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).

API Reference

Utility Functions