*.pyi files not installed

[thewtex]

Description

The Python interface files (*.pyi) are not installed into the install tree. As a result, they are missing from the 5.3rc4.post2 wheels.

Steps to Reproduce

1. Enable ITK_WRAP_PYTHON
2. ninja
3. DESTDIR=/tmp/itk-install ninja install
4. find /tmp/itk-install -name '*.pyi'

Expected behavior

The .pyi files are installed alongside the .py files.

Actual behavior

.pyi files are not installed.

Reproducibility

Always

Versions

ITK Git master, i.e.58ce6e84f2

Environment

Tested on Linux.

[hjmjohnson]

This is necessary to start getting the python system to be more consistent with remote modules: InsightSoftwareConsortium/ITKSphinxExamples#394

[hjmjohnson]

@thewtex I think I know how to manipulate the itk-stub files for installing, but I am not sure what is supposed to be done.

There is a variable called "PY_SITE_PACKAGES_PATH". That is sometimes set to CMAKE_INSTALL_PREFIX, and other times to the site-packages directory of the python interpreter.

Currently, the python stuff is installed to the python interpreter site-packages in the "itk" and "itk-stubs" directories, and I have confirmed that the type hints work in the PyCharm interpreter (after waiting for the indexing to complete).

I am not sure if this will allow for the stub files to be included in wheel packages, or if each wheel package will include duplicate copies of the itk-stub directories.

Please review the PR #3560 for the starting effort to make typehints more universally available.

Hans

[thewtex]

@hjmjohnson to be included in the wheels, the *.pyi files need to be installed into PY_SITE_PACKAGES_PATH -- I would think the PY_SITE_PACKAGES_PATH/itk path. How does the interpreter understand that it needs to look into PY_SITE_PACKAGES_PATH/itk-stubs?

[hjmjohnson]

@thewtex I followed the convention that would allow for making a separate type-hint package: https://peps.python.org/pep-0561/#stub-only-packages by putting the .pyi files in a separate directory.

This was "doing it the hardest way" initially, knowing that if we wanted to collapse it later, it would be relatively easy to identify and change "itk-stubs" -> "itk"

I'll make a PR to review tonight. It should be pretty easy.