From 20fa775bc55b326b7a77283c44115deef1393f67 Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Sun, 18 Aug 2019 10:25:06 -0400
Subject: [PATCH] refactor: remove async.parallel() calls

Re: #8073
---
 lib/helpers/updateValidators.js | 17 ++++++++++++++---
 lib/model.js                    | 17 +++++++++++++++--
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/lib/helpers/updateValidators.js b/lib/helpers/updateValidators.js
index 4eeecbb2c5e..f58f905f321 100644
--- a/lib/helpers/updateValidators.js
+++ b/lib/helpers/updateValidators.js
@@ -9,7 +9,6 @@ const ValidationError = require('../error/validation');
 const cleanPositionalOperators = require('./schema/cleanPositionalOperators');
 const flatten = require('./common').flatten;
 const modifiedPaths = require('./common').modifiedPaths;
-const parallel = require('async/parallel');
 
 /**
  * Applies validators and defaults to update and findOneAndUpdate operations,
@@ -214,7 +213,19 @@ module.exports = function(query, schema, castedDoc, options) {
   }
 
   return function(callback) {
-    parallel(validatorsToExecute, function() {
+    let numValidators = validatorsToExecute.length;
+    if (numValidators === 0) {
+      return _done();
+    }
+    for (const validator of validatorsToExecute) {
+      validator(function() {
+        if (--numValidators <= 0) {
+          _done();
+        }
+      });
+    }
+
+    function _done() {
       if (validationErrors.length) {
         const err = new ValidationError(null);
         for (let i = 0; i < validationErrors.length; ++i) {
@@ -223,6 +234,6 @@ module.exports = function(query, schema, castedDoc, options) {
         return callback(err);
       }
       callback(null);
-    });
+    }
   };
 };
diff --git a/lib/model.js b/lib/model.js
index 533e1abc951..af1a1e81241 100644
--- a/lib/model.js
+++ b/lib/model.js
@@ -37,7 +37,6 @@ const isPathSelectedInclusive = require('./helpers/projection/isPathSelectedIncl
 const get = require('./helpers/get');
 const leanPopulateMap = require('./helpers/populate/leanPopulateMap');
 const modifiedPaths = require('./helpers/update/modifiedPaths');
-const parallel = require('async/parallel');
 const parallelLimit = require('async/parallelLimit');
 const util = require('util');
 const utils = require('./utils');
@@ -3035,7 +3034,11 @@ Model.create = function create(doc, options, callback) {
       });
     });
 
-    parallel(toExecute, (error, res) => {
+    let numFns = toExecute.length;
+    if (numFns === 0) {
+      return cb(null, []);
+    }
+    const _done = (error, res) => {
       const savedDocs = [];
       const len = res.length;
       for (let i = 0; i < len; ++i) {
@@ -3053,6 +3056,16 @@ Model.create = function create(doc, options, callback) {
       } else {
         cb.apply(this, [null].concat(savedDocs));
       }
+    };
+
+    let _res = [];
+    toExecute.forEach((fn, i) => {
+      fn((err, res) => {
+        _res[i] = res;
+        if (--numFns <= 0) {
+          return _done(null, _res);
+        }
+      });
     });
   }, this.events);
 };