From a37273c1e4b93ed048e1d45818fe6c525480b121 Mon Sep 17 00:00:00 2001
From: Timothy Gu <timothygu99@gmail.com>
Date: Wed, 5 Apr 2017 22:30:25 -0700
Subject: util: use V8 C++ API for inspecting Promises

PR-URL: https://github.com/nodejs/node/pull/12254
Refs: https://github.com/nodejs/node/issues/11875
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Josh Gavant <josh.gavant@outlook.com>
---
 lib/util.js      | 62 ++++++++++++++++++++++----------------------------------
 src/node_util.cc | 30 +++++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 38 deletions(-)

diff --git a/lib/util.js b/lib/util.js
index a0e8bb3c1d..12280e412a 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -302,16 +302,6 @@ function ensureDebugIsInitialized() {
 }
 
 
-function inspectPromise(p) {
-  // Only create a mirror if the object is a Promise.
-  if (!binding.isPromise(p))
-    return null;
-  ensureDebugIsInitialized();
-  const mirror = Debug.MakeMirror(p, true);
-  return {status: mirror.status(), value: mirror.promiseValue().value_};
-}
-
-
 function formatValue(ctx, value, recurseTimes) {
   if (ctx.showProxy &&
       ((typeof value === 'object' && value !== null) ||
@@ -527,30 +517,25 @@ function formatValue(ctx, value, recurseTimes) {
                    'byteOffset',
                    'buffer');
     }
+  } else if (binding.isPromise(value)) {
+    braces = ['{', '}'];
+    formatter = formatPromise;
+  } else if (binding.isMapIterator(value)) {
+    constructor = { name: 'MapIterator' };
+    braces = ['{', '}'];
+    empty = false;
+    formatter = formatCollectionIterator;
+  } else if (binding.isSetIterator(value)) {
+    constructor = { name: 'SetIterator' };
+    braces = ['{', '}'];
+    empty = false;
+    formatter = formatCollectionIterator;
   } else {
-    var promiseInternals = inspectPromise(value);
-    if (promiseInternals) {
-      braces = ['{', '}'];
-      formatter = formatPromise;
-    } else {
-      if (binding.isMapIterator(value)) {
-        constructor = { name: 'MapIterator' };
-        braces = ['{', '}'];
-        empty = false;
-        formatter = formatCollectionIterator;
-      } else if (binding.isSetIterator(value)) {
-        constructor = { name: 'SetIterator' };
-        braces = ['{', '}'];
-        empty = false;
-        formatter = formatCollectionIterator;
-      } else {
-        // Unset the constructor to prevent "Object {...}" for ordinary objects.
-        if (constructor && constructor.name === 'Object')
-          constructor = null;
-        braces = ['{', '}'];
-        empty = true;  // No other data than keys.
-      }
-    }
+    // Unset the constructor to prevent "Object {...}" for ordinary objects.
+    if (constructor && constructor.name === 'Object')
+      constructor = null;
+    braces = ['{', '}'];
+    empty = true;  // No other data than keys.
   }
 
   empty = empty === true && keys.length === 0;
@@ -779,14 +764,15 @@ function formatCollectionIterator(ctx, value, recurseTimes, visibleKeys, keys) {
 }
 
 function formatPromise(ctx, value, recurseTimes, visibleKeys, keys) {
-  var output = [];
-  var internals = inspectPromise(value);
-  if (internals.status === 'pending') {
+  const output = [];
+  const [state, result] = binding.getPromiseDetails(value);
+
+  if (state === binding.kPending) {
     output.push('<pending>');
   } else {
     var nextRecurseTimes = recurseTimes === null ? null : recurseTimes - 1;
-    var str = formatValue(ctx, internals.value, nextRecurseTimes);
-    if (internals.status === 'rejected') {
+    var str = formatValue(ctx, result, nextRecurseTimes);
+    if (state === binding.kRejected) {
       output.push('<rejected> ' + str);
     } else {
       output.push(str);
diff --git a/src/node_util.cc b/src/node_util.cc
index 813995de79..fe01717131 100644
--- a/src/node_util.cc
+++ b/src/node_util.cc
@@ -14,6 +14,7 @@ using v8::Integer;
 using v8::Local;
 using v8::Object;
 using v8::Private;
+using v8::Promise;
 using v8::Proxy;
 using v8::Value;
 
@@ -43,6 +44,24 @@ using v8::Value;
   VALUE_METHOD_MAP(V)
 #undef V
 
+static void GetPromiseDetails(const FunctionCallbackInfo<Value>& args) {
+  // Return undefined if it's not a Promise.
+  if (!args[0]->IsPromise())
+    return;
+
+  auto isolate = args.GetIsolate();
+
+  Local<Promise> promise = args[0].As<Promise>();
+  Local<Array> ret = Array::New(isolate, 2);
+
+  int state = promise->State();
+  ret->Set(0, Integer::New(isolate, state));
+  if (state != Promise::PromiseState::kPending)
+    ret->Set(1, promise->Result());
+
+  args.GetReturnValue().Set(ret);
+}
+
 static void GetProxyDetails(const FunctionCallbackInfo<Value>& args) {
   // Return undefined if it's not a proxy.
   if (!args[0]->IsProxy())
@@ -148,8 +167,19 @@ void Initialize(Local<Object> target,
     Integer::NewFromUnsigned(env->isolate(), NODE_PUSH_VAL_TO_ARRAY_MAX),
     v8::ReadOnly).FromJust();
 
+#define V(name)                                                               \
+  target->Set(context,                                                        \
+              FIXED_ONE_BYTE_STRING(env->isolate(), #name),                   \
+              Integer::New(env->isolate(), Promise::PromiseState::name))      \
+    .FromJust()
+  V(kPending);
+  V(kFulfilled);
+  V(kRejected);
+#undef V
+
   env->SetMethod(target, "getHiddenValue", GetHiddenValue);
   env->SetMethod(target, "setHiddenValue", SetHiddenValue);
+  env->SetMethod(target, "getPromiseDetails", GetPromiseDetails);
   env->SetMethod(target, "getProxyDetails", GetProxyDetails);
 
   env->SetMethod(target, "startSigintWatchdog", StartSigintWatchdog);
-- 
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