If request method is HEAD don't allow writing body bytes.

doc/api/http.md

@@ -2144,9 +2144,10 @@ it will switch to implicit header mode and flush the implicit headers.
 This sends a chunk of the response body. This method may
 be called multiple times to provide successive parts of the body.
 
-In the `node:http` module, the response body is omitted when the
-request is a HEAD request. Similarly, the `204` and `304` responses
-_must not_ include a message body.
+Writing to the body is not allowed when the request method or response status
+do not support content. If an attempt is made to write to the body for a
+HEAD request or as part of a `204` or `304`response, a synchronous `Error`
+with the code `ERR_HTTP_BODY_NOT_ALLOWED` is thrown.
 
 `chunk` can be a string or a buffer. If `chunk` is a string,
 the second parameter specifies how to encode it into a byte stream.

lib/_http_outgoing.js

@@ -60,6 +60,7 @@ const {
     ERR_HTTP_HEADERS_SENT,
     ERR_HTTP_INVALID_HEADER_VALUE,
     ERR_HTTP_TRAILER_INVALID,
+    ERR_HTTP_BODY_NOT_ALLOWED,
     ERR_INVALID_HTTP_TOKEN,
     ERR_INVALID_ARG_TYPE,
     ERR_INVALID_ARG_VALUE,
@@ -884,6 +885,10 @@ function write_(msg, chunk, encoding, callback, fromEnd) {
     err = new ERR_STREAM_DESTROYED('write');
   }
 
+  if (!msg._hasBody) {
+    throw ERR_HTTP_BODY_NOT_ALLOWED()
+  }
+
   if (err) {
     if (!msg.destroyed) {
       onError(msg, err, callback);
@@ -916,13 +921,6 @@ function write_(msg, chunk, encoding, callback, fromEnd) {
     msg._implicitHeader();
   }
 
-  if (!msg._hasBody) {
-    debug('This type of response MUST NOT have a body. ' +
-          'Ignoring write() calls.');
-    process.nextTick(callback);
-    return true;
-  }
-
   if (!fromEnd && msg.socket && !msg.socket.writableCorked) {
     msg.socket.cork();
     process.nextTick(connectionCorkNT, msg.socket);

lib/internal/errors.js

@@ -1159,6 +1159,8 @@ E('ERR_HTTP2_TRAILERS_NOT_READY',
   'Trailing headers cannot be sent until after the wantTrailers event is ' +
   'emitted', Error);
 E('ERR_HTTP2_UNSUPPORTED_PROTOCOL', 'protocol "%s" is unsupported.', Error);
+E('ERR_HTTP_BODY_NOT_ALLOWED',
+  'Adding content for this request method or response status is not allowed.', Error);
 E('ERR_HTTP_CONTENT_LENGTH_MISMATCH',
   'Response body\'s content-length of %s byte(s) does not match the content-length of %s byte(s) set in header', Error);
 E('ERR_HTTP_HEADERS_SENT',

test/parallel/test-http-head-response-has-no-body-end.js

@@ -29,7 +29,7 @@ const http = require('http');
 
 const server = http.createServer(function(req, res) {
   res.writeHead(200);
-  res.end('FAIL'); // broken: sends FAIL from hot path.
+  res.end();
 });
 server.listen(0);
 

test/parallel/test-http-head-throw-on-response-body-write.js

@@ -0,0 +1,53 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const http = require('http');
+
+
+const server = http.createServer((req, res) => {
+  res.writeHead(204);
+  assert.throws(() => {
+    res.write('this is content');
+  }, {
+    code: 'ERR_HTTP_BODY_NOT_ALLOWED',
+    name: 'Error',
+    message: 'Adding content for this request method or response status is not allowed.'
+  })
+  res.end()
+});
+server.listen(0);
+
+server.on('listening', common.mustCall(function() {
+  const req = http.request({
+    port: this.address().port,
+    method: 'GET',
+    path: '/'
+  }, common.mustCall((res) => {
+    res.resume()
+    res.on('end', common.mustCall(function() {
+      server.close();
+    }));
+  }));
+  req.end();
+}));