AttributeError: type object 'async_generator_asend' has no attribute 'f_lineno'

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#699 opened on Oct 15, 2025 1 comment 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 4/5
Estimated time: 3-5 days
Newbie friendliness: 35/100

Issue type: Bug
Clarity: Needs clarification
Activity status: Stale
Tech stack: python
Domain: backend

Research direction

Reproduce the multipart upload with Python 3.12.11, uvloop 0.21.0, FastAPI, and uvicorn on Linux. Then inspect uvloop/loop.pyx around _asyncgen_finalizer_hook and uvloop/cbhandles.pyx around extract_stack, using the traceback.py call path as context. Done means async-generator cleanup no longer raises the reported AttributeError.

Written by the indexing model from the issue text.

Description

Bug Description

Getting AttributeError: type object 'async_generator_asend' has no attribute 'f_lineno' exceptions when handling multipart form uploads in FastAPI with uvloop.

Environment

Python version: 3.12.11
uvloop version: 0.21.0
OS: Linux (Docker)
Framework: FastAPI with uvicorn

Steps to Reproduce

Use FastAPI with uvloop enabled
Upload file via multipart form data
Exception appears in logs during async generator cleanup

Full Traceback

Exception ignored in: <async_generator object Request.stream at 0x7f6f1be8f920>
Traceback (most recent call last):
  File "uvloop/loop.pyx", line 3187, in uvloop.loop.Loop._asyncgen_finalizer_hook
  File "uvloop/loop.pyx", line 1289, in uvloop.loop.Loop.call_soon_threadsafe
  File "uvloop/cbhandles.pyx", line 329, in uvloop.loop.new_Handle
  File "uvloop/cbhandles.pyx", line 15, in uvloop.loop.Handle._set_loop
  File "uvloop/cbhandles.pyx", line 427, in uvloop.loop.extract_stack
  File "/usr/local/lib/python3.12/traceback.py", line 395, in extract
    return klass._extract_from_extended_frame_gen(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/traceback.py", line 418, in _extract_from_extended_frame_gen
    for f, (lineno, end_lineno, colno, end_colno) in frame_gen:
                                                     ^^^^^^^^^
  File "/usr/local/lib/python3.12/traceback.py", line 392, in extended_frame_gen
    for f, lineno in frame_gen:
                     ^^^^^^^^^
  File "/usr/local/lib/python3.12/traceback.py", line 336, in walk_stack
    yield f, f.f_lineno
             ^^^^^^^^^^
AttributeError: type object 'async_generator_asend' has no attribute 'f_lineno'

Dominant language: Cython
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