http: reject addTrailers after finish

Fixes: #62809

Author: ryuhei shima

lib/_http_outgoing.js

@@ -54,6 +54,7 @@ const {
     ERR_HTTP_BODY_NOT_ALLOWED,
     ERR_HTTP_CONTENT_LENGTH_MISMATCH,
     ERR_HTTP_HEADERS_SENT,
+    ERR_HTTP_TRAILERS_ALREADY_SENT,
     ERR_HTTP_INVALID_HEADER_VALUE,
     ERR_HTTP_TRAILER_INVALID,
     ERR_INVALID_ARG_TYPE,
@@ -977,6 +978,10 @@ function connectionCorkNT(conn) {
 }
 
 OutgoingMessage.prototype.addTrailers = function addTrailers(headers) {
+  if (this.finished) {
+    throw new ERR_HTTP_TRAILERS_ALREADY_SENT();
+  }
+
   this._trailer = '';
   const keys = ObjectKeys(headers);
   const isArray = ArrayIsArray(headers);

lib/internal/errors.js

@@ -1343,6 +1343,8 @@ 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',
   'Cannot %s headers after they are sent to the client', Error);
+E('ERR_HTTP_TRAILERS_ALREADY_SENT',
+  'Trailing headers have already been sent', Error);
 E('ERR_HTTP_INVALID_HEADER_VALUE',
   'Invalid value "%s" for header "%s"', TypeError, HideStackFramesError);
 E('ERR_HTTP_INVALID_STATUS_CODE', 'Invalid status code: %s', RangeError);

test/parallel/test-http-outgoing-proto.js

@@ -129,6 +129,16 @@ assert.throws(() => {
   message: 'Invalid character in trailer content ["404"]'
 });
 
+assert.throws(() => {
+  const outgoingMessage = new OutgoingMessage();
+  outgoingMessage.finished = true;
+  outgoingMessage.addTrailers({ 'x-foo': 'bar' });
+}, {
+  code: 'ERR_HTTP_TRAILERS_ALREADY_SENT',
+  name: 'Error',
+  message: 'Trailing headers have already been sent'
+});
+
 {
   const outgoingMessage = new OutgoingMessage();
   assert.strictEqual(outgoingMessage.destroyed, false);