net: Handle sync writable streams synchronously

This fixes the case where stderr doesn't flush before the process exits.

lib/_stream_writable.js

@@ -169,6 +169,9 @@ function onwrite(stream, er) {
 
   if (er) {
     if (cb) {
+      // If _write(chunk,cb) calls cb() in this tick, we still defer
+      // the *user's* write callback to the next tick.
+      // Never present an external API that is *sometimes* async!
       if (sync)
         process.nextTick(function() {
           cb(er);
@@ -184,8 +187,8 @@ function onwrite(stream, er) {
   state.length -= l;
 
   if (cb) {
-    // don't call the cb until the next tick if we're in sync mode.
-    // also, defer if we're about to write some more right now.
+    // Don't call the cb until the next tick if we're in sync mode.
+    // Also defer if we're about to write some more right now.
     if (sync || state.buffer.length)
       process.nextTick(cb);
     else

lib/net.js

@@ -595,9 +595,14 @@ Socket.prototype._write = function(dataEncoding, cb) {
     return this._destroy(errnoException(errno, 'write'), cb);
 
   writeReq.oncomplete = afterWrite;
-  writeReq.cb = cb;
-
   this._bytesDispatched += writeReq.bytes;
+
+  // If it was entirely flushed, we can write some more right now.
+  // However, if more is left in the queue, then wait until that clears.
+  if (this._handle.writeQueueSize === 0)
+    cb();
+  else
+    writeReq.cb = cb;
 };
 
 
@@ -640,7 +645,8 @@ function afterWrite(status, handle, req) {
   if (self !== process.stderr && self !== process.stdout)
     debug('afterWrite call cb');
 
-  req.cb.call(self);
+  if (req.cb)
+    req.cb.call(self);
 }
 
 

test/simple/test-stream2-stderr-sync.js

@@ -0,0 +1,130 @@
+// 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.
+
+// Make sure that sync writes to stderr get processed before exiting.
+
+var common = require('../common.js');
+var assert = require('assert');
+
+function parent() {
+  var spawn = require('child_process').spawn;
+  var assert = require('assert');
+  var i = 0;
+  children.forEach(function(_, c) {
+    var child = spawn(process.execPath, [__filename, '' + c]);
+    var err = '';
+
+    child.stderr.on('data', function(c) {
+      err += c;
+    });
+
+    child.on('close', function() {
+      assert.equal(err, 'child ' + c + '\nfoo\nbar\nbaz\n');
+      console.log('ok %d child #%d', ++i, c);
+      if (i === children.length)
+        console.log('1..' + i);
+    });
+  });
+}
+
+function child0() {
+  // Just a very simple wrapper around TTY(2)
+  // Essentially the same as stderr, but without all the net stuff.
+  var Writable = require('stream').Writable;
+  var util = require('util');
+
+  // a lowlevel stderr writer
+  var TTY = process.binding('tty_wrap').TTY;
+  var handle = new TTY(2, false);
+
+  util.inherits(W, Writable);
+
+  function W(opts) {
+    Writable.call(this, opts);
+  }
+
+  W.prototype._write = function(chunk, cb) {
+    var req = handle.writeUtf8String(chunk.toString() + '\n');
+    // here's the problem.
+    // it needs to tell the Writable machinery that it's ok to write
+    // more, but that the current buffer length is handle.writeQueueSize
+    req.oncomplete = afterWrite
+    if (req.writeQueueSize === 0)
+      req.cb = cb;
+    else
+      cb();
+  }
+  function afterWrite(status, handle, req) {
+    if (req.cb)
+      req.cb();
+  }
+
+  var w = new W
+  w.write('child 0');
+  w.write('foo');
+  w.write('bar');
+  w.write('baz');
+}
+
+// using console.error
+function child1() {
+  console.error('child 1');
+  console.error('foo');
+  console.error('bar');
+  console.error('baz');
+}
+
+// using process.stderr
+function child2() {
+  process.stderr.write('child 2\n');
+  process.stderr.write('foo\n');
+  process.stderr.write('bar\n');
+  process.stderr.write('baz\n');
+}
+
+// using a net socket
+function child3() {
+  var net = require('net');
+  var socket = new net.Socket({ fd: 2 });
+  socket.write('child 3\n');
+  socket.write('foo\n');
+  socket.write('bar\n');
+  socket.write('baz\n');
+}
+
+
+function child4() {
+  console.error('child 4\nfoo\nbar\nbaz');
+}
+
+function child5() {
+  process.stderr.write('child 5\nfoo\nbar\nbaz\n');
+}
+
+var children = [ child0, child1, child2, child3, child4, child5 ];
+
+if (!process.argv[2]) {
+  parent();
+} else {
+  children[process.argv[2]]();
+  // immediate process.exit to kill any waiting stuff.
+  process.exit();
+}