pybind11-stubgen generation expects netgen installed to sysroot

[StefanBruens]

Most packaging schemes do not installed into the prefix directly, but into a staging area set by the DESTDIR env variable.

This is handled fine and transparently by CMake for almost all install(...) invocations.

Exception here of course are any attempts to e.g. import netgen or similar, as done here:

netgen/python/CMakeLists.txt

Lines 35 to 36 in 3548984

	install(CODE "execute_process(COMMAND ${PYTHON_EXECUTABLE} -m pybind11_stubgen --no-setup-py netgen)")
	install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/../stubs/netgen-stubs/ DESTINATION ${NG_INSTALL_DIR_PYTHON}/netgen/ COMPONENT netgen)

For this to work, NG_INSTALL_DIR_PYTHON as expanded by cmakes DESTINATION must be part of the PYTHONPATH/sys.path, i.e. \${DESTDIR}/${NETGEN_PYTHON_DIR_ABSOLUTE}.

[ChrLackner]

Yes, is there a clean way to set python environment from cmake install dirs? Not sure how it works cross platform so that also all shared libraries are found correctly...
Would of course be nice if installers/ python virtual envs could work with stubs as well

[StefanBruens]

Something like this could work for COMMAND:

${PYTHON_EXECUTABLE} -c'import sys; import pybind11_stubgen; sys.path.append($_NG_PYTHON_INSTALL_DIR); pybind11_stubgen.main();'  --ignore-invalid defaultarg signature  --no-setup-py netgen

Maybe use sys.path.insert(0, xxx), so the install directory comes first, before any currently install netgen.
_NG_PYTHON_INSTALL_DIR should be set appropriately.

[StefanBruens]

There is one more problem when using DESTDIR (e.g. DESTDIR=/tmp/netgen_staging).

netgen/python/__init__.py

Lines 5 to 6 in ec0fc05

	_netgen_bin_dir=os.path.realpath(os.path.join(os.path.dirname(__file__),'..',config.NETGEN_PYTHON_RPATH_BIN))
	_netgen_lib_dir=os.path.realpath(os.path.join(os.path.dirname(__file__),'..',config.NETGEN_PYTHON_RPATH))

gets expanded by stubgen to something like, when creating __init__.pyi:

_netgen_bin_dir = '/tmp/netgen_staging/usr/bin'
_netgen_lib_dir = '/tmp/netgen_staging/usr/lib64/netgen'

Preferably, these private attributes would be simply ignored/omitted by stubgen. See sizmailov/pybind11-stubgen#81

[StefanBruens]

Still happens with 6.2.2404.