fs: make mkdir() call callback if mode is omitted

Fixes #2043.

lib/fs.js

@@ -360,6 +360,7 @@ fs.fsyncSync = function(fd) {
 };
 
 fs.mkdir = function(path, mode, callback) {
+  if (typeof mode === 'function') callback = mode;
   binding.mkdir(path, modeNum(mode, 511 /*=0777*/), callback || noop);
 };
 

test/simple/test-fs-mkdir.js

@@ -0,0 +1,84 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+var common = require('../common');
+var assert = require('assert');
+var path = require('path');
+var fs = require('fs');
+
+function unlink(pathname) {
+  try {
+    fs.rmdirSync(pathname);
+  } catch (e) {
+  }
+}
+
+(function() {
+  var ncalls = 0;
+  var pathname = common.tmpDir + '/test1';
+
+  unlink(pathname);
+
+  fs.mkdir(pathname, function(err) {
+    assert.equal(err, null);
+    assert.equal(path.existsSync(pathname), true);
+    ncalls++;
+  });
+
+  process.on('exit', function() {
+    unlink(pathname);
+    assert.equal(ncalls, 1);
+  });
+})();
+
+(function() {
+  var ncalls = 0;
+  var pathname = common.tmpDir + '/test2';
+
+  unlink(pathname);
+
+  fs.mkdir(pathname, 511 /*=0777*/, function(err) {
+    assert.equal(err, null);
+    assert.equal(path.existsSync(pathname), true);
+    ncalls++;
+  });
+
+  process.on('exit', function() {
+    unlink(pathname);
+    assert.equal(ncalls, 1);
+  });
+})();
+
+(function() {
+  var pathname = common.tmpDir + '/test3';
+
+  unlink(pathname);
+  fs.mkdirSync(pathname);
+
+  var exists = path.existsSync(pathname);
+  unlink(pathname);
+
+  assert.equal(exists, true);
+})();
+
+// Keep the event loop alive so the async mkdir() requests
+// have a chance to run (since they don't ref the event loop).
+process.nextTick(function(){});