gh-65697: Prevent configparser from writing keys it cannot properly read (#129270)

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Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/Lib/test/test_configparser.py b/Lib/test/test_configparser.py
index c2c82eb..1313ec2 100644
--- a/Lib/test/test_configparser.py
+++ b/Lib/test/test_configparser.py
@@ -2192,6 +2192,30 @@ class SectionlessTestCase(unittest.TestCase):
         self.assertEqual('2', cfg[configparser.UNNAMED_SECTION]['b'])
 
 
+class InvalidInputTestCase(unittest.TestCase):
+    """Tests for issue #65697, where configparser will write configs
+    it parses back differently. Ex: keys containing delimiters or
+    matching the section pattern"""
+
+    def test_delimiter_in_key(self):
+        cfg = configparser.ConfigParser(delimiters=('='))
+        cfg.add_section('section1')
+        cfg.set('section1', 'a=b', 'c')
+        output = io.StringIO()
+        with self.assertRaises(configparser.InvalidWriteError):
+            cfg.write(output)
+        output.close()
+
+    def test_section_bracket_in_key(self):
+        cfg = configparser.ConfigParser()
+        cfg.add_section('section1')
+        cfg.set('section1', '[this parses back as a section]', 'foo')
+        output = io.StringIO()
+        with self.assertRaises(configparser.InvalidWriteError):
+            cfg.write(output)
+        output.close()
+
+
 class MiscTestCase(unittest.TestCase):
     def test__all__(self):
         support.check__all__(self, configparser, not_exported={"Error"})