Change in Flag enum behaviour in v3.11rc2

philthompson10

Bug report

The default behaviour of Flag enums has chenged between Python v3.10 and v3.11

Your environment

Python v3.11rc2 on macOS

The following script...

from enum import Flag

class MethodHint(Flag):
    HiddenText = 0x10
    DigitsOnly = 0x01
    LettersOnly = 0x02
    OnlyMask = 0x0f

print(MethodHint.HiddenText|MethodHint.OnlyMask)

...raises a ValueError in v3.11 and prints...

MethodHint.HiddenText|OnlyMask|LettersOnly|DigitsOnly

in v3.10.

While it's not particularly sensible to bitwise-or a mask it is a significant change of behaviour without a deprecation period.

It will be common to have a mask value that covers more bits than currently defined when allowing for future expansion of the flags.