+
 // Check for correct interleaving of Promises and async/await
 (function () {
   const iterations = 10;

test/mjsunit/es8/async-await-no-constructor.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --allow-natives-syntax
+// Flags: --allow-natives-syntax --ignore-unhandled-promises
 
 'use strict';
 

test/mjsunit/harmony/modules-import-8.mjs

@@ -9,21 +9,24 @@ var ran = false;
 var x = {
   get toString() { return undefined; }
 };
-import(x);
+import(x).then(assertUnreachable, 
+    (e) => assertInstanceof(e, TypeError));
 
 var x = {
   toString() {
     throw new Error('42 is the answer');
   }
 };
-import(x);
+import(x).then(assertUnreachable, 
+    (e) => assertEquals(e.message, '42 is the answer'))
 
 var x = {
   get toString() {
     throw new Error('42 is the answer');
   }
 };
-import(x);
+import(x).then(assertUnreachable,
+    (e) => assertEquals(e.message, '42 is the answer'))
 
 async function test1() {
   try {

test/mjsunit/harmony/modules-import-top-level-await-exception-1.mjs

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --harmony-dynamic-import --harmony-top-level-await
+// Flags: --harmony-dynamic-import --harmony-top-level-await --ignore-unhandled-promises
 
 let ran = false;
 let m = import('modules-skip-2.mjs');

test/mjsunit/harmony/modules-import-top-level-await-exception-2.mjs

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --harmony-dynamic-import --harmony-top-level-await
+// Flags: --harmony-dynamic-import --harmony-top-level-await --ignore-unhandled-promises
 
 let ran = false;
 try {

test/mjsunit/harmony/modules-import-top-level-await-exception-3.mjs

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --harmony-dynamic-import --harmony-top-level-await
+// Flags: --harmony-dynamic-import --harmony-top-level-await --ignore-unhandled-promises
 
 let ran = false;
 try {

test/mjsunit/harmony/promise-all-settled.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --allow-natives-syntax --harmony-promise-all-settled
+// Flags: --allow-natives-syntax --harmony-promise-all-settled --ignore-unhandled-promises
 
 class MyError extends Error {}
 

test/mjsunit/harmony/promise-prototype-finally.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --allow-natives-syntax
+// Flags: --allow-natives-syntax --ignore-unhandled-promises
 
 load('test/mjsunit/test-async.js');
 

test/mjsunit/modules-reset.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --allow-natives-syntax
-
-import("./modules-skip-reset1.js").then(() => %AbortJS("must throw"));
-import("./modules-skip-reset3.js").then(() => %AbortJS("must throw"));
+import("./modules-skip-reset1.js").then(
+    () => assertUnreachable("must throw"), () => {});
+import("./modules-skip-reset3.js").then(
+    () => assertUnreachable("must throw"), () => {});

test/mjsunit/promise-perform-all-resolve-lookup.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
-// Flags: --allow-natives-syntax
+// Flags: --allow-natives-syntax --ignore-unhandled-promises
 
 let count = 0;
 class MyPromise extends Promise {

test/mjsunit/regress/regress-744292.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
-// Flags: --harmony-dynamic-import
+// Flags: --harmony-dynamic-import --ignore-unhandled-promises
 
 __v_1 = {
 };
@@ -10,7 +10,7 @@ function __f_8() {
   try {
     __f_8();
   } catch(e) {
-      import(__v_1);
+      import(__v_1).then();
   }
 }
 __f_8();

test/mjsunit/regress/regress-746909.js

@@ -4,5 +4,9 @@
 
 // Flags: --harmony-dynamic-import
 
-eval(`import('modules-skip-2.js');`);
-eval(`eval(import('modules-skip-2.js'));`);
+eval(`import('modules-skip-2.js');`).then(
+    assertUnreachable,
+    () => { /* ignore */});
+eval(`eval(import('modules-skip-2.js'));`).then(
+    assertUnreachable,
+    () => { /* ignore */});

test/mjsunit/regress/regress-chromium-1040238.js

@@ -23,4 +23,6 @@ let myIterable = {
   }
 };
 
-MyPromise.race(myIterable);
+MyPromise.race(myIterable).then(
+  assertUnreachable,
+  (e) => { assertEquals(e, "then throws")});

test/mjsunit/regress/regress-crbug-1015945.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --allow-natives-syntax --expose-async-hooks
+// Flags: --allow-natives-syntax --expose-async-hooks --ignore-unhandled-promises
 
 async function* foo() {
   await 1;

test/mjsunit/regress/regress-crbug-1038140.js

@@ -3,4 +3,5 @@
 // found in the LICENSE file.
 
