`IntFlag` breaks backward compatibility with `__repr__`

[Brendon-Mendicino]

Bug report

Bug description:

I was doing some testing with doctest for my python library, I noticed that the CI was failing for python3.10. The issue is that the __repr__ for IntFlag (but I assume for Flag in general) breaks backward compatibility due to printing the flags in reverse order.

from enum import IntFlag

class Flag(IntFlag):
    A = 1 << 0
    B = 1 << 1
    C = 1 << 2

print(f"{Flag.B | Flag.C!r}")
# output in python 3.10:
# <Flag.C|B: 6>
# output in python 3.11 onwards
# <Flag.B|C: 6>

CPython versions tested on:

3.10, 3.11, 3.12, 3.13

Operating systems tested on:

Linux

[efimov-mikhail]

Thanks for the report.
But IMO we can't "solve" it in sense that all Python versions will act the same way.
There're only 3.13 and 3.14 Python versions in bugfix stages, and we can't provide such changes in 3.10, 3.11, 3.12.

[ethanfurman]

The change was intentional. If you want to keep the reverse reprs, you can add the following to your own base flag class:

    @classmethod
    def _iter_member_(cls, value):
        yield from sorted(
                cls._iter_member_by_value_(value),
                key=lambda m: m._sort_order_,
                reverse=True,
                )

[Brendon-Mendicino]

Maybe you could add a parameter for the print order, for future version, like so

class Options(IntFlag, iter_order="low_to_high" | "high_to_low"):
    # ...

class IntFlag:
    def __init_subclass__(cls, **kwargs):
        self._iter_order = # ...

or something like this

[picnixz]

Considering it was changed in 3.11, we cannot backport this new option to 3.11 and later since 3.10, 3.11 and 3.12 are security-only. Sorry, but I will be closing this as not planned.