From 059f2960503eec1418c32226646f5a2af6ae85f0 Mon Sep 17 00:00:00 2001
From: Anna Henningsen <anna@addaleax.net>
Date: Fri, 14 Apr 2017 18:27:46 +0200
Subject: [PATCH] util: add internal bindings for promise handling

Add methods for creating, resolving and rejecting promises
using the V8 C++ API that does not require creation of extra
`resolve` and `reject` functions to `process.binding('util')`.

PR-URL: https://github.com/nodejs/node/pull/12442
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: William Kapke <william.kapke@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Teddy Katz <teddy.katz@gmail.com>
---
 src/node_util.cc                              | 35 ++++++++++++++++
 .../test-promise-internal-creation.js         | 41 +++++++++++++++++++
 2 files changed, 76 insertions(+)
 create mode 100644 test/parallel/test-promise-internal-creation.js

diff --git a/src/node_util.cc b/src/node_util.cc
index 5f3de643d4c2f3..3424739cc96688 100644
--- a/src/node_util.cc
+++ b/src/node_util.cc
@@ -12,6 +12,7 @@ using v8::Context;
 using v8::FunctionCallbackInfo;
 using v8::Integer;
 using v8::Local;
+using v8::Maybe;
 using v8::Object;
 using v8::Private;
 using v8::Promise;
@@ -147,6 +148,36 @@ void WatchdogHasPendingSigint(const FunctionCallbackInfo<Value>& args) {
 }
 
 
+void CreatePromise(const FunctionCallbackInfo<Value>& args) {
+  Local<Context> context = args.GetIsolate()->GetCurrentContext();
+  auto maybe_resolver = Promise::Resolver::New(context);
+  if (!maybe_resolver.IsEmpty())
+    args.GetReturnValue().Set(maybe_resolver.ToLocalChecked());
+}
+
+
+void PromiseResolve(const FunctionCallbackInfo<Value>& args) {
+  Local<Context> context = args.GetIsolate()->GetCurrentContext();
+  Local<Value> promise = args[0];
+  CHECK(promise->IsPromise());
+  if (promise.As<Promise>()->State() != Promise::kPending) return;
+  Local<Promise::Resolver> resolver = promise.As<Promise::Resolver>();  // sic
+  Maybe<bool> ret = resolver->Resolve(context, args[1]);
+  args.GetReturnValue().Set(ret.FromMaybe(false));
+}
+
+
+void PromiseReject(const FunctionCallbackInfo<Value>& args) {
+  Local<Context> context = args.GetIsolate()->GetCurrentContext();
+  Local<Value> promise = args[0];
+  CHECK(promise->IsPromise());
+  if (promise.As<Promise>()->State() != Promise::kPending) return;
+  Local<Promise::Resolver> resolver = promise.As<Promise::Resolver>();  // sic
+  Maybe<bool> ret = resolver->Reject(context, args[1]);
+  args.GetReturnValue().Set(ret.FromMaybe(false));
+}
+
+
 void Initialize(Local<Object> target,
                 Local<Value> unused,
                 Local<Context> context) {
@@ -192,6 +223,10 @@ void Initialize(Local<Object> target,
   env->SetMethod(target, "startSigintWatchdog", StartSigintWatchdog);
   env->SetMethod(target, "stopSigintWatchdog", StopSigintWatchdog);
   env->SetMethod(target, "watchdogHasPendingSigint", WatchdogHasPendingSigint);
+
+  env->SetMethod(target, "createPromise", CreatePromise);
+  env->SetMethod(target, "promiseResolve", PromiseResolve);
+  env->SetMethod(target, "promiseReject", PromiseReject);
 }
 
 }  // namespace util
diff --git a/test/parallel/test-promise-internal-creation.js b/test/parallel/test-promise-internal-creation.js
new file mode 100644
index 00000000000000..7142c872d9452e
--- /dev/null
+++ b/test/parallel/test-promise-internal-creation.js
@@ -0,0 +1,41 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const {
+  createPromise, promiseResolve, promiseReject
+} = process.binding('util');
+const { inspect } = require('util');
+
+common.crashOnUnhandledRejection();
+
+{
+  const promise = createPromise();
+  assert.strictEqual(inspect(promise), 'Promise { <pending> }');
+  promiseResolve(promise, 42);
+  assert.strictEqual(inspect(promise), 'Promise { 42 }');
+  promise.then(common.mustCall((value) => {
+    assert.strictEqual(value, 42);
+  }));
+}
+
+{
+  const promise = createPromise();
+  const error = new Error('foobar');
+  promiseReject(promise, error);
+  assert(inspect(promise).includes('<rejected> Error: foobar'));
+  promise.catch(common.mustCall((value) => {
+    assert.strictEqual(value, error);
+  }));
+}
+
+{
+  const promise = createPromise();
+  const error = new Error('foobar');
+  promiseReject(promise, error);
+  assert(inspect(promise).includes('<rejected> Error: foobar'));
+  promiseResolve(promise, 42);
+  assert(inspect(promise).includes('<rejected> Error: foobar'));
+  promise.catch(common.mustCall((value) => {
+    assert.strictEqual(value, error);
+  }));
+}