Core: typing for Option.default and a few other ClassVars (#2899)

* Core: typing for `Option.default` and a few other `Option` class variables

This is a replacement for https://github.com/ArchipelagoMW/Archipelago/pull/2173

You can read discussion there for issues we found for why we can't have more specific typing on `default`

instead of setting a default in `Option` (where we don't know the type), we check in the metaclass to make sure they have a default.

* NumericOption doesn't need the type annotation that brings out the mypy bug

* SoE default ClassVar

Options.py

@@ -41,6 +41,11 @@ class AssembleOptions(abc.ABCMeta):
         aliases = {name[6:].lower(): option_id for name, option_id in attrs.items() if
                    name.startswith("alias_")}
 
+        assert (
+            name in {"Option", "VerifyKeys"} or  # base abstract classes don't need default
+            "default" in attrs or
+            any(hasattr(base, "default") for base in bases)
+        ), f"Option class {name} needs default value"
         assert "random" not in aliases, "Choice option 'random' cannot be manually assigned."
 
         # auto-alias Off and On being parsed as True and False
@@ -96,7 +101,7 @@ T = typing.TypeVar('T')
 
 class Option(typing.Generic[T], metaclass=AssembleOptions):
     value: T
-    default = 0
+    default: typing.ClassVar[typing.Any]  # something that __init__ will be able to convert to the correct type
 
     # convert option_name_long into Name Long as display_name, otherwise name_long is the result.
     # Handled in get_option_name()
@@ -106,8 +111,9 @@ class Option(typing.Generic[T], metaclass=AssembleOptions):
     supports_weighting = True
 
     # filled by AssembleOptions:
-    name_lookup: typing.Dict[T, str]
-    options: typing.Dict[str, int]
+    name_lookup: typing.ClassVar[typing.Dict[T, str]]  # type: ignore
+    # https://github.com/python/typing/discussions/1460 the reason for this type: ignore
+    options: typing.ClassVar[typing.Dict[str, int]]
 
     def __repr__(self) -> str:
         return f"{self.__class__.__name__}({self.current_option_name})"
@@ -160,6 +166,8 @@ class FreeText(Option[str]):
     """Text option that allows users to enter strings.
     Needs to be validated by the world or option definition."""
 
+    default = ""
+
     def __init__(self, value: str):
         assert isinstance(value, str), "value of FreeText must be a string"
         self.value = value
@@ -811,7 +819,7 @@ class VerifyKeys(metaclass=FreezeValidKeys):
 
 
 class OptionDict(Option[typing.Dict[str, typing.Any]], VerifyKeys, typing.Mapping[str, typing.Any]):
-    default: typing.Dict[str, typing.Any] = {}
+    default = {}
     supports_weighting = False
 
     def __init__(self, value: typing.Dict[str, typing.Any]):
@@ -852,7 +860,7 @@ class OptionList(Option[typing.List[typing.Any]], VerifyKeys):
     # If only unique entries are needed and input order of elements does not matter, OptionSet should be used instead.
     # Not a docstring so it doesn't get grabbed by the options system.
 
-    default: typing.Union[typing.List[typing.Any], typing.Tuple[typing.Any, ...]] = ()
+    default = ()
     supports_weighting = False
 
     def __init__(self, value: typing.Iterable[typing.Any]):
@@ -878,7 +886,7 @@ class OptionList(Option[typing.List[typing.Any]], VerifyKeys):
 
 
 class OptionSet(Option[typing.Set[str]], VerifyKeys):
-    default: typing.Union[typing.Set[str], typing.FrozenSet[str]] = frozenset()
+    default = frozenset()
     supports_weighting = False
 
     def __init__(self, value: typing.Iterable[str]):