http: Return true on empty writes, not false

Otherwise, writing an empty string causes the whole program to grind to
a halt when piping data into http messages.

This wasn't as much of a problem (though it WAS a bug) in 0.8 and
before, because our hyperactive 'drain' behavior would mean that some
*previous* write() would probably have a pending drain event, and cause
things to start moving again.

lib/http.js

@@ -780,7 +780,9 @@ OutgoingMessage.prototype.write = function(chunk, encoding) {
     throw new TypeError('first argument must be a string or Buffer');
   }
 
-  if (chunk.length === 0) return false;
+  // If we get an empty string or buffer, then just do nothing, and
+  // signal the user to keep writing.
+  if (chunk.length === 0) return true;
 
   // TODO(bnoordhuis) Temporary optimization hack, remove in v0.11. We only
   // want to convert the buffer when we're sending:

test/simple/test-http-zero-length-write.js

@@ -0,0 +1,93 @@
+// 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 http = require('http');
+
+var Stream = require('stream');
+
+function getSrc() {
+  // An old-style readable stream.
+  // The Readable class prevents this behavior.
+  var src = new Stream();
+
+  // start out paused, just so we don't miss anything yet.
+  var paused = false;
+  src.pause = function() {
+    paused = true;
+  };
+  src.resume = function() {
+    paused = false;
+  };
+
+  var chunks = [ '', 'asdf', '', 'foo', '', 'bar', '' ];
+  var interval = setInterval(function() {
+    if (paused)
+      return
+
+    var chunk = chunks.shift();
+    if (chunk !== undefined) {
+      src.emit('data', chunk);
+    } else {
+      src.emit('end');
+      clearInterval(interval);
+    }
+  }, 1);
+
+  return src;
+}
+
+
+var expect = 'asdffoobar';
+
+var server = http.createServer(function(req, res) {
+  var actual = '';
+  req.setEncoding('utf8');
+  req.on('data', function(c) {
+    actual += c;
+  });
+  req.on('end', function() {
+    assert.equal(actual, expect);
+    getSrc().pipe(res);
+  });
+  server.close();
+});
+
+server.listen(common.PORT, function() {
+  var req = http.request({ port: common.PORT, method: 'POST' });
+  var actual = '';
+  req.on('response', function(res) {
+    res.setEncoding('utf8');
+    res.on('data', function(c) {
+      actual += c;
+    });
+    res.on('end', function() {
+      assert.equal(actual, expect);
+    });
+  });
+  getSrc().pipe(req);
+});
+
+process.on('exit', function(c) {
+  if (!c) console.log('ok');
+});