lib: refactor ServerResponse.prototype.writeHead

lib/_http_server.js

@@ -237,48 +237,50 @@ ServerResponse.prototype._implicitHeader = function _implicitHeader() {
   this.writeHead(this.statusCode);
 };
 
-ServerResponse.prototype.writeHead = writeHead;
-function writeHead(statusCode, reason, obj) {
+ServerResponse.prototype.writeHead = function(
+  statusCode,
+  statusMessage,
+  headers
+) {
   const originalStatusCode = statusCode;
 
   statusCode |= 0;
   if (statusCode < 100 || statusCode > 999) {
     throw new ERR_HTTP_INVALID_STATUS_CODE(originalStatusCode);
   }
 
-
-  if (typeof reason === 'string') {
-    // writeHead(statusCode, reasonPhrase[, headers])
-    this.statusMessage = reason;
-  } else {
+  if (headers === undefined && typeof statusMessage === 'object') {
     // writeHead(statusCode[, headers])
-    if (!this.statusMessage)
-      this.statusMessage = STATUS_CODES[statusCode] || 'unknown';
-    obj = reason;
+    headers = statusMessage;
+  } else if (typeof statusMessage === 'string') {
+    // writeHead(statusCode, reasonPhrase[, headers])
+    this.statusMessage = statusMessage;
   }
+  if (this.statusMessage == null)
+    this.statusMessage = STATUS_CODES[statusCode] || 'unknown';
   this.statusCode = statusCode;
 
-  let headers;
+  let _headers;
   if (this[kOutHeaders]) {
     // Slow-case: when progressive API and header fields are passed.
     let k;
-    if (obj) {
-      const keys = ObjectKeys(obj);
+    if (headers) {
+      const keys = ObjectKeys(headers);
       // Retain for(;;) loop for performance reasons
       // Refs: https://github.com/nodejs/node/pull/30958
       for (let i = 0; i < keys.length; i++) {
         k = keys[i];
-        if (k) this.setHeader(k, obj[k]);
+        if (k) this.setHeader(k, headers[k]);
       }
     }
     if (k === undefined && this._header) {
       throw new ERR_HTTP_HEADERS_SENT('render');
     }
     // Only progressive api is used
-    headers = this[kOutHeaders];
+    _headers = this[kOutHeaders];
   } else {
     // Only writeHead() called
-    headers = obj;
+    _headers = headers;
   }
 
   if (checkInvalidHeaderChar(this.statusMessage))
@@ -307,10 +309,10 @@ function writeHead(statusCode, reason, obj) {
     this.shouldKeepAlive = false;
   }
 
-  this._storeHeader(statusLine, headers);
+  this._storeHeader(statusLine, _headers);
 
   return this;
-}
+};
 
 // Docs-only deprecated: DEP0063
 ServerResponse.prototype.writeHeader = ServerResponse.prototype.writeHead;

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

@@ -150,7 +150,7 @@ const s = http.createServer(common.mustCall((req, res) => {
     case 'writeHead':
       res.statusCode = 404;
       res.setHeader('x-foo', 'keyboard cat');
-      res.writeHead(200, { 'x-foo': 'bar', 'x-bar': 'baz' });
+      res.writeHead(200, undefined, { 'x-foo': 'bar', 'x-bar': 'baz' });
       break;
 
     default: