Try to fix packaging tests using build_ext on Windows (#12678)

Lib/packaging/tests/support.py

@@ -306,23 +306,29 @@ def _get_xxmodule_path():
 
 
 def fixup_build_ext(cmd):
-    """Function needed to make build_ext tests pass on shared builds.
+    """Function needed to make build_ext tests pass.
 
-    When Python was build with --enable-shared, -L. is not good enough to find
-    the libpython<blah>.so.  This is because regrtest runs it under a tempdir,
-    not in the top level where the .so lives.  By the time we've gotten here,
-    Python's already been chdir'd to the tempdir.  This function work arounds
-    that.  Example use:
+    When Python was build with --enable-shared on Unix, -L. is not good
+    enough to find the libpython<blah>.so.  This is because regrtest runs
+    it under a tempdir, not in the top level where the .so lives.  By the
+    time we've gotten here, Python's already been chdir'd to the tempdir.
+
+    When Python was built with in debug mode on Windows, build_ext commands
+    need their debug attribute set, and it is not done automatically for
+    some reason.
+
+    This function handles both of these things.  Example use:
 
         cmd = build_ext(dist)
         support.fixup_build_ext(cmd)
         cmd.ensure_finalized()
     """
-    # To further add to the fun, we can't just add library_dirs to the
-    # Extension() instance because that doesn't get plumbed through to the
-    # final compiler command.
-    if (sysconfig.get_config_var('Py_ENABLE_SHARED') and
-        not sys.platform.startswith('win')):
+    if os.name == "nt":
+        cmd.debug = sys.executable.endswith("_d.exe")
+    elif sysconfig.get_config_var('Py_ENABLE_SHARED'):
+        # To further add to the shared builds fun on Unix, we can't just add
+        # library_dirs to the Extension() instance because that doesn't get
+        # plumbed through to the final compiler command.
         runshared = sysconfig.get_config_var('RUNSHARED')
         if runshared is None:
             cmd.library_dirs = ['.']
@@ -330,6 +336,7 @@ def fixup_build_ext(cmd):
             name, equals, value = runshared.partition('=')
             cmd.library_dirs = value.split(os.pathsep)
 
+
 try:
     from test.support import skip_unless_symlink
 except ImportError:

Lib/packaging/tests/test_command_build_ext.py

@@ -40,11 +40,6 @@ class BuildExtTestCase(support.TempdirManager,
         dist.package_dir = self.tmp_dir
         cmd = build_ext(dist)
         support.fixup_build_ext(cmd)
-
-        if os.name == "nt":
-            # On Windows, we must build a debug version iff running
-            # a debug build of Python
-            cmd.debug = sys.executable.endswith("_d.exe")
         cmd.build_lib = self.tmp_dir
         cmd.build_temp = self.tmp_dir
 
@@ -236,9 +231,6 @@ class BuildExtTestCase(support.TempdirManager,
         cmd.ensure_finalized()
         self.assertEqual(len(cmd.get_outputs()), 1)
 
-        if os.name == "nt":
-            cmd.debug = sys.executable.endswith("_d.exe")
-
         cmd.build_lib = os.path.join(self.tmp_dir, 'build')
         cmd.build_temp = os.path.join(self.tmp_dir, 'tempt')