Metadata-Version: 2.1
Name: flake8-no-pep420
Version: 2.7.0
Summary: A flake8 plugin to ban PEP-420 implicit namespace packages.
Home-page: https://github.com/adamchainz/flake8-no-pep420
Author: Adam Johnson
Author-email: me@adamj.eu
License: MIT
Project-URL: Changelog, https://github.com/adamchainz/flake8-no-pep420/blob/main/CHANGELOG.rst
Project-URL: Mastodon, https://fosstodon.org/@adamchainz
Project-URL: Twitter, https://twitter.com/adamchainz
Keywords: flake8
Classifier: Development Status :: 5 - Production/Stable
Classifier: Framework :: Flake8
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: MIT License
Classifier: Natural Language :: English
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3 :: Only
Classifier: Programming Language :: Python :: 3.8
Classifier: Programming Language :: Python :: 3.9
Classifier: Programming Language :: Python :: 3.10
Classifier: Programming Language :: Python :: 3.11
Classifier: Programming Language :: Python :: 3.12
Classifier: Typing :: Typed
Requires-Python: >=3.8
Description-Content-Type: text/x-rst
License-File: LICENSE
Requires-Dist: flake8 (!=3.2.0,>=3.0)

================
flake8-no-pep420
================

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A `flake8 <https://flake8.readthedocs.io/en/latest/index.html>`_ plugin to ban `PEP-420 <https://www.python.org/dev/peps/pep-0420/>`__ implicit namespace packages.

Requirements
============

Python 3.8 to 3.12 supported.

Installation
============

First, install with ``pip``:

.. code-block:: sh

     python -m pip install flake8-no-pep420

Second, if you define Flake8’s ``select`` setting, add the ``INP`` prefix to it.
Otherwise, the plugin should be active by default.

----

**Linting a Django project?**
Check out my book `Boost Your Django DX <https://adamchainz.gumroad.com/l/byddx>`__ which covers Flake8 and many other code quality tools.

----

Rationale
=========

Implicit namespace packages are directories of Python files without an ``__init__.py``.
They’re valid and importable, but they break *many* tools, such as:

* `unittest test discovery <https://bugs.python.org/issue23882>`__ (and by extension, Django’s test runner)
* `Coverage.py <https://github.com/nedbat/coveragepy/issues/1024>`__
* Mypy without its `--namespace-packages option <https://mypy.readthedocs.io/en/latest/command_line.html#import-discovery>`__
* `pytest <https://github.com/pytest-dev/pytest/issues/5147>`__

In most cases, tools fail silently, which can lead to a false sense of security:

* Tests may look legitimate but never run
* Code may be untested but not appear in coverage statistics
* Types may never be checked

PEP-420’s algorithm is non-trivial which is probably why such tools haven’t (yet) implemented it.

Rules
=====

INP001: File is part of an implicit namespace package. Add __init__.py?
-----------------------------------------------------------------------

flake8-no-pep420 will trigger this on the first line of any file that sits in a directory without an ``__init__.py`` file.

Often projects have a few root files *not* in packages, for which an ``__init__.py`` file should not be added.
For example, Django projects normally have a ``manage.py`` file in the root of their repository.
In these cases you can ignore the ``INP001`` error.
It’s possible to use ``# noqa: INP001`` to ignore the error in-line, but this isn’t possible if the first line is a `shebang <https://en.wikipedia.org/wiki/Shebang_(Unix)>`__, such as in Django’s ``manage.py``.
In such cases it’s preferable to use Flake8’s `per-file-ignores option <https://flake8.pycqa.org/en/latest/user/options.html#cmdoption-flake8-per-file-ignores>`__, for example in ``setup.cfg``:

.. code-block:: ini

    [flake8]
    # ...
    per-file-ignores =
        manage.py:INP001