From 208db5675ebfcf1decdb106f217a4d4ebf17aa17 Mon Sep 17 00:00:00 2001
From: Nikolai Vavilov <vvnicholas@gmail.com>
Date: Tue, 28 Feb 2017 16:13:49 +0200
Subject: [PATCH] fs: don't conflate data and callback in appendFile

PR-URL: https://github.com/nodejs/node/pull/11607
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
---
 lib/fs.js                            | 2 +-
 test/parallel/test-fs-append-file.js | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/lib/fs.js b/lib/fs.js
index 6273c975c1..25dad8bf2c 100644
--- a/lib/fs.js
+++ b/lib/fs.js
@@ -1320,7 +1320,7 @@ fs.writeFileSync = function(path, data, options) {
 };
 
 fs.appendFile = function(path, data, options, callback) {
-  callback = maybeCallback(arguments[arguments.length - 1]);
+  callback = maybeCallback(callback || options);
   options = getOptions(options, { encoding: 'utf8', mode: 0o666, flag: 'a' });
 
   // Don't make changes directly on options object
diff --git a/test/parallel/test-fs-append-file.js b/test/parallel/test-fs-append-file.js
index 025a0ed034..e3e4c273d3 100644
--- a/test/parallel/test-fs-append-file.js
+++ b/test/parallel/test-fs-append-file.js
@@ -144,6 +144,13 @@ fs.open(filename5, 'a+', function(e, fd) {
   });
 });
 
+// test that a missing callback emits a warning, even if the last argument is a
+// function.
+const filename6 = join(common.tmpDir, 'append6.txt');
+const warn = 'Calling an asynchronous function without callback is deprecated.';
+common.expectWarning('DeprecationWarning', warn);
+fs.appendFile(filename6, console.log);
+
 process.on('exit', function() {
   assert.strictEqual(12, ncallbacks);