 Promise.resolve = function() { return {}; };
-Promise.race([function() {}]);
+Promise.race([function() {}]).then(
+    () => assertUnreachable(), () => { /* ignore */})

test/mjsunit/regress/regress-v8-10604.js

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --ignore-unhandled-promises
+
 (async function test() {
   try {
     import('does_not_exist.mjs');

test/mjsunit/regress/regress-v8-9534.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --allow-natives-syntax --stack-size=50
+// Flags: --allow-natives-syntax --stack-size=50 --ignore-unhandled-promises
 
 let i = 0;
 function f() {

test/mjsunit/regress/wasm/regress-1051912.js

@@ -14,4 +14,5 @@ binary.emit_bytes([kUnknownSectionCode, 2, 1, 0]);
 binary.emit_bytes([kUnknownSectionCode, 2, 1, 0]);
 binary.emit_bytes([ kExprEnd]);
 let buffer = binary.trunc_buffer();
-WebAssembly.compile(buffer);
+WebAssembly.compile(buffer).then(
+    () => assertUnreachable(), () => {/* ignore */});

test/mjsunit/regress/wasm/regress-1073553.js

@@ -11,4 +11,4 @@ builder.addFunction(undefined, kSig_v_i) .addBodyWithEnd([
 // Intentionally add just a numeric opcode prefix without the index byte.
 
 const b = builder.toBuffer();
-WebAssembly.compile(b);
+WebAssembly.compile(b).then(() => assertUnreachable(), () => { /* ignore */ })

test/mjsunit/regress/wasm/regress-712569.js

@@ -9,7 +9,9 @@ Object.defineProperty(v11.__proto__, 0, {
   },
   set: function() {
     try {
-      WebAssembly.instantiate();
+      WebAssembly.instantiate().then(
+          () => assertUnreachable(),
+          () => { /* ignore */ });
       v11[0] = 0;
     } catch (e) {
       assertTrue(e instanceof RangeError);

test/mjsunit/regress/wasm/regress-824681.js

@@ -16,4 +16,5 @@ for (let i = 0; i < 100; ++i) {
   chain = chain.then(() => WebAssembly.instantiate(buffer));
 }
 chain.then(({module, instance}) => instance.exports.fun1155())
-    .then(res => print('Result of executing fun1155: ' + res));
+    .then(res => print('Result of executing fun1155: ' + res))
+    .catch(() => {/* ignore */});

test/mjsunit/regress/wasm/regress-948228.js

@@ -8,4 +8,4 @@ var {proxy, revoke} = Proxy.revocable({}, {});
 revoke();
 let builder = new WasmModuleBuilder();
 builder.addImport('m', 'q', kSig_v_v);
-WebAssembly.instantiate(builder.toModule(), proxy);
+WebAssembly.instantiate(builder.toModule(), proxy).catch(error => {});

test/test262/testcfg.py

@@ -218,6 +218,7 @@ class TestCase(testcase.D8TestCase):
 
   def _get_suite_flags(self):
     return (
+        ["--ignore-unhandled-promises"] +
         (["--throws"] if "negative" in self.test_record else []) +
         (["--allow-natives-syntax"]
          if "detachArrayBuffer.js" in self.test_record.get("includes", [])

test/webkit/fast/js/Promise-catch.js

@@ -21,7 +21,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Flags: --harmony
+// Flags: --harmony --ignore-unhandled-promises
 'use strict';
 description('Test Promise.prototype.catch.');
 

test/webkit/fast/js/Promise-static-all.js

@@ -21,7 +21,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Flags: --harmony
+// Flags: --harmony --ignore-unhandled-promises
 'use strict';
 description('Test Promise.all');
 

test/webkit/fast/js/Promise-static-race.js

@@ -21,7 +21,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Flags: --harmony
+// Flags: --harmony --ignore-unhandled-promises
 'use strict';
 description('Test Promise.race');