[Cython] Fix Windows builds

For some versions of Python, the DLL module extension included in the
sysconfig module is not correct. In that case, the file extension needs
to be constructed manually.

To make this information easier to get to, the JSON module is used to
parse data returned by sysconfig from the Python which will be building
the module.

interfaces/cython/SConscript

@@ -4,6 +4,7 @@ from os.path import join as pjoin
 from os.path import normpath
 from pathlib import Path
 from pkg_resources import parse_version
+import json
 from buildutils import *
 
 Import('env', 'build', 'install')
@@ -32,37 +33,54 @@ testFiles = localenv.RecursiveInstall('#interfaces/cython/cantera/test/data',
 build(testFiles)
 
 # Get information needed to build the Python module
-script = '\n'.join(("from sysconfig import *",
-                    "import numpy",
-                    "print(get_config_var('EXT_SUFFIX'))",
-                    "print(get_config_var('INCLUDEPY'))",
-                    "print(get_config_var('LDLIBRARY'))",
-                    "print(get_config_var('prefix'))",
-                    "print(get_python_version())",
-                    "print(numpy.get_include())"))
-info = get_command_output(localenv["python_cmd"], "-c", script)
-module_ext, inc, pylib, prefix, py_version, numpy_include = info.splitlines()[-6:]
+script = """\
+from sysconfig import *
+import numpy
+import json
+vars = get_config_vars()
+vars["plat"] = get_platform()
+vars["numpy_include"] = numpy.get_include()
+print(json.dumps(vars))
+"""
+info = json.loads(get_command_output(localenv["python_cmd"], "-c", script))
+module_ext = info["EXT_SUFFIX"]
+inc = info["INCLUDEPY"]
+pylib = info.get("LDLIBRARY")
+prefix = info["prefix"]
+py_version_short = parse_version(info["py_version_short"])
+py_version_full = parse_version(info["py_version"])
+numpy_include = info["numpy_include"]
 localenv.Prepend(CPPPATH=[Dir('#include'), inc, numpy_include])
 localenv.Prepend(LIBS=localenv['cantera_libs'])
 
+# Fix the module extension for Windows from the sysconfig library.
+# See https://github.com/python/cpython/pull/22088 and
+# https://bugs.python.org/issue39825
+if (
+    py_version_full < parse_version("3.8.7")
+    and localenv["OS"] == "Windows"
+    and module_ext == ".pyd"
+):
+    module_ext = f".cp{info['py_version_nodot']}-{info['plat'].replace('-', '_')}.pyd"
+
 # Don't print deprecation warnings for internal Python changes.
 # Only applies to Python 3.8. The field that is deprecated in Python 3.8
 # and causes the warnings to appear will be removed in Python 3.9 so no
 # further warnings should be issued.
-if localenv['HAS_CLANG'] and parse_version(py_version) == parse_version('3.8'):
+if localenv["HAS_CLANG"] and py_version_short == parse_version("3.8"):
     localenv.Append(CXXFLAGS='-Wno-deprecated-declarations')
 
 if localenv['OS'] == 'Darwin':
     localenv.Append(LINKFLAGS='-undefined dynamic_lookup')
 elif localenv['OS'] == 'Windows':
     localenv.Append(LIBPATH=prefix+'/libs')
     if localenv['toolchain'] == 'mingw':
-        localenv.Append(LIBS='python{}'.format(py_version.replace('.','')))
+        localenv.Append(LIBS=f"python{info['py_version_nodot']}")
         if localenv['OS_BITS'] == 64:
             localenv.Append(CPPDEFINES='MS_WIN64')
-        # fix for https://bugs.python.org/issue11566. Fixed in 3.7.3 and higher.
+        # Fix for https://bugs.python.org/issue11566. Fixed in 3.7.3 and higher.
         # See https://github.com/python/cpython/pull/11283
-        if parse_version(py_version) < parse_version("3.7.3"):
+        if py_version_full < parse_version("3.7.3"):
             localenv.Append(CPPDEFINES={"_hypot": "hypot"})
 elif localenv['OS'] == 'Cygwin':
     # extract 'pythonX.Y' from 'libpythonX.Y.dll.a'

interfaces/cython/setup.py

@@ -2,6 +2,4 @@
 
 extension = Extension("cantera._cantera", sources=[])
 
-setup(
-    ext_modules=[extension],
-)
+setup(ext_modules=[extension])