fix(build): don't import cuda.pathfinder in build_hooks.py

The build backends run in an isolated venv created by pyproject-build.
Although cuda-pathfinder is listed in build-system.requires and gets
installed, the cuda namespace package from backend-path=["."] shadows
the installed cuda-pathfinder, making `from cuda.pathfinder import ...`
fail with ModuleNotFoundError. This broke all CI wheel builds.

Revert _get_cuda_path() to use os.environ.get() directly with
CUDA_PATH > CUDA_HOME priority, and remove cuda-pathfinder from
build-system.requires (it was not there on main; our PR added it).

Made-with: Cursor

Author: rwgk

cuda_bindings/build_hooks.py

@@ -35,9 +35,10 @@
 
 @functools.cache
 def _get_cuda_path() -> str:
-    from cuda.pathfinder import get_cuda_path_or_home
-
-    cuda_path = get_cuda_path_or_home()
+    # Not using cuda.pathfinder.get_cuda_path_or_home() here because this
+    # build backend runs in an isolated venv where the cuda namespace package
+    # from backend-path shadows the installed cuda-pathfinder.
+    cuda_path = os.environ.get("CUDA_PATH", os.environ.get("CUDA_HOME"))
     if not cuda_path:
         raise RuntimeError("Environment variable CUDA_PATH or CUDA_HOME is not set")
     print("CUDA path:", cuda_path)

cuda_bindings/pyproject.toml

@@ -6,7 +6,6 @@ requires = [
     "setuptools_scm[simple]>=8",
     "cython>=3.2,<3.3",
     "pyclibrary>=0.1.7",
-    "cuda-pathfinder",
 ]
 build-backend = "build_hooks"
 backend-path = ["."]

cuda_core/build_hooks.py

@@ -30,9 +30,10 @@
 
 @functools.cache
 def _get_cuda_path() -> str:
-    from cuda.pathfinder import get_cuda_path_or_home
-
-    cuda_path = get_cuda_path_or_home()
+    # Not using cuda.pathfinder.get_cuda_path_or_home() here because this
+    # build backend runs in an isolated venv where the cuda namespace package
+    # from backend-path shadows the installed cuda-pathfinder.
+    cuda_path = os.environ.get("CUDA_PATH", os.environ.get("CUDA_HOME"))
     if not cuda_path:
         raise RuntimeError("Environment variable CUDA_PATH or CUDA_HOME is not set")
     print("CUDA path:", cuda_path)

cuda_core/pyproject.toml

@@ -7,7 +7,6 @@ requires = [
     "setuptools>=80",
     "setuptools-scm[simple]>=8",
     "Cython>=3.2,<3.3",
-    "cuda-pathfinder"
 ]
 build-backend = "build_hooks"
 backend-path = ["."]

cuda_core/tests/test_build_hooks.py

@@ -24,8 +24,6 @@
 
 import pytest
 
-from cuda.pathfinder import get_cuda_path_or_home
-
 # build_hooks.py imports Cython and setuptools at the top level, so skip if not available
 pytest.importorskip("Cython")
 pytest.importorskip("setuptools")
@@ -70,7 +68,6 @@ def _check_version_detection(
 
         build_hooks._get_cuda_path.cache_clear()
         build_hooks._determine_cuda_major_version.cache_clear()
-        get_cuda_path_or_home.cache_clear()
 
         mock_env = {
             k: v
@@ -95,7 +92,6 @@ def test_env_var_override(self, version):
         """CUDA_CORE_BUILD_MAJOR env var override works with various versions."""
         build_hooks._get_cuda_path.cache_clear()
         build_hooks._determine_cuda_major_version.cache_clear()
-        get_cuda_path_or_home.cache_clear()
         with mock.patch.dict(os.environ, {"CUDA_CORE_BUILD_MAJOR": version}, clear=False):
             result = build_hooks._determine_cuda_major_version()
             assert result == version
@@ -129,7 +125,6 @@ def test_missing_cuda_path_raises_error(self):
         """RuntimeError is raised when CUDA_PATH/CUDA_HOME not set and no env var override."""
         build_hooks._get_cuda_path.cache_clear()
         build_hooks._determine_cuda_major_version.cache_clear()
-        get_cuda_path_or_home.cache_clear()
         with (
             mock.patch.dict(os.environ, {}, clear=True),
             pytest.raises(RuntimeError, match="CUDA_PATH or CUDA_HOME"),