Platforms such as Termux on Android, and other exotic devices
do not provide a sem_open implementation on the OS level. This
is problematic, as the error resulting from this occurs when
calling multiprocessing.Pool, throwing an unhandled ImportError.
The issue itself is outlined in https://bugs.python.org/issue3770.
This change allows devices missing this system call to respond
to the missing feature by falling back to synchronous execution,
which appears to be the default behaviour if the multiprocessing
module is not found.
This change also adds a potential fix for developers working
on platforms where multiprocessing itself cannot be imported.
The existing code would set the name referencing the import to
None, but there are no clear checks to ensure this does not
result in an AttributeError later when multiprocessing.Pool
has accession attempts.
Existing users should see no difference in functionality, as they
will assumably already be able to use flake8, so will not be
missing this sem_open call.
Users on devices without the sem_open call will now be able
to use flake8 where they would be unable to before due to
unhandled ImportErrors.
Pytest 6.0.0rc1 attempts to log a repr of our mocked entry_point,
but it fails, becasue the repr metohod expects a valua attribute:
Reproducer:
$ tox -e py38 --force-dep 'pytest==6.0.0rc1'
...
Traceback (most recent call last):
File "/usr/lib/python3.8/logging/__init__.py", line 1081, in emit
msg = self.format(record)
File "/usr/lib/python3.8/logging/__init__.py", line 925, in format
return fmt.format(record)
File "/usr/lib/python3.8/logging/__init__.py", line 664, in format
record.message = record.getMessage()
File "/usr/lib/python3.8/logging/__init__.py", line 369, in getMessage
msg = msg % self.args
File "/tmp/flake8/.tox/py38/lib/python3.8/site-packages/flake8/plugins/manager.py", line 44, in __repr__
self.name, self.entry_point.value
File "/tmp/flake8/.tox/py38/lib/python3.8/site-packages/mock/mock.py", line 632, in __getattr__
raise AttributeError("Mock object has no attribute %r" % name)
AttributeError: Mock object has no attribute 'value'
This adds two new methods to the BaseFormatter class:
- beginning
- finished
These will indicate when Flake8 begins and finishes processing a file.
Closes#251
It seems likely that the multiprocessing module on Windows is not
capable of serializing an object with the structure that we have and
preserving the attributes we dynamically set on plugins (like the
FlakesChecker). To avoid issues like this with all plugins (although
we have only found this on Windows with the FlakesChecker), let's try
serializing the Checkers PluginTypeManager to a dictionary so that the
only object that a Queue is really trying to serialize/deserialize is
the FlakesChecker itself.
Related to #179
