1 files changed, 21 insertions, 9 deletions
diff --git a/Lib/configparser.py b/Lib/configparser.py
index 4344a9e..420dce7 100644
--- a/Lib/configparser.py
+++ b/Lib/configparser.py
@@ -160,7 +160,7 @@ __all__ = ("NoSectionError", "DuplicateOptionError", "DuplicateSectionError",
            "NoOptionError", "InterpolationError", "InterpolationDepthError",
            "InterpolationMissingOptionError", "InterpolationSyntaxError",
            "ParsingError", "MissingSectionHeaderError",
-           "MultilineContinuationError",
+           "MultilineContinuationError", "UnnamedSectionDisabledError",
            "ConfigParser", "RawConfigParser",
            "Interpolation", "BasicInterpolation",  "ExtendedInterpolation",
            "SectionProxy", "ConverterMapping",
@@ -362,6 +362,14 @@ class MultilineContinuationError(ParsingError):
         self.line = line
         self.args = (filename, lineno, line)
 
+
+class UnnamedSectionDisabledError(Error):
+    """Raised when an attempt to use UNNAMED_SECTION is made with the
+    feature disabled."""
+    def __init__(self):
+        Error.__init__(self, "Support for UNNAMED_SECTION is disabled.")
+
+
 class _UnnamedSection:
 
     def __repr__(self):
@@ -692,6 +700,10 @@ class RawConfigParser(MutableMapping):
         if section == self.default_section:
             raise ValueError('Invalid section name: %r' % section)
 
+        if section is UNNAMED_SECTION:
+            if not self._allow_unnamed_section:
+                raise UnnamedSectionDisabledError
+
         if section in self._sections:
             raise DuplicateSectionError(section)
         self._sections[section] = self._dict()
@@ -1203,20 +1215,20 @@ class RawConfigParser(MutableMapping):
         return self.BOOLEAN_STATES[value.lower()]
 
     def _validate_value_types(self, *, section="", option="", value=""):
-        """Raises a TypeError for non-string values.
+        """Raises a TypeError for illegal non-string values.
 
-        The only legal non-string value if we allow valueless
-        options is None, so we need to check if the value is a
-        string if:
-        - we do not allow valueless options, or
-        - we allow valueless options but the value is not None
+        Legal non-string values are UNNAMED_SECTION and falsey values if
+        they are allowed.
 
         For compatibility reasons this method is not used in classic set()
         for RawConfigParsers. It is invoked in every case for mapping protocol
         access and in ConfigParser.set().
         """
-        if not isinstance(section, str):
-            raise TypeError("section names must be strings")
+        if section is UNNAMED_SECTION:
+            if not self._allow_unnamed_section:
+                raise UnnamedSectionDisabledError
+        elif not isinstance(section, str):
+            raise TypeError("section names must be strings or UNNAMED_SECTION")
         if not isinstance(option, str):
             raise TypeError("option keys must be strings")
         if not self._allow_no_value or value: