ci: add optional dependency group to avoid installation of cupy when testing the FT builds

Author: cpcloud

ci/tools/run-tests

@@ -77,12 +77,18 @@ elif [[ "${test_module}" == "core" ]]; then
   echo "Installing core wheel"
   pwd
   ls
+
+  FREE_THREADING=""
+  if python -c 'import sys; assert not sys._is_gil_enabled()' 2> /dev/null; then
+    FREE_THREADING+="-ft"
+  fi
+
   if [[ "${LOCAL_CTK}" == 1 ]]; then
     # We already installed cuda-bindings, and all CTK components exist locally,
     # so just install the test dependencies.
-    pip install $(ls *.whl)["test-cu${TEST_CUDA_MAJOR}"]
+    pip install $(ls *.whl)["test-cu${TEST_CUDA_MAJOR}${FREE_THREADING}"]
   else
-    pip install $(ls *.whl)["cu${TEST_CUDA_MAJOR}","test-cu${TEST_CUDA_MAJOR}"]
+    pip install $(ls *.whl)["cu${TEST_CUDA_MAJOR}","test-cu${TEST_CUDA_MAJOR}${FREE_THREADING}"]
   fi
   popd
   pushd ./cuda_core

cuda_core/pyproject.toml

@@ -49,10 +49,16 @@ dependencies = [
 cu11 = ["cuda-bindings[all]==11.8.*"]
 cu12 = ["cuda-bindings[all]==12.*"]
 cu13 = ["cuda-bindings[all]==13.*"]
+# TODO: these should all be in development dependencies; optional dependencies
+# are for features exposed to *users*, not a dumping ground for all tooling
+# needed to build and test the project
 test = ["cython>=3.1", "setuptools", "pytest>=6.2.4"]
 test-cu11 = ["cuda-core[test]", "cupy-cuda11x", "cuda-toolkit[cudart]==11.*"]  # runtime headers needed by CuPy
 test-cu12 = ["cuda-core[test]", "cupy-cuda12x", "cuda-toolkit[cudart]==12.*"]  # runtime headers needed by CuPy
 test-cu13 = ["cuda-core[test]", "cupy-cuda13x", "cuda-toolkit[cudart]==13.*"]  # runtime headers needed by CuPy
+# free threaded build, cupy doesn't support free-threaded builds yet, so avoid installing it for now
+# TODO: cupy should support free threaded builds
+test-cu13-ft = ["cuda-core[test]", "cuda-toolkit[cudart]==13.*"]
 
 [project.urls]
 homepage = "https://nvidia.github.io/cuda-python/"