http: fix buffer writes to outgoing messages

lib/http.js

@@ -387,7 +387,7 @@ OutgoingMessage.prototype._buffer = function(data, encoding) {
   var lastEncoding = this.outputEncodings[length - 1];
   var lastData = this.output[length - 1];
 
-  if ((lastEncoding === encoding) ||
+  if ((encoding && lastEncoding === encoding) ||
       (!encoding && data.constructor === lastData.constructor)) {
     this.output[length - 1] = lastData + data;
     return false;

test/simple/test-http-client-upload-buf.js

@@ -0,0 +1,52 @@
+var common = require('../common');
+var assert = require('assert');
+var http = require('http');
+
+var N = 1024;
+var bytesRecieved = 0;
+var server_req_complete = false;
+var client_res_complete = false;
+
+var server = http.createServer(function(req, res) {
+  assert.equal('POST', req.method);
+
+  req.addListener('data', function(chunk) {
+    bytesRecieved += chunk.length;
+  });
+
+  req.addListener('end', function() {
+    server_req_complete = true;
+    console.log('request complete from server');
+    res.writeHead(200, {'Content-Type': 'text/plain'});
+    res.write('hello\n');
+    res.end();
+  });
+});
+server.listen(common.PORT);
+
+server.addListener('listening', function() {
+  var client = http.createClient(common.PORT);
+  var req = client.request('POST', '/');
+
+  req.write(new Buffer(N));
+  req.end();
+
+  common.error('client finished sending request');
+
+  req.addListener('response', function(res) {
+    res.setEncoding('utf8');
+    res.addListener('data', function(chunk) {
+      console.log(chunk);
+    });
+    res.addListener('end', function() {
+      client_res_complete = true;
+      server.close();
+    });
+  });
+});
+
+process.addListener('exit', function() {
+  assert.equal(N, bytesRecieved);
+  assert.equal(true, server_req_complete);
+  assert.equal(true, client_res_complete);
+});