build: Use find_namespace: to ensure discovery of package data

[matthewfeickert]

Description

Resolves #1880

Use find_namespace: in conjunction with include_package_data = True in setup.cfg to properly find package data (pyhf.data and pyhf.schemas) during build of sdist and wheel. The recommendation from setuptools is to treat the data/ and schemas/ subdirectories as namespace packages given PEP 420.

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• Tests are passing
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* Use `find_namespace:` in conjunction with `include_package_data = True` in setup.cfg
to properly find package data (pyhf.data and pyhf.schemas) during build of sdist
and wheel.
   - The recommendation from setuptools is to treat the data/ and schemas/ subdirectories as
     namespace packages given PEP 420 (https://peps.python.org/pep-0420/).
   - c.f. https://setuptools.pypa.io/en/stable/userguide/datafiles.html#subdirectory-for-data-files

[codecov]

Codecov Report

Merging #1881 (566a0af) into master (4682725) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1881   +/-   ##
=======================================
  Coverage   98.17%   98.17%           
=======================================
  Files          68       68           
  Lines        4322     4322           
  Branches      726      726           
=======================================
  Hits         4243     4243           
  Misses         46       46           
  Partials       33       33           

Flag	Coverage Δ
contrib	26.39% <ø> (ø)
doctest	60.73% <ø> (ø)
unittests-3.10	96.04% <ø> (ø)
unittests-3.7	96.02% <ø> (ø)

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[matthewfeickert]

$ python -m build .

is no longer reporting the SetuptoolsDeprecationWarning of Issue #1880. 👍 @henryiii, as the resident Scikit-HEP packaging expert, if we can bug you for a cross check here that would be great.

[henryiii]

Given you use a src/ directory, I think this is all that's needed. (If not, you'd need to ideally protect directories like tests and docs).

[matthewfeickert]

Thanks @henryiii!