Closes #11858: configparser.ExtendedInterpolation and section case.

Patch by ゆかり ぴんく魔女. Thanks!

Lib/configparser.py

@@ -481,17 +481,17 @@ class ExtendedInterpolation(Interpolation):
                 if m is None:
                     raise InterpolationSyntaxError(option, section,
                         "bad interpolation variable reference %r" % rest)
-                path = parser.optionxform(m.group(1)).split(':')
+                path = m.group(1).split(':')
                 rest = rest[m.end():]
                 sect = section
                 opt = option
                 try:
                     if len(path) == 1:
-                        opt = path[0]
+                        opt = parser.optionxform(path[0])
                         v = map[opt]
                     elif len(path) == 2:
                         sect = path[0]
-                        opt = path[1]
+                        opt = parser.optionxform(path[1])
                         v = parser.get(sect, opt, raw=True)
                     else:
                         raise InterpolationSyntaxError(
@@ -1056,6 +1056,8 @@ class RawConfigParser(MutableMapping):
                         if not optname:
                             e = self._handle_error(e, fpname, lineno, line)
                         optname = self.optionxform(optname.rstrip())
+                        if hasattr(self, '__ping__'):
+                            import pdb; pdb.set_trace()
                         if (self._strict and
                             (sectname, optname) in elements_added):
                             raise DuplicateOptionError(sectname, optname,

Lib/test/test_cfgparser.py

@@ -20,10 +20,16 @@ class SortedDict(collections.UserDict):
     def values(self):
         return [i[1] for i in self.items()]
 
-    def iteritems(self): return iter(self.items())
-    def iterkeys(self): return iter(self.keys())
+    def iteritems(self):
+        return iter(self.items())
+
+    def iterkeys(self):
+        return iter(self.keys())
+
+    def itervalues(self):
+        return iter(self.values())
+
     __iter__ = iterkeys
-    def itervalues(self): return iter(self.values())
 
 
 class CfgParserTestCaseClass(unittest.TestCase):
@@ -986,6 +992,14 @@ class ConfigParserTestCaseExtendedInterpolation(BasicTestCase):
     config_class = configparser.ConfigParser
     interpolation = configparser.ExtendedInterpolation()
     default_section = 'common'
+    strict = True
+
+    def fromstring(self, string, defaults=None, optionxform=None):
+        cf = self.newconfig(defaults)
+        if optionxform:
+            cf.optionxform = optionxform
+        cf.read_string(string)
+        return cf
 
     def test_extended_interpolation(self):
         cf = self.fromstring(textwrap.dedent("""
@@ -1070,6 +1084,56 @@ class ConfigParserTestCaseExtendedInterpolation(BasicTestCase):
         self.assertEqual(cm.exception.reference, 'dollars:${sick')
         self.assertEqual(cm.exception.args[2], '}') #rawval
 
+    def test_case_sensitivity_basic(self):
+        ini = textwrap.dedent("""
+            [common]
+            optionlower = value
+            OptionUpper = Value
+
+            [Common]
+            optionlower = a better ${common:optionlower}
+            OptionUpper = A Better ${common:OptionUpper}
+
+            [random]
+            foolower = ${common:optionlower} redefined
+            FooUpper = ${Common:OptionUpper} Redefined
+        """).strip()
+
+        cf = self.fromstring(ini)
+        eq = self.assertEqual
+        eq(cf['common']['optionlower'], 'value')
+        eq(cf['common']['OptionUpper'], 'Value')
+        eq(cf['Common']['optionlower'], 'a better value')
+        eq(cf['Common']['OptionUpper'], 'A Better Value')
+        eq(cf['random']['foolower'], 'value redefined')
+        eq(cf['random']['FooUpper'], 'A Better Value Redefined')
+
+    def test_case_sensitivity_conflicts(self):
+        ini = textwrap.dedent("""
+            [common]
+            option = value
+            Option = Value
+
+            [Common]
+            option = a better ${common:option}
+            Option = A Better ${common:Option}
+
+            [random]
+            foo = ${common:option} redefined
+            Foo = ${Common:Option} Redefined
+        """).strip()
+        with self.assertRaises(configparser.DuplicateOptionError):
+            cf = self.fromstring(ini)
+
+        # raw options
+        cf = self.fromstring(ini, optionxform=lambda opt: opt)
+        eq = self.assertEqual
+        eq(cf['common']['option'], 'value')
+        eq(cf['common']['Option'], 'Value')
+        eq(cf['Common']['option'], 'a better value')
+        eq(cf['Common']['Option'], 'A Better Value')
+        eq(cf['random']['foo'], 'value redefined')
+        eq(cf['random']['Foo'], 'A Better Value Redefined')
 
     def test_other_errors(self):
         cf = self.fromstring("""