python(MSVC): can't generate stubgen for some native python modules

[Mizux]

disclaimer: on my way to fix, just dumping the investigation process

Protocol

$ cmake --build temp_python39 --config Release --target python_package
...
$ rm temp_python39\python\stub_timestamp
$ cmake --build temp_python39 --config Release --target python_package

Observed

trace error:

...
 load C:\Users\corentinl\work\or-tools\temp_python39\python\ortools\.libs\zlib1.dll...
  load C:\Users\corentinl\work\or-tools\temp_python39\python\ortools\.libs\abseil_dll.dll...
  load C:\Users\corentinl\work\or-tools\temp_python39\python\ortools\.libs\utf8_validity.dll...
  load C:\Users\corentinl\work\or-tools\temp_python39\python\ortools\.libs\libprotobuf.dll...
  load C:\Users\corentinl\work\or-tools\temp_python39\python\ortools\.libs\highs.dll...
  Processed 1 modules
  Generated .\ortools/graph/python/min_cost_flow.pyi
  Processed 1 modules
  Generated .\ortools/constraint_solver/pywrapcp.pyi
  Processed 1 modules
  Generated .\ortools/linear_solver/pywraplp.pyi
ortools.linear_solver.python.model_builder_helper: Failed to import, skipping
...
ortools.sat.python.cp_model_helper: Failed to import, skipping

Investigation

Using dumpbin to figure out why it doesn't load.

$ cd temp_python39\python\ortools\linear_solver\python
$ dumpbin /imports model_build_helper.cp39-win_amd64.pyd | grep .dll
...
    re2.dll
    highs.dll
    libprotobuf.dll
    zlib1.dll
    abseil_dll.dll
    KERNEL32.dll
    MSVCP140.dll
    VCRUNTIME140_1.dll
    VCRUNTIME140.dll
...
$ cd temp_python39\python\ortools\sat\python
$ dumpbin /imports cp_model_helper.cp39-win_amd64.pyd  | grep .dll
   python39.dll
    libprotobuf.dll
    highs.dll
    zlib1.dll
    abseil_dll.dll
    KERNEL32.dll
    MSVCP140.dll
...

So it seems this module depends on re2.dll but we don't load it

or-tools/ortools/python/__init__.py.in

Lines 58 to 62 in c330aec

	for dll in ["zlib1.dll", "abseil_dll.dll", "utf8_validity.dll", "libprotobuf.dll", "highs.dll"]:
	dll_path = os.path.join(basedir, ".libs", dll)
	if os.path.exists(dll_path):
	print(f"load {dll_path}...")
	WinDLL(dll_path)

and

or-tools/cmake/python.cmake

Lines 558 to 569 in c330aec

	COMMAND ${CMAKE_COMMAND} -E
	$<IF:${need_unix_re2_lib},copy,true>
	$<${need_unix_re2_lib}:$<TARGET_SONAME_FILE:re2::re2>>
	${PYTHON_PROJECT}/.libs
	COMMAND ${CMAKE_COMMAND} -E
	$<IF:$<BOOL:${BUILD_Protobuf}>,copy,true>
	$<${need_unix_protobuf_lib}:$<TARGET_SONAME_FILE:protobuf::libprotobuf>>
	$<${need_unix_protobuf_lib}:$<TARGET_SONAME_FILE:utf8_validity>>
	$<${need_windows_protobuf_lib}:$<TARGET_FILE:protobuf::libprotobuf>>
	$<${need_windows_protobuf_lib}:$<TARGET_FILE:utf8_validity>>
	${PYTHON_PROJECT}/.libs