Consider the following package structure:

With the following setup.py contents:

from setuptools import setup, find_packages

setup(
    name='dfl_client',
    packages=find_packages(exclude=['*tests*']),
    include_package_data=True,
    package_data={"": ['py.typed', '*.pyi']},
)

When I package it using python setup.py sdist bdist_wheel, the resulting wheel:

• contains the py.typed file, which is good
• contains the tests folder, while it should be excluded according to the find_packages doc.

I spent hours trying to understand why with no success. Especially because it seems to work for other projects !

(I spent so many time trying to understand this stupid issue that I answer my own question hoping that can save time to others facing the same problem)

I finally found the culprit: it is a hidden interaction between setuptools_scm and the include_package_data=True flag.

By itself, include_package_data=True does not make the tests directory be included in the wheel. However if setuptools_scm is installed and the folder is under version control (and the tests directory is in the list of git-managed files), then the exclude directive does not seem to be taken into account anymore.

So the solution was simply to remove the include_package_data=True, that is actually not needed when package_data is present:

from setuptools import setup, find_packages

setup(
    name='dfl_client',
    packages=find_packages(exclude=['*tests*']),
    package_data={"": ['py.typed', '*.pyi']},
)

See setuptools doc on including files (that is actually very straightforward about include_package_data) and this related issue and workaround (the workaround seems to work for the wheel too, not only the sdist).