Use _version.py import instead of importlib.metadata for cuda-bindings detection

Replace importlib.metadata.distribution() with direct import of
cuda.bindings._version module. The former may incorrectly return
the cuda-core distribution when queried for 'cuda-bindings' in
isolated build environments (tested with Python 3.12 and pip 25.3).
This may be due to cuda-core metadata being written during the
build process before cuda-bindings is fully available, causing
importlib.metadata to return the wrong distribution.

Also ensure cuda-bindings is always required in build environment
by returning ['cuda-bindings'] instead of [] when already installed.
This ensures pip makes it available in isolated build environments
even if installed elsewhere.

Fix import sorting inconsistency for _version import in cuda_pathfinder
by adding 'isort: skip' directive.

Author: rwgk

cuda_core/build_hooks.py

@@ -9,8 +9,6 @@
 
 import functools
 import glob
-import importlib.metadata
-import json
 import os
 import re
 from pathlib import Path
@@ -197,33 +195,32 @@ def build_wheel(wheel_directory, config_settings=None, metadata_directory=None):
 def _check_cuda_bindings_installed():
     """Check if cuda-bindings is installed and validate its version.
 
+    Uses cuda.bindings._version module (generated by setuptools-scm) instead of
+    importlib.metadata.distribution() because the latter may incorrectly return
+    the cuda-core distribution when queried for "cuda-bindings" in isolated build
+    environments (tested with Python 3.12 and pip 25.3). This may be due to
+    cuda-core metadata being written during the build process before cuda-bindings
+    is fully available, causing importlib.metadata to return the wrong distribution.
+
     Returns:
         tuple: (is_installed: bool, is_editable: bool, major_version: str | None)
         If not installed, returns (False, False, None)
     """
     try:
-        bindings_dist = importlib.metadata.distribution("cuda-bindings")
-    except importlib.metadata.PackageNotFoundError:
+        import cuda.bindings._version as bv
+    except ModuleNotFoundError:
         return (False, False, None)
 
-    bindings_version = bindings_dist.version
-    bindings_major_version = bindings_version.split(".")[0]
+    # Determine repo root (parent of cuda_core)
+    repo_root = Path(__file__).resolve().parent.parent
 
-    # Check if it's an editable install using PEP 610 (direct_url.json)
-    # This is the standard method for Python 3.10+ and pip 20.1+
-    is_editable = False
-    try:
-        dist_location = Path(bindings_dist.locate_file(""))
-        # dist-info or egg-info directory
-        metadata_dir = dist_location.parent
-        direct_url_path = metadata_dir / "direct_url.json"
-        if direct_url_path.exists():
-            with open(direct_url_path) as f:
-                direct_url = json.load(f)
-                if direct_url.get("dir_info", {}).get("editable"):
-                    is_editable = True
-    except Exception:  # noqa: S110
-        pass
+    # Check if _version.py is under repo root (editable install)
+    version_file_path = Path(bv.__file__).resolve()
+    is_editable = repo_root in version_file_path.parents
+
+    # Extract major version from version tuple
+    bindings_version = bv.__version__
+    bindings_major_version = bindings_version.split(".")[0]
 
     return (True, is_editable, bindings_major_version)
 
@@ -232,10 +229,15 @@ def _get_cuda_bindings_require():
     """Determine cuda-bindings build requirement.
 
     Strategy:
-    1. If cuda-bindings is already installed (any version), don't require it (keep existing)
-    2. If installed from sources (editable), definitely keep it
-    3. Otherwise, if installed version major doesn't match CUDA major, raise error
-    4. If not installed, require matching CUDA major version
+    1. If not installed, require matching CUDA major version
+    2. If installed from sources (editable), require it without version constraint
+       (pip will keep the existing editable install)
+    3. If installed but not editable and version major doesn't match CUDA major, raise error
+    4. If installed and version matches, require it without version constraint
+       (pip will keep the existing installation)
+
+    Note: We always return a requirement (never empty list) to ensure cuda-bindings
+    is available in pip's isolated build environment, even if already installed elsewhere.
     """
     bindings_installed, bindings_editable, bindings_major = _check_cuda_bindings_installed()
 
@@ -244,9 +246,9 @@ def _get_cuda_bindings_require():
         cuda_major = _determine_cuda_major_version()
         return [f"cuda-bindings=={cuda_major}.*"]
 
-    # If installed from sources (editable), keep it (don't require anything)
+    # If installed from sources (editable), keep it
     if bindings_editable:
-        return []
+        return ["cuda-bindings"]
 
     # If installed but not editable, check version matches CUDA major
     cuda_major = _determine_cuda_major_version()
@@ -263,7 +265,7 @@ def _get_cuda_bindings_require():
         )
 
     # Installed and version matches (or is editable), keep it
-    return []
+    return ["cuda-bindings"]
 
 
 def get_requires_for_build_editable(config_settings=None):

cuda_pathfinder/cuda/pathfinder/__init__.py

@@ -3,8 +3,6 @@
 
 """cuda.pathfinder public APIs"""
 
-from cuda.pathfinder._version import __version__  # noqa: F401
-
 from cuda.pathfinder._dynamic_libs.load_dl_common import DynamicLibNotFoundError as DynamicLibNotFoundError
 from cuda.pathfinder._dynamic_libs.load_dl_common import LoadedDL as LoadedDL
 from cuda.pathfinder._dynamic_libs.load_nvidia_dynamic_lib import load_nvidia_dynamic_lib as load_nvidia_dynamic_lib
@@ -14,6 +12,8 @@
 from cuda.pathfinder._headers.find_nvidia_headers import find_nvidia_header_directory as find_nvidia_header_directory
 from cuda.pathfinder._headers.supported_nvidia_headers import SUPPORTED_HEADERS_CTK as _SUPPORTED_HEADERS_CTK
 
+from cuda.pathfinder._version import __version__  # noqa: F401  # isort: skip
+
 # Indirections to help Sphinx find the docstrings.
 #: Mapping from short CUDA Toolkit (CTK) library names to their canonical
 #: header basenames (used to validate a discovered include directory).