[Python-checkins] bpo-41517: do not allow Enums to be extended (GH-22271)
Miss Islington (bot)
webhook-mailer at python.org
Wed Sep 16 10:31:12 EDT 2020
https://github.com/python/cpython/commit/3f4012117bf80aa7c005f8fa6fb8e1f8b1aef5d5
commit: 3f4012117bf80aa7c005f8fa6fb8e1f8b1aef5d5
branch: 3.8
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2020-09-16T07:30:54-07:00
summary:
bpo-41517: do not allow Enums to be extended (GH-22271)
fix bug that let Enums be extended via multiple inheritance
(cherry picked from commit 3064dbf5df1021e85b507366a7ea448c8895efe7)
Co-authored-by: Ethan Furman <ethan at stoneleaf.us>
files:
A Misc/NEWS.d/next/Library/2020-09-15-22-43-30.bpo-41517.sLBH7g.rst
M Lib/enum.py
M Lib/test/test_enum.py
diff --git a/Lib/enum.py b/Lib/enum.py
index c892d738f8b38..4c1acc6e360bd 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -123,10 +123,12 @@ class EnumMeta(type):
"""Metaclass for Enum"""
@classmethod
def __prepare__(metacls, cls, bases):
+ # check that previous enum members do not exist
+ metacls._check_for_existing_members(cls, bases)
# create the namespace dict
enum_dict = _EnumDict()
# inherit previous flags and _generate_next_value_ function
- member_type, first_enum = metacls._get_mixins_(bases)
+ member_type, first_enum = metacls._get_mixins_(cls, bases)
if first_enum is not None:
enum_dict['_generate_next_value_'] = getattr(first_enum, '_generate_next_value_', None)
return enum_dict
@@ -142,7 +144,7 @@ def __new__(metacls, cls, bases, classdict):
ignore = classdict['_ignore_']
for key in ignore:
classdict.pop(key, None)
- member_type, first_enum = metacls._get_mixins_(bases)
+ member_type, first_enum = metacls._get_mixins_(cls, bases)
__new__, save_new, use_args = metacls._find_new_(classdict, member_type,
first_enum)
@@ -401,7 +403,7 @@ def _create_(cls, class_name, names, *, module=None, qualname=None, type=None, s
"""
metacls = cls.__class__
bases = (cls, ) if type is None else (type, cls)
- _, first_enum = cls._get_mixins_(bases)
+ _, first_enum = cls._get_mixins_(cls, bases)
classdict = metacls.__prepare__(class_name, bases)
# special processing needed for names?
@@ -480,7 +482,14 @@ def _convert(cls, *args, **kwargs):
return cls._convert_(*args, **kwargs)
@staticmethod
- def _get_mixins_(bases):
+ def _check_for_existing_members(class_name, bases):
+ for chain in bases:
+ for base in chain.__mro__:
+ if issubclass(base, Enum) and base._member_names_:
+ raise TypeError("%s: cannot extend enumeration %r" % (class_name, base.__name__))
+
+ @staticmethod
+ def _get_mixins_(class_name, bases):
"""Returns the type for creating enum members, and the first inherited
enum class.
@@ -505,7 +514,7 @@ def _find_data_type(bases):
elif not issubclass(base, Enum):
candidate = base
if len(data_types) > 1:
- raise TypeError('too many data types: %r' % data_types)
+ raise TypeError('%r: too many data types: %r' % (class_name, data_types))
elif data_types:
return data_types[0]
else:
diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index 32ff32cf17567..11e88dba6b5b3 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -1000,6 +1000,9 @@ class MoreColor(Color):
cyan = 4
magenta = 5
yellow = 6
+ with self.assertRaisesRegex(TypeError, "EvenMoreColor: cannot extend enumeration 'Color'"):
+ class EvenMoreColor(Color, IntEnum):
+ chartruese = 7
def test_exclude_methods(self):
class whatever(Enum):
diff --git a/Misc/NEWS.d/next/Library/2020-09-15-22-43-30.bpo-41517.sLBH7g.rst b/Misc/NEWS.d/next/Library/2020-09-15-22-43-30.bpo-41517.sLBH7g.rst
new file mode 100644
index 0000000000000..e7654711062ce
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-09-15-22-43-30.bpo-41517.sLBH7g.rst
@@ -0,0 +1 @@
+fix bug allowing Enums to be extended via multiple inheritance
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