Detect duplicate events' names

[Adamantios]

https://github.com/valory-xyz/baby-degen/pull/57#discussion_r1507253050

[DavidMinarsch]

Still unresolved. _MetaAbciApp._check_consistency in packages/valory/skills/abstract_round_abci/base.py:2067-2072 runs four checks — none of them detect duplicate event values:

• _check_required_class_attributes
• _check_initial_states_and_final_states
• _check_consistency_outgoing_transitions_from_non_final_states
• _check_db_constraints_consistency

Python's Enum silently aliases the second declaration when two members share a value, so a typo like:

class Event(Enum):
    BACKTEST_POSITIVE = "backtest_succeeded"
    BACKTEST_NEGATIVE = "backtest_failed"
    FOO = "backtest_failed"   # silently becomes an alias for BACKTEST_NEGATIVE

…compiles fine and causes transitions attached to Event.FOO to hit Event.BACKTEST_NEGATIVE's handler at runtime. Exactly the baby-degen bug that spawned this issue.

Sketch of the fix (~10 lines + a test):

@classmethod
def _check_event_values_unique(mcs, abci_app_cls: Type["AbciApp"]) -> None:
    """Reject AbciApps whose Event enum has duplicate values (which Python silently aliases)."""
    event_cls = None
    for event in abci_app_cls.transition_function:
        event_cls = type(event)
        break
    if event_cls is None:
        return
    # Use __members__ to see aliases; compare with the distinct-values set.
    distinct = {e.value for e in event_cls}
    aliased = [name for name, member in event_cls.__members__.items() if member.name != name]
    if aliased or len(event_cls) != len(distinct):
        raise ABCIAppInternalError(
            f"Event enum `{event_cls.__name__}` has duplicate values "
            f"(aliased members: {aliased}). Each Event member must have a unique value "
            f"to avoid silent transition-map collisions."
        )

Wire it into _check_consistency. Add test that instantiates an AbciApp with a dup-value Event and asserts ABCIAppInternalError.

Keeping this open as a tracker.