Extract patched functions as top-level functions

setuptools/msvc9_support.py

 import sys
 
+distutils = None
+unpatched = dict()
+
 def patch_for_specialized_compiler():
     """
     Patch functions in distutils.msvc9compiler to use the standalone compiler
     build for Python (Windows only). Fall back to original behavior when the
     standalone compiler is not available.
     """
+    global distutils
     try:
         distutils = __import__('distutils.msvc9compiler')
     except ImportError:
         # The module isn't available to be patched
         return
 
-    VC_BASE = r'Software\%sMicrosoft\DevDiv\VCForPython\%0.1f'
-    find_vcvarsall = distutils.msvc9compiler.find_vcvarsall
-    query_vcvarsall = distutils.msvc9compiler.query_vcvarsall
-    if find_vcvarsall and find_vcvarsall.__module__.startswith('setuptools.'):
+    if unpatched:
         # Already patched
         return
 
-    def _find_vcvarsall(version):
-        Reg = distutils.msvc9compiler.Reg
+    unpatched.update(vars(distutils.msvc9compiler))
+
+    distutils.msvc9compiler.find_vcvarsall = find_vcvarsall
+    distutils.msvc9compiler.query_vcvarsall = query_vcvarsall
+
+def find_vcvarsall(version):
+    Reg = distutils.msvc9compiler.Reg
+    VC_BASE = r'Software\%sMicrosoft\DevDiv\VCForPython\%0.1f'
+    try:
+        # Per-user installs register the compiler path here
+        productdir = Reg.get_value(VC_BASE % ('', version), "installdir")
+    except KeyError:
         try:
-            # Per-user installs register the compiler path here
-            productdir = Reg.get_value(VC_BASE % ('', version), "installdir")
+            # All-user installs on a 64-bit system register here
+            productdir = Reg.get_value(VC_BASE % ('Wow6432Node\\', version), "installdir")
         except KeyError:
-            try:
-                # All-user installs on a 64-bit system register here
-                productdir = Reg.get_value(VC_BASE % ('Wow6432Node\\', version), "installdir")
-            except KeyError:
-                productdir = None
+            productdir = None
 
-        if productdir:
-            import os
-            vcvarsall = os.path.join(productdir, "vcvarsall.bat")
-            if os.path.isfile(vcvarsall):
-                return vcvarsall
+    if productdir:
+        import os
+        vcvarsall = os.path.join(productdir, "vcvarsall.bat")
+        if os.path.isfile(vcvarsall):
+            return vcvarsall
 
-        return find_vcvarsall(version)
+    return unpatched['find_vcvarsall'](version)
 
-    def _query_vcvarsall(version, *args, **kwargs):
-        try:
-            return query_vcvarsall(version, *args, **kwargs)
-        except distutils.errors.DistutilsPlatformError:
-            exc = sys.exc_info()[1]
-            if exc and "vcvarsall.bat" in exc.args[0]:
-                message = 'Microsoft Visual C++ %0.1f is required (%s).' % (version, exc.args[0])
-                if int(version) == 9:
-                    # This redirection link is maintained by Microsoft.
-                    # Contact vspython@microsoft.com if it needs updating.
-                    raise distutils.errors.DistutilsPlatformError(
-                        message + ' Get it from http://aka.ms/vcpython27'
-                    )
-                raise distutils.errors.DistutilsPlatformError(message)
-            raise
-
-    distutils.msvc9compiler.find_vcvarsall = _find_vcvarsall
-    distutils.msvc9compiler.query_vcvarsall = _query_vcvarsall
+def query_vcvarsall(version, *args, **kwargs):
+    try:
+        return unpatched['query_vcvarsall'](version, *args, **kwargs)
+    except distutils.errors.DistutilsPlatformError:
+        exc = sys.exc_info()[1]
+        if exc and "vcvarsall.bat" in exc.args[0]:
+            message = 'Microsoft Visual C++ %0.1f is required (%s).' % (version, exc.args[0])
+            if int(version) == 9:
+                # This redirection link is maintained by Microsoft.
+                # Contact vspython@microsoft.com if it needs updating.
+                raise distutils.errors.DistutilsPlatformError(
+                    message + ' Get it from http://aka.ms/vcpython27'
+                )
+            raise distutils.errors.DistutilsPlatformError(message)
+        raise