http: writeHead if statusmessage is undefined dont override headers

PR-URL: #46173
Fixes: #32395
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

lib/_http_server.js

@@ -347,7 +347,7 @@ function writeHead(statusCode, reason, obj) {
     // writeHead(statusCode[, headers])
     if (!this.statusMessage)
       this.statusMessage = STATUS_CODES[statusCode] || 'unknown';
-    obj = reason;
+    obj ??= reason;
   }
   this.statusCode = statusCode;
 

test/parallel/test-http-write-head-2.js

@@ -59,3 +59,21 @@ const http = require('http');
     }));
   }));
 }
+
+{
+  const server = http.createServer(common.mustCall((req, res) => {
+    res.writeHead(200, undefined, [ 'foo', 'bar' ]);
+    res.end();
+  }));
+
+  server.listen(0, common.mustCall(() => {
+    http.get({ port: server.address().port }, common.mustCall((res) => {
+      assert.strictEqual(res.statusMessage, 'OK');
+      assert.strictEqual(res.statusCode, 200);
+      assert.strictEqual(res.headers.foo, 'bar');
+      res.resume().on('end', common.mustCall(() => {
+        server.close();
+      }));
+    }));
+  }));
+}