[jonathanberthias]

SCIP constants are currently exposed as plain integers grouped in classes. This prevents type checkers from distinguishing different constant families and leaves enum-related methods incompletely typed.

This PR replaces those classes with standard-library IntEnum and IntFlag classes, using IntFlag for event and timing masks. It updates the stubs, converts enum-valued getters to return enum members, and adjusts the existing tests.

Stage and event names now use .name directly. StageNames and EventNames remain available with integer keys for backward compatibility.

Fixes #1275.

[Joao-Dionisio]

Thank you @jonathanberthias! A couple of things:

• Can you please add a CHANGELOG entry?
• Can the things that take these as input also be changed in the stubs? Like includeHeur, etc.
• There is a minor slowdown in comparison with master, but it shouldn't be a big deal.

[jonathanberthias]

Thanks for the review @Joao-Dionisio! Indeed I had missed a few spots, should be better now 🤞

[Joao-Dionisio]

Thank you @jonathanberthias! I took the liberty of changing the code a bit, because it was inconsistent across Python versions, regarding the output. str(model.getStage()) gave PY_SCIP_STAGE.SOLVED on 3.9/3.10 but 10 on 3.11+, since IntEnum.__str__ changed in 3.11. I think the names are nicer, so I added:

from enum import Enum, Flag, IntEnum, IntFlag

def _format(self, spec):
    return str(self) if not spec else int.__format__(self, spec)

class _ScipEnum(IntEnum):
    __str__ = Enum.__str__
    __format__ = _format

class _ScipFlag(IntFlag):
    __str__ = Flag.__str__
    __format__ = _format

class PY_SCIP_STAGE(_ScipEnum): ...
class PY_SCIP_EVENTTYPE(_ScipFlag): ...

Let me know if you're alright with this, please :)

I also added stubs to the plugins.

[jonathanberthias]

Let me know if you're alright with this, please :)

This is a great idea! I guess this is what you meant here, I didn't think of the string representation 🤦

I was hesitant to type the plugins in case some users test types exactly, but I guess the same applies to all methods that return enum members now so it's the right call I would say. Very nice job 🎉

[Joao-Dionisio]

Thank you @jonathanberthias , and very nice job to you too as well!!