From 5bdab641da0afd8aa581dfbde4f82d88d337c4b5 Mon Sep 17 00:00:00 2001 From: Ethan Furman Date: Fri, 21 Sep 2018 19:03:09 -0700 Subject: bpo-29577: Enum: mixin classes don't mix well with already mixed Enums (GH-9328) * bpo-29577: allow multiple mixin classes --- Doc/library/enum.rst | 13 +- Lib/enum.py | 50 ++---- Lib/test/test_enum.py | 199 +++++++++++++++++++++ .../2018-09-14-20-00-47.bpo-29577.RzwKFD.rst | 1 + 4 files changed, 229 insertions(+), 34 deletions(-) create mode 100644 Misc/NEWS.d/next/Library/2018-09-14-20-00-47.bpo-29577.RzwKFD.rst diff --git a/Doc/library/enum.rst b/Doc/library/enum.rst index 6408c01..702eacd 100644 --- a/Doc/library/enum.rst +++ b/Doc/library/enum.rst @@ -387,10 +387,17 @@ whatever value(s) were given to the enum member will be passed into those methods. See `Planet`_ for an example. -Restricted subclassing of enumerations --------------------------------------- +Restricted Enum subclassing +--------------------------- -Subclassing an enumeration is allowed only if the enumeration does not define +A new :class:`Enum` class must have one base Enum class, up to one concrete +data type, and as many :class:`object`-based mixin classes as needed. The +order of these base classes is:: + + def EnumName([mix-in, ...,] [data-type,] base-enum): + pass + +Also, subclassing an enumeration is allowed only if the enumeration does not define any members. So this is forbidden:: >>> class MoreColor(Color): diff --git a/Lib/enum.py b/Lib/enum.py index 02405c8..0ccb30d 100644 --- a/Lib/enum.py +++ b/Lib/enum.py @@ -480,37 +480,25 @@ class EnumMeta(type): if not bases: return object, Enum - # double check that we are not subclassing a class with existing - # enumeration members; while we're at it, see if any other data - # type has been mixed in so we can use the correct __new__ - member_type = first_enum = None - for base in bases: - if (base is not Enum and - issubclass(base, Enum) and - base._member_names_): - raise TypeError("Cannot extend enumerations") - # base is now the last base in bases - if not issubclass(base, Enum): - raise TypeError("new enumerations must be created as " - "`ClassName([mixin_type,] enum_type)`") - - # get correct mix-in type (either mix-in type of Enum subclass, or - # first base if last base is Enum) - if not issubclass(bases[0], Enum): - member_type = bases[0] # first data type - first_enum = bases[-1] # enum type - else: - for base in bases[0].__mro__: - # most common: (IntEnum, int, Enum, object) - # possible: (, , - # , , - # ) - if issubclass(base, Enum): - if first_enum is None: - first_enum = base - else: - if member_type is None: - member_type = base + def _find_data_type(bases): + for chain in bases: + for base in chain.__mro__: + if base is object: + continue + elif '__new__' in base.__dict__: + if issubclass(base, Enum) and not hasattr(base, '__new_member__'): + continue + return base + + # ensure final parent class is an Enum derivative, find any concrete + # data type, and check that Enum has no members + first_enum = bases[-1] + if not issubclass(first_enum, Enum): + raise TypeError("new enumerations should be created as " + "`EnumName([mixin_type, ...] [data_type,] enum_type)`") + member_type = _find_data_type(bases) or object + if first_enum._member_names_: + raise TypeError("Cannot extend enumerations") return member_type, first_enum diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py index b8efb83..aadc11f 100644 --- a/Lib/test/test_enum.py +++ b/Lib/test/test_enum.py @@ -122,6 +122,22 @@ class TestHelpers(unittest.TestCase): '__', '___', '____', '_____',): self.assertFalse(enum._is_dunder(s)) +# for subclassing tests + +class classproperty: + + def __init__(self, fget=None, fset=None, fdel=None, doc=None): + self.fget = fget + self.fset = fset + self.fdel = fdel + if doc is None and fget is not None: + doc = fget.