[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 2896 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) {
+  MaybeHandle<Object> maybe_exception;

[adamk, 2016/09/08 22:28:18]

This should be declared right before it's used.

[gsathya, 2016/09/14 00:39:14]

Done.

+  Handle<JSObject> promise(container->promise(), this);
+  Handle<JSObject> thenable(container->thenable(), this);
+  Handle<JSFunction> then(container->then(), this);
+  Handle<JSFunction> resolve(container->resolve(), this);
+  Handle<JSFunction> reject(container->reject(), this);
+  Handle<Object> before_debug_event(container->before_debug_event(), this);
+  Handle<Object> after_debug_event(container->after_debug_event(), this);

[adamk, 2016/09/08 22:28:18]

I don't think you need all these handles up front, I'd create them as they're
necessary.

[gsathya, 2016/09/14 00:39:13]

Done.

+  Handle<Object> argv[] = {resolve, reject};

[adamk, 2016/09/08 22:28:18]

This can also move down to right before the call

[gsathya, 2016/09/14 00:39:13]

Done.

+
+  if (debug()->is_active() && (*before_debug_event)->IsJSObject()) {

[adamk, 2016/09/08 22:28:17]

Handles already overload operator-> so you don't need the double dereference.

Is this check needed in case debug is enabled between the time the job is
enqueued and when this code runs?

[gsathya, 2016/09/14 00:39:13]

Done.
Yeah.

+    Handle<JSObject> event_data(JSObject::cast(*before_debug_event), this);

[adamk, 2016/09/08 22:28:17]

No need to create a new handle here...

[gsathya, 2016/09/14 00:39:13]

Done.

+    debug()->OnAsyncTaskEvent(event_data);

[adamk, 2016/09/08 22:28:17]

...instead use Handle<JSObject>::cast(before_debug_event)

[gsathya, 2016/09/14 00:39:13]

Done.

+  }
+
+  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 =
+        Execution::Call(this, reject, factory()->undefined_value(),
+                        arraysize(reason_arg), reason_arg);
+  }
+
+  if (debug()->is_active() && (*after_debug_event)->IsJSObject()) {

[adamk, 2016/09/08 22:28:17]

Same applies here and below to the handling of after_debug_event

[gsathya, 2016/09/14 00:39:13]

Done.

+    Handle<JSObject> event_data(JSObject::cast(*after_debug_event), this);
+    debug()->OnAsyncTaskEvent(event_data);
+  }
+}
 
 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 24 matching lines @@
     DCHECK(num_tasks <= queue->length());
     set_pending_microtask_count(0);
     heap()->set_microtask_queue(heap()->empty_fixed_array());
 
     Isolate* isolate = this;
     FOR_WITH_HANDLE_SCOPE(isolate, int, i = 0, i, i < num_tasks, i++, {
       Handle<Object> microtask(queue->get(i), this);
       if (microtask->IsJSFunction()) {
         Handle<JSFunction> microtask_function =
             Handle<JSFunction>::cast(microtask);
         SaveContext save(this);

[adamk, 2016/09/08 22:28:17]

As discussed I think you might need to use most of this context handling stuff
as well.

I see some blink tests failing with suggestive-sounding error messages that
mention "contexts".

[gsathya, 2016/09/14 00:39:13]

Done.

         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()) {
           // 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 {
+        Handle<PromiseContainer> container =
+            Handle<PromiseContainer>::cast(microtask);
+        PromiseResolveThenableJob(container);
       }
     });
   }
 }
 
 
 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