Support building a pip package using scikit-build

CMakeLists.txt

@@ -43,6 +43,7 @@ option (NLOPT_OCTAVE "build octave bindings" ON)
 option (NLOPT_MATLAB "build matlab bindings" ON)
 option (NLOPT_GUILE "build guile bindings" ON)
 option (NLOPT_SWIG "use SWIG to build bindings" ON)
+option (NLOPT_PYTHON_SCIKIT_BUILD "generate a project folder for scikit-build" OFF)
 
 if (CMAKE_SOURCE_DIR STREQUAL PROJECT_SOURCE_DIR)
   option (NLOPT_TESTS "build unit tests" ON)

doc/docs/NLopt_Installation.md

@@ -126,6 +126,26 @@ To specify a particular version or location of Python, use the `Python_EXECUTABL
 cmake -DPython_EXECUTABLE=/usr/bin/python ..
 ```
 
+### Creating pip package
+
+To create a pip compatible package using wheels, you have to install [scikit-build](https://scikit-build.readthedocs.io/en/latest) and then configure cmake to generate a python project.
+
+```sh
+cmake -DNLOPT_PYTHON_SCIKIT_BUILD=ON -DBUILD_SHARED_LIBS=NO ..
+```
+
+Then to install the python package:
+
+```sh
+pip install src/swig/python
+```
+
+or to create a wheel:
+```sh
+pip wheel src/swig/python
+```
+
+
 GNU Guile plugins
 -----------------
 

src/swig/CMakeLists.txt

@@ -16,7 +16,40 @@ endif ()
 include_directories (${NLOPT_PRIVATE_INCLUDE_DIRS})
 set_source_files_properties (nlopt.i PROPERTIES CPLUSPLUS ON)
 
-if (NUMPY_FOUND AND Python_FOUND)
+if (NLOPT_PYTHON_SCIKIT_BUILD)
+  configure_file(
+    ${CMAKE_CURRENT_SOURCE_DIR}/python/CMakeLists.txt.in
+    ${CMAKE_CURRENT_BINARY_DIR}/python/CMakeLists.txt
+    @ONLY
+  )
+  configure_file(
+    ${CMAKE_CURRENT_SOURCE_DIR}/nlopt.i
+    ${CMAKE_CURRENT_BINARY_DIR}/python/nlopt.i
+    COPYONLY
+  )
+  configure_file(
+    ${CMAKE_CURRENT_SOURCE_DIR}/nlopt-python.i
+    ${CMAKE_CURRENT_BINARY_DIR}/python/nlopt-python.i
+    COPYONLY
+  )
+  configure_file(
+    ${CMAKE_CURRENT_SOURCE_DIR}/numpy.i
+    ${CMAKE_CURRENT_BINARY_DIR}/python/numpy.i
+    COPYONLY
+  )
+  configure_file(
+    ${CMAKE_CURRENT_SOURCE_DIR}/nlopt-exceptions.i
+    ${CMAKE_CURRENT_BINARY_DIR}/python/nlopt-exceptions.i
+    COPYONLY
+  )
+  configure_file(
+    ${CMAKE_CURRENT_SOURCE_DIR}/python/setup.py.in
+    ${CMAKE_CURRENT_BINARY_DIR}/python/setup.py
+    @ONLY
+  )
+endif()
+
+if (NUMPY_FOUND AND Python_FOUND AND NOT NLOPT_PYTHON_SCIKIT_BUILD)
 
   set (SWIG_MODULE_nlopt_python_EXTRA_DEPS nlopt-python.i numpy.i generate-cpp)
 

src/swig/python/CMakeLists.txt.in

@@ -0,0 +1,25 @@
+cmake_minimum_required(VERSION 3.18...3.22)
+
+project(_nlopt)
+
+find_package(PythonExtensions REQUIRED)
+find_package (NumPy REQUIRED)
+find_package (SWIG 3)
+include (UseSWIG)
+
+# Find NLopt C++ package
+set (NLopt_ROOT @CMAKE_CURRENT_BINARY_DIR@/../../)
+find_package (NLopt CONFIG REQUIRED)
+
+set (SWIG_MODULE__nlopt_EXTRA_DEPS nlopt-python.i numpy.i)
+set_source_files_properties (nlopt.i PROPERTIES CPLUSPLUS ON)
+swig_add_library (_nlopt LANGUAGE python SOURCES nlopt.i)
+set_property(TARGET _nlopt PROPERTY SWIG_INCLUDE_DIRECTORIES $<TARGET_PROPERTY:NLopt::nlopt,INTERFACE_INCLUDE_DIRECTORIES>)
+target_include_directories(_nlopt PRIVATE ${NumPy_INCLUDE_DIRS})
+target_link_libraries(_nlopt NLopt::nlopt)
+file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/__init__.py "from .nlopt import *")
+
+python_extension_module(_nlopt)
+install(TARGETS _nlopt LIBRARY DESTINATION nlopt)
+install (FILES ${CMAKE_CURRENT_BINARY_DIR}/nlopt.py DESTINATION nlopt)
+install (FILES ${CMAKE_CURRENT_BINARY_DIR}/__init__.py DESTINATION nlopt)

src/swig/python/setup.py.in

@@ -0,0 +1,8 @@
+from skbuild import setup
+
+setup(
+    name = 'nlopt',
+    version = '@NLOPT_MAJOR_VERSION@.@NLOPT_MINOR_VERSION@.@NLOPT_BUGFIX_VERSION@',
+    packages = ['nlopt'],
+    zip_safe = False
+)