Closes #21999: Handled empty strings correctly when in POSIX mode.

Lib/shlex.py

@@ -224,7 +224,7 @@ class shlex:
                     if self.debug >= 2:
                         print("shlex: I see punctuation in word state")
                     self.state = ' '
-                    if self.token:
+                    if self.token or (self.posix and quoted):
                         break   # emit current token
                     else:
                         continue

Lib/test/test_shlex.py

@@ -173,6 +173,18 @@ class ShlexTest(unittest.TestCase):
                              "%s: %s != %s" %
                              (self.data[i][0], l, self.data[i][1:]))
 
+    def testEmptyStringHandling(self):
+        """Test that parsing of empty strings is correctly handled."""
+        # see Issue #21999
+        expected = ['', ')', 'abc']
+
+        s = shlex.shlex("'')abc", posix=True)
+        slist = list(s)
+        self.assertEqual(slist, expected)
+        expected = ["''", ')', 'abc']
+        s = shlex.shlex("'')abc")
+        self.assertEqual(list(s), expected)
+
     def testQuote(self):
         safeunquoted = string.ascii_letters + string.digits + '@%_-+=:,./'
         unicode_sample = '\xe9\xe0\xdf'  # e + acute accent, a + grave, sharp s