gh-107538: [Enum] fix handling of inverted/negative values

Lib/enum.py

@@ -535,7 +535,7 @@ def __new__(metacls, cls, bases, classdict, *, boundary=None, _simple=False, **k
  # now set the __repr__ for the value
  classdict['_value_repr_'] = metacls._find_data_repr_(cls, bases)
  #
- # Flag structures (will be removed if final class is not a Flag
+ # Flag structures (will be removed if final class is not a Flag)
  classdict['_boundary_'] = (
  boundary
  or getattr(first_enum, '_boundary_', None)
@@ -544,6 +544,29 @@ def __new__(metacls, cls, bases, classdict, *, boundary=None, _simple=False, **k
  classdict['_singles_mask_'] = 0
  classdict['_all_bits_'] = 0
  classdict['_inverted_'] = None
+ # check for negative flag values and invert if found (using _proto_members)
+ if Flag is not None and bases and issubclass(bases[-1], Flag):
+ bits = 0
+ inverted = []
+ for n in member_names:
+ p = classdict[n]
+ if isinstance(p.value, int):
+ if p.value < 0:
+ inverted.append(p)
+ else:
+ bits |= p.value
+ elif p.value is None:
+ pass
+ elif isinstance(p.value, tuple) and p.value and isinstance(p.value[0], int):
+ if p.value[0] < 0:
+ inverted.append(p)
+ else:
+ bits |= p.value[0]
+ for p in inverted:
+ if isinstance(p.value, int):
+ p.value = bits & p.value
+ else:
+ p.value = (bits & p.value[0], ) + p.value[1:]
  try:
  classdict['_%s__in_progress' % cls] = True
  enum_class = super().__new__(metacls, cls, bases, classdict, **kwds)
@@ -1485,7 +1508,10 @@ def _missing_(cls, value):
  )
  if value < 0:
  neg_value = value
- value = all_bits + 1 + value
+ if cls._boundary_ in (EJECT, KEEP):
+ value = all_bits + 1 + value
+ else:
+ value = singles_mask & value
  # get members and unknown
  unknown = value & ~flag_mask
  aliases = value & ~singles_mask

Lib/test/test_enum.py

@@ -1001,12 +1001,18 @@ class OpenAB(self.enum_type):
  self.assertIs(~(A|B), OpenAB(252))
  self.assertIs(~AB_MASK, OpenAB(0))
  self.assertIs(~OpenAB(0), AB_MASK)
+ self.assertIs(OpenAB(~4), OpenAB(251))
  else:
  self.assertIs(~A, B)
  self.assertIs(~B, A)
+ self.assertIs(OpenAB(~1), B)
+ self.assertIs(OpenAB(~2), A)
  self.assertIs(~(A|B), OpenAB(0))
  self.assertIs(~AB_MASK, OpenAB(0))
  self.assertIs(~OpenAB(0), (A|B))
+ self.assertIs(OpenAB(~3), OpenAB(0))
+ self.assertIs(OpenAB(~4), OpenAB(3))
+ self.assertIs(OpenAB(~33), B)
  #
  class OpenXYZ(self.enum_type):
  X = 4
@@ -1030,13 +1036,38 @@ class OpenXYZ(self.enum_type):
  self.assertIs(~X, Y|Z)
  self.assertIs(~Y, X|Z)
  self.assertIs(~Z, X|Y)
+ self.assertIs(OpenXYZ(~4), Y|Z)
+ self.assertIs(OpenXYZ(~2), X|Z)
+ self.assertIs(OpenXYZ(~1), X|Y)
  self.assertIs(~(X|Y), Z)
  self.assertIs(~(X|Z), Y)
  self.assertIs(~(Y|Z), X)
  self.assertIs(~(X|Y|Z), OpenXYZ(0))
  self.assertIs(~XYZ_MASK, OpenXYZ(0))
  self.assertTrue(~OpenXYZ(0), (X|Y|Z))
 
+ def test_assigned_negative_value(self):
+ class X(self.enum_type):
+ A = auto()
+ B = auto()
+ C = A | B
+ D = ~A
+ self.assertEqual(list(X), [X.A, X.B])
+ self.assertIs(~X.A, X.B)
+ self.assertIs(X.D, X.B)
+ self.assertEqual(X.D.value, 2)
+ #
+ class Y(self.enum_type):
+ A = auto()
+ B = auto()
+ C = A | B
+ D = ~A
+ E = auto()
+ self.assertEqual(list(Y), [Y.A, Y.B, Y.E])
+ self.assertIs(~Y.A, Y.B|Y.E)
+ self.assertIs(Y.D, Y.B|Y.E)
+ self.assertEqual(Y.D.value, 6)
+
 
 class TestPlainEnumClass(_EnumTests, _PlainOutputTests, unittest.TestCase):
  enum_type = Enum
@@ -3668,6 +3699,8 @@ class SkipFlag(enum.Flag):
  C = 4 | B
  #
  self.assertTrue(SkipFlag.C in (SkipFlag.A|SkipFlag.C))
+ self.assertTrue(SkipFlag.B in SkipFlag.C)
+ self.assertIs(SkipFlag(~1), SkipFlag.B)
  self.assertRaisesRegex(ValueError, 'SkipFlag.. invalid value 42', SkipFlag, 42)
  #
  class SkipIntFlag(enum.IntFlag):
@@ -3676,6 +3709,8 @@ class SkipIntFlag(enum.IntFlag):
  C = 4 | B
  #
  self.assertTrue(SkipIntFlag.C in (SkipIntFlag.A|SkipIntFlag.C))
+ self.assertTrue(SkipIntFlag.B in SkipIntFlag.C)
+ self.assertIs(SkipIntFlag(~1), SkipIntFlag.B|SkipIntFlag.C)
  self.assertEqual(SkipIntFlag(42).value, 42)
  #
  class MethodHint(Flag):
@@ -4715,6 +4750,8 @@ class Color(Flag):
  BLUE = 4
  WHITE = -1
  # no error means success
+ self.assertEqual(list(Color.WHITE), [Color.RED, Color.GREEN, Color.BLUE])
+ self.assertEqual(Color.WHITE.value, 7)
 
 
 class TestInternals(unittest.TestCase):

Misc/NEWS.d/next/Library/2023-07-05-14-34-10.gh-issue-105497.HU5u89.rst

@@ -0,0 +1 @@
+Fix flag mask inversion when unnamed flags exist.

Misc/NEWS.d/next/Library/2025-04-08-07-25-10.gh-issue-107583.JGfbhq.rst

@@ -0,0 +1,4 @@
+Fix :class:`!Flag` inversion when flag set has missing values
+(:class:`!IntFlag` still flips all bits); fix negative assigned values
+during flag creation (both :class:`!Flag` and :class:`!IntFlag` ignore
+missing values).