#2304: fix incorporating Eric Smith's .format suggestion and tested on Ubuntu as well as Windows

Lib/subprocess.py

@@ -853,7 +853,7 @@ class Popen(object):
                 startupinfo.dwFlags |= _subprocess.STARTF_USESHOWWINDOW
                 startupinfo.wShowWindow = _subprocess.SW_HIDE
                 comspec = os.environ.get("COMSPEC", "cmd.exe")
-                args = comspec + " /c " + args
+                args = '{} /c "{}"'.format (comspec, args)
                 if (_subprocess.GetVersion() >= 0x80000000 or
                         os.path.basename(comspec).lower() == "command.com"):
                     # Win9x, or using command.com on NT. We need to

Lib/test/test_subprocess.py

@@ -1087,6 +1087,47 @@ class HelperFunctionTests(unittest.TestCase):
         self.assertEqual([(256, 999), (666,), (666,)], record_calls)
 
 
+@unittest.skipUnless(mswindows, "Windows-specific tests")
+class CommandsWithSpaces (BaseTestCase):
+
+    def setUp(self):
+        super().setUp()
+        f, fname = mkstemp(".py", "te st")
+        self.fname = fname.lower ()
+        os.write(f, b"import sys;"
+                    b"sys.stdout.write('%d %s' % (len(sys.argv), [a.lower () for a in sys.argv]))"
+        )
+        os.close(f)
+
+    def tearDown(self):
+        os.remove(self.fname)
+        super().tearDown()
+
+    def with_spaces(self, *args, **kwargs):
+        kwargs['stdout'] = subprocess.PIPE
+        p = subprocess.Popen(*args, **kwargs)
+        self.assertEqual(
+          p.stdout.read ().decode("mbcs"),
+          "2 [%r, 'ab cd']" % self.fname
+        )
+
+    def test_shell_string_with_spaces(self):
+        # call() function with string argument with spaces on Windows
+        self.with_spaces('"%s" "%s"' % (self.fname, "ab cd"), shell=1)
+
+    def test_shell_sequence_with_spaces(self):
+        # call() function with sequence argument with spaces on Windows
+        self.with_spaces([self.fname, "ab cd"], shell=1)
+
+    def test_noshell_string_with_spaces(self):
+        # call() function with string argument with spaces on Windows
+        self.with_spaces('"%s" "%s" "%s"' % (sys.executable, self.fname,
+                             "ab cd"))
+
+    def test_noshell_sequence_with_spaces(self):
+        # call() function with sequence argument with spaces on Windows
+        self.with_spaces([sys.executable, self.fname, "ab cd"])
+
 def test_main():
     unit_tests = (ProcessTestCase,
                   POSIXProcessTestCase,
@@ -1094,7 +1135,8 @@ def test_main():
                   ProcessTestCasePOSIXPurePython,
                   CommandTests,
                   ProcessTestCaseNoPoll,
-                  HelperFunctionTests)
+                  HelperFunctionTests,
+                  CommandsWithSpaces)
 
     support.run_unittest(*unit_tests)
     support.reap_children()