bpo-33251: Prevent ConfigParser.items returning items present in vars. (#6446)

* bpo-33251: ConfigParser.items no longer returns items present in vars.

Documentation for `ConfigParser.items()` states:
'Items present in vars no longer appear in the result.'

This fix aligns behaviour to that specified in the documentation.

Lib/configparser.py

@@ -846,6 +846,7 @@ class RawConfigParser(MutableMapping):
         except KeyError:
             if section != self.default_section:
                 raise NoSectionError(section)
+        orig_keys = list(d.keys())
         # Update with the entry specific variables
         if vars:
             for key, value in vars.items():
@@ -854,7 +855,7 @@ class RawConfigParser(MutableMapping):
             section, option, d[option], d)
         if raw:
             value_getter = lambda option: d[option]
-        return [(option, value_getter(option)) for option in d.keys()]
+        return [(option, value_getter(option)) for option in orig_keys]
 
     def popitem(self):
         """Remove a section from the parser and return it as

Lib/test/test_configparser.py

@@ -915,8 +915,7 @@ class ConfigParserTestCase(BasicTestCase, unittest.TestCase):
         self.check_items_config([('default', '<default>'),
                                  ('getdefault', '|<default>|'),
                                  ('key', '|value|'),
-                                 ('name', 'value'),
-                                 ('value', 'value')])
+                                 ('name', 'value')])
 
     def test_safe_interpolation(self):
         # See http://www.python.org/sf/511737
@@ -1093,8 +1092,7 @@ class RawConfigParserTestCase(BasicTestCase, unittest.TestCase):
         self.check_items_config([('default', '<default>'),
                                  ('getdefault', '|%(default)s|'),
                                  ('key', '|%(name)s|'),
-                                 ('name', '%(value)s'),
-                                 ('value', 'value')])
+                                 ('name', '%(value)s')])
 
     def test_set_nonstring_types(self):
         cf = self.newconfig()

Misc/NEWS.d/next/Library/2018-04-23-18-25-36.bpo-33251.C_K-J9.rst

@@ -0,0 +1,2 @@
+`ConfigParser.items()` was fixed so that key-value pairs passed in via `vars`
+are not included in the resulting output.