web: do not send content on HTTPError(204)

tornado/test/web_test.py

@@ -1691,6 +1691,18 @@ def test_204_headers(self):
  self.assertNotIn("Transfer-Encoding", response.headers)
 
 
+class Header204viaHTTPErrorTest(SimpleHandlerTestCase):
+ class Handler(RequestHandler):
+ def get(self):
+ raise HTTPError(204)
+
+ def test_204_headers_via_httperror(self):
+ response = self.fetch("/")
+ self.assertEqual(response.code, 204)
+ self.assertNotIn("Content-Length", response.headers)
+ self.assertNotIn("Transfer-Encoding", response.headers)
+
+
 class Header304Test(SimpleHandlerTestCase):
  class Handler(RequestHandler):
  def get(self):

tornado/web.py

@@ -1222,6 +1222,10 @@ def flush(self, include_footers: bool = False) -> "Future[None]":
  future.set_result(None)
  return future
 
+ def _should_not_send_content(self, status_code: int) -> bool:
+ """Check if we should not send body content for given `status_code`"""
+ return status_code in (204, 304) or (100 <= status_code < 200)
+
  def finish(self, chunk: Optional[Union[str, bytes, dict]] = None) -> "Future[None]":
  """Finishes this response, ending the HTTP request.
 
@@ -1255,10 +1259,9 @@ def finish(self, chunk: Optional[Union[str, bytes, dict]] = None) -> "Future[Non
  if self.check_etag_header():
  self._write_buffer = []
  self.set_status(304)
- if self._status_code in (204, 304) or (100 <= self._status_code < 200):
- assert not self._write_buffer, (
- "Cannot send body with %s" % self._status_code
- )
+ if self._should_not_send_content(self._status_code):
+ if self._write_buffer:
+ raise RuntimeError(f"Cannot send body with status code HTTP{self._status_code}")
  self._clear_representation_headers()
  elif "Content-Length" not in self._headers:
  content_length = sum(len(part) for part in self._write_buffer)
@@ -1349,7 +1352,9 @@ def write_error(self, status_code: int, **kwargs: Any) -> None:
  the "current" exception for purposes of methods like
  ``sys.exc_info()`` or ``traceback.format_exc``.
  """
- if self.settings.get("serve_traceback") and "exc_info" in kwargs:
+ if self._should_not_send_content(status_code):
+ self.finish()
+ elif self.settings.get("serve_traceback") and "exc_info" in kwargs:
  # in debug mode, try to send a traceback
  self.set_header("Content-Type", "text/plain")
  for line in traceback.format_exception(*kwargs["exc_info"]):