Feature: Use Enum for Signal Types in mesa_signals for Type Safety #3055
Description
The mesa_signals module uses plain strings for signal types, which lacks type safety and IDE support. There's a FIXME comment at line 48 in mesa/experimental/mesa_signals/mesa_signal.py acknowledging this:
# fixme can we make this an inner class enum?Issues:
- Typos caught only at runtime, not by IDE/type checkers
- No autocomplete for available signal types
- Hard to discover what signals an observable emits
To Reproduce
from mesa.experimental.mesa_signals import Observable, HasObservables
class MyModel(HasObservables):
wealth = Observable()
def __init__(self):
super().__init__()
self._wealth = 0
model = MyModel()
# Typo only caught at runtime
model.observe("wealth", "chang", lambda s: print(s.new)) # Should be "change"
# ValueError: you are trying to subscribe to a signal of chang on Observable wealth, which does not emit this signal_typeCurrent Behavior
# Must use magic strings
model.observe("wealth", "change", handler) # No autocomplete, easy to typo
# No way to discover available signals without reading sourceExpected Behavior
from mesa.experimental.mesa_signals import SignalType
# Type-safe with autocomplete
model.observe("wealth", SignalType.CHANGE, handler) # IDE suggests: CHANGE, DIRTY
# Typos caught by IDE/type checker immediately
model.observe("wealth", SignalType.CHANG, handler) # AttributeError in IDE
# Self-documenting
list(SignalType) # [SignalType.CHANGE, SignalType.DIRTY]Proposed Solution
Add a SignalType enum that inherits from str for backward compatibility:
from enum import Enum
class SignalType(str, Enum):
"""Signal types for observables."""
CHANGE = "change"
DIRTY = "dirty" # For future use
def __str__(self):
return self.value