pytest-dev / pytest-dev/pytest-forked

`ResourceWarning`/`PytestUnraisableExceptionWarning` with version 1.7.5

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Description

Pytest functions decorated with @pytest.mark.forked that were working fine on version 1.6.0 (previous PyPI release) are now failing on 1.7.5 (full error at the end):

ExceptionGroup: multiple unraisable exception warnings (2 sub-exceptions)
ResourceWarning: unclosed file <_io.TextIOWrapper name='.../stderr' mode='w' encoding='UTF-8'>

I believe it's due to this code which calls flush() without close(), introduced in c33e4e1efad870b3b9aa308e4ec8ac145884c83d:

https://github.com/pytest-dev/pytest-forked/blob/3e8450ba17b184b7070c7e93de140db2f87d9239/src/pytest_forked/__init__.py#L101-L106

The test fails with an ExceptionGroup containing two PytestUnraisableExceptionWarning errors, one each for unclosed stdout and stderr temp files.

Full error 
============================= test session starts ==============================
platform darwin -- Python 3.14.6, pytest-9.1.1, pluggy-1.6.0
rootdir: …
configfile: pytest.ini
plugins: anyio-4.14.0, forked-1.7.5
collected 1 item

tests/open_browser.py E                                                  [100%]

==================================== ERRORS ====================================
________________________ ERROR at setup of pytest_fork _________________________
+ Exception Group Traceback (most recent call last):
  |   File "…/.venv/lib/python3.14/site-packages/_pytest/runner.py", line 361, in from_call
  |     result: TResult | None = func()
  |                              ~~~~^^
  |   File "…/.venv/lib/python3.14/site-packages/_pytest/runner.py", line 250, in <lambda>
  |     lambda: runtest_hook(item=item, **kwds),
  |             ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^
  |   File "…/.venv/lib/python3.14/site-packages/pluggy/_hooks.py", line 512, in __call__
  |     return self._hookexec(self.name, self._hookimpls.copy(), kwargs, firstresult)
  |            ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |   File "…/.venv/lib/python3.14/site-packages/pluggy/_manager.py", line 120, in _hookexec
  |     return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
  |            ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |   File "…/.venv/lib/python3.14/site-packages/pluggy/_callers.py", line 167, in _multicall
  |     raise exception
  |   File "…/.venv/lib/python3.14/site-packages/pluggy/_callers.py", line 139, in _multicall
  |     teardown.throw(exception)
  |     ~~~~~~~~~~~~~~^^^^^^^^^^^
  |   File "…/.venv/lib/python3.14/site-packages/_pytest/logging.py", line 858, in pytest_runtest_setup
  |     yield
  |   File "…/.venv/lib/python3.14/site-packages/pluggy/_callers.py", line 139, in _multicall
  |     teardown.throw(exception)
  |     ~~~~~~~~~~~~~~^^^^^^^^^^^
  |   File "…/.venv/lib/python3.14/site-packages/_pytest/capture.py", line 895, in pytest_runtest_setup
  |     return (yield)
  |             ^^^^^
  |   File "…/.venv/lib/python3.14/site-packages/pluggy/_callers.py", line 121, in _multicall
  |     res = hook_impl.function(*args)
  |   File "…/.venv/lib/python3.14/site-packages/_pytest/unraisableexception.py", line 178, in pytest_runtest_setup
  |     collect_unraisable(item.config)
  |     ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  |   File "…/.venv/lib/python3.14/site-packages/_pytest/unraisableexception.py", line 81, in collect_unraisable
  |     raise ExceptionGroup("multiple unraisable exception warnings", errors)
  | ExceptionGroup: multiple unraisable exception warnings (2 sub-exceptions)
  +-+---------------- 1 ----------------
    | Traceback (most recent call last):
    |   File "…/.venv/lib/python3.14/site-packages/_pytest/capture.py", line 425, in resume
    |     setattr(sys, self.name, self.tmpfile)
    |     ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    | ResourceWarning: unclosed file <_io.TextIOWrapper name='/var/folders/mx/t3rtb4cn7xxfz8w_pcfdffhm0000gn/T/tmpq33e1t7y/stderr' mode='w' encoding='UTF-8'>
    | 
    | The above exception was the direct cause of the following exception:
    | 
    | Traceback (most recent call last):
    |   File "…/.venv/lib/python3.14/site-packages/_pytest/unraisableexception.py", line 67, in collect_unraisable
    |     warnings.warn(pytest.PytestUnraisableExceptionWarning(msg))
    |     ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    | pytest.PytestUnraisableExceptionWarning: Exception ignored while finalizing file <_io.FileIO name='/var/folders/mx/t3rtb4cn7xxfz8w_pcfdffhm0000gn/T/tmpq33e1t7y/stderr' mode='wb' closefd=True>: None
    | 
    +---------------- 2 ----------------
    | Traceback (most recent call last):
    |   File "…/.venv/lib/python3.14/site-packages/_pytest/capture.py", line 425, in resume
    |     setattr(sys, self.name, self.tmpfile)
    |     ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    | ResourceWarning: unclosed file <_io.TextIOWrapper name='/var/folders/mx/t3rtb4cn7xxfz8w_pcfdffhm0000gn/T/tmpq33e1t7y/stdout' mode='w' encoding='UTF-8'>
    | 
    | The above exception was the direct cause of the following exception:
    | 
    | Traceback (most recent call last):
    |   File "…/.venv/lib/python3.14/site-packages/_pytest/unraisableexception.py", line 67, in collect_unraisable
    |     warnings.warn(pytest.PytestUnraisableExceptionWarning(msg))
    |     ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    | pytest.PytestUnraisableExceptionWarning: Exception ignored while finalizing file <_io.FileIO name='/var/folders/mx/t3rtb4cn7xxfz8w_pcfdffhm0000gn/T/tmpq33e1t7y/stdout' mode='wb' closefd=True>: None
    | 
    +------------------------------------

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with src/pytest_forked/init.py at the cited lines 101-106 and reproduce a pytest function decorated with @pytest.mark.forked on version 1.7.5. Check the handling of stdout and stderr temporary files; done means the forked test completes without unclosed-file ResourceWarning or PytestUnraisableExceptionWarning errors.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
testing-qa
Issue type
Bug
Difficulty
2/5
Estimated time
1-3 hours
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
72/100

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