Error types defined in h11 and httpx

[ludo-lumapps]

I tried to catch a LocalProtocolError error from within a Client.post, but I realized that I wasn't catching the "correct" one.

  File ".../venv/lib64/python3.9/site-packages/httpx/_client.py", line 987, in post
    return self.request(
  File ".../venv/lib64/python3.9/site-packages/httpx/_client.py", line 728, in request
    return self.send(
  File ".../venv/lib64/python3.9/site-packages/httpx/_client.py", line 762, in send
    response = self._send_handling_auth(
  File ".../venv/lib64/python3.9/site-packages/httpx/_client.py", line 800, in _send_handling_auth
    response = self._send_handling_redirects(
  File ".../venv/lib64/python3.9/site-packages/httpx/_client.py", line 832, in _send_handling_redirects
    response = self._send_single_request(request, timeout)
  File ".../venv/lib64/python3.9/site-packages/httpx/_client.py", line 856, in _send_single_request
    (status_code, headers, stream, ext) = transport.request(
  File ".../venv/lib64/python3.9/site-packages/httpx/_transports/default.py", line 102, in request
    return self._pool.request(method, url, headers=headers, stream=stream, ext=ext)
  File ".../venv/lib64/python3.9/site-packages/httpcore/_sync/connection_pool.py", line 218, in request
    response = connection.request(
  File ".../venv/lib64/python3.9/site-packages/httpcore/_sync/connection.py", line 106, in request
    return self.connection.request(method, url, headers, stream, ext)
  File ".../venv/lib64/python3.9/site-packages/httpcore/_sync/http11.py", line 66, in request
    self._send_request_body(stream, timeout)
  File ".../venv/lib64/python3.9/site-packages/httpcore/_sync/http11.py", line 116, in _send_request_body
    self._send_event(event, timeout)
  File ".../venv/lib64/python3.9/site-packages/httpcore/_sync/http11.py", line 123, in _send_event
    bytes_to_send = self.h11_state.send(event)
  File ".../venv/lib64/python3.9/site-packages/h11/_connection.py", line 468, in send
    data_list = self.send_with_data_passthrough(event)
  File ".../venv/lib64/python3.9/site-packages/h11/_connection.py", line 501, in send_with_data_passthrough
    writer(event, data_list.append)
  File ".../venv/lib64/python3.9/site-packages/h11/_writers.py", line 60, in __call__
    self.send_eom(event.headers, write)
  File ".../venv/lib64/python3.9/site-packages/h11/_writers.py", line 83, in send_eom
    raise LocalProtocolError("Too little data for declared Content-Length")

Turns out I need to catch:
from h11 import LocalProtocolError
rather than
from httpx import LocalProtocolError

Is this normal?

[0xamlab]

Yes, this is still a leak in current releases. I reproduced it with httpx 0.28.1 and httpcore 1.0.9: a request whose Content-Length exceeds the actual body bytes raises h11._util.LocalProtocolError: Too little data for declared Content-Length, not httpx.LocalProtocolError.

httpx does expose httpx.LocalProtocolError and maps httpcore.LocalProtocolError to it at httpx/_transports/default.py:90. The gap is in httpcore: it wraps h11 exceptions only while building request headers at httpcore/_sync/http11.py:144. When the body is serialized, _send_event calls self._h11_state.send(event) directly at httpcore/_sync/http11.py:164 with no map_exceptions guard, so the raw h11 exception bubbles straight through.

So catching from h11 import LocalProtocolError is currently the reliable workaround; the proper fix belongs in httpcore.