fs: fix WriteStream fd leak

Close the file descriptor when a write operation fails.

Fixes #4387.

lib/fs.js

@@ -1493,10 +1493,19 @@ WriteStream.prototype.flush = function() {
 
     if (err) {
       self.writable = false;
-      if (cb) {
-        cb(err);
+
+      function emit() {
+        self.fd = null;
+        if (cb) cb(err);
+        self.emit('error', err);
       }
-      self.emit('error', err);
+
+      if (self.fd === null) {
+        emit();
+      } else {
+        fs.close(self.fd, emit);
+      }
+
       return;
     }
 

test/simple/test-fs-write-stream-err.js

@@ -0,0 +1,52 @@
+// 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 fs = require('fs');
+
+var stream = fs.createWriteStream(common.tmpDir + '/out');
+var err = new Error('BAM');
+
+stream.write(new Buffer(256), function() {
+  var fd = stream.fd;
+
+  fs.write = function() {
+    var cb = arguments[arguments.length - 1];
+    process.nextTick(function() {
+      cb(err);
+    });
+  };
+
+  fs.close = function(fd_, cb) {
+    assert.equal(fd_, fd);
+    process.nextTick(cb);
+  };
+
+  stream.write(new Buffer(256), common.mustCall(function(err_) {
+    assert.equal(err_, err);
+  }));
+
+  stream.on('error', common.mustCall(function(err_) {
+    assert.equal(stream.fd, null);
+    assert.equal(err_, err);
+  }));
+});