[3.12] gh-105497: [Enum] Fix Flag inversion when alias/mask members exist. (GH-105542) (#105572)

gh-105497: [Enum] Fix Flag inversion when alias/mask members exist. (GH-105542)

When inverting a Flag member (or boundary STRICT), only consider other canonical flags; when inverting an IntFlag member (or boundary KEEP), also consider aliases.
(cherry picked from commit 59f009e5898a006cdc8f5249be589de6edfe5cd0)

Co-authored-by: Ethan Furman <ethan@stoneleaf.us>

2 files changed, 46 insertions, 8 deletions

diff --git a/Lib/enum.py b/Lib/enum.py
index 62df304..92a9632 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -1463,12 +1463,11 @@ class Flag(Enum, boundary=STRICT):
         else:
             pseudo_member._name_ = None
         # use setdefault in case another thread already created a composite
-        # with this value, but only if all members are known
-        # note: zero is a special case -- add it
-        if not unknown:
-            pseudo_member = cls._value2member_map_.setdefault(value, pseudo_member)
-            if neg_value is not None:
-                cls._value2member_map_[neg_value] = pseudo_member
+        # with this value
+        # note: zero is a special case -- always add it
+        pseudo_member = cls._value2member_map_.setdefault(value, pseudo_member)
+        if neg_value is not None:
+            cls._value2member_map_[neg_value] = pseudo_member
         return pseudo_member
 
     def __contains__(self, other):
@@ -1544,8 +1543,8 @@ class Flag(Enum, boundary=STRICT):
                 # use all bits
                 self._inverted_ = self.__class__(~self._value_)
             else:
-                # calculate flags not in this member
-                self._inverted_ = self.__class__(self._flag_mask_ ^ self._value_)
+                # use canonical bits (i.e. calculate flags not in this member)
+                self._inverted_ = self.__class__(self._singles_mask_ ^ self._value_)
             if isinstance(self._inverted_, self.__class__):
                 self._inverted_._inverted_ = self
         return self._inverted_
diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index b4ac3ab..291213a 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -3045,6 +3045,33 @@ class OldTestFlag(unittest.TestCase):
         WHITE = RED|GREEN|BLUE
         BLANCO = RED|GREEN|BLUE
 
+    class Complete(Flag):
+        A = 0x01
+        B = 0x02
+
+    class Partial(Flag):
+        A = 0x01
+        B = 0x02
+        MASK = 0xff
+
+    class CompleteInt(IntFlag):
+        A = 0x01
+        B = 0x02
+
+    class PartialInt(IntFlag):
+        A = 0x01
+        B = 0x02
+        MASK = 0xff
+
+    class CompleteIntStrict(IntFlag, boundary=STRICT):
+        A = 0x01
+        B = 0x02
+
+    class PartialIntStrict(IntFlag, boundary=STRICT):
+        A = 0x01
+        B = 0x02
+        MASK = 0xff
+
     def test_or(self):
         Perm = self.Perm
         for i in Perm:
@@ -3103,6 +3130,18 @@ class OldTestFlag(unittest.TestCase):
         Open = self.Open
         self.assertIs(Open.WO & ~Open.WO, Open.RO)
         self.assertIs((Open.WO|Open.CE) & ~Open.WO, Open.CE)
+        Complete = self.Complete
+        self.assertIs(~Complete.A, Complete.B)
+        Partial = self.Partial
+        self.assertIs(~Partial.A, Partial.B)
+        CompleteInt = self.CompleteInt
+        self.assertIs(~CompleteInt.A, CompleteInt.B)
+        PartialInt = self.PartialInt
+        self.assertIs(~PartialInt.A, PartialInt(254))
+        CompleteIntStrict = self.CompleteIntStrict
+        self.assertIs(~CompleteIntStrict.A, CompleteIntStrict.B)
+        PartialIntStrict = self.PartialIntStrict
+        self.assertIs(~PartialIntStrict.A, PartialIntStrict.B)
 
     def test_bool(self):
         Perm = self.Perm