__doc__ + self.__doc__ = doc + + def __get__(self, instance, ownerclass): + return self.fget(ownerclass) + + # tests class TestEnum(unittest.TestCase): @@ -1730,6 +1746,102 @@ class TestEnum(unittest.TestCase): else: raise Exception('Exception not raised.') + def test_multiple_mixin(self): + class MaxMixin: + @classproperty + def MAX(cls): + max = len(cls) + cls.MAX = max + return max + class StrMixin: + def __str__(self): + return self._name_.lower() + class SomeEnum(Enum): + def behavior(self): + return 'booyah' + class AnotherEnum(Enum): + def behavior(self): + return 'nuhuh!' + def social(self): + return "what's up?" + class Color(MaxMixin, Enum): + RED = auto() + GREEN = auto() + BLUE = auto() + self.assertEqual(Color.RED.value, 1) + self.assertEqual(Color.GREEN.value, 2) + self.assertEqual(Color.BLUE.value, 3) + self.assertEqual(Color.MAX, 3) + self.assertEqual(str(Color.BLUE), 'Color.BLUE') + class Color(MaxMixin, StrMixin, Enum): + RED = auto() + GREEN = auto() + BLUE = auto() + self.assertEqual(Color.RED.value, 1) + self.assertEqual(Color.GREEN.value, 2) + self.assertEqual(Color.BLUE.value, 3) + self.assertEqual(Color.MAX, 3) + self.assertEqual(str(Color.BLUE), 'blue') + class Color(StrMixin, MaxMixin, Enum): + RED = auto() + GREEN = auto() + BLUE = auto() + self.assertEqual(Color.RED.value, 1) + self.assertEqual(Color.GREEN.value, 2) + self.assertEqual(Color.BLUE.value, 3) + self.assertEqual(Color.MAX, 3) + self.assertEqual(str(Color.BLUE), 'blue') + class CoolColor(StrMixin, SomeEnum, Enum): + RED = auto() + GREEN = auto() + BLUE = auto() + self.assertEqual(CoolColor.RED.value, 1) + self.assertEqual(CoolColor.GREEN.value, 2) + self.assertEqual(CoolColor.BLUE.value, 3) + self.assertEqual(str(CoolColor.BLUE), 'blue') + self.assertEqual(CoolColor.RED.behavior(), 'booyah') + class CoolerColor(StrMixin, AnotherEnum, Enum): + RED = auto() + GREEN = auto() + BLUE = auto() + self.assertEqual(CoolerColor.RED.value, 1) + self.assertEqual(CoolerColor.GREEN.value, 2) + self.assertEqual(CoolerColor.BLUE.value, 3) + self.assertEqual(str(CoolerColor.BLUE), 'blue') + self.assertEqual(CoolerColor.RED.behavior(), 'nuhuh!') + self.assertEqual(CoolerColor.RED.social(), "what's up?") + class CoolestColor(StrMixin, SomeEnum, AnotherEnum): + RED = auto() + GREEN = auto() + BLUE = auto() + self.assertEqual(CoolestColor.RED.value, 1) + self.assertEqual(CoolestColor.GREEN.value, 2) + self.assertEqual(CoolestColor.BLUE.value, 3) + self.assertEqual(str(CoolestColor.BLUE), 'blue') + self.assertEqual(CoolestColor.RED.behavior(), 'booyah') + self.assertEqual(CoolestColor.RED.social(), "what's up?") + class ConfusedColor(StrMixin, AnotherEnum, SomeEnum): + RED = auto() + GREEN = auto() + BLUE = auto() + self.assertEqual(ConfusedColor.RED.value, 1) + self.assertEqual(ConfusedColor.GREEN.value, 2) + self.assertEqual(ConfusedColor.BLUE.value, 3) + self.assertEqual(str(ConfusedColor.BLUE), 'blue') + self.assertEqual(ConfusedColor.RED.behavior(), 'nuhuh!') + self.assertEqual(ConfusedColor.RED.social(), "what's up?") + class ReformedColor(StrMixin, IntEnum, SomeEnum, AnotherEnum): + RED = auto() + GREEN = auto() + BLUE = auto() + self.assertEqual(ReformedColor.RED.value, 1) + self.assertEqual(ReformedColor.GREEN.value, 2) + self.assertEqual(ReformedColor.BLUE.value, 