gh-156353: Fix configparser space delimiter parsing

This commit fixes a bug introduced in gh-146333 where using a space as a delimiter would cause the option name parsing to incorrectly absorb the space.

The regular expressions _OPT_TMPL and _OPT_NV_TMPL have been adjusted to ensure that whitespace matches do not consume valid delimiters.

Signed-off-by: sundeep8967 <sundeep8967@gmail.com>

Author: sundeep8967

Lib/configparser.py

@@ -618,7 +618,7 @@ class RawConfigParser(MutableMapping):
     _OPT_TMPL = r"""
         (?P<option>                        # very permissive!
             (?:(?!{delim})\S)*             # non-delimiter non-whitespace
-            (?:\s+(?:(?!{delim})\S)+)*)    # optionally more words
+            (?:(?:(?!{delim})\s)+(?:(?!{delim})\S)+)*)    # optionally more words
         \s*(?P<vi>{delim})\s*              # any number of space/tab,
                                            # followed by any of the
                                            # allowed delimiters,
@@ -628,7 +628,7 @@ class RawConfigParser(MutableMapping):
     _OPT_NV_TMPL = r"""
         (?P<option>                        # very permissive!
             (?:(?!{delim})\S)*             # non-delimiter non-whitespace
-            (?:\s+(?:(?!{delim})\S)+)*)    # optionally more words
+            (?:(?:(?!{delim})\s)+(?:(?!{delim})\S)+)*)    # optionally more words
         \s*(?:                             # any number of space/tab,
         (?P<vi>{delim})\s*                 # optionally followed by
                                            # any of the allowed

Lib/test/test_configparser.py

@@ -358,6 +358,13 @@ def test_basic(self):
                 the larch {0[1]} 1
             """.format(self.delimiters)))
 
+    def test_space_delimiter(self):
+        # gh-156353: Space should be accepted as a delimiter
+        cf = self.newconfig(delimiters=(' ', '='))
+        cf.read_string("[all]\nfoo bar=baz")
+        self.assertEqual(cf.options('all'), ['foo'])
+        self.assertEqual(cf.get('all', 'foo'), 'bar=baz')
+
     def test_basic_from_dict(self):
         config = {
             "Foo Bar": {