Debugger: allow stepping into resolver from Promise constructor.

src/runtime/runtime-debug.cc

Index: src/runtime/runtime-debug.cc
diff --git a/src/runtime/runtime-debug.cc b/src/runtime/runtime-debug.cc
index 07737d09d7ed330b0b8f3e43ad5f94acd0b89ea5..35379a40884bfc4e51cb6caabf992904768fb4b9 100644
--- a/src/runtime/runtime-debug.cc
+++ b/src/runtime/runtime-debug.cc
@@ -1612,33 +1612,55 @@ RUNTIME_FUNCTION(Runtime_GetScript) {
 }
 
 
+bool DebugStepInIsActive(Debug* debug) {
+  return debug->is_active() && debug->IsStepping() &&
+         debug->last_step_action() == StepIn;
+}
+
+
 // Check whether debugger is about to step into the callback that is passed
-// to a built-in function such as Array.forEach.
+// to a built-in function such as Array.forEach. This check is done before
+// %DebugPrepareStepInIfStepping and is not strictly necessary. However, if it
+// returns false, we can skip %DebugPrepareStepInIfStepping, useful in loops.
 RUNTIME_FUNCTION(Runtime_DebugCallbackSupportsStepping) {
+  SealHandleScope shs(isolate);
   DCHECK(args.length() == 1);
-  Debug* debug = isolate->debug();
-  if (!debug->is_active() || !debug->IsStepping() ||
-      debug->last_step_action() != StepIn) {
+  if (!DebugStepInIsActive(isolate->debug())) {
     return isolate->heap()->false_value();
   }
-  CONVERT_ARG_CHECKED(Object, callback, 0);
+  CONVERT_ARG_CHECKED(Object, object, 0);
+  RUNTIME_ASSERT(object->IsJSFunction() || object->IsJSGeneratorObject());
   // We do not step into the callback if it's a builtin other than a bound,
   // or not even a function.
-  return isolate->heap()->ToBoolean(
-      callback->IsJSFunction() &&
-      (JSFunction::cast(callback)->IsSubjectToDebugging() ||
-       JSFunction::cast(callback)->shared()->bound()));
+  JSFunction* fun;
+  if (object->IsJSFunction()) {
+    fun = JSFunction::cast(object);
+  } else {
+    fun = JSGeneratorObject::cast(object)->function();
+  }
+  return isolate->heap()->ToBoolean(fun->IsSubjectToDebugging() ||
+                                    fun->shared()->bound());
+}
+
+
+void FloodDebugSubjectWithOneShot(Debug* debug, Handle<JSFunction> function) {
+  if (function->IsSubjectToDebugging() || function->shared()->bound()) {
+    // When leaving the function, step out has been activated, but not performed
+    // if we do not leave the builtin.  To be able to step into the function
+    // again, we need to clear the step out at this point.
+    debug->ClearStepOut();
+    debug->FloodWithOneShotGeneric(function);
+  }
 }
 
 
 // Set one shot breakpoints for the callback function that is passed to a
-// built-in function such as Array.forEach to enable stepping into the callback.
+// built-in function such as Array.forEach to enable stepping into the callback,
+// if we are indeed stepping and the callback is subject to debugging.
 RUNTIME_FUNCTION(Runtime_DebugPrepareStepInIfStepping) {
   DCHECK(args.length() == 1);
-  RUNTIME_ASSERT(isolate->debug()->is_active());
-
   Debug* debug = isolate->debug();
-  if (!debug->IsStepping()) return isolate->heap()->undefined_value();
+  if (!DebugStepInIsActive(debug)) return isolate->heap()->undefined_value();
 
   HandleScope scope(isolate);
   CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
@@ -1650,21 +1672,23 @@ RUNTIME_FUNCTION(Runtime_DebugPrepareStepInIfStepping) {
     fun = Handle<JSFunction>(
         Handle<JSGeneratorObject>::cast(object)->function(), isolate);
   }
-  // When leaving the function, step out has been activated, but not performed
-  // if we do not leave the builtin.  To be able to step into the function
-  // again, we need to clear the step out at this point.
-  debug->ClearStepOut();
-  debug->FloodWithOneShotGeneric(fun);
+
+  FloodDebugSubjectWithOneShot(debug, fun);
   return isolate->heap()->undefined_value();
 }
 
 
 RUNTIME_FUNCTION(Runtime_DebugPushPromise) {
-  DCHECK(args.length() == 2);
+  DCHECK(args.length() == 3);
   HandleScope scope(isolate);
   CONVERT_ARG_HANDLE_CHECKED(JSObject, promise, 0);
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 1);
+  CONVERT_ARG_HANDLE_CHECKED(Object, handler, 2);
   isolate->PushPromise(promise, function);
+  Debug* debug = isolate->debug();
+  if (handler->IsJSFunction() && DebugStepInIsActive(debug)) {
+    FloodDebugSubjectWithOneShot(debug, Handle<JSFunction>::cast(handler));
+  }
   return isolate->heap()->undefined_value();
 }