3) + self.assertEqual(str(ReformedColor.BLUE), 'blue') + self.assertEqual(ReformedColor.RED.behavior(), 'booyah') + self.assertEqual(ConfusedColor.RED.social(), "what's up?") + self.assertTrue(issubclass(ReformedColor, int)) + class TestOrder(unittest.TestCase): @@ -2093,6 +2205,49 @@ class TestFlag(unittest.TestCase): d = 6 self.assertEqual(repr(Bizarre(7)), '') + def test_multiple_mixin(self): + class AllMixin: + @classproperty + def ALL(cls): + members = list(cls) + all_value = None + if members: + all_value = members[0] + for member in members[1:]: + all_value |= member + cls.ALL = all_value + return all_value + class StrMixin: + def __str__(self): + return self._name_.lower() + class Color(AllMixin, Flag): + RED = auto() + GREEN = auto() + BLUE = auto() + self.assertEqual(Color.RED.value, 1) + self.assertEqual(Color.GREEN.value, 2) + self.assertEqual(Color.BLUE.value, 4) + self.assertEqual(Color.ALL.value, 7) + self.assertEqual(str(Color.BLUE), 'Color.BLUE') + class Color(AllMixin, StrMixin, Flag): + RED = auto() + GREEN = auto() + BLUE = auto() + self.assertEqual(Color.RED.value, 1) + self.assertEqual(Color.GREEN.value, 2) + self.assertEqual(Color.BLUE.value, 4) + self.assertEqual(Color.ALL.value, 7) + self.assertEqual(str(Color.BLUE), 'blue') + class Color(StrMixin, AllMixin, Flag): + RED = auto() + GREEN = auto() + BLUE = auto() + self.assertEqual(Color.RED.value, 1) + self.assertEqual(Color.GREEN.value, 2) + self.assertEqual(Color.BLUE.value, 4) + self.assertEqual(Color.ALL.value, 7) + self.assertEqual(str(Color.BLUE), 'blue') + @support.reap_threads def test_unique_composite(self): # override __eq__ to be identity only @@ -2468,6 +2623,49 @@ class TestIntFlag(unittest.TestCase): for f in Open: self.assertEqual(bool(f.value), bool(f)) + def test_multiple_mixin(self): + class AllMixin: + @classproperty + def ALL(cls): + members = list(cls) + all_value = None + if members: + all_value = members[0] + for member in members[1:]: + all_value |= member + cls.ALL = all_value + return all_value + class StrMixin: + def __str__(self): + return self._name_.lower() + class Color(AllMixin, IntFlag): + RED = auto() + GREEN = auto() + BLUE = auto() + self.assertEqual(Color.RED.value, 1) + self.assertEqual(Color.GREEN.value, 2) + self.assertEqual(Color.BLUE.value, 4) + self.assertEqual(Color.ALL.value, 7) + self.assertEqual(str(Color.BLUE), 'Color.BLUE') + class Color(AllMixin, StrMixin, IntFlag): + RED = auto() + GREEN = auto() + BLUE = auto() + self.assertEqual(Color.RED.value, 1) + self.assertEqual(Color.GREEN.value, 2) + self.assertEqual(Color.BLUE.value, 4) + self.assertEqual(Color.ALL.value, 7) + self.assertEqual(str(Color.BLUE), 'blue') + class Color(StrMixin, AllMixin, IntFlag): + RED = auto() + GREEN = auto() + BLUE = auto() + self.assertEqual(Color.RED.value, 1) + self.assertEqual(Color.GREEN.value, 2) + self.assertEqual(Color.BLUE.value, 4) + self.assertEqual(Color.ALL.value, 7) + self.assertEqual(str(Color.BLUE), 'blue') + @support.reap_threads def test_unique_composite(self): # override __eq__ to be identity only @@ -2553,6 +2751,7 @@ class TestUnique(unittest.TestCase): value = 4 + expected_help_output_with_docs = """\ Help on class Color in module %s: diff --git a/Misc/NEWS.d/next/Library/2018-09-14-20-00-47.bpo-29577.RzwKFD.rst b/Misc/NEWS.d/next/Library/2018-09-14-20-00-47.bpo-29577.RzwKFD.rst new file mode 100644 index 0000000..bd71ac4 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2018-09-14-20-00-47.bpo-29577.RzwKFD.rst @@ -0,0 +1 @@ +Support multiple mixin classes when creating Enums. -- cgit v0.12