my previous change did what I said it should not: it changed the current

directory to the directory in which the setup.py script lived (which made
__file__ wrong)

fixed, with test that the script is run in the current directory of the caller

Lib/distutils/core.py

@@ -212,7 +212,6 @@ def run_setup (script_name, script_args=None, stop_after="run"):
     save_argv = sys.argv
     g = {'__file__': script_name}
     l = {}
-    os.chdir(os.path.dirname(script_name) or os.curdir)
     try:
         try:
             sys.argv[0] = script_name

Lib/distutils/tests/test_core.py

@@ -3,6 +3,8 @@
 import StringIO
 import distutils.core
 import os
+import shutil
+import sys
 import test.test_support
 import unittest
 
@@ -16,21 +18,61 @@ from distutils.core import setup
 setup()
 """
 
+setup_prints_cwd = """\
+
+import os
+print os.getcwd()
+
+from distutils.core import setup
+setup()
+"""
+
 
 class CoreTestCase(unittest.TestCase):
 
-    def tearDown(self):
-        os.remove(test.test_support.TESTFN)
+    def setUp(self):
+        self.old_stdout = sys.stdout
+        self.cleanup_testfn()
 
-    def write_setup(self, text):
-        return fn
+    def tearDown(self):
+        sys.stdout = self.old_stdout
+        self.cleanup_testfn()
+
+    def cleanup_testfn(self):
+        path = test.test_support.TESTFN
+        if os.path.isfile(path):
+            os.remove(path)
+        elif os.path.isdir(path):
+            shutil.rmtree(path)
+
+    def write_setup(self, text, path=test.test_support.TESTFN):
+        open(path, "w").write(text)
+        return path
 
     def test_run_setup_provides_file(self):
         # Make sure the script can use __file__; if that's missing, the test
         # setup.py script will raise NameError.
-        fn = test.test_support.TESTFN
-        open(fn, "w").write(setup_using___file__)
-        distutils.core.run_setup(fn)
+        distutils.core.run_setup(
+            self.write_setup(setup_using___file__))
+
+    def test_run_setup_uses_current_dir(self):
+        # This tests that the setup script is run with the current directory
+        # as it's own current directory; this was temporarily broken by a
+        # previous patch when TESTFN did not use the current directory.
+        sys.stdout = StringIO.StringIO()
+        cwd = os.getcwd()
+
+        # Create a directory and write the setup.py file there:
+        os.mkdir(test.test_support.TESTFN)
+        setup_py = os.path.join(test.test_support.TESTFN, "setup.py")
+        distutils.core.run_setup(
+            self.write_setup(setup_prints_cwd, path=setup_py))
+
+        output = sys.stdout.getvalue()
+        open("/dev/tty", "w").write("\n\n%r\n\n\n" % (output,))
+        if output.endswith("\n"):
+            output = output[:-1]
+        self.assertEqual(cwd, output)
 
 
 def test_suite():