From 7a8fa6a57215aa3fb758744924cb4a647191660d Mon Sep 17 00:00:00 2001
From: Eva <evalott100@gmail.com>
Date: Wed, 5 Jun 2024 14:10:50 +0100
Subject: [PATCH] WIP: making suggested changes

---
 src/ophyd_async/core/signal_backend.py   | 7 +++++--
 src/ophyd_async/epics/_backend/common.py | 2 +-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/ophyd_async/core/signal_backend.py b/src/ophyd_async/core/signal_backend.py
index f42f198d58..dc42abd8dc 100644
--- a/src/ophyd_async/core/signal_backend.py
+++ b/src/ophyd_async/core/signal_backend.py
@@ -1,6 +1,7 @@
 from abc import abstractmethod
 from typing import (
     TYPE_CHECKING,
+    ClassVar,
     Dict,
     FrozenSet,
     Generic,
@@ -66,7 +67,7 @@ class _RuntimeEnumMeta(type):
 
         def __str__(cls):
             if hasattr(cls, "_choices"):
-                return f"RuntimeEnum{list(cls._choices.keys())}"
+                return f"RuntimeEnum{list(cls.choices)}"
             return "RuntimeEnum"
 
         @property
@@ -94,11 +95,13 @@ def __getitem__(cls, choices):
 
             # Create a new enum subclass
             class _RuntimeEnum(cls):
-                _choices = {choice: choice for choice in choices}
+                choices = choices_frozenset
 
             _RuntimeEnumMeta.__enum_classes_created[choices_frozenset] = _RuntimeEnum
             return _RuntimeEnum
 
     class RuntimeEnum(metaclass=_RuntimeEnumMeta):
+        choices: ClassVar[FrozenSet[str]]
+
         def __init__(self):
             raise RuntimeError("RuntimeEnum cannot be instantiated")
diff --git a/src/ophyd_async/epics/_backend/common.py b/src/ophyd_async/epics/_backend/common.py
index 36b2f79d72..b05f265357 100644
--- a/src/ophyd_async/epics/_backend/common.py
+++ b/src/ophyd_async/epics/_backend/common.py
@@ -13,7 +13,7 @@ def get_supported_values(
         return {x: x or "_" for x in pv_choices}
 
     if issubclass(datatype, RuntimeEnum):
-        pv_choices = datatype.choices
+        assert frozenset(pv_choices).issubset(datatype.choices)
     elif not issubclass(datatype, str):
         raise TypeError(f"{pv} is type Enum but doesn't inherit from String")
     elif issubclass(datatype, Enum):