Fix distutils tests on Windows (#12678).

- First, support.fixup_build_ext (already used to set proper
  library_dirs value under Unix shared builds) gains the ability to
  correctly set the debug attribute under Windows debug builds.

- Second, the filename for the extension module gets a _d suffix under
  debug builds.

- Third, the test code properly puts our customized build_ext object
  into an internal dictionary to make sure that the install command will
  later use our object instead of re-creating one.  That’s the downside
  of using low-level APIs in our test code: we have to manually push
  knobs and turn handles that would otherwise be handled behind the
  scenes.

Thanks to Nadeem for the testing.

tests/support.py

@@ -169,23 +169,29 @@ 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 = ['.']

tests/test_build_ext.py

@@ -47,10 +47,6 @@ class BuildExtTestCase(TempdirManager,
         dist.package_dir = self.tmp_dir
         cmd = build_ext(dist)
         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
 
@@ -305,9 +301,6 @@ class BuildExtTestCase(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')
 

tests/test_install.py

@@ -18,6 +18,14 @@ from distutils.extension import Extension
 
 from distutils.tests import support
 
+
+def _make_ext_name(modname):
+    if os.name == 'nt':
+        if sys.executable.endswith('_d.exe'):
+            modname += '_d'
+    return modname + sysconfig.get_config_var('SO')
+
+
 class InstallTestCase(support.TempdirManager,
                       support.EnvironGuard,
                       support.LoggingSilencer,
@@ -201,13 +209,13 @@ class InstallTestCase(support.TempdirManager,
         os.chdir(project_dir)
         support.copy_xxmodule_c(project_dir)
 
-        buildcmd = build_ext(dist)
-        support.fixup_build_ext(buildcmd)
-        buildcmd.ensure_finalized()
-        buildcmd.run()
+        buildextcmd = build_ext(dist)
+        support.fixup_build_ext(buildextcmd)
+        buildextcmd.ensure_finalized()
 
         cmd = install(dist)
         dist.command_obj['install'] = cmd
+        dist.command_obj['build_ext'] = buildextcmd
         cmd.root = install_dir
         cmd.record = os.path.join(project_dir, 'RECORD')
         cmd.ensure_finalized()
@@ -220,7 +228,7 @@ class InstallTestCase(support.TempdirManager,
             f.close()
 
         found = [os.path.basename(line) for line in content.splitlines()]
-        expected = ['xx%s' % sysconfig.get_config_var('SO'),
+        expected = [_make_ext_name('xx'),
                     'UNKNOWN-0.0.0-py%s.%s.egg-info' % sys.version_info[:2]]
         self.assertEqual(found, expected)