fs.watchFile fixes

doc/api/fs.markdown

@@ -576,6 +576,9 @@ These stat objects are instances of `fs.Stat`.
 If you want to be notified when the file was modified, not just accessed
 you need to compare `curr.mtime` and `prev.mtime`.
 
+_Note: when an `fs.watchFile` operation results in an `ENOENT` error, it will
+invoke the callback once. This is a change in functionality since v0.10._
+
 _Note: `fs.watch` is more efficient than `fs.watchFile` and `fs.unwatchFile`.
 `fs.watch` should be used instead of `fs.watchFile` and `fs.unwatchFile`
 when possible._

lib/fs.js

@@ -1305,28 +1305,27 @@ StatWatcher.prototype.stop = function() {
 
 const statWatchers = new Map();
 
-fs.watchFile = function(filename) {
+fs.watchFile = function(filename, options, listener) {
   nullCheck(filename);
   filename = pathModule.resolve(filename);
   var stat;
-  var listener;
 
-  var options = {
+  var defaults = {
     // Poll interval in milliseconds. 5007 is what libev used to use. It's
     // a little on the slow side but let's stick with it for now to keep
     // behavioral changes to a minimum.
     interval: 5007,
     persistent: true
   };
 
-  if (arguments[1] !== null && typeof arguments[1] === 'object') {
-    options = util._extend(options, arguments[1]);
-    listener = arguments[2];
+  if (options !== null && typeof options === 'object') {
+    options = util._extend(defaults, options);
   } else {
-    listener = arguments[1];
+    listener = options;
+    options = defaults;
   }
 
-  if (!listener) {
+  if (typeof listener !== 'function') {
     throw new Error('watchFile requires a listener function');
   }
 

test/parallel/test-fs-watchfile.js

@@ -0,0 +1,26 @@
+'use strict';
+
+const fs = require('fs');
+const path = require('path');
+const assert = require('assert');
+const common = require('../common');
+const fixtures = path.join(__dirname, '..', 'fixtures');
+
+// Basic usage tests.
+assert.throws(function() {
+  fs.watchFile('./some-file');
+}, /watchFile requires a listener function/);
+
+assert.throws(function() {
+  fs.watchFile('./another-file', {}, 'bad listener');
+}, /watchFile requires a listener function/);
+
+assert.throws(function() {
+  fs.watchFile(new Object(), function() {});
+}, /Path must be a string/);
+
+// Test ENOENT. Should fire once.
+const enoentFile = path.join(fixtures, 'empty', 'non-existent-file');
+fs.watchFile(enoentFile, common.mustCall(function(curr, prev) {
+  fs.unwatchFile(enoentFile);
+}));