Closes #777

When scikit-build assembles dpctl, it runs cmake with _skbuild/*/cmake-build being
as its build directory, _skbuild/*/cmake-install being its install directory. It then
runs setuptools.setup to execute build_py steps using _skbuild/*/setuptools as its
build_base. Since sycl interface library is registered in package-data, it is copied
from cmake-install (where is has symbolic links) to setuptools (where unpatched
setuptools.command.build_py command follows them).

Then, when running install_lib step, files from _skbuild/*/setuptools/lib/dpctl are
copied into site-packages/dpctl using copy_tree, which also follows symbolic links,
hence turning them into hard links).

This PR transfers logic from pre-scikit-build setup.py to fix hard links as post
setuptools.command.install.run() step).

A test is added to tests/test_service.py to verify that on Linux some of library files
are symbolic links.

dpctl/tests/test_service.py

@@ -23,6 +23,7 @@
 import os
 import os.path
 import re
+import sys
 
 import pytest
 
@@ -129,3 +130,25 @@ def test_dev_utils():
     with pytest.raises(ValueError):
         with ctx_mngr(log_dir="/not_a_dir"):
             dpctl.SyclDevice().parent_device
+
+
+def test_syclinterface():
+    install_dir = os.path.dirname(os.path.abspath(dpctl.__file__))
+    paths = glob.glob(os.path.join(install_dir, "*DPCTLSyclInterface*"))
+    if "linux" in sys.platform:
+        assert len(paths) > 1 and any(
+            [os.path.islink(fn) for fn in paths]
+        ), "All library instances are hard links"
+    elif sys.platform in ["win32", "cygwin"]:
+        exts = []
+        for fn in paths:
+            _, file_ext = os.path.splitext(fn)
+            exts.append(file_ext.lower())
+        assert (
+            "lib" in exts
+        ), "Installation does not have DPCTLSyclInterface.lib"
+        assert (
+            "dll" in exts
+        ), "Installation does not have DPCTLSyclInterface.dll"
+    else:
+        raise RuntimeError("Unsupported system")

setup.py

@@ -14,14 +14,18 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import glob
 import os.path
 import pathlib
 import shutil
+import sys
 
 import skbuild
 import skbuild.setuptools_wrap
 import skbuild.utils
 from setuptools import find_packages
+from skbuild.command.build_py import build_py as _skbuild_build_py
+from skbuild.command.install import install as _skbuild_install
 
 import versioneer
 
@@ -30,11 +34,6 @@
     long_description = file.read()
 
 
-def _get_cmdclass():
-    cmdclass = versioneer.get_cmdclass()
-    return cmdclass
-
-
 def cleanup_destination(cmake_manifest):
     """Delete library files from dpctl/ folder before
     letting skbuild copy them over to avoid errors.
@@ -52,7 +51,9 @@ def cleanup_destination(cmake_manifest):
     return cmake_manifest
 
 
-def _patched_copy_file(src_file, dest_file, hide_listing=True):
+def _patched_copy_file(
+    src_file, dest_file, hide_listing=True, preserve_mode=True
+):
     """Copy ``src_file`` to ``dest_file`` ensuring parent directory exists.
 
     By default, message like `creating directory /path/to/package` and
@@ -79,6 +80,42 @@ def _patched_copy_file(src_file, dest_file, hide_listing=True):
 skbuild.setuptools_wrap._copy_file = _patched_copy_file
 
 
+class BuildPyCmd(_skbuild_build_py):
+    def copy_file(self, src, dst, preserve_mode=True):
+        _patched_copy_file(src, dst, preserve_mode=preserve_mode)
+        return (dst, 1)
+
+
+class InstallCmd(_skbuild_install):
+    def run(self):
+        ret = super().run()
+        if "linux" in sys.platform:
+            dpctl_build_dir = os.path.join(
+                os.path.dirname(__file__), self.build_lib, "dpctl"
+            )
+            dpctl_install_dir = os.path.join(self.install_libbase, "dpctl")
+            for fn in glob.glob(
+                os.path.join(dpctl_install_dir, "*DPCTLSyclInterface.so*")
+            ):
+                os.remove(fn)
+                shutil.copy(
+                    src=os.path.join(dpctl_build_dir, os.path.basename(fn)),
+                    dst=dpctl_install_dir,
+                    follow_symlinks=False,
+                )
+        return ret
+
+
+def _get_cmdclass():
+    cmdclass = versioneer.get_cmdclass(
+        cmdclass={
+            "build_py": BuildPyCmd,
+            "install": InstallCmd,
+        }
+    )
+    return cmdclass
+
+
 skbuild.setup(
     name="dpctl",
     version=versioneer.get_version(),