From 15f3f0b4833f20ee4af4e87cdec1c02aa7625688 Mon Sep 17 00:00:00 2001
From: Dan Fabulich <dan.fabulich@redfin.com>
Date: Tue, 30 May 2017 14:34:27 -0700
Subject: [PATCH] fs: promisify exists correctly

---
 lib/fs.js                            | 11 ++++++++++-
 test/parallel/test-fs-promisified.js |  7 +++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/lib/fs.js b/lib/fs.js
index 37dcba0b3bd517..9f3a1fad5b00af 100644
--- a/lib/fs.js
+++ b/lib/fs.js
@@ -28,7 +28,7 @@ const constants = process.binding('constants').fs;
 const { S_IFIFO, S_IFLNK, S_IFMT, S_IFREG, S_IFSOCK } = constants;
 const util = require('util');
 const pathModule = require('path');
-const { isUint8Array } = process.binding('util');
+const { isUint8Array, createPromise, promiseResolve } = process.binding('util');
 
 const binding = process.binding('fs');
 const fs = exports;
@@ -376,6 +376,15 @@ fs.exists = function(path, callback) {
   }
 };
 
+Object.defineProperty(fs.exists, internalUtil.promisify.custom, {
+  value: (path) => {
+    const promise = createPromise();
+    fs.exists(path, (exists) => promiseResolve(promise, exists));
+    return promise;
+  }
+});
+
+
 fs.existsSync = function(path) {
   try {
     handleError((path = getPathFromURL(path)));
diff --git a/test/parallel/test-fs-promisified.js b/test/parallel/test-fs-promisified.js
index 12bd5d6fa1f954..ac6e22f9690821 100644
--- a/test/parallel/test-fs-promisified.js
+++ b/test/parallel/test-fs-promisified.js
@@ -9,6 +9,7 @@ common.crashOnUnhandledRejection();
 
 const read = promisify(fs.read);
 const write = promisify(fs.write);
+const exists = promisify(fs.exists);
 
 {
   const fd = fs.openSync(__filename, 'r');
@@ -29,3 +30,9 @@ common.refreshTmpDir();
     fs.closeSync(fd);
   }));
 }
+
+{
+  exists(__filename).then(common.mustCall((x) => {
+    assert.strictEqual(x, true);
+  }));
+}