From 4ef95d551085a5fffcc5a417e8ab6379e98e4e51 Mon Sep 17 00:00:00 2001
From: "steven.bethard" <devnull@localhost>
Date: Mon, 20 Apr 2009 00:41:33 +0000
Subject: Add support for empty string arguments and arguments that contain
 spaces.

---
 argparse.py           |  8 ++++++++
 test/test_argparse.py | 22 ++++++++++++++++++++--
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/argparse.py b/argparse.py
index 83fac14..bb641e2 100644
--- a/argparse.py
+++ b/argparse.py
@@ -1785,6 +1785,14 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
         return result
 
     def _parse_optional(self, arg_string):
+        # if it's an empty string, it was meant to be a positional
+        if not arg_string:
+            return None
+
+        # if it contains a space, it was meant to be a positional
+        if ' ' in arg_string:
+            return None
+
         # if it doesn't start with a prefix, it was meant to be positional
         if not arg_string[0] in self.prefix_chars:
             return None
diff --git a/test/test_argparse.py b/test/test_argparse.py
index ba1a3ba..dd66239 100644
--- a/test/test_argparse.py
+++ b/test/test_argparse.py
@@ -203,8 +203,9 @@ class ParserTesterMetaclass(type):
 
             def test_successes(self, tester):
                 parser = self._get_parser(tester)
-                for args_str, expected_ns in tester.successes:
-                    args = args_str.split()
+                for args, expected_ns in tester.successes:
+                    if isinstance(args, str):
+                        args = args.split()
                     result_ns = self._parse_args(parser, args)
                     tester.assertEqual(expected_ns, result_ns)
 
@@ -1045,6 +1046,23 @@ class TestOptionalsNumericAndPositionals(ParserTestCase):
     ]
 
 
+class TestEmptyAndSpaceContainingArguments(ParserTestCase):
+
+    argument_signatures = [
+        Sig('x', nargs='?'),
+        Sig('-y'),
+    ]
+    failures = ['-y']
+    successes = [
+        ([''], NS(x='', y=None)),
+        (['a badger'], NS(x='a badger', y=None)),
+        (['-a badger'], NS(x='-a badger', y=None)),
+        (['-y', ''], NS(x=None, y='')),
+        (['-y', 'a badger'], NS(x=None, y='a badger')),
+        (['-y', '-a badger'], NS(x=None, y='-a badger')),
+    ]
+
+
 class TestNargsZeroOrMore(ParserTestCase):
     """Tests specifying an args for an Optional that accepts zero or more"""
 
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