Take into account possible missing header file on Windows

Author: rhpvorderman

setup.py

@@ -32,6 +32,17 @@
 BUILD_CACHE_FILE = Path(os.environ.get("PYTHON_ISAL_BUILD_CACHE_FILE",
                                        DEFAULT_CACHE_FILE))
 
+EXTENSIONS = [
+        Extension("isal.isal_zlib", ["src/isal/isal_zlibmodule.c"]),
+        Extension("isal.igzip_lib", ["src/isal/igzip_libmodule.c"]),
+    ]
+
+# This does not add the extension on windows for dynamic linking. The required
+# header file might be missing.
+if not (SYSTEM_IS_WINDOWS and
+        os.getenv("PYTHON_ISAL_LINK_DYNAMIC") is not None):
+    EXTENSIONS.append(Extension("isal._isal", ["src/isal/_isalmodule.c"]))
+
 
 class BuildIsalExt(build_ext):
     def build_extension(self, ext):
@@ -186,9 +197,5 @@ def build_isa_l(compiler_command: str, compiler_options: str):
         "Operating System :: Microsoft :: Windows",
     ],
     python_requires=">=3.7",  # We use METH_FASTCALL
-    ext_modules=[
-        Extension("isal.isal_zlib", ["src/isal/isal_zlibmodule.c"]),
-        Extension("isal.igzip_lib", ["src/isal/igzip_libmodule.c"]),
-        Extension("isal._isal", ["src/isal/_isalmodule.c"])
-    ]
+    ext_modules=EXTENSIONS
 )

src/isal/__init__.py

@@ -5,13 +5,19 @@
 # This file is part of python-isal which is distributed under the
 # PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2.
 
-from . import _isal
-
-ISAL_MAJOR_VERSION: int = _isal.ISAL_MAJOR_VERSION
-ISAL_MINOR_VERSION: int = _isal.ISAL_MINOR_VERSION
-ISAL_PATCH_VERSION: int = _isal.ISAL_PATCH_VERSION
-ISAL_VERSION: str = _isal.ISAL_VERSION
+from typing import Optional
 
+try:
+    from . import _isal
+    ISAL_MAJOR_VERSION: Optional[int] = _isal.ISAL_MAJOR_VERSION
+    ISAL_MINOR_VERSION: Optional[int] = _isal.ISAL_MINOR_VERSION
+    ISAL_PATCH_VERSION: Optional[int] = _isal.ISAL_PATCH_VERSION
+    ISAL_VERSION: Optional[str] = _isal.ISAL_VERSION
+except ImportError:
+    ISAL_MAJOR_VERSION = None
+    ISAL_MINOR_VERSION = None
+    ISAL_PATCH_VERSION = None
+    ISAL_VERSION = None
 
 __all__ = [
     "ISAL_MAJOR_VERSION",

tests/test_zlib_compliance.py

@@ -41,6 +41,9 @@
 
 class VersionTestCase(unittest.TestCase):
 
+    @unittest.skipIf(os.getenv("PYTHON_ISAL_LINK_DYNAMIC") is not None and
+                     sys.platform.startswith("win"),
+                     "Header file missing on windows")
     def test_library_version(self):
         # Test that the major version of the actual library in use matches the
         # major version that we were compiled against. We can't guarantee that