[api] Expose PreviewEntries as public API

Turn `debug::EntriesPreview` into a public API.
This is a straightforward approach to addressing
nodejs/node#20409
(not relying on functionality behind `--allow-natives-syntax`)
in Node.js.

Refs: nodejs/node#20409
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I7021e5846012a55a82c488408ded6591f6b139e7
Reviewed-on: https://chromium-review.googlesource.com/1057467
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53226}

include/v8.h

@@ -3672,6 +3672,17 @@ class V8_EXPORT Object : public Value {
    */
   Isolate* GetIsolate();
 
+  /**
+   * If this object is a Set, Map, WeakSet or WeakMap, this returns a
+   * representation of the elements of this object as an array.
+   * If this object is a SetIterator or MapIterator, this returns all
+   * elements of the underlying collection, starting at the iterator's current
+   * position.
+   * For other types, this will return an empty MaybeLocal<Array> (without
+   * scheduling an exception).
+   */
+  MaybeLocal<Array> PreviewEntries(bool* is_key_value);
+
   static Local<Object> New(Isolate* isolate);
 
   V8_INLINE static Object* Cast(Value* obj);

src/api.cc

@@ -9543,21 +9543,20 @@ int debug::EstimatedValueSize(Isolate* v8_isolate, v8::Local<v8::Value> value) {
   return i::Handle<i::HeapObject>::cast(object)->Size();
 }
 
-v8::MaybeLocal<v8::Array> debug::EntriesPreview(Isolate* v8_isolate,
-                                                v8::Local<v8::Value> value,
-                                                bool* is_key_value) {
-  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(v8_isolate);
-  ENTER_V8_NO_SCRIPT_NO_EXCEPTION(isolate);
-  if (value->IsMap()) {
+v8::MaybeLocal<v8::Array> v8::Object::PreviewEntries(bool* is_key_value) {
+  if (IsMap()) {
     *is_key_value = true;
-    return value.As<Map>()->AsArray();
+    return Map::Cast(this)->AsArray();
   }
-  if (value->IsSet()) {
+  if (IsSet()) {
     *is_key_value = false;
-    return value.As<Set>()->AsArray();
+    return Set::Cast(this)->AsArray();
   }
 
-  i::Handle<i::Object> object = Utils::OpenHandle(*value);
+  i::Handle<i::JSReceiver> object = Utils::OpenHandle(this);
+  i::Isolate* isolate = object->GetIsolate();
+  Isolate* v8_isolate = reinterpret_cast<Isolate*>(isolate);
+  ENTER_V8_NO_SCRIPT_NO_EXCEPTION(isolate);
   if (object->IsJSWeakCollection()) {
     *is_key_value = object->IsJSWeakMap();
     return Utils::ToLocal(i::JSWeakCollection::GetEntries(

src/debug/debug-interface.h

@@ -212,10 +212,6 @@ void ResetBlackboxedStateCache(Isolate* isolate,
 
 int EstimatedValueSize(Isolate* isolate, v8::Local<v8::Value> value);
 
-v8::MaybeLocal<v8::Array> EntriesPreview(Isolate* isolate,
-                                         v8::Local<v8::Value> value,
-                                         bool* is_key_value);
-
 enum Builtin {
   kObjectKeys,
   kObjectGetPrototypeOf,

src/inspector/v8-debugger.cc

@@ -29,8 +29,10 @@ v8::MaybeLocal<v8::Array> collectionsEntries(v8::Local<v8::Context> context,
   v8::Isolate* isolate = context->GetIsolate();
   v8::Local<v8::Array> entries;
   bool isKeyValue = false;
-  if (!v8::debug::EntriesPreview(isolate, value, &isKeyValue).ToLocal(&entries))
+  if (!value->IsObject() ||
+      !value.As<v8::Object>()->PreviewEntries(&isKeyValue).ToLocal(&entries)) {
     return v8::MaybeLocal<v8::Array>();
+  }
 
   v8::Local<v8::Array> wrappedEntries = v8::Array::New(isolate);
   CHECK(!isKeyValue || wrappedEntries->Length() % 2 == 0);