FindNumPy finds system numpy, not virtual env numpy #524
Description
I'm using scikit-build to build python-control/Slycot in a conda virtual environment. I don't think I have any unusual environment variables or any other strange setup. I also think it's reasonable to expect the virtual-env Numpy (etc.) to be preferred to the system Numpy (etc.).
The CMakeLists.txt below demonstrates what I think is the problem; it's unfortunately specific to my virtual-env for _numpy_include_dir, which is the result of numpy.get_include().
One could argue that if numpy.get_include() succeeds, one doesn't need find_path.
cmake_minimum_required(VERSION 3.11.0)
project(noproject VERSION 0.0.1 LANGUAGES NONE)
message(STATUS "CMAKE_SYSTEM_INCLUDE_PATH: ${CMAKE_SYSTEM_INCLUDE_PATH}")
message(STATUS "CMAKE_SYSTEM_PREFIX_PATH: ${CMAKE_SYSTEM_PREFIX_PATH}")
set(_numpy_include_dir "/home/rory/.miniconda3/envs/slycotdev/lib/python3.8/site-packages/numpy/core/include")
find_path(NumPy_INCLUDE_DIR_1
numpy/arrayobject.h
PATHS "${_numpy_include_dir}"
NO_DEFAULT_PATH
)
find_path(NumPy_INCLUDE_DIR_2
numpy/arrayobject.h
PATHS "${_numpy_include_dir}"
)
message(STATUS "NumPy_INCLUDE_DIR_1: ${NumPy_INCLUDE_DIR_1}")
message(STATUS "NumPy_INCLUDE_DIR_2: ${NumPy_INCLUDE_DIR_2}")
Output:
-- CMAKE_SYSTEM_INCLUDE_PATH: /usr/include/X11
-- CMAKE_SYSTEM_PREFIX_PATH: /usr/local;/usr;/;/home/rory/.miniconda3/envs/slycotdev;/usr/local;/usr/X11R6;/usr/pkg;/opt
-- NumPy_INCLUDE_DIR_1: /home/rory/.miniconda3/envs/slycotdev/lib/python3.8/site-packages/numpy/core/include
-- NumPy_INCLUDE_DIR_2: /usr/include
-- Configuring done
-- Generating done
-- Build files have been written to: /home/rory/projects/slycot/cmake-weirdness/build
This is a feature of CMake; see end of https://cmake.org/cmake/help/latest/command/find_path.html. Why the search order is first CMAKE_SYSTEM_PREFIX_PATH and then the specified paths I don't understand (that page says "The default search order is designed to be most-specific to least-specific for common use cases.").
A simple (and so possibly entirely incorrect!) fix is to do what is suggested in the find_pathdocs:
find_path(NumPy_INCLUDE_DIR
numpy/arrayobject.h
PATHS "${_numpy_include_dir}" "${PYTHON_INCLUDE_DIR}"
PATH_SUFFIXES numpy/core/include
NO_DEFAULT_PATH
)
find_path(NumPy_INCLUDE_DIR
numpy/arrayobject.h
PATHS "${_numpy_include_dir}" "${PYTHON_INCLUDE_DIR}"
PATH_SUFFIXES numpy/core/include
)