test: test case for multiple res.writeHead and res.getHeader

PR-URL: #45508
Fixes: #36721
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

lib/_http_server.js

@@ -331,6 +331,11 @@ ServerResponse.prototype._implicitHeader = function _implicitHeader() {
 
 ServerResponse.prototype.writeHead = writeHead;
 function writeHead(statusCode, reason, obj) {
+
+  if (this._header) {
+    throw new ERR_HTTP_HEADERS_SENT('write');
+  }
+
   const originalStatusCode = statusCode;
 
   statusCode |= 0;

test/parallel/test-domain-multi.js

@@ -46,8 +46,9 @@ const server = http.createServer((req, res) => {
 
   b.on('error', common.mustCall((er) => {
     if (res) {
-      res.writeHead(500);
-      res.end('An error occurred');
+      // Introduce an error on the client by writing unexpected data.
+      // The client is now expecting a chunk header so any letter will have the parser throw an error.
+      res.socket.write('H');
     }
     // res.writeHead(500), res.destroy, etc.
     server.close();

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

@@ -58,7 +58,6 @@ const s = http.createServer(common.mustCall((req, res) => {
   }, {
     code: 'ERR_HTTP_HEADERS_SENT',
     name: 'Error',
-    message: 'Cannot render headers after they are sent to the client'
   });
 
   res.end();
@@ -76,3 +75,24 @@ function runTest() {
     response.resume();
   }));
 }
+
+{
+  const server = http.createServer(common.mustCall((req, res) => {
+    res.writeHead(200, [ 'test', '1' ]);
+    assert.throws(() => res.writeHead(200, [ 'test2', '2' ]), {
+      code: 'ERR_HTTP_HEADERS_SENT',
+      name: 'Error',
+    });
+    res.end();
+  }));
+
+  server.listen(0, common.mustCall(() => {
+    http.get({ port: server.address().port }, (res) => {
+      assert.strictEqual(res.headers.test, '1');
+      assert.strictEqual('test2' in res.headers, false);
+      res.resume().on('end', common.mustCall(() => {
+        server.close();
+      }));
+    });
+  }));
+}