How Checks are Run¶
In Flake8 2.x, Flake8 delegated check running to pep8. In 3.0 Flake8
takes on that responsibility. This has allowed for simpler
handling of the --jobs parameter (using multiprocessing) and
simplified our fallback if something goes awry with concurrency.
At the lowest level we have a FileChecker. Instances of FileChecker are
created for each file to be analyzed by Flake8. Each instance, has a copy
of all of the plugins registered with setuptools in the flake8.extension
entry-point group.
The FileChecker instances are managed by an instance of Manager. The
Manager instance handles creating sub-processes with
multiprocessing module and falling back to running checks in serial if
an operating system level error arises. When creating FileChecker instances,
the Manager is responsible for determining if a particular file has been
excluded.
Processing Files¶
Unfortunately, since Flake8 took over check running from pep8/pycodestyle,
it also had to take over parsing and processing files for the checkers
to use. Since it couldn’t reuse pycodestyle’s functionality (since it did not
separate cleanly the processing from check running) that function was isolated
into the FileProcessor class. We moved
several helper functions into the flake8.processor module (see also
Processor Utility Functions).