[promises] Move PromiseResolveThenableJob to c++

src/isolate.cc

 // Copyright 2012 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.
 
 #include "src/isolate.h"
 
 #include <stdlib.h>
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
@@ skipping 2941 matching lines @@
   if (promise_reject_callback_ == NULL) return;
   Handle<JSArray> stack_trace;
   if (event == v8::kPromiseRejectWithNoHandler && value->IsJSObject()) {
     stack_trace = GetDetailedStackTrace(Handle<JSObject>::cast(value));
   }
   promise_reject_callback_(v8::PromiseRejectMessage(
       v8::Utils::PromiseToLocal(promise), event, v8::Utils::ToLocal(value),
       v8::Utils::StackTraceToLocal(stack_trace)));
 }
 
+void Isolate::PromiseResolveThenableJob(Handle<PromiseContainer> container) {
+  Handle<JSFunction> then(container->then(), this);
+  SaveContext save(this);
+  set_context(then->context()->native_context());
+  handle_scope_implementer_->EnterMicrotaskContext(
+      handle(then->context(), this));
+
+  Handle<Object> before_debug_event(container->before_debug_event(), this);
+  if (debug()->is_active() && before_debug_event->IsJSObject()) {
+    debug()->OnAsyncTaskEvent(Handle<JSObject>::cast(before_debug_event));
+  }
+
+  MaybeHandle<Object> maybe_exception;
+  Handle<JSReceiver> thenable(container->thenable(), this);
+  Handle<JSFunction> resolve(container->resolve(), this);
+  Handle<JSFunction> reject(container->reject(), this);
+  Handle<Object> argv[] = {resolve, reject};
+  MaybeHandle<Object> result = Execution::TryCall(
+      this, then, thenable, arraysize(argv), argv, &maybe_exception);
+
+  Handle<Object> reason;
+  if (maybe_exception.ToHandle(&reason)) {
+    Handle<Object> reason_arg[] = {reason};
+    MaybeHandle<Object> status =

[adamk, 2016/09/19 21:42:35]

No need to assign this anymore, now that TryCall swallows the exception.

+        Execution::TryCall(this, reject, factory()->undefined_value(),
+                           arraysize(reason_arg), reason_arg);
+  }
+
+  Handle<Object> after_debug_event(container->after_debug_event(), this);
+  if (debug()->is_active() && after_debug_event->IsJSObject()) {
+    debug()->OnAsyncTaskEvent(Handle<JSObject>::cast(after_debug_event));
+  }
+
+  handle_scope_implementer_->LeaveMicrotaskContext();
+}
 
 void Isolate::EnqueueMicrotask(Handle<Object> microtask) {
-  DCHECK(microtask->IsJSFunction() || microtask->IsCallHandlerInfo());
+  DCHECK(microtask->IsJSFunction() || microtask->IsCallHandlerInfo() ||
+         microtask->IsPromiseContainer());
   Handle<FixedArray> queue(heap()->microtask_queue(), this);
   int num_tasks = pending_microtask_count();
   DCHECK(num_tasks <= queue->length());
   if (num_tasks == 0) {
     queue = factory()->NewFixedArray(8);
     heap()->set_microtask_queue(*queue);
   } else if (num_tasks == queue->length()) {
     queue = factory()->CopyFixedArrayAndGrow(queue, num_tasks);
     heap()->set_microtask_queue(*queue);
   }
@@ skipping 34 matching lines @@
         SaveContext save(this);
         set_context(microtask_function->context()->native_context());
         handle_scope_implementer_->EnterMicrotaskContext(
             handle(microtask_function->context(), this));
         MaybeHandle<Object> maybe_exception;
         MaybeHandle<Object> result = Execution::TryCall(
             this, microtask_function, factory()->undefined_value(), 0, NULL,
             &maybe_exception);
         handle_scope_implementer_->LeaveMicrotaskContext();
         // If execution is terminating, just bail out.
         if (result.is_null() && maybe_exception.is_null()) {

[adamk, 2016/09/19 21:42:35]

It worries me a little bit that we're now missing this code. Could you factor it
out of the if-else somehow?

For a little background: it's trying to determine if the exception that was
thrown is due to someone calling Isolate::TerminateExecution, e.g. if this is a
Worker thread being torn down.

           // Clear out any remaining callbacks in the queue.
           heap()->set_microtask_queue(heap()->empty_fixed_array());
           set_pending_microtask_count(0);
           return;
         }
-      } else {
+      } else if (microtask->IsCallHandlerInfo()) {
         Handle<CallHandlerInfo> callback_info =
             Handle<CallHandlerInfo>::cast(microtask);
         v8::MicrotaskCallback callback =
             v8::ToCData<v8::MicrotaskCallback>(callback_info->callback());
         void* data = v8::ToCData<void*>(callback_info->data());
         callback(data);
+      } else {
+        PromiseResolveThenableJob(Handle<PromiseContainer>::cast(microtask));
       }
     });
   }
 }
 
 
 void Isolate::AddMicrotasksCompletedCallback(
     MicrotasksCompletedCallback callback) {
   for (int i = 0; i < microtasks_completed_callbacks_.length(); i++) {
     if (callback == microtasks_completed_callbacks_.at(i)) return;
@@ skipping 166 matching lines @@
   // Then check whether this scope intercepts.
   if ((flag & intercept_mask_)) {
     intercepted_flags_ |= flag;
     return true;
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace v8