feat(setup): support using system CMake (#188)

Co-authored-by: Xuehai Pan <XuehaiPan@pku.edu.cn>

Author: mgorny

CHANGELOG.md

@@ -13,7 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
--
+- Support using system `cmake` executable during setup by [@mgorny](https://github.com/mgorny) in [#188](https://github.com/metaopt/optree/pull/188).
 
 ### Changed
 

README.md

@@ -64,6 +64,10 @@ Or, clone this repo and install manually:
 ```bash
 git clone --depth=1 https://github.com/metaopt/optree.git
 cd optree
+
+# export CMAKE_EXECUTABLE="/path/to/custom/cmake"
+# export CMAKE_BUILD_TYPE="Debug"
+# export pybind11_DIR="/path/to/custom/pybind11"
 pip3 install .
 ```
 

pyproject.toml

@@ -1,7 +1,7 @@
 # Package ######################################################################
 
 [build-system]
-requires = ["setuptools", "cmake >= 3.18", "pybind11 >= 2.12"]
+requires = ["setuptools", "pybind11 >= 2.12"]
 build-backend = "setuptools.build_meta"
 
 [project]

setup.py

@@ -21,14 +21,21 @@ def __init__(self, name, source_dir='.', target=None, **kwargs):
         self.source_dir = Path(source_dir).absolute()
         self.target = target if target is not None else name.rpartition('.')[-1]
 
+    @classmethod
+    def cmake_executable(cls):
+        cmake = os.getenv('CMAKE_EXECUTABLE', '')
+        if not cmake:
+            cmake = shutil.which('cmake')
+        return cmake
+
 
 class cmake_build_ext(build_ext):  # noqa: N801
     def build_extension(self, ext):  # noqa: C901
         if not isinstance(ext, CMakeExtension):
             super().build_extension(ext)
             return
 
-        cmake = shutil.which('cmake')
+        cmake = ext.cmake_executable()
         if cmake is None:
             raise RuntimeError('Cannot find CMake executable.')
 
@@ -141,4 +148,5 @@ def vcs_version(name, path):
         version=version.__version__,
         cmdclass={'build_ext': cmake_build_ext},
         ext_modules=[CMakeExtension('optree._C', source_dir=HERE)],
+        setup_requires=(['cmake >= 3.18'] if CMakeExtension.cmake_executable() is None else []),
     )