From 1bcae49e655f776e3a7b329ec28c93fd63edbbb3 Mon Sep 17 00:00:00 2001
From: XadillaX <i@2333.moe>
Date: Sun, 25 Apr 2021 11:07:07 +0800
Subject: [PATCH 1/2] process: make `process.nextTick()` awaitable

---
 doc/api/process.md                  | 17 ++++++++++++++++-
 lib/internal/process/task_queues.js | 20 ++++++++++++++++++++
 test/parallel/test-next-tick.js     | 15 +++++++++++++--
 3 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/doc/api/process.md b/doc/api/process.md
index 2212cc9c8958a9..9298022ef71016 100644
--- a/doc/api/process.md
+++ b/doc/api/process.md
@@ -1639,7 +1639,7 @@ console.log(process.memoryUsage.rss());
 // 35655680
 ```
 
-## `process.nextTick(callback[, ...args])`
+## `process.nextTick([callback][, ...args])`
 <!-- YAML
 added: v0.1.26
 changes:
@@ -1650,6 +1650,7 @@ changes:
 
 * `callback` {Function}
 * `...args` {any} Additional arguments to pass when invoking the `callback`
+* Returns: {Promise} containing {undefined} if no `callback` provided
 
 `process.nextTick()` adds `callback` to the "next tick queue". This queue is
 fully drained after the current operation on the JavaScript stack runs to
@@ -1669,6 +1670,20 @@ console.log('scheduled');
 // nextTick callback
 ```
 
+If no `callback` function is provided, a `Promise` will be returned.
+
+```js
+async function output() {
+  await process.nextTick();
+  console.log('scheduled');
+}
+output();
+console.log('immediately');
+// Output:
+// immediately
+// scheduled
+```
+
 This is important when developing APIs in order to give users the opportunity
 to assign event handlers *after* an object has been constructed but before any
 I/O has occurred:
diff --git a/lib/internal/process/task_queues.js b/lib/internal/process/task_queues.js
index 2a14b9dea68080..9883d80e03a8a5 100644
--- a/lib/internal/process/task_queues.js
+++ b/lib/internal/process/task_queues.js
@@ -40,6 +40,10 @@ const {
   validateFunction,
 } = require('internal/validators');
 
+const {
+  createDeferredPromise,
+} = require('internal/util');
+
 const { AsyncResource } = require('async_hooks');
 
 // *Must* match Environment::TickInfo::Fields in src/env.h.
@@ -99,9 +103,22 @@ function processTicksAndRejections() {
   setHasRejectionToWarn(false);
 }
 
+function nextTickDefaultCallback(resolve) {
+  resolve();
+}
+
 // `nextTick()` will not enqueue any callback when the process is about to
 // exit since the callback would not have a chance to be executed.
 function nextTick(callback) {
+  let promise;
+
+  if (!arguments.length) {
+    const defered = createDeferredPromise();
+    promise = defered.promise;
+    const { resolve } = defered;
+    callback = nextTickDefaultCallback.bind(undefined, resolve);
+  }
+
   validateCallback(callback);
 
   if (process._exiting)
@@ -109,6 +126,7 @@ function nextTick(callback) {
 
   let args;
   switch (arguments.length) {
+    case 0:
     case 1: break;
     case 2: args = [arguments[1]]; break;
     case 3: args = [arguments[1], arguments[2]]; break;
@@ -132,6 +150,8 @@ function nextTick(callback) {
   if (initHooksExist())
     emitInit(asyncId, 'TickObject', triggerAsyncId, tickObject);
   queue.push(tickObject);
+
+  if (promise) return promise;
 }
 
 function runMicrotask() {
diff --git a/test/parallel/test-next-tick.js b/test/parallel/test-next-tick.js
index 47823f45bcf7e2..891d0e0ff5494f 100644
--- a/test/parallel/test-next-tick.js
+++ b/test/parallel/test-next-tick.js
@@ -54,10 +54,21 @@ process.nextTick(function() {
   assert.strictEqual(this, undefined);
 }, 1, 2, 3, 4);
 
-process.nextTick(() => {
+assert.strictEqual(process.nextTick(() => {
   assert.deepStrictEqual(this, {});
-}, 1, 2, 3, 4);
+}, 1, 2, 3, 4), undefined);
+
+const array = [];
+async function schedule() {
+  const p = process.nextTick();
+  assert(p instanceof Promise);
+  await p;
+  array.push(1);
+}
+schedule();
+array.push(2);
 
 process.on('exit', function() {
+  assert.deepStrictEqual(array, [ 2, 1 ]);
   process.nextTick(common.mustNotCall());
 });

From 522ba7a8694ecb515b698092774f919a905fb144 Mon Sep 17 00:00:00 2001
From: XadillaX <i@2333.moe>
Date: Sun, 25 Apr 2021 14:37:01 +0800
Subject: [PATCH 2/2] f

---
 lib/internal/process/task_queues.js | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/lib/internal/process/task_queues.js b/lib/internal/process/task_queues.js
index 9883d80e03a8a5..dd5f09a36c1551 100644
--- a/lib/internal/process/task_queues.js
+++ b/lib/internal/process/task_queues.js
@@ -110,13 +110,11 @@ function nextTickDefaultCallback(resolve) {
 // `nextTick()` will not enqueue any callback when the process is about to
 // exit since the callback would not have a chance to be executed.
 function nextTick(callback) {
-  let promise;
+  let deferred;
 
   if (!arguments.length) {
-    const defered = createDeferredPromise();
-    promise = defered.promise;
-    const { resolve } = defered;
-    callback = nextTickDefaultCallback.bind(undefined, resolve);
+    deferred = createDeferredPromise();
+    callback = nextTickDefaultCallback.bind(undefined, deferred.resolve);
   }
 
   validateCallback(callback);
@@ -151,7 +149,7 @@ function nextTick(callback) {
     emitInit(asyncId, 'TickObject', triggerAsyncId, tickObject);
   queue.push(tickObject);
 
-  if (promise) return promise;
+  if (deferred) return deferred.promise;
 }
 
 function runMicrotask() {