Merge pull request #12 from diegoferigo/fix/win

Fix importing build extension for Python >= 3.8 in Windows

.github/workflows/python.yml

@@ -23,14 +23,6 @@ jobs:
           - ubuntu-20.04
           - macos-latest
           - windows-latest
-        include:
-          # https://github.com/diegoferigo/cmake-build-extension/issues/8
-          - os: windows-latest
-            python-version: 3.8
-            experimental: true
-          - os: windows-latest
-            python-version: 3.9
-            experimental: true
 
     steps:
 

examples/swig/setup.cfg

@@ -20,7 +20,9 @@ packages = find:
 package_dir =
     =src
 python_requires = >=3.6
-install_requires = numpy
+install_requires =
+    numpy
+    cmake-build-extension
 
 [options.packages.find]
 where = src

examples/swig/setup.py

@@ -1,3 +1,4 @@
+import inspect
 import sys
 from pathlib import Path
 
@@ -7,11 +8,21 @@
 with open(Path(__file__).parent.absolute() / "README.md", encoding="utf-8") as f:
     long_description = f.read()
 
+init_py = inspect.cleandoc(
+    """
+    from cmake_build_extension import build_extension_env
+    
+    with build_extension_env():
+        from . import bindings
+    """
+)
+
 setup(
     ext_modules=[
         CMakeExtension(
             name="mymath",
             install_prefix="mymath",
+            write_top_level_init=init_py,
             source_dir=str(Path(__file__).parent.absolute()),
             cmake_configure_options=[
                 f"-DPython3_ROOT_DIR={Path(sys.prefix)}",

src/cmake_build_extension/__init__.py

@@ -1,3 +1,48 @@
+import os
+from contextlib import contextmanager
+from pathlib import Path
+
 from . import build_ext_option
 from .build_extension import BuildExtension
 from .cmake_extension import CMakeExtension
+
+
+@contextmanager
+def build_extension_env():
+    """
+    Creates a context in which build extensions can be imported.
+
+    It fixes a change of behaviour of Python >= 3.8 in Windows:
+    https://docs.python.org/3/whatsnew/3.8.html#bpo-36085-whatsnew
+
+    Other related resources:
+
+    - https://stackoverflow.com/a/23805306
+    - https://www.mail-archive.com/dev@subversion.apache.org/msg40414.html
+
+    Example:
+
+    .. code-block:: python
+
+        from cmake_build_extension import build_extension_env
+
+        with build_extension_env():
+            from . import bindings
+    """
+
+    cookies = []
+
+    # Windows and Python >= 3.8
+    if hasattr(os, "add_dll_directory"):
+
+        for path in os.environ.get("PATH", "").split(os.pathsep):
+
+            if path and Path(path).is_absolute() and Path(path).is_dir():
+                cookies.append(os.add_dll_directory(path))
+
+    try:
+        yield
+
+    finally:
+        for cookie in cookies:
+            cookie.close()