gh-129678: ConfigParser: do not write an empty unnamed section (GH-129679)

Co-authored-by: Petr Viktorin <[email protected]>

Author: PalmtopTiger

Lib/configparser.py

@@ -959,7 +959,7 @@ def write(self, fp, space_around_delimiters=True):
         if self._defaults:
             self._write_section(fp, self.default_section,
                                     self._defaults.items(), d)
-        if UNNAMED_SECTION in self._sections:
+        if UNNAMED_SECTION in self._sections and self._sections[UNNAMED_SECTION]:
             self._write_section(fp, UNNAMED_SECTION, self._sections[UNNAMED_SECTION].items(), d, unnamed=True)
 
         for section in self._sections:

Lib/test/test_configparser.py

@@ -2161,6 +2161,14 @@ def test_no_section(self):
         self.assertEqual('1', cfg2[configparser.UNNAMED_SECTION]['a'])
         self.assertEqual('2', cfg2[configparser.UNNAMED_SECTION]['b'])
 
+    def test_empty_unnamed_section(self):
+        cfg = configparser.ConfigParser(allow_unnamed_section=True)
+        cfg.add_section(configparser.UNNAMED_SECTION)
+        cfg.add_section('section')
+        output = io.StringIO()
+        cfg.write(output)
+        self.assertEqual(output.getvalue(), '[section]\n\n')
+
     def test_add_section(self):
         cfg = configparser.ConfigParser(allow_unnamed_section=True)
         cfg.add_section(configparser.UNNAMED_SECTION)

Misc/NEWS.d/next/Library/2025-02-05-15-17-31.gh-issue-129678.GIUrmV.rst

@@ -0,0 +1 @@
+:class:`configparser.ConfigParser`: do not write an empty unnamed section