bpo-33217: Raise TypeError for non-Enum lookups in Enums (GH-6651)

* bpo-33217: Raise TypeError for non-Enum lookups in Enums

Doc/library/enum.rst

@@ -976,7 +976,7 @@ Enum Classes
 The :class:`EnumMeta` metaclass is responsible for providing the
 :meth:`__contains__`, :meth:`__dir__`, :meth:`__iter__` and other methods that
 allow one to do things with an :class:`Enum` class that fail on a typical
-class, such as `list(Color)` or `some_var in Color`.  :class:`EnumMeta` is
+class, such as `list(Color)` or `some_enum_var in Color`.  :class:`EnumMeta` is
 responsible for ensuring that various other methods on the final :class:`Enum`
 class are correct (such as :meth:`__new__`, :meth:`__getnewargs__`,
 :meth:`__str__` and :meth:`__repr__`).

Lib/enum.py

@@ -303,6 +303,10 @@ class EnumMeta(type):
         return cls._create_(value, names, module=module, qualname=qualname, type=type, start=start)
 
     def __contains__(cls, member):
+        if not isinstance(member, Enum):
+            raise TypeError(
+                "unsupported operand type(s) for 'in': '%s' and '%s'" % (
+                    type(member).__qualname__, cls.__class__.__qualname__))
         return isinstance(member, cls) and member._name_ in cls._member_map_
 
     def __delattr__(cls, attr):
@@ -705,7 +709,9 @@ class Flag(Enum):
 
     def __contains__(self, other):
         if not isinstance(other, self.__class__):
-            return NotImplemented
+            raise TypeError(
+                "unsupported operand type(s) for 'in': '%s' and '%s'" % (
+                    type(other).__qualname__, self.__class__.__qualname__))
         return other._value_ & self._value_ == other._value_
 
     def __repr__(self):

Lib/test/test_enum.py

@@ -325,7 +325,10 @@ class TestEnum(unittest.TestCase):
     def test_contains(self):
         Season = self.Season
         self.assertIn(Season.AUTUMN, Season)
-        self.assertNotIn(3, Season)
+        with self.assertRaises(TypeError):
+            3 in Season
+        with self.assertRaises(TypeError):
+            'AUTUMN' in Season
 
         val = Season(3)
         self.assertIn(val, Season)
@@ -1752,6 +1755,13 @@ class TestFlag(unittest.TestCase):
         AC = 3
         CE = 1<<19
 
+    class Color(Flag):
+        BLACK = 0
+        RED = 1
+        GREEN = 2
+        BLUE = 4
+        PURPLE = RED|BLUE
+
     def test_str(self):
         Perm = self.Perm
         self.assertEqual(str(Perm.R), 'Perm.R')
@@ -1954,7 +1964,21 @@ class TestFlag(unittest.TestCase):
         test_pickle_dump_load(self.assertIs, FlagStooges.CURLY|FlagStooges.MOE)
         test_pickle_dump_load(self.assertIs, FlagStooges)
 
-    def test_containment(self):
+    def test_contains(self):
+        Open = self.Open
+        Color = self.Color
+        self.assertFalse(Color.BLACK in Open)
+        self.assertFalse(Open.RO in Color)
+        with self.assertRaises(TypeError):
+            'BLACK' in Color
+        with self.assertRaises(TypeError):
+            'RO' in Open
+        with self.assertRaises(TypeError):
+            1 in Color
+        with self.assertRaises(TypeError):
+            1 in Open
+
+    def test_member_contains(self):
         Perm = self.Perm
         R, W, X = Perm
         RW = R | W
@@ -2072,6 +2096,13 @@ class TestIntFlag(unittest.TestCase):
         AC = 3
         CE = 1<<19
 
+    class Color(IntFlag):
+        BLACK = 0
+        RED = 1
+        GREEN = 2
+        BLUE = 4
+        PURPLE = RED|BLUE
+
     def test_type(self):
         Perm = self.Perm
         Open = self.Open
@@ -2340,7 +2371,23 @@ class TestIntFlag(unittest.TestCase):
         self.assertEqual(len(lst), len(Thing))
         self.assertEqual(len(Thing), 0, Thing)
 
-    def test_containment(self):
+    def test_contains(self):
+        Open = self.Open
+        Color = self.Color
+        self.assertTrue(Color.GREEN in Color)
+        self.assertTrue(Open.RW in Open)
+        self.assertFalse(Color.GREEN in Open)
+        self.assertFalse(Open.RW in Color)
+        with self.assertRaises(TypeError):
+            'GREEN' in Color
+        with self.assertRaises(TypeError):
+            'RW' in Open
+        with self.assertRaises(TypeError):
+            2 in Color
+        with self.assertRaises(TypeError):
+            2 in Open
+
+    def test_member_contains(self):
         Perm = self.Perm
         R, W, X = Perm
         RW = R | W
@@ -2359,6 +2406,8 @@ class TestIntFlag(unittest.TestCase):
         self.assertFalse(R in WX)
         self.assertFalse(W in RX)
         self.assertFalse(X in RW)
+        with self.assertRaises(TypeError):
+            self.assertFalse('test' in RW)
 
     def test_bool(self):
         Perm = self.Perm

Misc/NEWS.d/next/Library/2018-04-30-13-29-47.bpo-33217.TENDzd.rst

@@ -0,0 +1,2 @@
+Raise :exc:`TypeError` when looking up non-Enum objects in Enum classes and
+Enum members.