Fixed field merging with progressive fields on writeHead()

lib/http.js

@@ -303,9 +303,6 @@ function OutgoingMessage() {
   this._trailer = '';
 
   this.finished = false;
-  
-  this._headers = {};
-  this._headerNames = {};
 }
 util.inherits(OutgoingMessage, stream.Stream);
 
@@ -507,6 +504,8 @@ OutgoingMessage.prototype.setHeader = function(name, value) {
   }
 
   var key = name.toLowerCase();
+  this._headers = this._headers || {};
+  this._headerNames = this._headerNames || {};
   this._headers[key] = value;
   this._headerNames[key] = name;
 };
@@ -521,6 +520,8 @@ OutgoingMessage.prototype.getHeader = function(name) {
     throw new Error("Can't use mutable header APIs after sent.");
   }
 
+  if (!this._headers) return;
+
   var key = name.toLowerCase();
   return this._headers[key];
 };
@@ -535,6 +536,8 @@ OutgoingMessage.prototype.removeHeader = function(name) {
     throw new Error("Can't remove headers after they are sent.");
   }
 
+  if (!this._headers) return;
+
   var key = name.toLowerCase();
   delete this._headers[key];
   delete this._headerNames[key];
@@ -545,6 +548,9 @@ OutgoingMessage.prototype._renderHeaders = function() {
   if (this._header) {
     throw new Error("Can't render headers after they are sent to the client.");
   }
+
+  if (!this._headers) return {};
+
   var headers = {};
   var keys = Object.keys(this._headers);
   for (var i = 0, l = keys.length; i < l; i++) {
@@ -754,7 +760,7 @@ ServerResponse.prototype.writeContinue = function() {
 };
 
 ServerResponse.prototype._implicitHeader = function() {
-  this.writeHead(this.statusCode, this._renderHeaders());
+  this.writeHead(this.statusCode);
 };
 
 ServerResponse.prototype.writeHead = function(statusCode) {
@@ -768,10 +774,36 @@ ServerResponse.prototype.writeHead = function(statusCode) {
     headerIndex = 1;
   }
 
-  if (typeof arguments[headerIndex] == 'object') {
-    headers = arguments[headerIndex];
+  var obj = arguments[headerIndex];
+
+  if (obj && this._headers) {
+    // Slow-case: when progressive API and header fields are passed.
+    headers = this._renderHeaders();
+
+    if (Array.isArray(obj)) {
+      // handle array case
+      // TODO: remove when array is no longer accepted
+      var field;
+      for (var i = 0, len = obj.length; i < len; ++i) {
+        field = obj[i][0];
+        if (field in headers) {
+          obj.push([field, headers[field]]);
+        }
+      }
+      headers = obj;
+
+    } else {
+      // handle object case
+      for (var k in obj) {
+        if (k) headers[k] = obj[k];
+      }
+    }
+  } else if (this._headers) {
+    // only progressive api is used
+    headers = this._renderHeaders();
   } else {
-    headers = {};
+    // only writeHead() called
+    headers = obj;
   }
 
   var statusLine = 'HTTP/1.1 ' + statusCode.toString() + ' ' +

test/simple/test-http-mutable-headers.js

@@ -48,6 +48,12 @@ var s = http.createServer(function(req, res) {
       res.setHeader('transfer-encoding', 'chunked');
       assert.equal(res.getHeader('Transfer-Encoding'), 'chunked');
       break;
+
+    case 'writeHead':
+      res.statusCode = 404;
+      res.setHeader('x-foo', 'keyboard cat');
+      res.writeHead(200, { 'x-foo': 'bar', 'x-bar': 'baz' });
+      break;
   }
 
   res.statusCode = 201;
@@ -92,6 +98,13 @@ function nextTest () {
 
       case 'transferEncoding':
         assert.equal(response.headers['transfer-encoding'], 'chunked');
+        test = 'writeHead';
+        break;
+
+      case 'writeHead':
+        assert.equal(response.headers['x-foo'], 'bar');
+        assert.equal(response.headers['x-bar'], 'baz');
+        assert.equal(200, response.statusCode);
         test = 'end';
         break;
 
@@ -114,6 +127,6 @@ function nextTest () {
 
 
 process.on('exit', function() {
-  assert.equal(3, testsComplete);
+  assert.equal(4, testsComplete);
 });